Document:

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                                                                  EXHIBIT 10.23

                                                                  EXECUTION COPY

                               SECURITY AGREEMENT

         This SECURITY AGREEMENT, dated as of October 13, 2000, is made by
ZymeTx, Inc., a corporation organized under the laws of the State of Delaware,
with its principal offices located at 800 Research Parkway, Suite 100, Oklahoma
City, Oklahoma 73104, (the "Grantor") in favor of the investors identified on
Schedule A hereto (the "Lenders"), severally and not jointly.

                                   WITNESSETH:

         WHEREAS, the Grantor and Lenders have entered into a Purchase Agreement
dated [DATE] (as the same may be amended or modified from time to time, together
with all exhibits and schedules, the "Purchase Agreement") which provides for
Lenders to purchase 5% Senior Secured Convertible Debentures ("Debentures") of
the Grantor on the terms and conditions set forth therein; and

         WHEREAS, it is a requirement under the Purchase Agreement that the
Grantor shall have executed and delivered to the Lenders a security agreement
providing for the grant to Lenders of a security interest in all assets of the
Grantor.

         NOW, THEREFORE, in consideration of the mutual promises and covenants
contained herein and in order to induce the Lenders to purchase the Debentures
pursuant to the Purchase Agreement, the Grantor hereby agrees with the Lenders
as follows:

                             SECTION 1: DEFINITIONS

         1.1 DEFINITIONS. The following words shall have the following meanings
when used in this Security Agreement. All terms used herein not otherwise
defined in this Security Agreement shall have the meanings attributed to such
terms in the Purchase Agreement, and if not defined in the Purchase Agreement,
then the New York Uniform Commercial Code, as may be amended from time to time.
All references to dollar amounts shall mean amounts in lawful money of the
United States of America.

         "Account Grantor" means any person who is or who may become obligated
under, with respect to, or on account of an Account.

         "Accounts" means all presently existing and hereafter arising accounts,
contract rights (including under licenses), and all other forms of obligations
owing to the Grantor or any subsidiaries or joint ventures thereof arising out
of the sale or lease of goods or the rendition of services by such persons, or
arising out of the sale or lease of goods or the rendition of services by a
person other than such persons and acquired by such persons from such person by
assignment or purchase, including, without limitation, rights to payment with
respect to accounts of the direct or indirect subsidiaries of the Grantor that
are sold or assigned to the Grantor,

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irrespective of whether earned by performance, and any and all credit insurance,
guaranties, or security therefor.

         "Collateral" means each of the following: all assets of the Grantor or
any of its subsidiaries, including, without limitation, the Equipment; General
Intangibles; the Intellectual Property Collateral; the Accounts; the Inventory;
and the proceeds and products, whether tangible or intangible, of any of the
foregoing including proceeds of insurance covering any or all of the Collateral,
and any and all tangible or intangible, real or personal, property resulting
from the sale, exchange, collection, or other disposition of the Collateral, or
any portion thereof or interest therein, and the proceeds of any and all of the
foregoing.

         "Event of Default" means and includes any of the Events of Default set
forth in Section 3.1.

         "Equipment" means all machinery, equipment, office machinery,
furniture, fixtures, conveyors, tools, materials, storage and handling
equipment, computer equipment and hardware including central processing units,
terminals, drives, memory units, printers, keyboards, screens, peripherals and
input or output devices, automotive equipment, trucks, molds dies, stamps, motor
vehicles and other equipment of every kind and nature and wherever situated now
or hereafter directly or indirectly owned by the Grantor or its subsidiaries or
in which the Grantor or its subsidiaries may have any interest together with all
additions and accessions thereto, all replacements and all accessories and parts
therefor, all manuals, blueprints, know-how, warranties and records in
connection therewith, all rights against suppliers, warrantors, manufacturers,
sellers or others in connection therewith, and together with all substitutions
for any of the foregoing.

         "General Intangibles" shall mean all "General Intangibles," as such
term is defined in Section 9-106 of the Uniform Commercial Code of the State of
New York, now or hereafter directly or indirectly owned by the Grantor or its
subsidiaries, including, without limitation, Intellectual Property Collateral
and, to the extent, if any, not included therein, present and future trade
secrets and other proprietary information; trademarks, trade names and trademark
applications, service marks, business names, logos and the goodwill of the
business relating thereto; copyrights and copyright applications and all
tangible property embodying the copyrights; unpatented inventions (whether or
not patentable); designs; research and development results; patent applications
and patents; customer contracts; license agreements related to any of the
foregoing and the income therefrom; books, records, computer tapes or disks,
flow diagrams, specification sheets, source codes, object codes, and other
physical manifestations of the foregoing.

         "Indebtedness" means all amounts due and owing to the Lenders pursuant
to Debentures or the other Transaction Documents, together with all reasonable
expenses and disbursements relating to enforcement thereof, including, without
limitation, reasonable legal fees and disbursements.

         "Intellectual Property Collateral" means the following, existing
anywhere throughout the world:

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         All United States, international and foreign patents, patent
applications and statutory invention registrations, including, without
limitation, the patents and patent applications set forth in Schedule __ hereto
(as such Schedule __ may be supplemented from time to time by supplements to
this Agreement), together with all reissues, divisions, continuations,
continuations-in-part, extensions and reexaminations thereof, all inventions
therein, all rights therein provided by international treaties or conventions
and all improvements thereto, and all other rights of any kind whatsoever of the
Grantor accruing thereunder or pertaining thereto (the "Patents");

         All United States, international and foreign trademarks (including,
without limitation, service marks), certification marks, collective marks, trade
dress, logos, domain names, product configurations, trade names, business names,
corporate names and other source identifiers, whether or not registered, whether
currently in use or not, including, without limitation, all common law rights
and registrations and applications for registration thereof, including, without
limitation, the trademark registrations and trademark applications set forth in
Schedule C hereto (as such Schedule C may be supplemented from time to time by
supplements to this Agreement) and all other marks registered in the U.S. Patent
and Trademark Office or in any office or agency of any State or Territory of the
United States or any foreign jurisdiction, and all rights therein provided by
international treaties or conventions, all reissues, extensions and renewals of
any of the foregoing, together in each case with the goodwill of the business
connected therewith and symbolized thereby, and all rights corresponding thereto
throughout the world and all other rights of any kind whatsoever of the Grantor
accruing thereunder or pertaining thereto (the "Trademarks");

         All United States, international and foreign copyrights, copyright
applications, copyright registrations and like protections in each work of
authorship, whether statutory or common law, whether published or unpublished,
any renewals or extensions thereof, all copyrights of works based on,
incorporated in, derived from, or relating to works covered by such copyrights,
including, without limitation, the copyright registrations and copyright
applications set forth in Schedule C hereto (as such Schedule C may be
supplemented from time to time, together with all rights corresponding thereto
throughout the world and all other rights of any kind whatsoever of the Grantor
accruing thereunder or pertaining thereto (the "Copyrights");

         All United States, international and foreign confidential and
proprietary information, including, without limitation, know-how, trade secrets,
manufacturing and production processes and techniques, inventions, research and
development information, technical data, financial, marketing and business data,
pricing and cost information, business and marketing plans and customer and
supplier lists and information (the "Trade Secrets");

         All United States, international and foreign computer software programs
and databases (including, without limitation, source code, object code and all
related applications and data files), firmware, and documentation and materials
relating thereto, and all rights with respect to the foregoing, together with
any and all options, warranties, service contracts, program services, test
rights, maintenance rights, improvement rights, renewal rights and
indemnifications and any substitutions, replacements, additions or model
conversions of any of the foregoing (the "Computer Software ");

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         All United States, international and foreign license agreements,
permits, authorizations and franchises, whether with respect to the Patents,
Trademarks, Copyrights, Trade Secrets or Computer Software, or with respect to
the patents, trademarks, copyrights, trade secrets, computer software or other
proprietary right of any other Person, including, without limitation, the
license agreements set forth in Schedule C hereto (as such Schedule C may be
supplemented from time to time, and all income, royalties and other payments now
or hereafter due and/or payable with respect thereto (the "Licenses"); and

         Any and all claims for damages for past, present and future
infringement, misappropriation or breach with respect to the Patents,
Trademarks, Copyrights, Trade Secrets, Computer Software or Licenses, with the
right, but not the obligation, to sue for and collect, or otherwise recover,
such damages.

         "Inventory" means all present and future inventory in which the Grantor
or any subsidiaries or joint ventures thereof have any interest, including goods
(whether finished or unfinished) held for sale or lease or to be furnished under
a contract of service and all of such persons' present and future raw materials,
work in process, finished goods, and packing and shipping materials, wherever
located, and any documents of title representing any of the above.

         "Permitted Liens" means any purchase money security interest existing
on the date of this Agreement and securing the purchase of the Equipment.

         "Registration Rights Agreement" means the Registration Rights
Agreement, dated as of October 13, 2000 by and among the Grantor and the
Lenders.

         "Security Agreement" means this Security Agreement, as this Security
Agreement may be amended or modified from time to time, together with all
exhibits and schedules attached to this Security Agreement from time to time.

SECTION 2: GRANT OF SECURITY INTEREST; OBLIGATIONS OF THE GRANTOR

         2.1 GRANT OF SECURITY INTEREST. As collateral security for all of the
Indebtedness, the Grantor hereby grants to Lenders a continuing first priority
perfected security interest in all currently existing and hereafter acquired or
arising Collateral to secure prompt repayment of any and all Indebtedness and to
secure prompt performance by the Grantor of each of its covenants and duties
under the Debentures, and the other Transaction Documents. The Grantor further
agrees that Lenders shall have the rights stated in this Security Agreement with
respect to the Collateral in addition to all other rights which Lenders may have
by law, by contract or in equity.

         2.2 REPRESENTATIONS AND OBLIGATIONS OF THE GRANTOR. The Grantor
represents, warrants and covenants to Lenders as follows:

               (a)  Perfection of Security Interest. The Grantor agrees to
                    execute at any time and from time to time such financing
                    statements and to take whatever other actions are requested
                    by Lenders to perfect and continue Lenders' first priority

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                    security interest in the Collateral. Upon request of the
                    Lenders, the Grantor will deliver to the Lenders copies of
                    any and all documents evidencing or constituting the
                    Collateral and upon request of the Lenders following the
                    occurrence of an Event of Default (as defined in Section 3.1
                    hereof), such Grantor will deliver the originals of such
                    documents to the Lenders. Upon request of the Lenders, the
                    Grantor will note Lenders' interest, as the case may be,
                    upon any and all Accounts if not delivered to Lenders for
                    possession by Lenders. Lenders may at any time and from time
                    to time, and without further authorization from the Grantor,
                    file a carbon, photographic or other reproduction of any
                    financing statement or of this Security Agreement for use as
                    a financing statement. The Grantor will reimburse Lenders
                    for all reasonable expenses for the perfection and the
                    continuation of the perfection of Lenders' security interest
                    in the Collateral, including reasonable attorneys fees. The
                    Grantor will promptly notify Lenders of any change in its
                    name including any change to the assumed business names of
                    the Grantor. This is a continuing Security Agreement and
                    will continue in effect until all of the Indebtedness is
                    paid in full and Lenders shall release their interest in the
                    Collateral upon the full and final payment and satisfaction
                    of the Indebtedness. If payment is made by the Grantor,
                    whether voluntarily or otherwise, or by any third party, on
                    the Indebtedness and thereafter Lenders are forced to remit
                    the amount of that payment to the Grantor's trustee in
                    bankruptcy or to any similar person under any federal, state
                    or foreign bankruptcy law or other law for the relief of
                    Grantor, the Indebtedness shall be considered unpaid for the
                    purpose of enforcement of this Security Agreement.

               (b)  Ownership. The Grantor is the legal and beneficial owner of
                    the Collateral free and clear of any Lien, claim, option or
                    right of others, except for the security interest created
                    under this Agreement. No effective financing statement or
                    other instrument similar in effect covering all or any part
                    of the Collateral or listing the Grantor or any trade name
                    of the Grantor as debtor is on file in any recording office.

               (c)  Necessary Actions. All filings and other actions necessary
                    or desirable to perfect and protect the security interest in
                    the Collateral of the Grantor created under this Agreement
                    have been duly made or taken and are in full force and
                    effect or will be taken within five (5) business days after
                    Closing, and this Agreement creates in favor of the Lenders
                    a valid and, together with such filings and other actions,
                    perfected first priority security interest in the Collateral
                    of the Grantor, securing the payment of the Indebtedness.

               (d)  All Collateral. The Intellectual Property Collateral set
                    forth on Schedule __ hereto includes all of the Patents,
                    Trademarks, Copyrights, and Licenses owned by the Grantor as
                    of the Effective Date.

               (e)  Filings. The Grantor has made or performed or, after the
                    Effective Date, will perform all filings, recordings and
                    other acts and has paid all required fees and taxes to
                    maintain and protect its interest in each and every item of
                    Intellectual

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                    Property Collateral listed on Schedule __ in full force and
                    effect, and to protect and maintain its interest therein
                    including, without limitation, recordations of any of its
                    interests in the Patents and Trademarks with the U.S. Patent
                    and Trademark Office and in corresponding national and
                    international offices, and recordation of any of its
                    interests in the Copyrights with the U.S. Copyright Office
                    and in corresponding national and international offices. The
                    Grantor has used proper statutory notice in connection with
                    its use of each Patent, Trademark and Copyright.

               (f)  Trade Secrets. To the best of the Grantor's acknowledge, (A)
                    none of the Trade Secrets of the Grantor has been used,
                    divulged, disclosed or appropriated to the detriment of the
                    Grantor for the benefit of any other Person other than the
                    Grantor; (B) no employee, independent contractor or agent of
                    the Grantor has misappropriated any trade secrets of any
                    other Person in the course of the performance of his or her
                    duties as an employee, independent contractor or agent of
                    the Grantor; and (C) no employee, independent contractor or
                    agent of the Grantor is in default or breach of any term of
                    any employment agreement, non-disclosure agreement,
                    assignment of inventions agreement or similar agreement or
                    contract relating in any way to the protection, ownership,
                    development, use or transfer of the Grantor's Intellectual
                    Property Collateral.

               (g)  Further Assurances. The Grantor agrees that from time to
                    time, at the expense of the Grantor, the Grantor will
                    promptly execute and deliver all further instruments and
                    documents, and take all further action, that may be
                    necessary or desirable, or that the Lenders may reasonably
                    request, in order to perfect and protect any pledge,
                    assignment or security interest granted or purported to be
                    granted by the Grantor hereunder or to enable the Lenders to
                    exercise and enforce its rights and remedies hereunder with
                    respect to any Collateral of the Grantor. Without limiting
                    the generality of the foregoing, the Grantor will promptly
                    with respect to Collateral of the Grantor: (i) if any
                    Collateral shall be evidenced by a promissory note or other
                    instrument or chattel paper, deliver and pledge to the
                    Lenders hereunder such note or instrument or chattel paper
                    duly endorsed and accompanied by duly executed instruments
                    of transfer or assignment, all in form and substance
                    reasonably satisfactory to the Lenders; (ii) execute and
                    file such financing or continuation statements, or
                    amendments thereto, and such other instruments or notices,
                    as may be necessary or desirable, or as the Lenders may
                    reasonably request, in order to perfect and preserve the
                    security interest granted or purported to be granted by the
                    Grantor hereunder; and (iii) deliver to the Lenders evidence
                    that all other action that the Lenders may deem reasonably
                    necessary or desirable in order to perfect and protect the
                    security interest created by the Grantor under this
                    Agreement has been taken. The Grantor hereby authorizes the
                    Lenders to file one or more financing or continuation
                    statements, and amendments thereto, relating to all or any
                    part of the Collateral of the Grantor without the signature
                    of the Grantor where permitted by law. A photocopy or other
                    reproduction of this Agreement or any financing statement
                    covering the

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                    Collateral or any part thereof shall be sufficient as a
                    financing statement where permitted by law.

               (h)  Intellectual Property Collateral. With respect to each item
                    of its Intellectual Property Collateral listed on Schedule
                    C, the Grantor, in accordance with its reasonable business
                    judgment, agrees to take, at its expense, all necessary
                    steps, including, without limitation, in the U.S. Patent and
                    Trademark Office, the U.S. Copyright Office and any other
                    governmental authority, to (i) maintain the validity and
                    enforceability of each such item of Intellectual Property
                    Collateral and maintain each such item of Intellectual
                    Property Collateral in full force and effect, and (ii)
                    pursue the registration and maintenance of each patent,
                    trademark, or copyright registration or application, now or
                    hereafter included in the Intellectual Property Collateral
                    of the Grantor, including, without limitation, the payment
                    of required fees and taxes, the filing of responses to
                    office actions issued by the U.S. Patent and Trademark
                    Office, the U.S. Copyright Office or other governmental
                    authorities, the filing of applications for renewal or
                    extension, the filing of affidavits under Sections 8 and 15
                    of the U.S. Trademark Act, the filing of divisional,
                    continuation, continuation-in-part, reissue and renewal
                    applications or extensions, the payment of maintenance fees
                    and the participation in interference, reexamination,
                    opposition, cancellation, infringement and misappropriation
                    proceedings. No Grantor shall, without the written consent
                    of the Lenders, discontinue use of or otherwise abandon any
                    Intellectual Property Collateral, or abandon any right to
                    file an application for letters patent, trademark, or
                    copyright.

               (i)  Certain Notices. The Grantor agrees to notify the Lender
                    within five (5) business days if the Grantor learns (i) that
                    any item of the Intellectual Property Collateral may have
                    become abandoned, placed in the public domain, invalid or
                    unenforceable, or of any adverse determination or
                    development regarding the Grantor's ownership of any of the
                    Intellectual Property Collateral or its right to register
                    the same or to keep and maintain and enforce the same, or
                    (ii) of any adverse determination or the institution of any
                    proceeding (including, without limitation, the institution
                    of any proceeding in the U.S. Patent and Trademark Office or
                    any court) regarding any item of the Intellectual Property
                    Collateral. In the event that any Grantor becomes aware that
                    any item of the Intellectual Property Collateral material to
                    the business of any Grantor is being infringed or
                    misappropriated by a third party, the Grantor shall promptly
                    notify the Lawyers and shall take such actions, at its
                    expense, as are reasonable and appropriate under the
                    circumstances to protect such Intellectual Property
                    Collateral, including, without limitation, suing for
                    infringement or misappropriation and for an injunction
                    against such infringement or misappropriation.

               (j)  Certain Steps. The Grantor shall take all steps which are
                    reasonable and appropriate under the circumstances to
                    preserve and protect each item of its Intellectual Property
                    Collateral material to its business, including, without

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                    limitation, maintaining the quality of any and all products
                    or services used or provided in connection with any of the
                    Trademarks, consistent with the quality of the products and
                    services as of the date hereof, and taking all steps
                    necessary to ensure that all licensed users of any of the
                    Trademarks use such consistent standards of quality.

               (k)  After Acquired Property. The Grantor agrees that, should it
                    obtain an ownership interest in any item of the type which
                    would be considered Collateral (the "After-Acquired
                    Property"), (i) the provisions of Section __ shall
                    automatically apply thereto, (ii) any such After-Acquired
                    Property and, in the case of trademarks, the goodwill of the
                    business connected therewith or symbolized thereby, shall
                    automatically become part of the Collateral subject to the
                    terms and conditions of this Agreement with respect thereto,
                    (iii) the Grantor shall give prompt written notice thereof
                    to the Lenders in accordance herewith and (iv) the Grantor
                    shall execute and deliver to the Lenders a Security
                    Agreement Supplement in a form requested by the Lenders
                    covering such After-Acquired Property as "Additional
                    Collateral" thereunder and as defined therein, and, as is
                    necessary shall record such Security Agreement Supplement
                    with the U.S. Patent and Trademark Office, the U.S.
                    Copyright Office and any other governmental authorities as
                    is necessary or desirable to perfect the security interest
                    hereunder in such After-Acquired Property.

               (l)  Power of Attorney. The Grantor hereby irrevocably makes,
                    constitutes, and appoints each Lender (and all of such
                    Lender's general partners, officers, employees, or agents
                    designated by such Lender) as its true and lawful attorney,
                    with power to: (i) sign the Grantor's name on any of the
                    documents described hereunder or on any other similar
                    documents to be executed, recorded, or filed in order to
                    perfect or continue perfected Lenders' security interest in
                    the Collateral; (ii) at any time that an Event of Default
                    has occurred and is continuing, execute, sign and endorse
                    the Grantor's name on any invoice or bill of lading relating
                    to any Account, drafts against Account Debtors, schedules
                    and assignments of Accounts, verifications of Accounts, and
                    notices to Account Debtor; (iii) send requests for
                    verification of Accounts; (iv) at any time that an Event of
                    Default has occurred and is continuing, execute, sign and
                    endorse the Grantor's name on any checks, notices,
                    instruments, acceptances, money orders, drafts, warrants or
                    other item of payment or security that may come into
                    Lenders' possession; (v) at any time that an Event of
                    Default has occurred and is continuing, demand, collect,
                    receive, receipt for, sue and recover all sums of money or
                    other property which may now or hereafter become due, owing
                    or payable from the Collateral; (vi) file any claim or
                    claims or, following an Event of Default, take any action or
                    institute or take part in any proceedings, either in its own
                    name or in the name of the Grantor, or otherwise, which in
                    the discretion of Lenders may seem to be necessary or
                    advisable; (vii) at any time that an Event of Default has
                    occurred and following acceleration of the Indebtedness,
                    direct the Account Grantor and other persons sending mail to
                    the Grantor to send all

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                    mail relating to the Collateral to the Lenders; (viii) at
                    any time that an Event of Default has occurred and is
                    continuing, make, settle, and adjust all claims under the
                    Grantor' policies of insurance and make all determinations
                    and decisions with respect to such policies of insurance;
                    and (ix) at any time that an Event of Default has occurred
                    and following acceleration of the Indebtedness, settle and
                    adjust disputes and claims respecting the Accounts directly
                    with Account Grantor, for amounts and upon terms which
                    Lenders determine to be reasonable, and Lenders may cause to
                    be executed and delivered any documents and releases which
                    Lenders determine to be necessary. The appointment of
                    Lenders as the Grantor's attorneys, and each and every one
                    of Lenders' rights and powers, being coupled with an
                    interest, is irrevocable and shall remain in full force and
                    effect until all of the Indebtedness has been fully repaid
                    and performed.

               (m)  No Violation. The execution and delivery of this Security
                    Agreement does not violate any law or agreement governing
                    the Grantor or to which the Grantor is a party, and the
                    Grantor' certificate or articles of incorporation and bylaws
                    or other constating documents do not prohibit any term or
                    condition of this Security Agreement. The execution and
                    delivery hereof is in the interest of the Grantor.

               (n)  Enforceability of Collateral. With respect to the Accounts,
                    the Collateral is enforceable in accordance with its terms,
                    is genuine, and complies in all material respects with
                    applicable laws concerning form, content and manner of
                    preparation and execution, and, to the best the knowledge of
                    the Grantor, all persons appearing to be obligated on the
                    Collateral have authority and capacity to contract and are
                    in fact obligated as they appear to be on the Collateral.

               (o)  Accounts. All Accounts existing as of the date hereof are
                    good and valid Accounts representing an undisputed, bona
                    fide indebtedness incurred by the Account Debtors, and there
                    exists no set-offs or counterclaims against any such
                    Accounts and no agreements under which any deductions or
                    discounts may be claimed with any Account Debtor except as
                    disclosed to Lenders in writing.

               (p)  Removal of Collateral; Transactions Involving Collateral. To
                    the extent the Collateral consists of Accounts, the records
                    and other documents pertaining to the Collateral shall be
                    kept at the offices of the Grantor at the address specified
                    in the preamble, or at such other locations as are
                    reasonably acceptable to Lenders. Except for transactions in
                    the ordinary course of business in accordance with past
                    practice or for sales or dispositions on arm's length terms
                    and for fair equivalent value, the Grantor shall not sell,
                    offer to sell, or otherwise transfer, dispose of or encumber
                    the Collateral. The Grantor shall not pledge, mortgage,
                    encumber or otherwise permit the Collateral to be subject to
                    any lien, security interest, encumbrance, or charge, other
                    than the security interest provided for in this Security
                    Agreement and Permitted Liens,

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                    without the prior written consent of Lenders which may be
                    withheld for any reason in Lenders' sole discretion.

               (q)  Title. The Grantor represents and warrants to Lenders that
                    as of the date hereof, the Grantor holds good and marketable
                    title to the Collateral, free and clear of all liens and
                    encumbrances except for the lien of this Security Agreement
                    and Permitted Liens. No financing statement or other
                    evidence of a lien or transfer covering any of the
                    Collateral is on file in any public office in any
                    jurisdiction other than those which reflect the security
                    interest created by this Security Agreement or Permitted
                    Liens. The Grantor shall defend Lenders' rights in the
                    Collateral against any and all claims and demands.

               (r)  Prepayments. The Grantor represents and warrants to Lenders
                    that none of the Collateral has been prepaid by any Account
                    Debtor for any Accounts.

               (s)  Collateral Schedules and Locations. Upon Lenders' request,
                    on a monthly basis, the Grantor shall deliver to Lenders
                    schedules of the Collateral, including such information as
                    Lenders may require, including without limitation names and
                    addresses of Account Debtors and agings of Accounts,
                    including without limitation the location of mobile goods or
                    changes in any certificates of title, and identification of
                    Intellectual Property Collateral, including but not limited
                    to name or title, application and registration number, and
                    the jurisdiction in which such collateral is located or
                    filed. The Grantor represents and warrants to Lenders that a
                    detailed list of the Collateral existing as of the date
                    hereof is set forth on Schedule B attached hereto, and such
                    Schedule B (x) is true, accurate and complete in all
                    material respects, (y) identifies those items of Collateral
                    which contain a certificate of title along with the
                    jurisdiction of such certificates, and (z) those items of
                    Collateral which are mobile goods along with the present
                    location of such goods. Schedule B shall be updated monthly
                    by the Grantor to reflect any changes thereto. (t)
                    Application of Payments Received With Respect to Collateral.
                    Any amounts received by or on behalf of the Grantor with
                    respect to any Account pledged as Collateral hereunder shall
                    be applied in accordance with the Debentures.

               (u)  Possession and Collection of Accounts. Following an Event of
                    Default and following acceleration of the Indebtedness, the
                    records and documents evidencing the Accounts pledged as
                    Collateral hereunder shall, upon Lenders' request, be
                    delivered to Lenders or their agent and held in accordance
                    with the terms of this Security Agreement.

               (v)  Maintenance and Inspection of Collateral. The Grantor shall
                    maintain or cause to be maintained all tangible Collateral
                    in good condition and repair except for ordinary wear and
                    tear. The Grantor will not commit or permit material damage
                    to or destruction of the Collateral or any material part of
                    the Collateral. Lenders and their designated representatives
                    and agents shall have

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                    the right at all reasonable times, upon reasonable advance
                    notice, to examine, inspect, and audit the Collateral
                    wherever located and the books, records or any property
                    which is otherwise used in connection with the Collateral.
                    The Grantor shall immediately notify Lenders of all material
                    cases involving the return, rejection, repossession, loss or
                    damage of or to any Collateral; of any request for credit or
                    adjustment or of any other dispute arising with respect to
                    the Collateral; and generally of all happenings and events
                    materially adversely affecting the Collateral or the value
                    or the amount of the Collateral.

               (w)  Taxes, Assessments and Liens. The Grantor will pay when due
                    all taxes, assessments and liens upon the Collateral, its
                    use or operation, upon this Security Agreement. The Grantor
                    may withhold any such payment or may elect to contest any
                    lien if the Grantor is in good faith conducting an
                    appropriate proceeding to contest the obligation to pay and
                    so long as Lenders' interest in the Collateral is not
                    jeopardized in Lenders' sole opinion. If any of the
                    Collateral is subjected to a lien which is not discharged
                    within thirty (30) days, the Grantor shall deposit with
                    Lenders cash, a sufficient corporate surety bond or other
                    security satisfactory to Lenders (in their discretion) in an
                    amount adequate to provide for the discharge of the lien
                    plus any interest, reasonable costs, attorneys' fees or
                    other charges that could accrue as a result of foreclosure
                    or sale of the Collateral. In any contest the Grantor shall
                    defend themselves and Lenders and shall satisfy any final
                    adverse judgment before enforcement against the Collateral.
                    The Grantor shall name Lenders as an additional obligee
                    under any surety bond furnished in such contest proceedings.

               (x)  Incorporation by Reference. The Grantor hereby restates and
                    affirms all representations, warranties and agreements
                    contained in the Purchase Agreement, the terms and
                    conditions of which are hereby incorporated herein by
                    reference.

               (y)  Compliance With Governmental Requirements. The Grantor shall
                    comply promptly with all laws, ordinances and regulations of
                    all governmental authorities applicable to the production,
                    disposition, or use of the Collateral, non-compliance with
                    which would have a material adverse effect on the Collateral
                    or the business of the Grantor. The Grantor may contest in
                    good faith any such law, ordinance or regulation and
                    withhold compliance during any proceeding, including
                    appropriate appeals, so long as Lenders' interest in the
                    Collateral, in Lenders' sole opinion, is not jeopardized.

               (z)  Insurance. The Grantor shall comply with all insurance
                    requirements and provisions set forth in the Purchase
                    Agreement.

               (aa) The Grantor's Right to Possession and to Collect Accounts.
                    Until the occurrence of an Event of Default and acceleration
                    of Indebtedness and except as otherwise provided herein with
                    respect to the Accounts, the Grantor may have possession of
                    the tangible personal property and beneficial use of all the

                                       11
<PAGE>   12

                    Collateral and may use it in any lawful manner not
                    inconsistent with this Security Agreement or the Transaction
                    Documents, provided that the Grantor's right to possession
                    and beneficial use shall not apply to any Collateral where
                    possession of the Collateral by Lenders is required by law
                    to perfect Lenders' security interest in such Collateral. At
                    any time an Event of Default and following acceleration of
                    Indebtedness, Lenders may exercise their right to directly
                    collect the Accounts and to notify Account Debtors to make
                    payments directly to Lenders for application to the
                    Indebtedness, and the Grantor authorize and directs the
                    Account Debtors, if Lenders exercise such right, to make
                    payments on the Accounts to Lenders. If Lenders at any time
                    have possession of any Collateral, whether before or after
                    an Event of Default, Lenders shall be deemed to have
                    exercised reasonable care in the custody and preservation of
                    the Collateral if Lenders take such action for that purpose
                    as the Grantor shall reasonably request or as Lenders, in
                    Lenders' sole reasonable discretion, shall deem appropriate
                    under the circumstances, but failure to honor any request by
                    the Grantor shall not of itself be deemed to be a failure to
                    exercise reasonable care. Lenders shall not be required to
                    take any steps necessary to preserve any rights in the
                    Collateral against prior parties, nor to protect, preserve
                    or maintain any security interest given to secure the
                    Collateral. Lenders shall have the right to direct who shall
                    collect and service the Accounts.

               (bb) Transactions with Others. Lenders may (i) extend time for
                    payment or other performance, (ii) grant a renewal or change
                    in terms or conditions, or (iii) compromise, compound or
                    release any obligation, with the Grantor, endorsers or any
                    guarantor of the Indebtedness as Lenders deem advisable,
                    without obtaining the prior written consent of the Grantor,
                    and no such act or failure to act shall affect Lenders'
                    rights against the Grantor or the Collateral.

               (cc) Expenditures by Lenders. If not discharged or paid when due,
                    and provided that such items have not been contested as
                    permitted herein Lenders may (but shall not be obligated to)
                    discharge or pay any amounts required to be discharged or
                    paid by the Grantor under this Security Agreement, including
                    without limitation all taxes, liens, security interests,
                    encumbrances, and other claims, at any time levied or placed
                    on the Collateral. Lenders also may (but shall not be
                    obligated to) pay all reasonable costs for insuring,
                    maintaining and preserving the Collateral. All such
                    expenditures incurred or paid by Lenders for such purposes
                    will then bear interest at the then rate charged under the
                    Debentures from the date incurred or paid by Lenders to the
                    date of repayment by the Grantor. All such expenses shall
                    become a part of the Indebtedness and, at Lenders' option,
                    will (i) be payable on demand or (ii) be added to the
                    balance of the Debentures, becoming a part of the
                    outstanding principal amount due and payable on the
                    applicable Interest Payment Dates (as defined in the
                    Debentures). This Security Agreement also will secure
                    payment of these amounts. Such right under this subsection
                    shall be in addition to all other rights and remedies to
                    which Lenders may be entitled upon the occurrence of an
                    Event of Default.

                                       12
<PAGE>   13

               (dd) Sale or Factoring of Accounts; Release of Accounts. Except
                    with respect to Permitted Liens, the Grantor shall not sell
                    or otherwise transfer or encumber any of the Accounts
                    without Lenders' written consent. It is expressly agreed
                    that Lenders are under no obligation to grant such a consent
                    and will do so only in its sole and absolute discretion on
                    terms and conditions they deem acceptable in their sole and
                    absolute discretion.

               (ee) Location. The Grantor represents and warrants that all of
                    the Collateral is located in the United States.

               (ff) In the event that in the future, any Accounts or Inventory
                    are held by Subsidiaries, affiliates or joint ventures of
                    the Grantor other than the Grantor, then the Grantor shall
                    cause such entities to grant the Lenders an exclusive first
                    priority lien in such Accounts and Inventory, to cause such
                    entities to enter into security agreements reasonably
                    satisfactory to Lenders, and to take all actions necessary
                    to perfect such security interests.

         2.3 NON-PUBLIC INFORMATION. Notwithstanding any other provision of this
Agreement, the Grantor shall be under no obligation to provide, and shall not
provide, material non-public information to the Lenders without the prior
written consent of those Lenders.

SECTION 3: EVENTS OF DEFAULT; REMEDIES

         3.1 EVENTS OF DEFAULT. Each of the following shall constitute an Event
of Default under this Security Agreement:

               (a)  Event of Default under Transaction Documents. The occurrence
                    of an Event of Default under the Transaction Documents.

               (b)  Other Defaults. Failure of the Grantor to comply with or to
                    perform when due or required (after any applicable cure
                    period) any term, obligation, covenant or condition
                    contained in the Transaction Documents or in any other
                    agreement or instruments between Lenders and the Grantor.

               (c)  False Statements. Any warranty, representation or statement
                    made or furnished to Lenders by the Grantor under the
                    Transaction Documents is false or misleading in any material
                    respect, either now or at the time made or furnished.

               (d)  Defective Collateralization. As a result of any act or
                    failure to act by the Grantor, the Transaction Documents
                    cease to be in full force and effect (including failure of
                    the Grantor to create a valid and perfected security
                    interest or lien as intended) at any time and for any
                    reason, or if any of the Collateral is materially impaired.

               (e)  Insolvency. The dissolution or termination of Grantor's
                    existence as a going business, the insolvency of Grantor,
                    the appointment of a receiver for any part of Grantor's
                    property, any assignment for the benefit of creditors, or
                    the

                                       13
<PAGE>   14

                    commencement of any insolvency proceeding by or against the
                    Grantor, which proceeding shall not have been dismissed
                    within forty-five (45) days thereafter.

               (f)  Creditor Proceedings. Commencement of foreclosure, whether
                    by judicial proceeding, self-help, repossession or any other
                    method, by any creditor of the Grantor (with respect to
                    indebtedness equal to or in excess of $25,000) against the
                    Collateral or any other collateral securing the
                    Indebtedness. This includes a garnishment of any of any
                    Grantor's accounts, including without limitation deposit
                    accounts. However, this Event of Default shall not apply if
                    there is a good faith dispute by the Grantor as to the
                    validity or reasonableness of the claim which is the basis
                    of the creditor proceeding and if the Grantor gives Lenders
                    written notice of the creditor proceeding and deposits with
                    Lenders monies or a surety bond for the creditor proceeding,
                    in an amount determined by Lenders, in their sole
                    discretion, as being an adequate reserve or bond for the
                    dispute.

         3.2 RIGHTS AND REMEDIES ON DEFAULT. If an Event of Default occurs and
is continuing under this Security Agreement, at any time thereafter, Lenders
shall have all the rights of a secured party under the New York Uniform
Commercial Code. In addition and without limitation, Lenders may exercise any
one or more of the following rights and remedies:

               (a)  Accelerate Indebtedness. Lenders may declare the entire
                    Indebtedness immediately due and payable, upon three
                    business days' notice, if prior notice with respect to the
                    Event of Default shall not have been previously given.

               (b)  Assemble Collateral. Lenders may require the Grantor to
                    deliver to Lenders all or any portion of the Collateral and
                    other documents relating to the Collateral. Lenders may
                    require the Grantor to assemble the Collateral and make it
                    available to Lenders at a place to be designated by Lenders.
                    Lenders also shall have full power to enter upon the
                    property of the Grantor to take possession of and remove the
                    Collateral.

               (c)  Sell the Collateral. Lenders shall have full power to sell,
                    lease, transfer, or otherwise deal with the Collateral or
                    proceeds thereof in its own name or that of the Grantor.
                    Lenders may sell the Collateral at public auction or private
                    sale. Unless the Collateral threatens to decline speedily in
                    value or is of a type customarily sold on a recognized
                    market, Lenders will give the Grantor reasonable notice of
                    the time after which any private sale or any other intended
                    disposition of the Collateral is to be made. The
                    requirements of reasonable notice shall be met if such
                    notice is given at least ten (10) days before the time of
                    the sale or disposition. All expenses relating to the
                    disposition of the Collateral, including without limitation
                    the expenses of retaking, holding, insuring, preparing for
                    sale and selling the Collateral, shall become a part of the
                    Indebtedness secured by this Security Agreement and shall be
                    payable on demand, with interest at the lower of six percent
                    (6%) per annum above Citibank's (or any successor's price
                    rate) or the highest rate

                                       14
<PAGE>   15

                    permitted by law from date of expenditure until repaid.

               (d)  Foreclosure. Maintain a judicial suit for foreclosure and
                    sale of the Collateral.

               (e)  Appoint Receiver. To the extent permitted by applicable law,
                    Lenders shall have the following rights and remedies
                    regarding the appointment of a receiver: (i) Lenders may
                    have a receiver appointed as a matter of right, and (ii) all
                    reasonable fees of the receiver and the receiver's attorney
                    shall become part of the Indebtedness secured by this
                    Security Agreement and shall be payable on demand, with
                    interest at the lower of six percent (6%) per annum above
                    Citibank's (or any successor's) prime rate or the highest
                    rate permitted by law from date of expenditure until repaid.

               (f)  Transfer Title. Effect transfer of title upon sale of all or
                    part of the Collateral. For this purpose, the Grantor
                    irrevocably appoints Lenders, acting singly, as its
                    attorneys-in-fact to execute endorsements, assignments and
                    instruments in the name of the Grantor as shall be necessary
                    or reasonable.

               (g)  Collect Revenues, Apply Accounts. Lenders, either themselves
                    or through a receiver, may collect the payments, rents,
                    income, and revenues from the Collateral. Lenders may at any
                    time in their discretion transfer any Collateral into their
                    own names or that of their nominees and receive the
                    payments, rents, income, and revenues therefrom and hold the
                    same as security for the Indebtedness or apply it to payment
                    of the Indebtedness in such order of preference as Lenders
                    may determine. Lenders may demand, collect, receipt for,
                    settle, compromise, adjust, sue for, foreclose, or realize
                    on the Collateral as Lenders may determine, whether or not
                    the Indebtedness is then due. For these purposes, Lenders
                    may, on behalf of and in the name of the Grantor, following
                    an Event of Default and acceleration of Indebtedness, direct
                    Account Debtor and other parties sending mail relating to
                    the Collateral to Grantor, to send such mail directly to the
                    Lenders; and endorse Debentures, checks, drafts, money
                    orders, documents of title, instruments and items pertaining
                    to payment, shipment, or storage of any Collateral. To
                    facilitate collection, Lenders may, following an Event
                    Default, notify Account Debtor and obligors on any
                    Collateral to make payments directly to Lenders.

               (h)  Obtain Deficiency. If Lenders choose to sell any or all of
                    the Collateral and/or pursue any other remedy available
                    hereunder, under any other agreement, at law or in equity,
                    Lenders may obtain a judgment against the Grantor for any
                    deficiency remaining on the Indebtedness due to Lenders
                    after application of all amounts received from the exercise
                    of the rights provided in this Security Agreement. The
                    Grantor shall be liable for a deficiency even if the
                    transaction described in this Subsection is a sale of
                    accounts or chattel paper.

               (i)  Application of Proceeds. The proceeds of any foreclosure or
                    realization upon the Collateral shall be applied:

                                       15
<PAGE>   16

                    (A)  First, to the reasonable costs and expenses of
                         collection;

                    (B)  Second, to overdue interest and fees;

                    (C)  Third, to the outstanding principal amount of the
                         Indebtedness; and

                    (D)  Fourth, any excess to the Grantor or other party or
                         parties in accordance with applicable law or court
                         order.

               (j)  Other Rights and Remedies. Lenders shall have and may
                    exercise any or all rights and remedies they may have
                    available at law, in equity, or otherwise.

         3.3 CUMULATIVE REMEDIES. All of Lenders' rights and remedies, whether
evidenced by this Security Agreement the other Transaction Documents by any
other writing, shall be cumulative and may be exercised singularly or
concurrently. Election by Lenders to pursue any remedy shall not exclude pursuit
of any other remedy, and an election to make expenditures or to take action to
perform an obligation of the Grantor under this Security Agreement, after the
Grantor's failure to perform, shall not affect Lenders' right to declare a
default and to exercise their remedies. The Lenders shall not be required to
proceed against or exercise its remedies with respect to any Collateral prior to
or in lieu of pursuing any other remedy.

SECTION 4: MISCELLANEOUS PROVISIONS

         4.1 ENTIRE AGREEMENT; AMENDMENTS. This Security Agreement, together
with the other Transaction Documents, constitutes the entire understanding and
agreement of the parties as to the matters set forth in this Security Agreement.
No alteration of or amendment to this Security Agreement shall be effective
unless given in writing and signed by the party or parties sought to be charged
or bound by the alteration or amendment.

         4.2 CHOICE OF LAW AND VENUE; JURY TRIAL WAIVER. THE VALIDITY OF THIS
SECURITY AGREEMENT, ITS CONSTRUCTION, INTERPRETATION, AND ENFORCEMENT, AND THE
RIGHTS OF THE PARTIES HERETO SHALL BE DETERMINED UNDER, GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH THE INTERNAL LAWS OF THE STATE OF NEW YORK. THE
PARTIES IRREVOCABLY AND UNCONDITIONALLY AGREE (1) THAT ALL ACTIONS OR
PROCEEDINGS ARISING IN CONNECTION WITH THIS SECURITY AGREEMENT SHALL BE TRIED
AND LITIGATED ONLY IN THE STATE AND FEDERAL COURTS LOCATED IN THE STATE OF NEW
YORK, COUNTY OF NEW YORK AND THAT THE PARTIES SHALL BE SUBJECT TO THE
JURISDICTION OF SUCH COURTS, AND ONLY SUCH COURTS AND (2) THAT SERVICE OF
PROCESS BY CERTIFIED MAIL, RETURN RECEIPT REQUESTED (AND SERVICE SO MADE SHALL
BE DEEMED COMPLETE FIVE DAYS AFTER THE SAME HAS BEEN POSTED AS AFORESAID) OR BY
PERSONAL SERVICE SHALL BE DEEMED IN EVERY RESPECT EFFECTIVE SERVICE UPON SUCH
PARTY IN ANY SUCH SUIT OR PROCEEDING. EACH PARTY WAIVES, TO THE EXTENT PERMITTED
UNDER APPLICABLE LAW, ANY RIGHT EACH MAY HAVE TO ASSERT THE DOCTRINE OF FORUM
NON CONVENIENS OR TO OBJECT TO VENUE TO THE EXTENT ANY PROCEEDING IS BROUGHT IN
ACCORDANCE WITH THIS SECTION 4.2. THE GRANTOR AND LENDERS HEREBY WAIVE THEIR

                                       16
<PAGE>   17

RESPECTIVE RIGHTS TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR
ARISING OUT OF THIS SECURITY AGREEMENT OR ANY OF THE ACTIONS CONTEMPLATED
HEREIN, INCLUDING WITHOUT LIMITATION CONTRACT CLAIMS, TORT CLAIMS, BREACH OF
DUTY CLAIMS, AND ALL OTHER COMMON LAW OR STATUTORY CLAIMS. THE GRANTOR AND
LENDERS REPRESENT THAT EACH HAS REVIEWED THIS WAIVER AND EACH KNOWINGLY AND
VOLUNTARILY WAIVES ITS JURY TRIAL RIGHTS FOLLOWING CONSULTATION WITH LEGAL
COUNSEL. IN THE EVENT OF LITIGATION, A COPY OF THIS AGREEMENT MAY BE FILED AS A
WRITTEN CONSENT TO A TRIAL BY THE COURT.

         4.3 ATTORNEYS' FEES; EXPENSES. The Grantor agrees to pay, jointly and
severally upon demand all of Lenders' costs and expenses, including without
limitation reasonable attorneys' fees and legal expenses, incurred in connection
with the enforcement of this Security Agreement. Lenders may pay someone else to
help enforce this Security Agreement, and the Grantor shall pay the reasonable
costs and expenses of such enforcement. Costs and expenses include without
limitation Lenders' reasonable attorneys' fees and legal expenses whether or not
there is a lawsuit, including without limitation reasonable attorneys' fees and
legal expenses for bankruptcy proceedings (and including efforts to modify or
vacate any automatic stay or injunction), appeals, and any anticipated
post-judgment collection services. The Grantor also shall pay all court costs
and such additional fees as may be directed by the court.

         4.4 CAPTION HEADINGS. Caption headings in this Security Agreement are
for convenience purposes only and are not to be used to interpret or define the
provisions of this Security Agreement.

         4.5 NOTICES. All notices required to be given under this Security
Agreement shall be given in writing and shall be effective when actually
delivered or seven (7) days after being deposited in the United States mail,
first class, postage prepaid, addressed to the party to whom the notice is to be
given or, if via facsimile, when sent via facsimile transmission to the party to
whom the notice is to be given and confirmation of such transmission has been
received, at the address and/or facsimile number shown below:

         if to Lenders:

                  Palladin Opportunity Fund, LLC and Halifax Fund, L.P.
                  195 Maplewood Avenue
                  Maplewood, New Jersey 07040
                  Facsimile: (973) 313-6491

         With a copy to:

                  Kleinberg, Kaplan, Wolff & Cohen, P.C.
                  551 Fifth Avenue, 18th Floor
                  New York, New York 10176
                  Attention: Christopher P. Davis, Esq.
                  Facsimile: (212) 986-8866

                                       17
<PAGE>   18

         If to the Grantor

                  ZymeTx, Inc.
                  800 Research Parkway, Suite 100
                  Oklahoma City, Oklahoma 73104
                  Attention: G. Carl Gibson
                  Facsimile: (405) 271-1708

                  And

                  Phillips McFall McCaffrey McVay & Murrah, P.C.
                  Twelfth Floor
                  One Leadership Square
                  211 North Robinson
                  Oklahoma City, Oklahoma 73102
                  Attention: Douglas A. Branch, Esq.
                  Facsimile: (405) 235-4562

Any party may change its address for notices under this Security Agreement by
giving formal written notice to the other parties, specifying that the purpose
of the notice is to change the party's address. For notice purposes, the Grantor
agrees to keep Lenders informed at all times of the Grantor' current addresses.

         4.6 SEVERABILITY. The parties acknowledge and agree that the Lenders
are not agents or partners of each other, that all representations, warranties,
covenants and agreements of the Lenders hereunder are several and not joint,
that no Lender shall have any responsibility or liability for the
representations, warrants, agreements, acts or omissions of any other Lender,
and that any rights granted to "Lenders" hereunder shall be enforceable by each
Lender hereunder. If a court of competent jurisdiction finds any provision of
this Security Agreement to be invalid or unenforceable as to any person or
circumstance, such finding shall not render that provision invalid or
unenforceable as to any other persons or circumstances. If feasible, any such
offending provision shall be deemed to be modified to be within the limits of
enforceability or validity; however, if the offending provision cannot be so
modified, it shall be stricken, and all other provisions of this Security
Agreement in all other respects shall remain valid and enforceable and such
offending provision shall not be affected in any other jurisdiction.

         4.7 SUCCESSOR INTERESTS. Subject to the limitations set forth above on
transfer of the Collateral, this Security Agreement shall be binding upon and
inure to the benefit of the parties, their successors and assigns. The Grantor
shall not, however, have the right to assign this Security Agreement without the
prior written consent of Lenders which may be withheld for any reason in
Lenders' sole discretion.

         4.8 WAIVER. Lenders shall not be deemed to have waived any rights under
this Security Agreement unless such waiver is given in writing and signed by
Lenders. No delay or omission on the part of Lenders in exercising any right
shall operate as a waiver of such right or

                                       18
<PAGE>   19

any other right. A waiver by Lenders of a provision of this Security Agreement
shall not prejudice or constitute a waiver of Lenders' right otherwise to demand
strict compliance with that provision or any other provision of this Security
Agreement. No prior waiver by Lenders, nor any course of dealing between Lenders
and the Grantor, shall constitute a waiver of any of Lenders' rights or of any
of the Grantor's obligations as to any future transactions. Whenever the consent
of Lenders is required under this Security Agreement, the granting of such
consent by Lenders in any instance shall not constitute continuing consent to
subsequent instances where such consent is required and in all cases such
consent may be granted or withheld in the sole discretion of Lenders.

         4.9 INDEMNITY. Except to the extent caused directly by Lenders' gross
negligence or wilful misconduct, the Grantor agrees to indemnify, pay and hold
each Lender and the officers, partners, directors, employees, agents and
affiliates of each Lender (collectively, the "indemnitees") harmless from and
against any and all liabilities, obligations, losses, damages, penalties,
actions, judgments, suits, claims, costs, expenses and disbursements of any kind
or nature whatsoever (including, without limitation, the reasonable fees and
disbursements of counsel) that may be imposed on, incurred by, or asserted
against any indemnitee, in any manner relating to or arising out of this
Security Agreement and any action undertaken or contemplated hereby. This
indemnification shall survive the satisfaction and payment of the Indebtedness
and termination of this Security Agreement.

                            [SIGNATURE PAGE FOLLOWS]

                                       19
<PAGE>   20

         IN WITNESS WHEREOF, the parties hereto have caused this Security
Agreement to be executed as of the date first written above.

                                    ZYMETX, INC.

                                    By:
                                       ----------------------------------------
                                        Norman R. Proulx
                                        Chief Executive Officer

                                    PALLADIN OPPORTUNITY FUND, LLC.
                                    By: Palladin Asset Management, L.L.C.
                                        Managing Member

                                    By:
                                       ----------------------------------------
                                        Robert Chender
                                        Managing Member

                                    HALIFAX FUND, L.P.
                                    By: The Palladin Group, L.P.
                                        Attorney-in-Fact

                                    By: Palladin Capital Management, LLC
                                        General Partner

                                    By:
                                       ----------------------------------------
                                        Robert Chender
                                        Managing Member

                                       20
<PAGE>   21

                                   SCHEDULE A

                         IDENTITY AND ADDRESS OF LENDERS

INVESTOR

Palladin Opportunity Fund, LLC 195
Maplewood Avenue
Maplewood, N.J. 07040

Halifax Fund, L.P.
195 Maplewood Avenue
Maplewood, N.J. 07040

<PAGE>   22

                                   SCHEDULE B

                    IDENTIFICATION AND LOCATION OF COLLATERAL

                             PLEASE SEE ATTACHMENTS.<PAGE>   1
                                                                     EXHIBIT 4.9

================================================================================

                           SOUTHSIDE BANCSHARES, INC.

                                       AND

                            WILMINGTON TRUST COMPANY,
                              AS INDENTURE TRUSTEE

                                    INDENTURE

               _____% CONVERTIBLE SUBORDINATED DEBENTURES DUE 2030

                         DATED AS OF NOVEMBER ___, 2000

================================================================================

<PAGE>   2

                                TABLE OF CONTENTS
<TABLE>
<CAPTION>

                                                                                                                      Page
                                                                                                                      ----
<S>                                                                                                                   <C>
ARTICLE I
         DEFINITIONS....................................................................................................2
         Section 1.1 Definitions of Terms...............................................................................2

ARTICLE II
         ISSUE, DESCRIPTION, TERMS, CONDITIONS REGISTRATION AND EXCHANGE OF THE DEBENTURES.............................11
         Section 2.1       Designation and Principal Amount............................................................11
         Section 2.2       Maturity....................................................................................11
         Section 2.3       Form and Payment............................................................................12
         Section 2.4       [Intentionally Left Blank]..................................................................12
         Section 2.5       Interest....................................................................................12
         Section 2.6       Execution and Authentications...............................................................13
         Section 2.7       Registration of Transfer and Exchange.......................................................14
         Section 2.8       Temporary Debentures....................................................................... 15
         Section 2.9       Mutilated, Destroyed, Lost or Stolen Debentures.............................................15
         Section 2.10      Cancellation................................................................................16
         Section 2.11      Benefit of Indenture........................................................................16
         Section 2.12      Authenticating Agent........................................................................17

ARTICLE III
         REDEMPTION OF DEBENTURES......................................................................................17
         Section 3.1       Redemption..................................................................................17
         Section 3.2       Special Event Redemption....................................................................17
         Section 3.3       Optional Redemption by Company..............................................................18
         Section 3.4       Notice of Redemption........................................................................19
         Section 3.5       Payment Upon Redemption.....................................................................20
         Section 3.6       No Sinking Fund.............................................................................21

ARTICLE IV
         CONVERSION OF DEBENTURES......................................................................................21
         Section 4.1       Conversion Rights...........................................................................21
         Section 4.2       Conversion Procedures.......................................................................21
         Section 4.3       Conversion Ratio Adjustments................................................................23
         Section 4.4       Reclassification, Consolidation, Merger or Sale of Assets...................................27
         Section 4.5       Notice of Adjustments of Conversion Ratio...................................................28
         Section 4.6       Prior Notice of Certain Events..............................................................28
</TABLE>

                                       i

<PAGE>   3
<TABLE>
<S>                                                                                                                    <C>
         Section 4.7       Certain Defined Terms.......................................................................29
         Section 4.8       Dividend or Interest Reinvestment Plans.....................................................30
         Section 4.9       Certain Additional Rights...................................................................30
         Section 4.10      Trustee Not Responsible for Determining Conversion Ratio or Adjustments.....................31

ARTICLE V
         EXTENSION OF INTEREST PAYMENT PERIOD..........................................................................31
         Section 5.1       Extension of Interest Payment Period........................................................31
         Section 5.2       Notice of Extension.........................................................................32
         Section 5.3       Limitation on Transactions..................................................................32

ARTICLE VI
         PARTICULAR COVENANTS OF THE COMPANY...........................................................................33
         Section 6.1       Payment of Principal and Interest...........................................................33
         Section 6.2       Maintenance of Agency.......................................................................33
         Section 6.3       Paying Agents...............................................................................34
         Section 6.4       Appointment to Fill Vacancy in Office of Trustee............................................35
         Section 6.5       Compliance with Consolidation Provisions....................................................35
         Section 6.6       Limitation on Transactions..................................................................35
         Section 6.7       Covenants as to the Trust...................................................................36
         Section 6.8       Covenants as to Purchases...................................................................36
         Section 6.9       Waiver of Usury, Stay or Extension Laws.....................................................36

ARTICLE VII
         DEBENTUREHOLDERS' LISTS AND REPORTS BY THE COMPANY AND THE TRUSTEE............................................37
         Section 7.1       Company to Furnish Trustee Names and Addresses of Debentureholders..........................37
         Section 7.2       Preservation of Information Communications with Debentureholders............................37
         Section 7.3       Reports by the Company......................................................................37
         Section 7.4       Reports by the Trustee......................................................................38

ARTICLE VIII
         REMEDIES OF THE TRUSTEE AND DEBENTUREHOLDERS ON EVENT OF DEFAULT..............................................38
         Section 8.1       Events of Default...........................................................................39
         Section 8.2       Collection of Indebtedness and Suits for Enforcement by Trustee.............................40
         Section 8.3       Application of Moneys Collected.............................................................42
         Section 8.4       Limitation on Suits.........................................................................42
         Section 8.5       Rights and Remedies Cumulative; Delay or Omission not Waiver................................43
</TABLE>

                                       ii
<PAGE>   4
<TABLE>
<S>                                                                                                                    <C>
         Section 8.6       Control by Debentureholders.................................................................43
         Section 8.7       Undertaking to Pay Costs....................................................................44
         Section 8.8       Direct Action; Right of Set-Off.............................................................44

ARTICLE IX
         FORM OF DEBENTURE AND ORIGINAL ISSUE..........................................................................45
         Section 9.1       Form of Debenture...........................................................................45
         Section 9.2       Original Issue of Debentures................................................................45

ARTICLE X
         CONCERNING THE TRUSTEE........................................................................................45
         Section 10.1      Certain Duties and Responsibilities of the Trustee..........................................45
         Section 10.2      Notice of Defaults..........................................................................46
         Section 10.3      Certain Rights of Trustee...................................................................47
         Section 10.4      Trustee Not Responsible for Recitals, etc. .................................................48
         Section 10.5      May Hold Debentures.........................................................................48
         Section 10.6      Moneys Held in Trust........................................................................49
         Section 10.7      Compensation and Reimbursement..............................................................49
         Section 10.8      Reliance on Officers' Certificate...........................................................49
         Section 10.9      Disqualification:  Conflicting Interests....................................................50
         Section 10.10     Corporate Trustee Required; Eligibility.....................................................50
         Section 10.11     Resignation and Removal; Appointment of Successor...........................................50
         Section 10.12     Acceptance of Appointment by Successor......................................................51
         Section 10.13     Merger, Conversion, Consolidation or Succession to Business.................................52
         Section 10.14     Preferential Collection of Claims Against the Company.......................................52

ARTICLE XI
         CONCERNING THE DEBENTUREHOLDERS...............................................................................53
         Section 11.1      Evidence of Action by Holders...............................................................53
         Section 11.2      Proof of Execution by Debentureholders......................................................53
         Section 11.3      Who May be Deemed Owners....................................................................54
         Section 11.4      Certain Debentures Owned by Company Disregarded.............................................54
         Section 11.5      Actions Binding on Future Debentureholders..................................................54

ARTICLE XII
         SUPPLEMENTAL INDENTURES.......................................................................................55
         Section 12.1      Supplemental Indentures Without the Consent of Debentureholders.............................55
         Section 12.2      Supplemental Indentures with Consent of Debentureholders....................................56
         Section 12.3      Effect of Supplemental Indentures...........................................................56
         Section 12.4      Debentures Affected by Supplemental Indentures..............................................57
         Section 12.5      Execution of Supplemental Indentures........................................................57
</TABLE>

                                      iii

<PAGE>   5
<TABLE>
<S>                                                                                                                    <C>
ARTICLE XIII
         SUCCESSOR CORPORATION.........................................................................................58
         Section 13.1      Company May Consolidate, etc. ..............................................................58
         Section 13.2      Successor Corporation Substituted...........................................................58
         Section 13.3      Evidence of Consolidation, etc. to Trustee..................................................59

ARTICLE XIV
         SATISFACTION AND DISCHARGE....................................................................................59
         Section 14.1      Satisfaction and Discharge of Indenture.....................................................59
         Section 14.2      Discharge of Obligations....................................................................60
         Section 14.3      Deposited Moneys to be Held in Trust........................................................60
         Section 14.4      Payment of Monies Held by Paying Agents.....................................................60
         Section 14.5      Repayment to Company........................................................................60

ARTICLE XV
         IMMUNITY OF INCORPORATORS, STOCKHOLDERS, OFFICERS AND DIRECTORS...............................................61
         Section 15.1      No Recourse.................................................................................61

ARTICLE XVI
         MISCELLANEOUS PROVISIONS......................................................................................61
         Section 16.1      Effect on Successors and Assigns............................................................61
         Section 16.2      Actions by Successor........................................................................62
         Section 16.3      Surrender of Company Powers.................................................................62
         Section 16.4      Notices.....................................................................................62
         Section 16.5      Governing Law...............................................................................62
         Section 16.6      Treatment of Debentures as Debt.............................................................62
         Section 16.7      Compliance Certificates and Opinions........................................................62
         Section 16.8      Payments on Business Days...................................................................63
         Section 16.9      Conflict with Trust Indenture Act...........................................................63
         Section 16.10     Counterparts................................................................................63
         Section 16.11     Separability................................................................................63
         Section 16.12     Assignment..................................................................................64
         Section 16.13     Acknowledgment of Rights....................................................................64

ARTICLE XVII
         SUBORDINATION OF DEBENTURES...................................................................................64
         Section 17.1      Agreement to Subordinate....................................................................64
         Section 17.2      Default on Senior Debt, Subordinated Debt or Additional Senior Obligations..................65
</TABLE>

                                       iv

<PAGE>   6

<TABLE>

<S>                                                                                                                    <C>

         Section 17.3      Liquidation; Dissolution; Bankruptcy........................................................65
         Section 17.4      Subrogation.................................................................................66
         Section 17.5      Trustee to Effectuate Subordination.........................................................67
         Section 17.6      Notice by the Company.......................................................................67
         Section 17.7      Rights of the Trustee; Holders of Senior Indebtedness.......................................68
         Section 17.8      Subordination may not be Impaired...........................................................69
</TABLE>

                                       v
<PAGE>   7

                              CROSS-REFERENCE TABLE
<TABLE>
<CAPTION>

SECTION OF
TRUST INDENTURE ACT                                                                                  SECTION OF
OF 1939, AS AMENDED                                                                                  INDENTURE
-------------------                                                                                  ---------
<S>                                                                                                  <C>
310(a)................................................................................................ 10.10
310(b)................................................................................................  10.9
      ................................................................................................ 10.11
310(c)....................................................................................... Not Applicable
311(a)................................................................................................ 10.14
311(b)................................................................................................ 10.14
311(c)....................................................................................... Not Applicable
312(a).................................................................................................. 7.1
      ............................................................................................... 7.2(a)
312(b)............................................................................................... 7.2(c)
312(c)............................................................................................... 7.2(c)
313(a)............................................................................................... 7.4(a)
313(b)............................................................................................... 7.4(b)
313(c)............................................................................................... 7.4(a)
      ............................................................................................... 7.4(b)
313(d)............................................................................................... 7.4(c)
314(a)............................................................................................... 7.3(a)
314(b)....................................................................................... Not Applicable
314(c)................................................................................................. 16.7
314(d)....................................................................................... Not Applicable
314(e)................................................................................................. 16.7
314(f)....................................................................................... Not Applicable
315(a).............................................................................................. 10.1(a)
      ................................................................................................. 10.3
315(b)................................................................................................. 10.2
315(c).............................................................................................. 10.1(a)
315(d).............................................................................................. 10.1(b)
315(e).................................................................................................. 8.7
316(a).................................................................................................. 1.1
      .................................................................................................. 8.6
316(b)............................................................................................... 8.4(b)
316(c).............................................................................................. 11.1(b)
317(a).................................................................................................. 8.2
317(b).................................................................................................. 6.3
318(a)................................................................................................. 16.9
</TABLE>

                                       vi
<PAGE>   8

     Note: This reconciliation and tie sheet shall not, for any purpose, be
           deemed to be a part of the Indenture

                                      vii
<PAGE>   9

                                    INDENTURE

         INDENTURE, dated as of November ___, 2000, between SOUTHSIDE
BANCSHARES, INC., a Texas corporation (the "Company") and WILMINGTON TRUST
COMPANY, a Delaware banking corporation duly organized and existing under the
laws of the State of Delaware as trustee (the "Trustee");

                                    RECITALS

         WHEREAS, for its lawful corporate purposes, the Company has duly
authorized the execution and delivery of this Indenture to provide for the
issuance of securities to be known as its _____% Convertible Subordinated
Debentures due 2030 (hereinafter referred to as the "Debentures"), the form and
substance of such Debentures and the terms, provisions and conditions thereof to
be set forth as provided in this Indenture;

         WHEREAS, Southside Capital Trust II, a Delaware statutory business
trust (the "Trust"), has offered to the public up to $17,250,000 aggregate
liquidation amount of its Preferred Securities (as defined herein) and proposes
to invest the proceeds from such offering, together with the proceeds of the
issuance and sale by the Trust to the Company of up to $533,510 aggregate
liquidation amount of its Common Securities (as defined herein), in up to
$17,783,510 aggregate principal amount of the Debentures;

         WHEREAS, the Company has requested that the Trustee execute and deliver
this Indenture;

         WHEREAS, all requirements necessary to make this Indenture a valid
instrument in accordance with its terms, and to make the Debentures, when
executed by the Company and authenticated and delivered by the Trustee, the
valid obligations of the Company, have been performed, and the execution and
delivery of this Indenture have been duly authorized in all respects;

         WHEREAS, to provide the terms and conditions upon which the Debentures
are to be authenticated, issued and delivered, the Company has duly authorized
the execution of this Indenture; and

         WHEREAS, all things necessary to make this Indenture a valid agreement
of the Company, in accordance with its terms, have been done.

         NOW, THEREFORE, in consideration of the premises and the purchase of
the Debentures by the holders thereof, it is mutually covenanted and agreed as
follows for the equal and ratable benefit of the holders of the Debentures:

<PAGE>   10

                                    ARTICLE I

                                   DEFINITIONS

SECTION 1.1       DEFINITIONS OF TERMS.

         The terms defined in this Section 1.1 (except as in this Indenture
otherwise expressly provided or unless the context otherwise requires) for all
purposes of this Indenture and of any indenture supplemental hereto shall have
the respective meanings specified in this Section 1.1 and shall include the
plural as well as the singular. All other terms used in this Indenture that are
defined in the Trust Indenture Act, or that are by reference in the Trust
Indenture Act defined in the Securities Act (except as herein otherwise
expressly provided or unless the context otherwise requires), shall have the
meanings assigned to such terms in the Trust Indenture Act and in the Securities
Act as in force at the date of the execution of this instrument. All accounting
terms used herein and not expressly defined shall have the meanings assigned to
such terms in accordance with Generally Accepted Accounting Principles.

         "Accelerated Maturity Date" means if the Company elects to accelerate
the Maturity Date in accordance with Section 2.2(c), the date selected by the
Company which is prior to the Scheduled Maturity Date, but is after December 31,
2005.

         "Additional Interest" shall have the meaning set forth in Section
2.5(c).

         "Additional Senior Obligations" means all indebtedness of the Company
whether incurred on or prior to the date of this Indenture or thereafter
incurred, for claims in respect of derivative products such as interest and
foreign exchange rate contracts, commodity contracts and similar arrangements;
provided, however, that Additional Senior Obligations does not include claims in
respect of Senior Debt or Subordinated Debt or obligations which, by their
terms, are expressly stated to be not superior in right of payment to the
Debentures or to rank pari passu in right of payment with the Debentures
(including, without limitation, the Company's 8.50% Junior Subordinated
Debentures due 2028, issued to Southside Capital Trust I). For purposes of this
definition, "claim" shall have the meaning assigned thereto in Section 101(4) of
the United States Bankruptcy Code of 1978, as amended.

         "Administrative Trustees" shall have the meaning set forth in the Trust
Agreement.

         "Affiliate" means, with respect to a specified Person, (a) any Person
directly or indirectly owning, controlling or holding with power to vote 10% or
more of the outstanding voting securities or other ownership interests of the
specified Person; (b) any Person 10% or more of whose outstanding voting
securities or other ownership interests are directly or indirectly owned,
controlled or held with power to vote by the specified Person; (c) any Person
directly or indirectly controlling, controlled by, or under common control with
the specified Person; (d) a partnership in which the specified Person is a
general

                                       2
<PAGE>   11

partner; (e) any officer or director of the specified Person; and (f) if
the specified Person is an individual, any entity of which the specified Person
is an officer, director or general partner.

         "Authenticating Agent" means an authenticating agent with respect to
the Debentures appointed by the Trustee pursuant to Section 2.12.

         "Bankruptcy Law" means Title 11, U.S. Code, or any similar federal or
state law for the relief of debtors.

         "Board of Directors" means the Board of Directors of the Company or any
duly authorized committee of such Board or any other duly designated officers of
the Company.

         "Board Resolution" means a copy of a resolution certified by the
Secretary or an Assistant Secretary of the Company to have been duly adopted by
the Board of Directors and to be in full force and effect on the date of such
certification.

         "Business Day" means, with respect to the Debentures, any day other
than a Saturday or a Sunday or a day on which federal or state banking
institutions in the Borough of Manhattan, The City of New York, are authorized
or required by law, executive order or regulation to close, or a day on which
the Corporate Trust Office of the Trustee or the Property Trustee is closed for
business.

         "Capital Treatment Event" means the receipt by the Company and the
Trust of an Opinion of Counsel, rendered by a law firm having a recognized
national bank regulatory practice, to the effect that, as a result of any
amendment to, or change (including any announced prospective change) in, the
laws (or any regulations thereunder) of the United States or any political
subdivision thereof or therein, or as a result of any official or administrative
pronouncement or action or judicial decision interpreting or applying such laws
or regulations, which amendment or change is effective or which pronouncement or
decision is announced on or after the date of issuance of the Preferred
Securities under the Trust Agreement, there is more than an insubstantial risk
of impairment of the Company's ability to treat the Preferred Securities (or any
substantial portion thereof) as Tier 1 capital (or the then equivalent thereof),
for purposes of the capital adequacy guidelines of the Federal Reserve, as then
in effect and applicable to the Company; provided, however, that the Trust or
the Company shall have requested and received such an Opinion of Counsel with
regard to such matters within a reasonable period of time after the Trust or the
Company shall have become aware of the possible occurrence of any such event;
provided, however, that the inability of the Company to treat all or any portion
of the Liquidation Amount of the Preferred Securities as Tier 1 Capital shall
not constitute the basis for a Capital Treatment Event if such inability results
from the Company having cumulative preferred stock, minority interests in
consolidated subsidiaries, or any other class of security or interest which the
Federal Reserve now or may hereafter accord Tier 1 Capital treatment in excess
of the amount which may qualify for treatment as Tier 1 Capital under applicable
capital adequacy guidelines of the Federal Reserve; provided, further, however,
that the distribution of Junior Subordinated

                                       3
<PAGE>   12

Debentures in connection with the dissolution of the Trust shall not in and of
itself constitute a Capital Treatment Event.

         "Certificate" means a certificate signed by the principal executive
officer, the principal financial officer, the principal accounting officer, the
treasurer or any vice president of the Company. The Certificate need not comply
with the provisions of Section 16.7.

         "Change in 1940 Act Law" shall have the meaning set forth in the
definition of "Investment Company Event."

         "Commission" means the Securities and Exchange Commission.

         "Common Securities" means undivided beneficial interests in the assets
of the Trust which rank pari passu with the Preferred Securities; provided,
however, that upon the occurrence of an Event of Default, the rights of holders
of Common Securities to payment in respect of distributions and payments upon
liquidation, redemption and otherwise are subordinated to the rights of holders
of Preferred Securities.

         "Common Stock" means the common stock, no par value, of the Company.

         "Company" means Southside Bancshares, Inc., a corporation duly
organized and existing under the laws of the State of Texas, and, subject to the
provisions of Article XIII, shall also include its successors and assigns.

         "Compounded Interest" shall have the meaning set forth in Section 5.1.

         "Conversion Agent" means the Person appointed to act on behalf of the
holders of the Preferred Securities in effecting the conversion of Preferred
Securities to Debentures and Debentures to Common Stock as and in the manner set
forth in the Trust Agreement and this Indenture.

         "Conversion Price" means $____.

         "Conversion Ratio" has the meaning set forth in Section 4.1.

         "Conversion Request" means (a) the irrevocable request to be given by a
Debentureholder to the Conversion Agent directing the Conversion Agent to
convert the Debentures into shares of Common Stock, and (b) the irrevocable
request to be given by a holder of Preferred Securities to the Conversion Agent
directing the Conversion Agent to exchange such stock on behalf of such holder.

         "Corporate Trust Office" means the office of the Trustee at which, at
any particular time, its corporate trust business shall be principally
administered, which office at the date hereof is located at

                                       4
<PAGE>   13

[RODNEY SQUARE NORTH, 1100 NORTH MARKET STREET, WILMINGTON, DELAWARE
19890-0001], Attention: Corporate Trust Administration.

         "Coupon Rate" shall have the meaning set forth in Section 2.5.

         "Custodian" means any receiver, trustee, assignee, liquidator, or
similar official under any Bankruptcy Law.

         "Debentures" shall have the meaning set forth in the Recitals hereto.

         "Debentureholder," "holder of Debentures," "registered holder," or
other similar term, means the Person or Persons in whose name or names a
particular Debenture shall be registered on the books of the Company or the
Trustee kept for that purpose in accordance with the terms of this Indenture.

         "Debenture Register" shall have the meaning set forth in Section
2.7(b).

         "Debenture Registrar" shall have the meaning set forth in Section
2.7(b).

         "Debt" means with respect to any Person, whether recourse is to all or
a portion of the assets of such Person and whether or not contingent, (i) every
obligation of such Person for money borrowed; (ii) every obligation of such
Person evidenced by bonds, debentures, notes or other similar instruments,
including obligations incurred in connection with the acquisition of property,
assets or businesses; (iii) every reimbursement obligation of such Person with
respect to letters of credit, bankers' acceptances or similar facilities issued
for the account of such Person; (iv) every obligation of such Person issued or
assumed as the deferred purchase price of property or services (but excluding
trade accounts payable or accrued liabilities arising in the ordinary course of
business); (v) every capital lease obligation of such Person; and (vi) and every
obligation of the type referred to in clauses (i) through (v) of another Person
and all dividends of another Person the payment of which, in either case, such
Person has guaranteed or is responsible or liable, directly or indirectly, as
obligor or otherwise.

         "Default" means any event, act or condition that with notice or lapse
of time, or both, would constitute an Event of Default.

         "Deferred Interest" shall have the meaning set forth in Section 5.1.

         "Direct Action" shall have the meaning set forth in Section 8.8.

         "Dissolution Event" means that as a result of the occurrence and
continuation of a Special Event, the Trust is to be dissolved in accordance with
the Trust Agreement and the Debentures held by the Property Trustee are to be
distributed to the holders of the Trust Securities issued by the Trust pro rata
in accordance with the Trust Agreement.

                                       5
<PAGE>   14

         "Event of Default" means, with respect to the Debentures, any event
specified in Section 8.1, which has continued for the period of time, if any,
and after the giving of the notice, if any, therein designated.

         "Exchange Act," means the Securities Exchange Act of 1934, as amended,
as in effect at the date of execution of this Indenture.

         "Extended Interest Payment Period" shall have the meaning set forth in
Section 5.1.

         "Federal Reserve" means the Board of Governors of the Federal Reserve
System.

         "Generally Accepted Accounting Principles" means such accounting
principles as are generally accepted at the time of any computation required
hereunder.

         "Governmental Obligations" means securities that are (i) direct
obligations of the United States of America for the payment of which its full
faith and credit is pledged; or (ii) obligations of a Person controlled or
supervised by and acting as an agency or instrumentality of the United States of
America, the payment of which is unconditionally guaranteed as a full faith and
credit obligation by the United States of America that, in either case, are not
callable or redeemable at the option of the issuer thereof, and shall also
include a depositary receipt issued by a bank (as defined in Section 3(a)(2) of
the Securities Act) as custodian with respect to any such Governmental
Obligation or a specific payment of principal of or interest on any such
Governmental Obligation held by such custodian for the account of the holder of
such depositary receipt; provided, however, that (except as required by law)
such custodian is not authorized to make any deduction from the amount payable
to the holder of such depositary receipt from any amount received by the
custodian in respect of the Governmental Obligation or the specific payment of
principal of or interest on the Governmental Obligation evidenced by such
depositary receipt.

         "Herein," "hereof," and "hereunder," and other words of similar import,
refer to this Indenture as a whole and not to any particular Article, Section or
other subdivision.

         "Indenture" means this instrument as originally executed or as it may
from time to time be supplemented or amended by one or more indentures
supplemental hereto entered into in accordance with the terms hereof.

         "Interest Payment Date," when used with respect to any installment of
interest on the Debentures, means the date specified in the Debenture or in an
indenture supplemental hereto with respect to the Debentures as the fixed date
on which an installment of interest with respect to the Debentures is due and
payable.

         "Investment Company Act," means the Investment Company Act of 1940, as
amended, as in effect at the date of execution of this Indenture.

                                        6

<PAGE>   15

         "Investment Company Event" means the receipt by the Trust and the
Company of an Opinion of Counsel, rendered by a law firm having a recognized
national tax and securities law practice, to the effect that, as a result of the
occurrence of a change in law or regulation or a change in interpretation or
application of law or regulation by any legislative body, court, governmental
agency or regulatory authority (a "Change in 1940 Act Law"), the Trust is or
shall be considered an "investment company" that is required to be registered
under the Investment Company Act, which Change in 1940 Act Law becomes effective
on or after the date of original issuance of the Preferred Securities under the
Trust Agreement; provided, however, that the Trust or the Company shall have
requested and received such an Opinion of Counsel with regard to such matters
within a reasonable period of time after the Trust or the Company shall have
become aware of the possible occurrence of any such event.

         "Maturity Date" means the date on which the Debentures mature and on
which the principal shall be due and payable together with all accrued and
unpaid interest thereon including Compounded Interest and Additional Interest,
if any.

         "Ministerial Action" shall have the meaning set forth in Section 3.2.

         "Officers' Certificate" means a certificate signed by the President or
an Executive Vice President and by the Chief Financial Officer or the Treasurer
or an Assistant Treasurer or the Secretary or an Assistant Secretary of the
Company that is delivered to the Trustee in accordance with the terms hereof.
Each such certificate shall include the statements provided for in Section 16.7,
if and to the extent required by the provisions thereof.

         "Opinion of Counsel" means an opinion in writing of independent,
outside legal counsel for the Company that is delivered to the Trustee in
accordance with the terms hereof. Each such opinion shall include the statements
provided for in Section 16.7, if and to the extent required by the provisions
thereof.

         "Outstanding," when used in reference to the Debentures, means, subject
to the provisions of Section 11.4, as of any particular time, all Debentures
theretofore authenticated and delivered by the Trustee under this Indenture,
except (a) Debentures theretofore canceled by the Trustee or any paying agent,
or delivered to the Trustee or any paying agent for cancellation or that have
previously been canceled; (b) Debentures or portions thereof for the payment or
redemption of which moneys or Governmental Obligations in the necessary amount
shall have been deposited in trust with the Trustee or with any paying agent
(other than the Company) or shall have been set aside and segregated in trust by
the Company (if the Company shall act as its own paying agent); provided,
however, that if such Debentures or portions of such Debentures are to be
redeemed prior to the maturity thereof, notice of such redemption shall have
been given as in Article III provided, or provision satisfactory to the Trustee
shall have been made for giving such notice; and (c) Debentures in lieu of or in
substitution for which other Debentures shall have been authenticated and
delivered pursuant to the terms of Section 2.7; provided, however, that in
determining whether the holders of the requisite percentage of Debentures have
given any request, notice, consent or waiver hereunder, Debentures held by the
Company or any Affiliate of the Company shall not

                                        7

<PAGE>   16

be included; provided, further, that the Trustee shall be protected in relying
upon any request, notice, consent or waiver unless a Responsible Officer of the
Trustee shall have actual knowledge that the holder of such Debenture is the
Company or an Affiliate thereof.

         "Person" means any individual, corporation, partnership, joint-venture,
joint-stock company, limited liability company, trust, unincorporated
organization or government or any agency or political subdivision thereof.

         "Predecessor Debenture" means every previous Debenture evidencing all
or a portion of the same debt as that evidenced by such particular Debenture;
and, for the purposes of this definition, any Debenture authenticated and
delivered under Section 2.9 in lieu of a lost, destroyed or stolen Debenture
shall be deemed to evidence the same debt as the lost, destroyed or stolen
Debenture.

         "Preferred Securities" means the _____% Cumulative Convertible Trust
Preferred Securities representing undivided beneficial interests in the assets
of the Trust which rank pari passu with Common Securities issued by the Trust;
provided, however, that upon the occurrence of an Event of Default, the rights
of holders of Common Securities to payment in respect of distributions and
payments upon liquidation, redemption and otherwise are subordinated to the
rights of holders of Preferred Securities.

         "Preferred Securities Guarantee" means any guarantee that the Company
may enter into with the Trustee or other Persons that operates directly or
indirectly for the benefit of holders of Preferred Securities.

         "Property Trustee" has the meaning set forth in the Trust Agreement.

         "Redemption Price" shall have the meaning set forth in Section 3.2.

         "Responsible Officer" when used with respect to the Trustee means any
officer within the Corporate Trust Office of the Trustee with direct
responsibility for the administration of this Indenture, including any vice
president, any assistant vice president, any assistant secretary or any other
officer or assistant officer of the Trustee who customarily performs functions
similar to those performed by the Persons who at the time shall be such
officers, respectively, or to whom any corporate trust matter is referred
because of his or her knowledge of and familiarity with the particular subject.

         "Scheduled Maturity Date" means December 31, 2030.

         "Securities Act," means the Securities Act of 1933, as amended, as in
effect at the date of execution of this instrument.

         "Senior Debt" means the principal of (and premium, if any) and
interest, if any (including interest accruing on or after the filing of any
petition in bankruptcy or for reorganization relating to the Company

                                        8

<PAGE>   17

whether or not such claim for post-petition interest is allowed in such
proceeding), on Debt, whether incurred on or prior to the date of this Indenture
or thereafter incurred, unless, in the instrument creating or evidencing the
same or pursuant to which the same is outstanding, it is provided that such
obligations are not superior in right of payment to the Debentures or to other
Debt which is pari passu with, or subordinated to, the Debentures (including,
without limitation, the Company's 8.50% Junior Subordinated Debentures due 2028,
issued to Southside Capital Trust I), provided, however, that Senior Debt shall
not be deemed to include (i) any Debt of the Company which when incurred and
without respect to any election under section 1111(b) of the United States
Bankruptcy Code of 1978, as amended, was without recourse to the Company; (ii)
any Debt of the Company owed to any of its subsidiaries; (iii) Debt owed to any
employee of the Company; (iv) Debt which by its terms is subordinated to trade
accounts payable or accrued liabilities arising in the ordinary course of
business to the extent that payments made to the holders of such Debt by the
holders of the Debentures as a result of the subordination provisions of this
Indenture would be greater than they otherwise would have been as a result of
any obligation of such holders to pay amounts over to the obligees on such trade
accounts payable or accrued liabilities arising in the ordinary course of
business as a result of subordination provisions to which such Debt is subject;
and (v) Debt which constitutes Subordinated Debt.

         "Senior Indebtedness" shall have the meaning set forth in Section 17.1.

         "Special Event" means a Tax Event, an Investment Company Event or a
Capital Treatment Event.

         "Subordinated Debt" means the principal of (and premium, if any) and
interest, if any (including interest accruing on or after the filing of any
petition in bankruptcy or for reorganization relating to the Company whether or
not such claim for post-petition interest is allowed in such proceeding), on
Debt, whether incurred on or prior to the date of this Indenture or thereafter
incurred, which is by its terms expressly provided to be junior and subordinate
to Senior Debt of the Company and on any Debt of the Company under debt
securities (and guarantees in respect of these debt securities) initially issued
to any trust, or a trustee of a trust, partnership or other entity affiliated
with the Company that is, directly or indirectly, a financing vehicle of the
Company in connection with the issuance by that entity of preferred securities
or other securities which are intended to qualify for Tier 1 capital treatment,
unless those debt securities are by their terms convertible into Common Stock of
the Company; provided, however, that Subordinated Debt will not be deemed to
include (i) any Debt of the Company which when incurred and without respect to
any election under section 1111(b) of the United States Bankruptcy Code of 1978,
as amended, was without recourse to the Company, (ii) any Debt of the Company
owed to any of its subsidiaries, (iii) any Debt owed to any employee of the
Company, (iv) any Debt which by its terms is subordinated to trade accounts
payable or accrued liabilities arising in the ordinary course of business to the
extent that payments made to the holders of such Debt by the holders of the
Subordinated Debentures as a result of the subordination provisions of the
Indenture would be greater than they otherwise would have been as a result of
any obligation of such holders to pay amounts over to the obligees on such trade
accounts payable or accrued liabilities arising in the ordinary course of
business as a result of subordination provisions to which such Debt is subject,
and (v) Debt which constitutes Senior Debt.

                                        9

<PAGE>   18

         "Subsidiary" means, with respect to any Person, (i) any corporation at
least a majority of whose outstanding Voting Stock shall at the time be owned,
directly or indirectly, by such Person or by one or more of its Subsidiaries or
by such Person and one or more of its Subsidiaries; (ii) any general
partnership, limited liability company, joint venture, trust or similar entity,
at least a majority of whose outstanding partnership or similar interests shall
at the time be owned by such Person, or by one or more of its Subsidiaries, or
by such Person and one or more of its Subsidiaries; and (iii) any limited
partnership of which such Person or any of its Subsidiaries is a general
partner.

         "Tax Event" means the receipt by the Company and the Trust of an
Opinion of Counsel, rendered by a law firm having a recognized national tax and
securities practice, to the effect that, as a result of any amendment to, or
change (including any announced prospective change) in, the laws (or any
regulations thereunder) of the United States or any political subdivision or
taxing authority thereof or therein, or as a result of any official
administrative pronouncement or judicial decision interpreting or applying such
laws or regulations, which amendment or change is effective or which
pronouncement or decision is announced on or after the date of issuance of the
Preferred Securities under the Trust Agreement, there is more than an
insubstantial risk that (i) the Trust is, or shall be within 90 days after the
date of such Opinion of Counsel, subject to United States federal income tax
with respect to income received or accrued on the Debentures; (ii) interest
payable by the Company on the Debentures is not, or within 90 days after the
date of such Opinion of Counsel, shall not be, deductible by the Company, in
whole or in part, for United States federal income tax purposes; or (iii) the
Trust is, or shall be within 90 days after the date of such Opinion of Counsel,
subject to more than a de minimis amount of other taxes, duties, assessments or
other governmental charges; provided, however, that the Trust or the Company
shall have requested and received such an Opinion of Counsel with regard to such
matters within a reasonable period of time after the Trust or the Company shall
have become aware of the possible occurrence of any of the events described in
clauses (i) through (iii) above.

         "Trust" means Southside Capital Trust II, a Delaware statutory business
trust.

         "Trust Agreement" means the Amended and Restated Trust Agreement, dated
as of November ___, 2000, of the Trust.

         "Trustee" means Wilmington Trust Company and, subject to the provisions
of Article X, shall also include its successors and assigns, and, if at any time
there is more than one Person acting in such capacity hereunder, "Trustee" shall
mean each such Person.

         "Trust Indenture Act," means the Trust Indenture Act of 1939, as
amended, subject to the provisions of Sections 12.1, 12.2, and 13.1, as in
effect at the date of execution of this instrument.

         "Trust Securities" means the Common Securities and Preferred
Securities, collectively.

                                       10

<PAGE>   19

         "Voting Stock," as applied to stock of any Person, means shares,
interests, participations or other equivalents in the equity interest (however
designated) in such Person having ordinary voting power for the election of a
majority of the directors (or the equivalent) of such Person, other than shares,
interests, participations or other equivalents having such power only by reason
of the occurrence of a contingency.

                                   ARTICLE II

                      ISSUE, DESCRIPTION, TERMS, CONDITIONS
                   REGISTRATION AND EXCHANGE OF THE DEBENTURES

SECTION 2.1       DESIGNATION AND PRINCIPAL AMOUNT.

         There is hereby authorized Debentures designated the "_____%
Convertible Subordinated Debentures due 2030," limited in aggregate principal
amount to $17,783,510 which amount shall be as set forth in any written order of
the Company for the authentication and delivery of Debentures pursuant to
Section 2.6.

SECTION 2.2       MATURITY.

         (a) The Maturity Date shall be either:

                  (i) the Scheduled Maturity Date; or

                  (ii) if the Company elects to accelerate the Maturity Date to
be a date prior to the Scheduled Maturity Date in accordance with Section
2.2(c), the Accelerated Maturity Date.

         (b) the Company may at any time before the day which is 90 days before
the Scheduled Maturity Date and after December 31, 2005, elect to shorten the
Maturity Date only once to the Accelerated Maturity Date provided that the
Company has received the prior approval of the Federal Reserve if then required
under applicable capital guidelines, policies or regulations of the Federal
Reserve.

         (c) if the Company elects to accelerate the Maturity Date in accordance
with Section 2.2(b), the Company shall give notice to the Trustee and the Trust
(unless the Trust is not the holder of the Debentures, in which case the Trustee
will give notice to the holders of the Debentures) of the acceleration of the
Maturity Date and the Accelerated Maturity Date at least 30 days and no more
than 180 days before the Accelerated Maturity Date; provided, however that
nothing provided in this Section 2.2 shall limit the Company's rights, as
provided in Article III hereof, to redeem all or a portion of the Debentures at
such time or times on or after December 31, 2003, as the Company may so
determine, or at any time upon the occurrence of a Special Event.

                                       11

<PAGE>   20

SECTION 2.3       FORM AND PAYMENT.

         The Debentures shall be issued in fully registered certificated form
without interest coupons. Principal and interest on the Debentures issued in
certificated form shall be payable, the transfer of such Debentures shall be
registrable and such Debentures shall be exchangeable for Debentures bearing
identical terms and provisions at the office or agency of the Trustee; provided,
however, that payment of interest may be made at the option of the Company by
check mailed to the holder at such address as shall appear in the Debenture
Register or by wire transfer to an account maintained by the holder as specified
in the Debenture Register, provided that the holder provides proper transfer
instructions by the regular record date. Notwithstanding the foregoing, so long
as the holder of any Debentures is the Property Trustee, the payment of
principal of and interest (including Compounded Interest and Additional
Interest, if any) on such Debentures held by the Property Trustee shall be made
at such place and to such account as may be designated by the Property Trustee.

SECTION 2.4       [INTENTIONALLY LEFT BLANK].

SECTION 2.5       INTEREST.

         (a) Each Debenture shall bear interest at the rate of _____% per annum
(the "Coupon Rate") from the original date of issuance until the principal
thereof becomes due and payable, and on any overdue principal and (to the extent
that payment of such interest is enforceable under applicable law) on any
overdue installment of interest at the Coupon Rate, compounded quarterly,
payable (subject to the provisions of Article V) quarterly in arrears on March
31, June 30, September 30 and December 31 of each year (each, an "Interest
Payment Date"), commencing on December 31, 2000 to the Person in whose name such
Debenture or any Predecessor Debenture is registered, at the close of business
on the regular record date for such interest installment, which shall be the
fifteenth day of the last month of the calendar quarter.

         (b) The amount of interest payable for any period shall be computed on
the basis of a 360-day year of twelve 30-day months. The amount of interest
payable for any period shorter than a full quarterly period for which interest
is computed, shall be computed on the basis of the number of days elapsed in a
360-day year of twelve 30-day months. In the event that any date on which
interest is payable on the Debentures is not a Business Day, then payment of
interest payable on such date shall be made on the next succeeding day which is
a Business Day (and without any interest or other payment in respect of any such
delay) except that, if such Business Day is in the next succeeding calendar
year, such payment shall be made on the immediately preceding Business Day (and
without any reduction of interest or any other payment in respect of any such
acceleration), in each case with the same force and effect as if made on the
date such payment was originally payable.

         (c) If, at any time while the Property Trustee is the holder of any
Debentures, the Trust or the Property Trustee is required to pay any taxes,
duties, assessments or governmental charges of whatever

                                       12

<PAGE>   21

nature (other than withholding taxes) imposed by the United States, or any other
taxing authority, then, in any case, the Company shall pay as additional
interest ("Additional Interest") on the Debentures held by the Property Trustee,
such additional amounts as shall be required so that the net amounts received
and retained by the Trust and the Property Trustee after paying such taxes,
duties, assessments or other governmental charges shall be equal to the amounts
the Trust and the Property Trustee would have received had no such taxes,
duties, assessments or other government charges been imposed.

SECTION 2.6       EXECUTION AND AUTHENTICATIONS.

         (a) The Debentures shall be signed on behalf of the Company by its
President or one of its Executive Vice Presidents or Chief Financial Officer or
Treasurer, under its corporate seal attested by its Secretary or one of its
Assistant Secretaries. Signatures may be in the form of a manual or facsimile
signature. The Company may use the facsimile signature of any Person who shall
have been a President or Executive Vice President thereof, or of any Person who
shall have been a Secretary or Assistant Secretary thereof, notwithstanding the
fact that at the time the Debentures shall be authenticated and delivered or
disposed of such Person shall have ceased to be the President or a Vice
President, or the Secretary or an Assistant Secretary, of the Company (and any
such signature shall be binding on the Company). The seal of the Company may be
in the form of a facsimile of such seal and may be impressed, affixed, imprinted
or otherwise reproduced on the Debentures. The Debentures may contain such
notations, legends or endorsements required by law, stock exchange rule or
usage. Each Debenture shall be dated the date of its authentication by the
Trustee.

         (b) A Debenture shall not be valid until authenticated manually by an
authorized signatory of the Trustee, or by an Authenticating Agent. Such
signature shall be conclusive evidence that the Debenture so authenticated has
been duly authenticated and delivered hereunder and that the holder is entitled
to the benefits of this Indenture.

         (c) At any time and from time to time after the execution and delivery
of this Indenture, the Company may deliver Debentures executed by the Company to
the Trustee for authentication, together with a written order of the Company for
the authentication and delivery of such Debentures signed by its President or
any Executive Vice President and its Chief Financial Officer or the Treasurer or
any Assistant Treasurer, and the Trustee in accordance with such written order
shall authenticate and deliver such Debentures.

         (d) In authenticating such Debentures and accepting the additional
responsibilities under this Indenture in relation to such Debentures, the
Trustee shall be entitled to receive, and (subject to Section 10.1) shall be
fully protected in relying upon, an Opinion of Counsel stating that the form and
terms thereof have been established in conformity with the provisions of this
Indenture.

                                       13

<PAGE>   22

         (e) The Trustee shall not be required to authenticate such Debentures
if the issue of such Debentures pursuant to this Indenture shall affect the
Trustee's own rights, duties or immunities under the Debentures and this
Indenture or otherwise in a manner that is not reasonably acceptable to the
Trustee.

SECTION 2.7       REGISTRATION OF TRANSFER AND EXCHANGE.

         (a) Debentures may be exchanged upon presentation thereof at the office
or agency of the Company designated for such purpose in the Borough of
Manhattan, The City of New York, or at the office of the Debenture Registrar,
for other Debentures and for a like aggregate principal amount in denominations
of integral multiples of $10, upon payment of a sum sufficient to cover any tax
or other governmental charge in relation thereto, all as provided in this
Section 2.7. In respect of any Debentures so surrendered for exchange, the
Company shall execute, the Trustee shall authenticate and such office or agency
shall deliver in exchange therefor the Debenture or Debentures that the
Debentureholder making the exchange shall be entitled to receive, bearing
numbers not contemporaneously outstanding.

         (b) The Company shall keep, or cause to be kept, at its office or
agency designated for such purpose in the Borough of Manhattan, The City of New
York, or at the office of the Debenture Registrar or such other location
designated by the Company a register or registers (herein referred to as the
"Debenture Register") in which, subject to such reasonable regulations as the
Debenture Registrar (as defined below) may prescribe, the Company shall register
the Debentures and the transfers of Debentures as in this Article II provided
and which at all reasonable times shall be open for inspection by the Trustee.
The registrar for the purpose of registering Debentures and transfer of
Debentures as herein provided shall initially be the Trustee and thereafter as
may be appointed by the Company as authorized by Board Resolution (the
"Debenture Registrar"). Upon surrender for transfer of any Debenture at the
office or agency of the Company designated for such purpose, the Company shall
execute, the Trustee shall authenticate and such office or agency shall deliver
in the name of the transferee or transferees a new Debenture or Debentures for a
like aggregate principal amount. All Debentures presented or surrendered for
exchange or registration of transfer, as provided in this Section 2.7, shall be
accompanied (if so required by the Company or the Debenture Registrar) by a
written instrument or instruments of transfer, in form satisfactory to the
Company or the Debenture Registrar, duly executed by the registered holder or by
such holder's duly authorized attorney in writing.

         (c) No service charge shall be made for any exchange or registration of
transfer of Debentures, or issue of new Debentures in case of partial
redemption, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge in relation thereto, other than exchanges
pursuant to Section 2.8, Section 3.5(b) and Section 12.4 not involving any
transfer.

         (d) The Company shall not be required (i) to issue, exchange or
register the transfer of any Debentures during a period beginning at the opening
of business 15 days before the day of the mailing of a notice of redemption of
less than all the Outstanding Debentures and ending at the close of business on

                                       14

<PAGE>   23

the day of such mailing; nor (ii) to register the transfer of or exchange any
Debentures or portions thereof called for redemption.

         (e) Debentures may only be transferred, in whole or in part, in
accordance with the terms and conditions set forth in this Indenture. Any
transfer or purported transfer of any Debenture not made in accordance with this
Indenture shall be null and void.

SECTION 2.8       TEMPORARY DEBENTURES.

         Pending the preparation of definitive Debentures, the Company may
execute, and the Trustee shall authenticate and deliver, temporary Debentures
(printed, lithographed, or typewritten). Such temporary Debentures shall be
substantially in the form of the definitive Debentures in lieu of which they are
issued, but with such omissions, insertions and variations as may be appropriate
for temporary Debentures, all as may be determined by the Company. Every
temporary Debenture shall be executed by the Company and be authenticated by the
Trustee upon the same conditions and in substantially the same manner, and with
like effect, as the definitive Debentures. Without unnecessary delay the Company
shall execute and shall furnish definitive Debentures and thereupon any or all
temporary Debentures may be surrendered in exchange therefor (without charge to
the holders), at the office or agency of the Company designated for the purpose
in the Borough of Manhattan, The City of New York, and the Trustee shall
authenticate and such office or agency shall deliver in exchange for such
temporary Debentures an equal aggregate principal amount of definitive
Debentures, unless the Company advises the Trustee to the effect that definitive
Debentures need not be executed and furnished until further notice from the
Company. Until so exchanged, the temporary Debentures shall be entitled to the
same benefits under this Indenture as definitive Debentures authenticated and
delivered hereunder.

SECTION 2.9       MUTILATED, DESTROYED, LOST OR STOLEN DEBENTURES.

         (a) In case any temporary or definitive Debenture shall become
mutilated or be destroyed, lost or stolen, the Company (subject to the next
succeeding sentence) shall execute, and upon the Company's request the Trustee
(subject as aforesaid) shall authenticate and deliver, a new Debenture bearing a
number not contemporaneously outstanding, in exchange and substitution for the
mutilated Debenture, or in lieu of and in substitution for the Debenture so
destroyed, lost, stolen or mutilated. In every case the applicant for a
substituted Debenture shall furnish to the Company and the Trustee such security
or indemnity as may be required by them to save each of them harmless, and, in
every case of destruction, loss or theft, the applicant shall also furnish to
the Company and the Trustee evidence to their satisfaction of the destruction,
loss or theft of the applicant's Debenture and of the ownership thereof. The
Trustee may authenticate any such substituted Debenture and deliver the same
upon the written request or authorization of the President or any Vice President
and the Chief Financial Officer or the Treasurer or any Assistant Treasurer of
the Company. Upon the issuance of any substituted Debenture, the Company may
require the payment of a sum sufficient to cover any tax or other governmental
charge that may be imposed in relation thereto and any other expenses (including
the fees and expenses of the Trustee) connected therewith. In case any

                                       15

<PAGE>   24

Debenture that has matured or is about to mature shall become mutilated or be
destroyed, lost or stolen, the Company may, instead of issuing a substitute
Debenture, pay or authorize the payment of the same (without surrender thereof
except in the case of a mutilated Debenture) if the applicant for such payment
shall furnish to the Company and the Trustee such security or indemnity as they
may require to save them harmless, and, in case of destruction, loss or theft,
evidence to the satisfaction of the Company and the Trustee of the destruction,
loss or theft of such Debenture and of the ownership thereof.

         (b) Every replacement Debenture issued pursuant to the provisions of
this Section 2.9 shall constitute an additional contractual obligation of the
Company whether or not the mutilated, destroyed, lost or stolen Debenture shall
be found at any time, or be enforceable by anyone, and shall be entitled to all
the benefits of this Indenture equally and proportionately with any and all
other Debentures duly issued hereunder. All Debentures shall be held and owned
upon the express condition that the foregoing provisions are exclusive with
respect to the replacement or payment of mutilated, destroyed, lost or stolen
Debentures, and shall preclude (to the extent lawful) any and all other rights
or remedies, notwithstanding any law or statute existing or hereafter enacted to
the contrary with respect to the replacement or payment of negotiable
instruments or other securities without their surrender.

SECTION 2.10      CANCELLATION.

         All Debentures surrendered for the purpose of payment, redemption,
exchange, conversion or registration of transfer shall, if surrendered to the
Company or any paying agent, be delivered to the Trustee for cancellation, or,
if surrendered to the Trustee, shall be canceled by it, and no Debentures shall
be issued in lieu thereof except as expressly required or permitted by any of
the provisions of this Indenture. On request of the Company at the time of such
surrender, the Trustee shall deliver to the Company canceled Debentures held by
the Trustee. In the absence of such request the Trustee may dispose of canceled
Debentures in accordance with its standard procedures and deliver a certificate
of disposition to the Company. If the Company shall otherwise acquire any of the
Debentures, however, such acquisition shall not operate as a redemption or
satisfaction of the indebtedness represented by such Debentures unless and until
the same are delivered to the Trustee for cancellation.

SECTION 2.11      BENEFIT OF INDENTURE.

         Nothing in this Indenture or in the Debentures, express or implied,
shall give or be construed to give to any Person, other than the parties hereto
and the holders of the Debentures (and, with respect to the provisions of
Article XVII, the holders of Senior Indebtedness) any legal or equitable right,
remedy or claim under or in respect of this Indenture, or under any covenant,
condition or provision herein contained; all such covenants, conditions and
provisions being for the sole benefit of the parties hereto and of the holders
of the Debentures (and, with respect to the provisions of Article XVII, the
holders of Senior Indebtedness).

                                       16

<PAGE>   25

SECTION 2.12      AUTHENTICATING AGENT.

         (a) So long as any of the Debentures remain Outstanding there may be an
Authenticating Agent for any or all such Debentures, which Authenticating Agent
the Trustee shall have the right to appoint. Said Authenticating Agent shall be
authorized to act on behalf of the Trustee to authenticate Debentures issued
upon exchange, transfer or partial redemption thereof, and Debentures so
authenticated shall be entitled to the benefits of this Indenture and shall be
valid and obligatory for all purposes as if authenticated by the Trustee
hereunder. All references in this Indenture to the authentication of Debentures
by the Trustee shall be deemed to include authentication by an Authenticating
Agent. Each Authenticating Agent shall be acceptable to the Company and shall be
a corporation that has a combined capital and surplus, as most recently reported
or determined by it, sufficient under the laws of any jurisdiction under which
it is organized or in which it is doing business to conduct a trust business,
and that is otherwise authorized under such laws to conduct such business and is
subject to supervision or examination by federal or state authorities. If at any
time any Authenticating Agent shall cease to be eligible in accordance with
these provisions, it shall resign immediately.

         (b) Any Authenticating Agent may at any time resign by giving written
notice of resignation to the Trustee and to the Company. The Trustee may at any
time (and upon request by the Company shall) terminate the agency of any
Authenticating Agent by giving written notice of termination to such
Authenticating Agent and to the Company. Upon resignation, termination or
cessation of eligibility of any Authenticating Agent, the Trustee may appoint an
eligible successor Authenticating Agent acceptable to the Company. Any successor
Authenticating Agent, upon acceptance of its appointment hereunder, shall become
vested with all the rights, powers and duties of its predecessor hereunder as if
originally named as an Authenticating Agent pursuant hereto.

                                   ARTICLE III

                            REDEMPTION OF DEBENTURES

SECTION 3.1       REDEMPTION.

         Subject to the Company having received prior approval of the Federal
Reserve, if then required under the applicable capital guidelines, policies or
regulations of the Federal Reserve, the Company may redeem the Debentures issued
hereunder on and after the dates set forth in and in accordance with the terms
of this Article III.

SECTION 3.2       SPECIAL EVENT REDEMPTION.

         Subject to the Company having received the prior approval of the
Federal Reserve, if then required under the applicable capital guidelines,
policies or regulations of the Federal Reserve, if a Special Event has occurred
and is continuing, then, notwithstanding Section 3.3(a) but subject to Section
3.3(b), the

                                       17

<PAGE>   26

Company shall have the right upon not less than 30 days' nor more than 60 days'
notice to the holders of the Debentures to redeem the Debentures, in whole but
not in part, for cash within 180 days following the occurrence of such Special
Event (the "180-Day Period") at a redemption price equal to 100% of the
principal amount to be redeemed plus any accrued and unpaid interest thereon to
the date of such redemption (the "Redemption Price"), provided that if at the
time there is available to the Company the opportunity to eliminate, within the
180-Day Period, a Tax Event by taking some ministerial action (a "Ministerial
Action"), such as filing a form or making an election, or pursuing some other
similar reasonable measure which has no adverse effect on the Company, the Trust
or the holders of the Trust Securities issued by the Trust, the Company shall
pursue such Ministerial Action in lieu of redemption, and, provided further,
that the Company shall have no right to redeem the Debentures pursuant to this
Section 3.2 while it is pursuing any Ministerial Action pursuant to its
obligations hereunder, and, provided further, that, if it is determined that the
taking of a Ministerial Action would not eliminate the Tax Event within the 180
Day Period, the Company's right to redeem the Debentures pursuant to this
Section 3.2 shall be restored and it shall have no further obligations to pursue
the Ministerial Action. The Redemption Price shall be paid prior to 12:00 noon,
New York time, on the date of such redemption or such earlier time as the
Company determines, provided that the Company shall deposit with the Trustee an
amount sufficient to pay the Redemption Price by 10:00 a.m., New York time, on
the date such Redemption Price is to be paid.

SECTION 3.3       OPTIONAL REDEMPTION BY COMPANY.

         (a) Subject to the provisions of Section 3.3(c), except as otherwise
may be specified in this Indenture, the Company shall have the right to redeem
the Debentures, in whole or in part, from time to time, (i) on or after December
31, 2005, at a Redemption Price equal to 100% of the principal amount to be
redeemed plus any accrued and unpaid interest thereon to the date of such
redemption; (ii) on or after December 31, 2003 but before December 31, 2004, at
a Redemption Price equal to ____% of the principal amount to be redeemed plus
any accrued and unpaid interest thereon to the date of such redemption; and
(iii) on or after December 31, 2004 but before December 31, 2005, at a
Redemption Price equal to ____% of the principal to be redeemed plus any accrued
and unpaid interest thereon to the date of such redemption. The Company may
elect to redeem the Debentures pursuant to (ii) and (iii) above only if the
stock price for the Company's common stock has been at least 125% of the
Conversion Price for a period of twenty consecutive business days ending within
five days of the date of notice of redemption. Any redemption pursuant to this
Section 3.3(a) shall be made upon not less than 30 days' nor more than 60 days'
notice to the holder of the Debentures, at the Redemption Price. If the
Debentures are only partially redeemed pursuant to this Section 3.3(a), the
Debentures shall be redeemed pro rata or by lot or in such other manner as the
Trustee shall deem appropriate and fair in its discretion. The Redemption Price
shall be paid prior to 12:00 noon, New York time, on the date of such redemption
or at such earlier time as the Company determines provided that the Company
shall deposit with the Trustee an amount sufficient to pay the Redemption Price
by 10:00 a.m., New York time, on the date such Redemption Price is to be paid.

                                       18

<PAGE>   27

         (b) Subject to the provisions of Section 3.3(c), the Company shall have
the right to redeem Debentures at any time and from time to time in a principal
amount equal to the Liquidation Amount (as defined in the Trust Agreement) of
any Preferred Securities purchased and beneficially owned by the Company, plus
an additional principal amount of Debentures equal to the Liquidation Amount (as
defined in the Trust Agreement) of that number of Common Securities that bears
the same proportion to the total number of Common Securities then outstanding as
the number of Preferred Securities to be redeemed bears to the total number of
Preferred Securities then outstanding. Such Debentures shall be redeemed
pursuant to this Section 3.3(b) only in exchange for and upon surrender by the
Company to the Property Trustee of the Preferred Securities and a proportionate
amount of Common Securities, whereupon the Property Trustee shall cancel the
Preferred Securities and Common Securities so surrendered and a Like Amount (as
defined in the Trust Agreement) of Debentures shall be extinguished by the
Trustee and shall no longer be deemed Outstanding.

         (c) If a partial redemption of the Debentures would result in the
delisting of the Preferred Securities issued by the Trust from The Nasdaq
National Market(sm) or any national securities exchange or other organization on
which the Preferred Securities are then listed or quoted, the Company shall not
be permitted to effect such partial redemption and may only redeem the
Debentures in whole.

SECTION 3.4       NOTICE OF REDEMPTION.

         (a) Except in the case of a redemption pursuant to Section 3.3(b), in
case the Company shall desire to exercise such right to redeem all or, as the
case may be, a portion of the Debentures in accordance with the right reserved
so to do, the Company shall, or shall cause the Trustee to upon receipt of 45
days' written notice from the Company (which notice shall, in the event of a
partial redemption, include a representation to the effect that such partial
redemption will not result in the delisting of the Preferred Securities as
described in Section 3.3(c) above), give notice of such redemption to holders of
the Debentures to be redeemed by mailing, first class postage prepaid, a notice
of such redemption not less than 30 days and not more than 60 days before the
date fixed for redemption to such holders at their last addresses as they shall
appear upon the Debenture Register unless a shorter period is specified in the
Debentures to be redeemed. Any notice that is mailed in the manner herein
provided shall be conclusively presumed to have been duly given, whether or not
the registered holder receives the notice. In any case, failure duly to give
such notice to the holder of any Debenture designated for redemption in whole or
in part, or any defect in the notice, shall not affect the validity of the
proceedings for the redemption of any other Debentures. In the case of any
redemption of Debentures prior to the expiration of any restriction on such
redemption provided in the terms of such Debentures or elsewhere in this
Indenture, the Company shall furnish the Trustee with an Officers' Certificate
evidencing compliance with any such restriction. Each such notice of redemption
shall specify the date fixed for redemption and the Redemption Price and shall
state that payment of the Redemption Price shall be made at the office or agency
of the Company in the Borough of Manhattan, The City of New York or at the
Corporate Trust Office, upon presentation and surrender of such Debentures, that
interest accrued to the date fixed for redemption shall be paid as specified in
said notice and that from and after said date interest shall cease to accrue. If
less than all the

                                       19

<PAGE>   28

Debentures are to be redeemed, the notice to the holders of the Debentures shall
specify the particular Debentures to be redeemed. If the Debentures are to be
redeemed in part only, the notice shall state the portion of the principal
amount thereof to be redeemed and shall state that on and after the redemption
date, upon surrender of such Debenture, a new Debenture or Debentures in
principal amount equal to the unredeemed portion thereof shall be issued.

         (b) Except in the case of redemption pursuant to Section 3.3(b), if
less than all the Debentures are to be redeemed, the Company shall give the
Trustee at least 45 days' notice in advance of the date fixed for redemption as
to the aggregate principal amount of Debentures to be redeemed, and thereupon
the Trustee shall select, pro rata or by lot or in such other manner as it shall
deem appropriate and fair in its discretion, the portion or portions (equal to
$10 or any integral multiple thereof) of the Debentures to be redeemed and shall
thereafter promptly notify the Company in writing of the numbers of the
Debentures to be redeemed, in whole or in part. The Company may, if and whenever
it shall so elect pursuant to the terms hereof, by delivery of instructions
signed on its behalf by its Chairman, its President or any Vice President,
instruct the Trustee or any paying agent to call all or any part of the
Debentures for redemption and to give notice of redemption in the manner set
forth in this Section 3.4, such notice to be in the name of the Company or its
own name as the Trustee or such paying agent may deem advisable. In any case in
which notice of redemption is to be given by the Trustee or any such paying
agent, the Company shall deliver or cause to be delivered to, or permit to
remain with, the Trustee or such paying agent, as the case may be, such
Debenture Register, transfer books or other records, or suitable copies or
extracts therefrom, sufficient to enable the Trustee or such paying agent to
give any notice by mail that may be required under the provisions of this
Section 3.4.

SECTION 3.5       PAYMENT UPON REDEMPTION.

         (a) If the giving of notice of redemption shall have been completed as
above provided, the Debentures or portions of Debentures to be redeemed
specified in such notice shall become due and payable on the date and at the
place stated in such notice at the applicable Redemption Price, and interest on
such Debentures or portions of Debentures shall cease to accrue on and after the
date fixed for redemption, unless the Company shall default in the payment of
such Redemption Price with respect to any such Debenture or portion thereof. On
presentation and surrender of such Debentures on or after the date fixed for
redemption at the place of payment specified in the notice, said Debentures
shall be paid and redeemed at the Redemption Price (but if the date fixed for
redemption is an Interest Payment Date, the interest installment payable on such
date shall be payable to the registered holder at the close of business on the
applicable record date pursuant to Section 3.3).

         (b) Upon presentation of any Debenture that is to be redeemed in part
only, the Company shall execute and the Trustee shall authenticate and the
office or agency where the Debenture is presented shall deliver to the holder
thereof, at the expense of the Company, a new Debenture of authorized
denomination in principal amount equal to the unredeemed portion of the
Debenture so presented.

                                       20

<PAGE>   29

SECTION 3.6       NO SINKING FUND.

         The Debentures are not entitled to the benefit of any sinking fund.

                                   ARTICLE IV

                            CONVERSION OF DEBENTURES

SECTION 4.1       CONVERSION RIGHTS.

         Subject to and upon compliance with the provisions of this Article IV,
the Debentures are convertible, at the option of the Debentureholder, at any
time after ________, 2000, and on or before the close of business on the
Business Day immediately preceding the date of repayment of such Debentures,
whether at maturity or upon redemption, into fully paid and nonassessable shares
of Common Stock at an initial conversion ratio of _____ shares of Common Stock
for each $10 in aggregate principal amount of Debentures (equal to an initial
conversion price of $_____ per share of Common Stock), subject to adjustment as
described in this Article IV (the "Conversion Ratio"). A Debentureholder may
convert any portion of the principal amount of the Debentures into that number
of fully paid and nonassessable shares of Common Stock (calculated as to each
conversion to the nearest 1/100th of a share) obtained by multiplying (x) the
quotient obtained by dividing the principal amount of the Debentures to be
converted by $10.00 by (y) the Conversion Ratio. In case a Debenture or portion
thereof is called for redemption, such conversion right in respect of the
Debenture or portion so called shall expire at the close of business on the
Business Day immediately preceding the corresponding Maturity Date, unless the
Company defaults in making the payment due upon redemption.

SECTION 4.2       CONVERSION PROCEDURES.

         (a) To convert all or a portion of the Debentures, the Debentureholder
thereof shall deliver to the Conversion Agent an irrevocable Conversion Request
setting forth the principal amount of Debentures to be converted, together with
the name or names, if other than the Debentureholder, in which the shares of
Common Stock should be issued upon conversion and, if such Debentures are in
certificate form, surrender to the Conversion Agent the Debentures to be
converted, duly endorsed or assigned to the Company or in blank. In addition, a
holder of Preferred Securities may exercise its right under the Trust Agreement
to exchange such Preferred Securities for Debentures which shall be converted
into Common Stock by delivering to the Conversion Agent an irrevocable
Conversion Request setting forth the information called for by the preceding
sentence and directing the Conversion Agent (i) to exchange such Preferred
Security for a portion of the Debentures held by the Trust (at an exchange rate
of $10 principal amount of Debentures for each Preferred Security), and (ii) to
immediately convert such Debentures, on behalf of such Debentureholder, into
Common Stock pursuant to this Article IV and, if such Preferred Securities are
in certificate form, surrendering such Preferred Securities, duly endorsed or
assigned to the Company or in blank. So long as any Preferred Securities are
outstanding, the Trust shall not convert any

                                       21

<PAGE>   30

Debentures except pursuant to a Conversion Request delivered to the Conversion
Agent by a holder of Preferred Securities.

         If a Conversion Request is delivered on or after the regular record
date and prior to the subsequent Interest Payment Date, the Debentureholder
shall be required to pay to the Company the interest payable to the
Debentureholder on the subsequent Interest Payment Date prior to receiving the
shares of Common Stock, and shall be entitled to receive the interest payable on
the subsequent Interest Payment Date, on the portion of Debentures to be
converted notwithstanding the conversion thereof prior to such Interest Payment
Date. Except as provided in the immediately preceding sentence, the Company
shall not make, or be required to make, any payment, allowance or adjustment for
accumulated and unpaid interest, whether or not in arrears, on converted
Debentures; provided, however, that if notice of redemption of Debentures is
mailed or otherwise given to Debentureholder, then, if any Debentureholder
converts any Debentures into Common Stock on any date on or after the date on
which such notice of prepayment is mailed or otherwise given, and if such date
of conversion falls on any day from and including the first day of an Extended
Interest Payment Period and on or prior to the Interest Payment Date upon which
such Extended Interest Payment Period ends, such converting Debentureholder
shall be entitled to receive either (i) if the date of such conversion falls
after a regular record date and on or prior to the next succeeding Interest
Payment Date, all accrued and unpaid interest on such Debentures (including
interest thereon, if any, to the extent permitted by applicable law) to such
Interest Payment Date, or (ii) if the date of such conversion does not fall on a
date described in clause (i) above, all accrued and unpaid interest on such
Debentures (including interest thereon, if any, to the extent permitted by
applicable law) to the most recent Interest Payment Date prior to the date of
such conversion, which interest shall, in either such case, be paid to such
converting Debentureholder unless the date of conversion of such Debentures is
on or prior to the Interest Payment Date upon which such Extended Interest
Payment Period ends and after the regular record date for such Interest Payment
Date, in which case such interest shall be paid to the person who was the
Debentureholder at the close of business on such regular record date. Except as
otherwise set forth above in this paragraph, in the case of any Debenture which
is converted, interest which is payable after the date of conversion of such
Debenture shall not be payable, and the Company shall not make nor be required
to make any other payment, adjustment or allowance with respect to accrued but
unpaid interest (including Additional Interest, if any) on the Debentures being
converted, which shall be deemed to be paid in full. If any Debenture called for
redemption is converted, any money deposited with the Trustee or with any paying
agent or so segregated and held in trust for the redemption of such Debenture
shall (subject to any right of the Debentureholder) be paid to the Company upon
Company Request or, if then held by the Company, shall be discharged from such
trust.

         Each conversion shall be deemed to have been effected immediately prior
to close of business on the day on which the Conversion Request was received
(the "Conversion Date") by the Conversion Agent from the Debentureholder or from
a holder of the Preferred Securities effecting a conversion thereof pursuant to
its conversion rights under the Trust Agreement, as the case may be. The Person
or Persons entitled to receive the Common Stock issuable upon such conversion
shall be treated for all purposes as a record holder or holders of such Common
Stock as of the Conversion Date. As promptly as practicable

                                       22

<PAGE>   31

on or after the Conversion Date, the Company shall issue and deliver at the
office of the Conversion Agent, unless otherwise directed by the Debentureholder
in the Conversion Request, a certificate or certificates for the number of full
shares of Common Stock issuable upon such conversion, together with the cash
payment, if any, in lieu of any fraction of any share to the Person or Persons
entitled to receive the same. The Conversion Agent shall deliver such
certificate or certificates to each Person or Persons.

         (b) Subject to any right of the Debentureholder, the Company's delivery
upon conversion of the fixed number of shares of Common Stock into which the
Debentures are convertible (together with the cash payment, if any, in lieu of
fractional shares) shall be deemed to satisfy the Company's obligation to pay
the principal amount at maturity of the portion of Debentures so converted and
any unpaid interest (including Additional Interest, if any) accrued on such
Debentures at the time of such conversion.

         (c) No fractional shares of Common Stock shall be issued as a result of
conversion, but in lieu thereof, the Company shall pay to the Conversion Agent a
cash adjustment in an amount equal to the same fraction of the last reported
sale price of such fractional interest on the date on which the Debentures or
Preferred Securities, as the case may be, were duly surrendered to the
Conversion Agent for conversion, or, if such day is not a Trading Day, on the
next Trading Day, and the Conversion Agent in turn shall make such payment, if
any, to the Debentureholder or the holder of the Preferred Securities so
converted.

         (d) In the event of the conversion of any Debenture in part only, a new
Debenture or Debentures for the unconverted portion thereof shall be issued in
the name of the Debentureholder thereof upon the cancellation thereof in
accordance with Section 2.9.

         (e) In effecting the conversion transactions described in this Section
4.2, the Conversion Agent is acting as agent of the holders of Preferred
Securities (in the exchange of Preferred Securities for Debentures) and as agent
of the Debentureholders (in the conversion of Debentures into Common Stock), as
the case may be, directing it to effect such conversion transactions. The
Conversion Agent is hereby authorized (i) to exchange Preferred Securities for
Debentures held by the Trust from time to time in connection with the conversion
of such Preferred Securities in accordance with this Article IV, and (ii) to
convert all or a portion of the Debentures into Common Stock and thereupon to
deliver such shares of Common Stock in accordance with the provisions of this
Article IV and to deliver to the Trust a new Debenture or Debentures for any
resulting unconverted principal amount.

SECTION 4.3       CONVERSION RATIO ADJUSTMENTS.

         The Conversion Ratio shall be subject to adjustment (without
duplication) from time to time as follows:

         (a) In case the Company shall, while any of the Debentures are
outstanding, (i) pay a dividend or make a distribution with respect to its
Common Stock in shares of Common Stock, (ii) subdivide its outstanding shares of
Common Stock, (iii) combine its outstanding shares of Common Stock into a
smaller

                                       23

<PAGE>   32

number of shares, or (iv) issue by reclassification of its shares of Common
Stock any shares of capital stock of the Company, then the Conversion Ratio in
effect immediately prior to such action shall be adjusted so that the holders of
any Debentures thereafter surrendered for conversion shall be entitled to
receive the number of shares of capital stock of the Company which he would have
owned immediately following such action had such Debentures been converted
immediately prior thereto. An adjustment made pursuant to this Section 4.3(a)
shall become effective immediately after the record date in the case of a
dividend or other distribution and shall become effective immediately after the
effective date in case of a subdivision, combination or reclassification (or
immediately after the record date if a record date shall have been established
for such event). If, as a result of an adjustment made pursuant to this Section
4.3(a), the holder of any Debenture thereafter surrendered for conversion shall
become entitled to receive shares of two or more classes or series of capital
stock of the Company, the Board of Directors (whose determination shall be
conclusive and shall be described in a Board Resolution filed with the Trustee)
shall determine the allocation of the adjusted Conversion Ratio between or among
shares of such classes or series of capital stock.

         (b) In case the Company shall, while any of the Debentures are
outstanding, issue rights or warrants to all holders of its Common Stock
entitling them (for a period expiring within 45 days after the record date
mentioned in this Section 4.3(b)) to subscribe for or purchase shares of Common
Stock at a price per share less than the Current Market Price (as defined below)
per share of Common Stock on such record date, then the Conversion Ratio for the
Debentures shall be adjusted so that the same shall equal the ratio determined
by multiplying the Conversion Ratio in effect immediately prior to the date of
issuance of such rights or warrants by a fraction of which the numerator shall
be the number of shares of Common Stock outstanding on the date of issuance of
such rights or warrants plus the number of additional shares of Common Stock
offered for subscription or purchase, and of which the denominator shall be the
number of shares of Common Stock outstanding on the date of issuance of such
rights or warrants plus the number of shares which the aggregate offering price
of the total number of shares so offered for subscription or purchase would
purchase at such Current Market Price. Such adjustment shall become effective
immediately after the record date for the determination of shareholders entitled
to receive such rights or warrants. For the purposes of this Section 4.3(b), the
number of shares of Common Stock at any time outstanding shall not include
shares held in the treasury of the Company. The Company shall not issue any
rights or warrants in respect of the shares of Common Stock held in the treasury
of the Company. In case any rights or warrants referred to in this Section
4.3(b) in respect of which an adjustment shall have been made shall expire
unexercised within 45 days after the same shall have been distributed or issued
by the Company, the Conversion Ratio shall be readjusted at the time of such
expiration to the Conversion Ratio that would have been in effect if no
adjustment had been made on account of the distribution or issuance of such
expired rights or warrants.

         (c) Subject to the last sentence of this Section 4.3(c), in case the
Company shall, by dividend or otherwise, distribute to all holders of its Common
Stock evidences of its indebtedness, shares of any class or series of capital
stock, cash or assets (including securities, but excluding any rights or
warrants referred to in Section 4.3(b), any dividend or distribution paid
exclusively in cash and any dividend or

                                       24

<PAGE>   33

distribution referred to in Section 4.3(a)), then the Conversion Ratio shall be
increased so that the same shall equal the ratio determined by multiplying the
Conversion Ratio in effect immediately prior to the effectiveness of the
Conversion Ratio increase contemplated by this Section 4.3(c) by a fraction of
which the numerator shall be the Current Market Price per share of Common Stock
on the date fixed for the payment of such distribution (the "Reference Date"),
and of which the denominator shall be, the Current Market Price per share of the
Common Stock on the Reference Date less the fair market value (as determined in
good faith by the Board of Directors, whose determination shall be conclusive
and described in a Board Resolution), on the Reference Date, of the portion of
the evidences of indebtedness, shares of capital stock, cash and assets so
distributed applicable to one share of Common Stock, such increase to become
effective immediately prior to the opening of business on the day following the
Reference Date. In the event that such dividend or distribution is not so paid
or made, the Conversion Ratio shall again be adjusted to be the Conversion Ratio
which would then be in effect if such dividend or distribution had not occurred.
If the Board of Directors determines the fair market value of any distribution
for purposes of this Section 4.3(c) by reference to the actual or when issued
trading market for any securities comprising such distribution, it must in doing
so consider the prices in such market over the same period used in computing the
Current Market Price per share of Common Stock. For purposes of this Section
4.3(c), any dividend or distribution that includes shares of Common Stock or
rights or warrants to subscribe for or purchase shares of Common Stock shall be
deemed instead to be (1) a dividend or distribution of the evidences of
indebtedness, shares of capital stock, cash or assets other than such shares of
Common Stock or such rights or warrants (making any Conversion Ratio increase
required by this Section 4.3(c)) immediately followed by (2) a dividend or
distribution of such shares of Common Stock or such rights or warrants (making
any further Conversion Ratio increase required by Section 4.3(a) or 4.3 (b)),
except (A) the Reference Date of such dividend or distribution as defined in
this Section 4.3(c) shall be substituted as (a) "the record date in the case of
a dividend or other distribution," and (b) "the record date for the
determination of shareholders entitled to receive such rights or warrants," and
(c) "the date fixed for such determination" within the meaning of Sections
4.3(a) and 4.3(b), and (B) any shares of Common Stock included in such dividend
or distribution shall not be deemed outstanding for purposes of computing any
adjustment of the Conversion Ratio in Section 4.3(a).

         (d) In case the Company shall pay or make a dividend or other
distribution on its Common Stock exclusively in cash (excluding all cash
dividends paid out of the retained earnings of the Company), then the Conversion
Ratio shall be increased so that the same shall equal the ratio determined by
multiplying the Conversion Ratio in effect immediately prior to the
effectiveness of the Conversion Ratio increase contemplated by this Section
4.3(d) by a fraction of which the numerator shall be the Current Market Price
per share of the Common Stock, and of which the denominator shall be the Current
Market Price per share of Common Stock on the date fixed for the payment of such
distribution less the amount of cash so distributed and not excluded as provided
applicable to one share of Common Stock on the date fixed for the payment of
such distribution, such increase to become effective immediately prior to the
opening of business on the day following the date fixed for the payment of such
distribution; provided, however, that in the event the portion of the cash so
distributed applicable to one share of Common Stock is equal to or greater than
the Current Market Price per share of the Common Stock on the record date
mentioned

                                       25

<PAGE>   34

above, in lieu of the foregoing adjustment, adequate provision shall be made so
that each Debentureholder shall have the right to receive upon conversion the
amount of cash such Debentureholder would have received had such Debentureholder
converted each Debenture immediately prior to the record date for the
distribution of the cash. In the event that such dividend or distribution is not
so paid or made, the Conversion Ratio shall again be adjusted to be the
Conversion Ratio which would then be in effect if such record date had not been
fixed.

         (e) In case a tender or exchange offer (other than an odd-lot offer)
made by the Company or any subsidiary of the Company for all or any portion of
the Common Stock shall expire and such tender or exchange offer shall involve
the payment by the Company or such subsidiary of consideration per share of
Common Stock having a fair market value (as determined in good faith by the
Board of Directors, whose determination shall be conclusive and described in a
Board Resolution) at the last time (the "Expiration Time") tenders or exchanges
may be made pursuant to such tender or exchange offer (as it shall have been
amended) that exceeds 110% of the Current Market Price per share of Common Stock
on the Trading Day next succeeding the Expiration Time, then the Conversion
Ratio shall be increased so that the same shall equal the ratio determined by
multiplying the Conversion Ratio in effect immediately prior to the
effectiveness of the Conversion Ratio increase contemplated by this Section
4.3(e) by a fraction of which the numerator shall be the sum of (x) the fair
market value (determined as aforesaid) of the aggregate consideration payable to
shareholders based on the acceptance (up to any maximum specified in the terms
of the tender or exchange offer) of all shares validly tendered or exchanged and
not withdrawn as of the Expiration Time (the shares deemed so accepted, up to
any such maximum, being referred to as the "Purchased Shares"), and (y) the
product of the number of shares of Common Stock outstanding (less any Purchased
Shares) at the Expiration Time and the Current Market Price per share of Common
Stock on the Trading Day next succeeding the Expiration Time, and of which the
denominator shall be the number of shares of Common Stock outstanding (including
any tendered or exchanged shares) at the Expiration Time multiplied by the
Current Market Price per share of Common Stock on the Trading Day next
succeeding the Expiration Time, such increase to become effective immediately
prior to the opening of business on the day following the Expiration Time.

         (f) For the purpose of any computation under Sections 4.3(b), (c), (d)
or (e), the "Current Market Price" per share of Common Stock on any date in
question shall be deemed to be the average of the daily Closing Prices for the
five consecutive Trading Days selected by the Company commencing not more than
20 Trading Days before, and ending not later than the earlier of the day in
question or, if applicable, the day before the "ex" date with respect to the
issuance or distribution requiring such computation; provided, however, that if
another event occurs that would require an adjustment pursuant to Sections
4.3(a) through (e), inclusive, the Board of Directors may make such adjustments
to the Closing Prices during such five Trading Day period as it deems
appropriate to effectuate the intent of the adjustments in this Section 4.3, in
which case any such determination by the Board of Directors shall be set forth
in a Board Resolution and shall be conclusive. For purposes of this Section
4.3(f), the term "ex" date, (i) when used with respect to any issuance or
distribution, means the first date on which the Common Stock trades regular way
on The Nasdaq National Market(sm) or on such successor securities quotation

                                       26

<PAGE>   35

system as the Common Stock may be listed or in the relevant market from which
the Closing Prices were obtained without the right to receive such issuance or
distribution, and (ii) when used with respect to any tender or exchange offer,
means the first date on which the Common Stock trades regular way on such
securities exchange or in such market after the Expiration Time of such offer.

         (g) The Company may make such increases in the Conversion Ratio, in
addition to those required by Sections (a) through (e), as it considers to be
advisable to avoid or diminish any income tax to holders of Common Stock or
rights to purchase Common Stock resulting from any dividend or distribution of
stock (or rights to acquire stock) or from any event treated as such for income
tax purposes. The Company from time to time may increase the Conversion Ratio by
any amount for any period of time if the period is at least 20 days, the
increase is irrevocable during the period, and the Board of Directors shall have
made a determination that such increase would be in the best interest of the
Company, which determination shall be conclusive. Whenever the Conversion Ratio
is increased pursuant to the preceding sentence, the Company shall mail to
Debentureholders of record a notice of the increase at least fifteen days prior
to the date the increased Conversion Ratio takes effect, and such notice shall
state the increased Conversion Ratio and the period it shall be in effect.

         (h) No adjustment in the Conversion Ratio shall be required unless such
adjustment would require an increase or decrease of at least 1% in the
Conversion Ratio; provided, however, that any adjustments which by reason of
this Section 4.3(h) are not required to be made shall be carried forward and
taken into account in determining whether any subsequent adjustment shall be
required. The adjusted Conversion Ratio will be rounded to four decimal places.

         (i) If any action would require adjustment of the Conversion Ratio
pursuant to more than one of the provisions described above, only one adjustment
shall be made and such adjustment shall be the amount of adjustment that has the
highest absolute value to the Debentureholders.

SECTION 4.4       RECLASSIFICATION, CONSOLIDATION, MERGER OR SALE OF ASSETS.

         In the event that the Company shall be a party to any transaction,
including without limitation (a) any recapitalization or reclassification of the
Common Stock (other than a change in par value, or from par value to no par
value, or from no par value to par value, or as a result of a subdivision or
combination of the Common Stock), (b) any consolidation of the Company with, or
merger of the Company into any other Person, any merger of another Person into
the Company (other than a merger which does not result in a reclassification,
conversion, exchange or cancellation of outstanding shares of Common Stock of
the Company), (c) any sale, transfer or lease of all or substantially all of the
assets of the Company, or (d) any compulsory share exchange, in each case
pursuant to which the Common Stock is converted into the right to receive other
securities, cash or other property, then lawful provision shall be made as part
of the terms of such transaction whereby the holder of each Debenture then
outstanding shall have the right thereafter to convert each Debenture only into
the kind and amount of securities, cash or other property receivable

                                       27

<PAGE>   36

upon consummation of such transaction by a holder of the number of shares of
Common Stock of the Company into which such Debenture could have been converted
immediately prior to such transaction.

         The Company or the Person formed by such consolidation or resulting
from such merger or which acquired such assets or which acquires the shares of
the Company, as the case may be, shall make provision in its certificate or
articles of incorporation or other constituent document to establish such right.
Such certificate or articles of incorporation or other constituent document
shall provide for adjustments which, for events subsequent to the effective date
of such certificate or articles of incorporation or other constitution document,
shall be as nearly equivalent as may be practicable to the adjustments provided
for in this Article IV. The above provisions shall similarly apply to successive
transactions of the foregoing type.

SECTION 4.5       NOTICE OF ADJUSTMENTS OF CONVERSION RATIO.

         Whenever the Conversion Ratio is adjusted as herein provided:

         (a) The Company shall compute the adjusted Conversion Ratio and shall
prepare a certificate signed by the Chairman of the Board, President or a Vice
President of the Company and by its Treasurer or an Assistant Treasurer of the
Company setting forth the adjusted Conversion Ratio and showing in reasonable
detail the facts upon which such adjustment is based, and such certificate shall
forthwith be filed with the Trustee, the Conversion Agent and the transfer agent
for the Preferred Securities and the Debentures; and

         (b) a notice stating that the Conversion Ratio has been adjusted and
setting forth the adjusted Conversion Ratio shall as soon as practicable be
mailed by the Company to all record holders of Preferred Securities and the
Debentures at their last addresses as they appear upon the stock transfer books
of the Company and the Trust.

SECTION 4.6       PRIOR NOTICE OF CERTAIN EVENTS.

         In case:

         (a) the Company shall (i) declare any dividend (or any other
distribution) on its Common Stock, other than (A) a dividend payable in shares
of Common Stock, or (B) a dividend payable in cash that would not require an
adjustment pursuant to Section 4.3(c) or (d), or (ii) authorize a tender or
exchange offer that would require an adjustment pursuant to Section 4.3(e);

         (b) the Company shall authorize the granting to all holders of Common
Stock of rights or warrants to subscribe for or purchase any shares of stock of
any class or series or of any other rights or warrants;

                                       28

<PAGE>   37

         (c) of any reclassification of Common Stock (other than a subdivision
or combination of the outstanding Common Stock, or a change in par value, or
from par value to no par value, or from no par value to par value), or of any
consolidation or merger to which the Company is a party and for which approval
of any shareholders of the Company shall be required, or the sale or transfer of
all or substantially all of the assets of the Company or of any compulsory share
exchange whereby the Common Stock is converted into other securities, cash or
other property; or

         (d) of the voluntary or involuntary dissolution, liquidation or winding
up of the Company; then the Company shall (1) if any Preferred Securities are
outstanding, cause to be filed with the transfer agent for the Preferred
Securities, and shall cause to be mailed to the holders of record of the
Preferred Securities, at their last addresses as they shall appear upon the
securities register of the Trust, or (2) shall cause to be mailed to all
Debentureholders at their last addresses as they shall appear in the Debenture
Register, at least fifteen days prior to the applicable record or effective date
hereinafter specified, a notice stating (x) the date on which a record (if any)
is to be taken for the purpose of such dividend, distribution, rights or
warrants or, if a record is not to be taken, the date as of which the holders of
Common Stock of record to be entitled to such dividend, distribution, rights or
warrants are to be determined, or (y) the date on which such reclassification,
consolidation, merger, sale, transfer, share exchange, dissolution, liquidation
or winding up is expected to become effective, and the date as of which it is
expected that holders of Common Stock of record shall be entitled to exchange
their shares of Common Stock for securities, cash or other property deliverable
upon such reclassification, consolidation, merger, sale, transfer, share
exchange, dissolution, liquidation or winding up (but no failure to mail such
notice or any defect therein or in the mailing thereof shall affect the validity
of the corporate action required to be specified in such notice).

SECTION 4.7       CERTAIN DEFINED TERMS.

         The following definitions shall apply to terms used in this Article IV:

         (a) "Closing Prices" of any security on any day shall mean the last
reported sale price for such security, regular way, on such day or, if no sale
takes place on such day, the average of the reported closing bid and asked
prices on such day, regular way, of such security, in either case as reported on
the National Market System of the National Association of Securities Dealers,
Inc. or, if such security is not quoted or admitted to trading on such quotation
system, on the principal quotation system on which such security is listed or
admitted to trading or quoted, or, if not listed or admitted to trading or
quoted on any national securities exchange or quotation system, the average of
the closing bid and asked prices of such security in the over-the-counter market
on the day in question as reported by the National Quotation Bureau
Incorporated, or a similar generally accepted reporting service, or, if not so
available in such manner, as furnished by any Nasdaq member firm selected from
time to time by the Board of Directors for that purpose or, if not so available
in such manner, as otherwise determined in good faith by the Board of Directors.

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         (b) "Trading Day" shall mean a day on which securities are traded on
the national securities exchange or quotation system used to determine the
Closing Price.

SECTION 4.8       DIVIDEND OR INTEREST REINVESTMENT PLANS.

         Notwithstanding the foregoing provisions, the issuance of any shares of
Common Stock pursuant to any plan providing for the reinvestment of dividends or
interest payable on securities of the Company and the investment of additional
optional amounts in shares of Common Stock under any such plan, and the issuance
of any shares of Common Stock or options or rights to purchase such shares
pursuant to any employee benefit plan or program of the Company or pursuant to
any option, warrant, right or exercisable, exchangeable or convertible security
outstanding as of the date the Debentures were first issued, shall not be deemed
to constitute an issuance of Common Stock or exercisable, exchangeable or
convertible securities by the Company to which any of the adjustment provisions
described above shall apply. There also shall be no adjustment of the Conversion
Ratio in case of the issuance of any stock (or securities convertible into or
exchangeable for stock) of the Company except as specifically described in this
Article IV.

SECTION 4.9       CERTAIN ADDITIONAL RIGHTS.

         In case the Company shall, by dividend or otherwise, declare or make a
distribution on its Common Stock referred to in Section 4.3(c) or (d)
(including, without limitation, dividends or distributions referred to in the
last sentence of Section 4.3(c)), then the Debentureholders, upon the conversion
thereof subsequent to the close of business on the date fixed for the
determination of shareholders entitled to receive such distribution and prior to
the effectiveness of the Conversion Ratio adjustment in respect of such
distribution, also shall be entitled to receive for each share of Common Stock
into which the Debentures are converted, the portion of the shares of Common
Stock, rights, warrants, evidences of indebtedness, shares of capital stock,
cash and assets so distributed applicable to one share of Common Stock;
provided, however, that, at the election of the Company (whose election shall be
evidenced by a Board Resolution) with respect to all Debentureholders so
converting, the Company may, in lieu of distributing to such Debentureholder any
portion of such distribution not consisting of cash or securities of the
Company, pay such Debentureholder an amount in cash equal to the fair market
value thereof (as determined in good faith by the Board of Directors, whose
determination shall be conclusive and described in a Board Resolution). If any
conversion of Debentures described in the immediately preceding sentence occurs
prior to the payment date for a distribution to holders of Common Stock which
the Debentureholders so converted is entitled to receive in accordance with the
immediately preceding sentence, the Company may elect (such election to be
evidenced by a Board Resolution) to distribute to such Debentureholder a due
bill for the shares of Common Stock, rights, warrants, evidences of
indebtedness, shares of capital stock, cash or assets to which such
Debentureholder is so entitled, provided, that such due bill (i) meets any
applicable requirements of the principal national securities quotation system or
other market on which the Common Stock is then traded, and (ii) requires payment
or delivery of such shares of Common Stock, rights,

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<PAGE>   39

warrants, evidences of indebtedness, shares of capital stock, cash or assets no
later than the date of payment or delivery thereof to holders of shares of
Common Stock receiving such distribution.

SECTION 4.10      TRUSTEE NOT RESPONSIBLE FOR DETERMINING CONVERSION RATIO OR
                  ADJUSTMENTS.

         Neither the Trustee nor any Conversion Agent shall at any time be under
any duty or responsibility to any Debentureholder to determine whether any facts
exist which may require any adjustment of the Conversion Ratio, or with respect
to the nature or extent of any such adjustment when made, or with respect to the
method employed, or herein or in any supplemental indenture provided to be
employed, in making the same. Neither the Trustee nor any Conversion Agent shall
be accountable with respect to the validity or value (or the kind of account) of
any shares of Common Stock or of any securities or property, which may at any
time be issued or delivered upon the conversion of any Debenture; and neither
the Trustee nor any Conversion Agent makes any representation with respect
thereto. Neither the Trustee nor any Conversion Agent shall be responsible for
any failure of the Company to make any cash payment or to issue, transfer or
deliver any shares of Common Stock or stock certificates or other securities or
property upon the surrender of any Debenture for the purpose of conversion, or,
except as expressly herein provided, to comply with any of the covenants of the
Company contained in Article VI or this Article IV.

                                    ARTICLE V

                      EXTENSION OF INTEREST PAYMENT PERIOD

SECTION 5.1       EXTENSION OF INTEREST PAYMENT PERIOD.

         The Company shall have the right, at any time and from time to time
during the term of the Debentures so long as no Event of Default has occurred
and is continuing, to defer payments of interest by extending the interest
payment period of such Debentures for a period not exceeding 20 consecutive
quarters (the "Extended Interest Payment Period"), during which Extended
Interest Payment Period no interest shall be due and payable; provided that no
Extended Interest Payment Period may extend beyond the Maturity Date or end on a
date other than an Interest Payment Date. To the extent permitted by applicable
law, interest, the payment of which has been deferred because of the extension
of the interest payment period pursuant to this Section 5.1, shall bear interest
thereon at the Coupon Rate compounded quarterly for each quarter of the Extended
Interest Payment Period ("Compounded Interest"). At the end of the Extended
Interest Payment Period, the Company shall calculate (and deliver such
calculation to the Trustee) and pay all interest accrued and unpaid on the
Debentures, including any Additional Interest and Compounded Interest (together,
"Deferred Interest") that shall be payable to the holders of the Debentures in
whose names the Debentures are registered in the Debenture Register on the first
record date after the end of the Extended Interest Payment Period. Before the
termination of any Extended Interest Payment Period, the Company may further
extend such period so long as no Event of Default has occurred and is
continuing, provided that such period together with all such further extensions
thereof shall not exceed 20

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<PAGE>   40

consecutive quarters, or extend beyond the Maturity Date of the Debentures or
end on a date other than an Interest Payment Date. Upon the termination of any
Extended Interest Payment Period and upon the payment of all Deferred Interest
then due, the Company may commence a new Extended Interest Payment Period,
subject to the foregoing requirements. No interest shall be due and payable
during an Extended Interest Payment Period, except at the end thereof, but the
Company may prepay at any time all or any portion of the interest accrued during
an Extended Interest Payment Period.

SECTION 5.2       NOTICE OF EXTENSION.

         (a) If the Property Trustee is the only registered holder of the
Debentures at the time the Company selects an Extended Interest Payment Period,
the Company shall give written notice to the Administrative Trustees, the
Property Trustee and the Trustee of its selection of such Extended Interest
Payment Period two Business Days before the earlier of (i) the next succeeding
date on which Distributions on the Trust Securities issued by the Trust are
payable; or (ii) the date the Trust is required to give notice of the record
date, or the date such Distributions are payable, to The Nasdaq National
Market(sm) or other applicable self-regulatory organization or to holders of the
Preferred Securities issued by the Trust, but in any event at least one Business
Day before such record date.

         (b) If the Property Trustee is not the only holder of the Debentures at
the time the Company selects an Extended Interest Payment Period, the Company
shall give the holders of the Debentures and the Trustee written notice of its
selection of such Extended Interest Payment Period at least two Business Days
before the earlier of (i) the next succeeding Interest Payment Date; or (ii) the
date the Company is required to give notice of the record or payment date of
such interest payment to The Nasdaq National Market(sm) or other applicable
self-regulatory organization or to holders of the Debentures.

         (c) The quarter in which any notice is given pursuant to paragraphs (a)
or (b) of this Section 5.2 shall be counted as one of the 20 quarters permitted
in the maximum Extended Interest Payment Period permitted under Section 5.1.

SECTION 5.3       LIMITATION ON TRANSACTIONS.

         If (i) the Company shall exercise its right to defer payment of
interest as provided in Section 5.1, or (ii) there shall have occurred and be
continuing any Event of Default, then (a) the Company shall not declare or pay
any dividend on, make any distributions with respect to, or redeem, purchase,
acquire or make a liquidation payment with respect to, any of its capital stock
(other than (A) dividends or distributions in common stock of the Company, or
any declaration of a non-cash dividend in connection with the implementation of
a shareholder rights plan, or the issuance of stock under any such plan in the
future, or the redemption or repurchase of any such rights pursuant thereto, (B)
purchases of common stock of the Company related to the rights under any of the
Company's benefit plans for its directors, officers or employees, or (C) as a
result of a reclassification of its capital stock for another class of its
capital stock); (b) the Company shall not make any payment of interest,
principal or premium, if any, or repay, repurchase

                                       32

<PAGE>   41

or redeem any debt securities issued by the Company which rank pari passu with
or junior to the Debentures (including, without limitation, the Company's 8.50%
Junior Subordinated Debentures due 2028, issued to Southside Capital Trust I) or
make any guarantee payment with respect to any guarantee by the Company of the
debt securities of any subsidiary of the Company if such guarantee ranks pari
passu with or junior to the Debentures (including, without limitation, the
Company's 8.50% Junior Subordinated Debentures due 2028, issued to Southside
Capital Trust I); provided, however, that notwithstanding the foregoing the
Company may make payments pursuant to its obligations under the Preferred
Securities Guarantee; and (c) the Company shall not redeem, purchase or acquire
less than all of the outstanding Debentures or any of the Preferred Securities.

                                   ARTICLE VI

                       PARTICULAR COVENANTS OF THE COMPANY

SECTION 6.1       PAYMENT OF PRINCIPAL AND INTEREST.

         The Company shall duly and punctually pay or cause to be paid the
principal of and interest on the Debentures at the time and place and in the
manner provided herein. Each such payment of the principal of and interest on
the Debentures shall relate only to the Debentures, shall not be combined with
any other payment of the principal of or interest on any other obligation of the
Company, and shall be clearly and unmistakably identified as pertaining to the
Debentures.

SECTION 6.2       MAINTENANCE OF AGENCY.

         So long as any of the Debentures remain Outstanding, the Company shall
maintain, or shall cause to be maintained, an office or agency in the Borough of
Manhattan, The City of New York, and at such other location or locations as may
be designated as provided in this Section 6.2, where (i) Debentures may be
presented for payment; (ii) Debentures may be presented as hereinabove
authorized for registration of transfer, conversion or exchange; and (iii)
notices and demands to or upon the Company in respect of the Debentures and this
Indenture may be given or served, such designation to continue with respect to
such office or agency until the Company shall, by written notice signed by its
President or an Executive Vice President and delivered to the Trustee, designate
some other office or agency for such purposes or any of them. If at any time the
Company shall fail to maintain any such required office or agency or shall fail
to furnish the Trustee with the address thereof, such presentations, notices and
demands may be made or served at the Corporate Trust Office of the Trustee, and
the Company hereby appoints the Trustee as its agent to receive all such
presentations, notices and demands. In addition to any such office or agency,
the Company may from time to time designate one or more offices or agencies
outside of the Borough of Manhattan, The City of New York, where the Debentures
may be presented for registration or transfer and for exchange in the manner
provided herein, and the Company may from time to time rescind such designation
as the Company may deem desirable or expedient; provided, however, that no such

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<PAGE>   42

designation or rescission shall in any manner relieve the Company of its
obligation to maintain any such office or agency in the Borough of Manhattan,
The City of New York, for the purposes above mentioned. The Company shall give
the Trustee prompt written notice of any such designation or rescission thereof.

SECTION 6.3       PAYING AGENTS.

         (a) The Company shall be the initial paying agent. If the Company shall
appoint one or more paying agents for the Debentures, other than the Trustee,
the Company shall cause each such paying agent to execute and deliver to the
Trustee an instrument in which such agent shall agree with the Trustee, subject
to the provisions of this Section 6.3:

                  (i) that it shall hold all sums held by it as such agent for
the payment of the principal of or interest on the Debentures (whether such sums
have been paid to it by the Company or by any other obligor of such Debentures)
in trust for the benefit of the Persons entitled thereto;

                  (ii) that it shall give the Trustee notice of any failure by
the Company (or by any other obligor of such Debentures) to make any payment of
the principal of or interest on the Debentures when the same shall be due and
payable;

                  (iii) that it shall, at any time during the continuance of any
failure referred to in the preceding paragraph (a)(ii) above, upon the written
request of the Trustee, forthwith pay to the Trustee all sums so held in trust
by such paying agent; and

                  (iv) that it shall perform all other duties of paying agent as
set forth in this Indenture.

         (b) If the Company shall act as its own paying agent with respect to
the Debentures, it shall on or before each due date of the principal of or
interest on such Debentures, set aside, segregate and hold in trust for the
benefit of the Persons entitled thereto a sum sufficient to pay such principal
or interest so becoming due on Debentures until such sums shall be paid to such
Persons or otherwise disposed of as herein provided and shall promptly notify
the Trustee of such action, or any failure (by it or any other obligor on such
Debentures) to take such action. Whenever the Company shall have one or more
paying agents for the Debentures, it shall, prior to each due date of the
principal of or interest on any Debentures, deposit with the paying agent a sum
sufficient to pay the principal or interest so becoming due, such sum to be held
in trust for the benefit of the Persons entitled to such principal or interest,
and (unless such paying agent is the Trustee) the Company shall promptly notify
the Trustee of this action or failure so to act.

         (c) Notwithstanding anything in this Section 6.3 to the contrary, (i)
the agreement to hold sums in trust as provided in this Section 6.3 is subject
to the provisions of Section 14.3 and 14.4; and (ii) the Company may at any
time, for the purpose of obtaining the satisfaction and discharge of this
Indenture or for any other purpose, pay, or direct any paying agent to pay, to
the Trustee all sums held in trust by the Company or such paying agent, such
sums to be held by the Trustee upon the same terms and conditions

                                       34

<PAGE>   43

as those upon which such sums were held by the Company or such paying agent;
and, upon such payment by any paying agent to the Trustee, such paying agent
shall be released from all further liability with respect to such money.

SECTION 6.4       APPOINTMENT TO FILL VACANCY IN OFFICE OF TRUSTEE.

         The Company, whenever necessary to avoid or fill a vacancy in the
office of Trustee, shall appoint, in the manner provided in Section 10.11, a
Trustee, so that there shall at all times be a Trustee hereunder.

SECTION 6.5       COMPLIANCE WITH CONSOLIDATION PROVISIONS.

         The Company shall not, while any of the Debentures remain outstanding,
consolidate with, or merge into, or merge into itself, or sell or convey all or
substantially all of its property to any other company unless the provisions of
Article XIII hereof are complied with.

SECTION 6.6       LIMITATION ON TRANSACTIONS.

         If Debentures are issued to the Trust or a Trustee of the Trust in
connection with the issuance of Trust Securities by the Trust and (i) there
shall have occurred any event that would constitute an Event of Default; (ii)
the Company shall be in default with respect to any of its obligations under the
Preferred Securities Guarantee relating to the Trust; or (iii) the Company shall
have given notice of its election to defer payments of interest on such
Debentures by extending the interest payment period as provided in this
Indenture and such period, or any extension thereof, shall be continuing, then
(a) the Company shall not declare or pay any dividend on, make any distributions
with respect to, or redeem, purchase, acquire or make a liquidation payment with
respect to, any of its capital stock (other than (A) dividends or distributions
in common stock of the Company, or any declaration of a non-cash dividend in
connection with the implementation of a shareholder rights plan, or the issuance
of stock under any such plan in the future, or the redemption or repurchase of
any such rights pursuant thereto, (B) purchases of common stock of the Company
related to the rights under any of the Company's benefit plans for its
directors, officers or employees, or (C) as a result of a reclassification of
its capital stock); and (b) the Company shall not make any payment of interest,
principal or premium, if any, or repay, repurchase or redeem any debt securities
issued by the Company which rank pari passu with or junior to the Debentures or
make any guarantee payments with respect to any guarantee by the Company of the
debt securities of any subsidiary of the Company if such guarantee ranks pari
passu with or junior in interest to the Debentures; provided, however, that the
Company may make payments pursuant to its obligations under the Preferred
Securities Guarantee; and (c) the Company shall not redeem, purchase or acquire
less than all of the outstanding Debentures or any of the Preferred Securities.

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<PAGE>   44

SECTION 6.7       COVENANTS AS TO THE TRUST.

         For so long as such Trust Securities of the Trust remain outstanding,
the Company shall (i) maintain 100% direct or indirect ownership of the Common
Securities of the Trust; provided, however, that any permitted successor of the
Company under this Indenture may succeed to the Company's ownership of the
Common Securities; (ii) not voluntarily terminate, wind up or liquidate the
Trust, except upon prior approval of the Federal Reserve if then so required
under applicable capital guidelines, policies or regulations of the Federal
Reserve and use its reasonable efforts to cause the Trust (a) to remain a
business trust (and to avoid involuntary termination, winding up or
liquidation), except in connection with a distribution of Debentures, the
redemption of all of the Trust Securities of the Trust or certain mergers,
consolidations or amalgamations, each as permitted by the Trust Agreement; and
(b) to otherwise continue not to be treated as an association taxable as a
corporation or partnership for United States federal income tax purposes; (iii)
use its reasonable efforts to cause each holder of Trust Securities to be
treated as owning an individual beneficial interest in the Debentures; and (iv)
the Company, and any successor to the Company, shall use best efforts to
maintain the eligibility of the Preferred Securities for quotation or listing on
any national securities exchange or other organization on which the Preferred
Securities are then quoted or listed (including, if applicable, the Nasdaq
National Market) and shall use best efforts to keep the Preferred Securities so
quoted or listed for so long as the Preferred Securities remain outstanding. In
connection with the distribution of the Debentures to the holders of the
Preferred Securities issued by the Trust upon a Dissolution Event, the Company
shall use its best efforts to list such Debentures on The Nasdaq National
Market(sm) or on such other exchange as the Preferred Securities are then
listed. For so long as the Debentures remain outstanding the Company shall
fulfill all reporting and filing obligations under the Securities Exchange Act
of 1934, as amended, as applicable to companies having a class of securities
registered under Section 12(b) or 12(g) thereunder.

SECTION 6.8       COVENANTS AS TO PURCHASES.

         Except upon the exercise by the Company of its right to redeem the
Debentures pursuant to Section 3.2 upon the occurrence and continuation of a
Special Event or pursuant to Section 3.3(b), prior to December 31, 2003, the
Company shall not purchase any Debentures, in whole or in part, from the Trust.

SECTION 6.9       WAIVER OF USURY, STAY OR EXTENSION LAWS.

         The Company shall not at any time insist upon, or plead, or in any
manner whatsoever claim or take the benefit or advantage of, any usury, stay or
extension law wherever enacted, now or at any time hereafter in force, which may
affect the covenants or the performances of this Indenture, and the Company (to
the extent that it may lawfully do so) hereby expressly waives all benefit or
advantage of any such law, and covenants that it will not hinder, delay or
impede the execution of any power herein granted to the Trustee, but will suffer
and permit the execution of every such power as though no such law had been
enacted.

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<PAGE>   45

                                   ARTICLE VII

                       DEBENTUREHOLDERS' LISTS AND REPORTS
                         BY THE COMPANY AND THE TRUSTEE

SECTION 7.1       COMPANY TO FURNISH TRUSTEE NAMES AND ADDRESSES OF
                  DEBENTUREHOLDERS.

         The Company shall furnish or cause to be furnished to the Trustee (a)
on a quarterly basis on each regular record date (as described in Section 2.5) a
list, in such form as the Trustee may reasonably require, of the names and
addresses of the holders of the Debentures as of such regular record date,
provided that the Company shall not be obligated to furnish or cause to furnish
such list at any time that the list shall not differ in any respect from the
most recent list furnished to the Trustee by the Company (in the event the
Company fails to provide such list on a quarterly basis, the Trustee shall be
entitled to rely on the most recent list provided by the Company); and (b) at
such other times as the Trustee may request in writing within 30 days after the
receipt by the Company of any such request, a list of similar form and content
as of a date not more than 15 days prior to the time such list is furnished;
provided, however, that, in either case, no such list need be furnished if the
Trustee shall be the Debenture Registrar.

SECTION 7.2       PRESERVATION OF INFORMATION COMMUNICATIONS WITH
                  DEBENTUREHOLDERS.

         (a) The Trustee shall preserve, in as current a form as is reasonably
practicable, all information as to the names and addresses of the holders of
Debentures contained in the most recent list furnished to it as provided in
Section 7.1 and as to the names and addresses of holders of Debentures received
by the Trustee in its capacity as registrar for the Debentures (if acting in
such capacity).

         (b) The Trustee may destroy any list furnished to it as provided in
Section 7.1 upon receipt of a new list so furnished.

         (c) Debentureholders may communicate as provided in Section 312(b) of
the Trust Indenture Act with other Debentureholders with respect to their rights
under this Indenture or under the Debentures.

SECTION 7.3       REPORTS BY THE COMPANY.

         (a) The Company covenants and agrees to file with the Trustee, within
15 days after the Company is required to file the same with the Commission,
copies of the annual reports and of the information, documents and other reports
(or copies of such portions of any of the foregoing as the Commission may from
time to time by rules and regulations prescribe) that the Company may be
required to file with the Commission pursuant to Section 13 or Section 15(d) of
the Exchange Act; or, if the Company is not required to file information,
documents or reports pursuant to either of such sections, then

                                       37

<PAGE>   46

to file with the Trustee and the Commission, in accordance with the rules and
regulations prescribed from time to time by the Commission, such of the
supplementary and periodic information, documents and reports that may be
required pursuant to Section 13 of the Exchange Act in respect of a security
listed and registered on a national securities exchange as may be prescribed
from time to time in such rules and regulations.

         (b) The Company covenants and agrees to file with the Trustee and the
Commission, in accordance with the rules and regulations prescribed from time to
time by the Commission, such additional information, documents and reports with
respect to compliance by the Company with the conditions and covenants provided
for in this Indenture as may be required from time to time by such rules and
regulations.

         (c) The Company covenants and agrees to transmit by mail, first class
postage prepaid, or reputable overnight delivery service that provides for
evidence of receipt, to the Debentureholders, as their names and addresses
appear upon the Debenture Register, within 30 days after the filing thereof with
the Trustee, such summaries of any information, documents and reports required
to be filed by the Company pursuant to subsections (a) and (b) of this Section
7.3 as may be required by rules and regulations prescribed from time to time by
the Commission.

SECTION 7.4       REPORTS BY THE TRUSTEE.

         (a) On or before July 31 in each year in which any of the Debentures
are Outstanding, the Trustee shall transmit by mail, first class postage
prepaid, to the Debentureholders, as their names and addresses appear upon the
Debenture Register, a brief report dated as of the preceding June 30, if and to
the extent required under Section 313(a) of the Trust Indenture Act.

         (b) The Trustee shall comply with Section 313(b) and 313(c) of the
Trust Indenture Act.

         (c) A copy of each such report shall, at the time of such transmission
to Debentureholders, be filed by the Trustee with the Company, with each stock
exchange upon which any Debentures are listed (if so listed) and also with the
Commission. The Company agrees to notify the Trustee when any Debentures become
listed on any stock exchange.

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<PAGE>   47

                                  ARTICLE VIII

                  REMEDIES OF THE TRUSTEE AND DEBENTUREHOLDERS
                               ON EVENT OF DEFAULT

SECTION 8.1       EVENTS OF DEFAULT.

         (a) Whenever used herein with respect to the Debentures, "Event of
Default" means any one or more of the following events that has occurred and is
continuing:

                  (i) the Company defaults in the payment of any installment of
interest upon any of the Debentures, as and when the same shall become due and
payable, and continuance of such default for a period of 30 days; provided,
however, that a valid extension of an interest payment period by the Company in
accordance with the terms of this Indenture shall not constitute a default in
the payment of interest for this purpose;

                  (ii) the Company defaults in the payment of the principal on
the Debentures as and when the same shall become due and payable whether at
maturity, upon redemption, by declaration or otherwise;

                  (iii) the Company fails to observe or perform any other of its
covenants or agreements with respect to the Debentures for a period of 90 days
after the date on which written notice of such failure, requiring the same to be
remedied and stating that such notice is a "Notice of Default" hereunder, shall
have been given to the Company by the Trustee, by registered or certified mail,
or to the Company and the Trustee by the holders of at least 25% in principal
amount of the Debentures at the time Outstanding;

                  (iv) the Company pursuant to or within the meaning of any
Bankruptcy Law (i) commences a voluntary case; (ii) consents to the entry of an
order for relief against it in an involuntary case; (iii) consents to the
appointment of a Custodian of it or for all or substantially all of its
property; or (iv) makes a general assignment for the benefit of its creditors;

                  (v) a court of competent jurisdiction enters an order under
any Bankruptcy Law that (i) is for relief against the Company in an involuntary
case; (ii) appoints a Custodian of the Company for all or substantially all of
its property; or (iii) orders the liquidation of the Company, and the order or
decree remains unstayed and in effect for 90 days; or

                  (vi) the Trust shall have voluntarily or involuntarily
dissolved, wound-up its business or otherwise terminated its existence except in
connection with (i) the distribution of Debentures to holders of Trust
Securities in liquidation of their interests in the Trust; (ii) the redemption
of all of the outstanding Trust Securities of the Trust; or (iii) certain
mergers, consolidations or amalgamations, each as permitted by the Trust
Agreement.

                                       39

<PAGE>   48

         (b) In each and every such case referred to in paragraph (i) through
(vi) of this Section 8.1(a), unless the principal of all the Debentures shall
have already become due and payable, either the Trustee or the holders of not
less than 25% in aggregate principal amount of the Debentures then Outstanding
hereunder, by notice in writing to the Company (and to the Trustee if given by
such Debentureholders) may declare the principal of all the Debentures to be due
and payable immediately, and upon any such declaration the same shall become and
shall be immediately due and payable, notwithstanding anything contained in this
Indenture or in the Debentures.

         (c) At any time after the principal of the Debentures shall have been
so declared due and payable, and before any judgment or decree for the payment
of the moneys due shall have been obtained or entered as hereinafter provided,
the holders of a majority in aggregate principal amount of the Debentures then
Outstanding hereunder, by written notice to the Company and the Trustee, may
rescind and annul such declaration and its consequences if: (i) the Company has
paid or deposited with the Trustee a sum sufficient to pay all matured
installments of interest upon all the Debentures and the principal of any and
all Debentures that shall have become due otherwise than by acceleration (with
interest upon such principal, and, to the extent that such payment is
enforceable under applicable law, upon overdue installments of interest, at the
rate per annum expressed in the Debentures to the date of such payment or
deposit) and the amount payable to the Trustee under Section 10.7; and (ii) any
and all Events of Default under this Indenture, other than the nonpayment of
principal on Debentures that shall not have become due by their terms, shall
have been remedied or waived as provided in Section 8.6. No such rescission and
annulment shall extend to or shall affect any subsequent default or impair any
right consequent thereon.

         (d) In case the Trustee shall have proceeded to enforce any right with
respect to Debentures under this Indenture and such proceedings shall have been
discontinued or abandoned because of such rescission or annulment or for any
other reason or shall have been determined adversely to the Trustee, then and in
every such case the Company and the Trustee shall be restored respectively to
their former positions and rights hereunder, and all rights, remedies and powers
of the Company and the Trustee shall continue as though no such proceedings had
been taken.

SECTION 8.2       COLLECTION OF INDEBTEDNESS AND SUITS FOR ENFORCEMENT BY
                  TRUSTEE.

         (a) The Company covenants that (1) in case it shall default in the
payment of any installment of interest on any of the Debentures, and such
default shall have continued for a period of 30 days; or (2) in case it shall
default in the payment of the principal of any of the Debentures when the same
shall have become due and payable, whether upon maturity of the Debentures or
upon redemption or upon declaration or otherwise, then, upon demand of the
Trustee, the Company shall pay to the Trustee, for the benefit of the holders of
the Debentures, the whole amount that then shall have become due and payable on
all such Debentures for principal or interest, or both, as the case may be, with
interest upon the overdue principal and (to the extent that payment of such
interest is enforceable under applicable law and, if the Debentures are held by
the Trust or a trustee of the Trust, without duplication of any other amounts
paid

                                       40

<PAGE>   49

by the Trust or trustee in respect thereof) upon overdue installments of
interest at the rate per annum expressed in the Debentures; and, in addition
thereto, such further amount as shall be sufficient to cover the costs and
expenses of collection, and the amount payable to the Trustee under Section
10.7.

         (b) If the Company shall fail to pay such amounts set forth in Section
8.2(a) forthwith upon such demand, the Trustee, in its own name and as trustee
of an express trust, shall be entitled and empowered to institute any action or
proceedings at law or in equity for the collection of the sums so due and
unpaid, and may prosecute any such action or proceeding to judgment or final
decree, and may enforce any such judgment or final decree against the Company or
other obligor upon the Debentures and collect the moneys adjudged or decreed to
be payable in the manner provided by law out of the property of the Company or
other obligor upon the Debentures, wherever situated.

         (c) In case of any receivership, insolvency, liquidation, bankruptcy,
reorganization, readjustment, arrangement, composition or judicial proceedings
affecting the Company, the Trust, or the creditors or property of either, the
Trustee shall have power to intervene in such proceedings and take any action
therein that may be permitted by the court and shall (except as may be otherwise
provided by law) be entitled to file such proofs of claim and other papers and
documents as may be necessary or advisable in order to have the claims of the
Trustee and of the holders of the Debentures allowed for the entire amount due
and payable by the Company under this Indenture at the date of institution of
such proceedings and for any additional amount that may become due and payable
by the Company after such date, and to collect and receive any moneys or other
property payable or deliverable on any such claim, and to distribute the same
after the deduction of the amount payable to the Trustee under Section 10.7; and
any receiver, assignee or trustee in bankruptcy or reorganization is hereby
authorized by each of the holders of the Debentures to make such payments to the
Trustee, and, in the event that the Trustee shall consent to the making of such
payments directly to such Debentureholders, to pay to the Trustee any amount due
it under Section 10.7.

         (d) All rights of action and of asserting claims under this Indenture,
or under any of the terms established with respect to the Debentures, may be
enforced by the Trustee without the possession of any of such Debentures, or the
production thereof at any trial or other proceeding relative thereto, and any
such suit or proceeding instituted by the Trustee shall be brought in its own
name as trustee of an express trust, and any recovery of judgment shall, after
provision for payment to the Trustee of any amounts due under Section 10.7, be
for the ratable benefit of the holders of the Debentures. In case of an Event of
Default hereunder, the Trustee may in its discretion proceed to protect and
enforce the rights vested in it by this Indenture by such appropriate judicial
proceedings as the Trustee shall deem most effectual to protect and enforce any
of such rights, either at law or in equity or in bankruptcy or otherwise,
whether for the specific enforcement of any covenant or agreement contained in
this Indenture or in aid of the exercise of any power granted in this Indenture,
or to enforce any other legal or equitable right vested in the Trustee by this
Indenture or by law. Nothing contained herein shall be deemed to authorize the
Trustee to authorize or consent to or accept or adopt on behalf of any
Debentureholder any plan of reorganization, arrangement,

                                       41

<PAGE>   50

adjustment or composition affecting the Debentures or the rights of any holder
thereof or to authorize the Trustee to vote in respect of the claim of any
Debentureholder in any such proceeding.

SECTION 8.3       APPLICATION OF MONEYS COLLECTED.

         Any moneys or other assets collected by the Trustee pursuant to this
Article VIII with respect to the Debentures shall be applied in the following
order, at the date or dates fixed by the Trustee and, in case of the
distribution of such moneys or other assets on account of principal or interest,
upon presentation of the Debentures, and notation thereon the payment, if only
partially paid, and upon surrender thereof if fully paid:

         FIRST: To the payment of costs and expenses of collection and of all
         amounts payable to the Trustee under Section 10.7;

         SECOND: To the payment of all Senior Indebtedness of the Company if and
         to the extent required by Article XVII; and

         THIRD: To the payment of the amounts then due and unpaid upon the
         Debentures for principal and interest, in respect of which or for the
         benefit of which such money has been collected, ratably, without
         preference or priority of any kind, according to the amounts due and
         payable on such Debentures for principal and interest, respectively.

SECTION 8.4       LIMITATION ON SUITS.

         (a) Except as set forth in this Indenture, no holder of any Debenture
shall have any right by virtue or by availing of any provision of this Indenture
to institute any suit, action or proceeding in equity or at law upon or under or
with respect to this Indenture or for the appointment of a receiver or trustee,
or for any other remedy hereunder, unless (i) such holder previously shall have
given to the Trustee written notice of an Event of Default and of the
continuance thereof with respect to the Debentures specifying such Event of
Default, as hereinbefore provided; (ii) the holders of not less than 25% in
aggregate principal amount of the Debentures then Outstanding shall have made
written request upon the Trustee to institute such action, suit or proceeding in
its own name as trustee hereunder; (iii) such holder or holders shall have
offered to the Trustee such reasonable indemnity as it may require against the
costs, expenses and liabilities to be incurred therein or thereby; (iv) the
Trustee for 60 days after its receipt of such notice, request and offer of
indemnity, shall have failed to institute any such action, suit or proceeding;
and (v) during such 60 day period, the holders of a majority in principal amount
of the Debentures do not give the Trustee a direction inconsistent with the
request.

         (b) Notwithstanding anything contained herein to the contrary or any
other provisions of this Indenture, the right of any holder of the Debentures to
receive payment of the principal of and interest on the Debentures, as therein
provided, on or after the respective due dates expressed in such Debenture (or

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<PAGE>   51

in the case of redemption, on the redemption date), or to institute suit for the
enforcement of any such payment on or after such respective dates or redemption
date, shall not be impaired or affected without the consent of such holder and
by accepting a Debenture hereunder it is expressly understood, intended and
covenanted by the taker and holder of every Debenture with every other such
taker and holder and the Trustee, that no one or more holders of Debentures
shall have any right in any manner whatsoever by virtue or by availing of any
provision of this Indenture to affect, disturb or prejudice the rights of the
holders of any other of such Debentures, or to obtain or seek to obtain priority
over or preference to any other such holder, or to enforce any right under this
Indenture, except in the manner herein provided and for the equal, ratable and
common benefit of all holders of Debentures. For the protection and enforcement
of the provisions of this Section 8.4, each and every Debentureholder and the
Trustee shall be entitled to such relief as can be given either at law or in
equity.

SECTION 8.5       RIGHTS AND REMEDIES CUMULATIVE; DELAY OR OMISSION NOT WAIVER.

         (a) Except as otherwise provided in Section 2.9(b), all powers and
remedies given by this Article VIII to the Trustee or to the Debentureholders
shall, to the extent permitted by law, be deemed cumulative and not exclusive of
any other powers and remedies available to the Trustee or the holders of the
Debentures, by judicial proceedings or otherwise, to enforce the performance or
observance of the covenants and agreements contained in this Indenture or
otherwise established with respect to such Debentures.

         (b) No delay or omission of the Trustee or of any holder of any of the
Debentures to exercise any right or power accruing upon any Event of Default
occurring and continuing as aforesaid shall impair any such right or power, or
shall be construed to be a waiver of any such default or on acquiescence
therein; and, subject to the provisions of Section 8.4, every power and remedy
given by this Article VIII or by law to the Trustee or the Debentureholders may
be exercised from time to time, and as often as shall be deemed expedient, by
the Trustee or by the Debentureholders.

SECTION 8.6       CONTROL BY DEBENTUREHOLDERS.

         The holders of a majority in aggregate principal amount of the
Debentures at the time Outstanding, determined in accordance with Section 11.4,
shall have the right to direct the time, method and place of conducting any
proceeding for any remedy available to the Trustee, or exercising any trust or
power conferred on the Trustee; provided, however, that such direction shall not
be in conflict with any rule of law or with this Indenture. Subject to the
provisions of Section 10.1, the Trustee shall have the right to decline to
follow any such direction if the Trustee in good faith shall, by a Responsible
Officer or Officers of the Trustee, determine that the proceeding so directed
would involve the Trustee in personal liability. The holders of a majority in
aggregate principal amount of the Debentures at the time Outstanding affected
thereby, determined in accordance with Section 11.4, may on behalf of the
holders of all of the Debentures waive any past default in the performance of
any of the covenants contained herein and its consequences, except (i) a default
in the payment of the principal of, or interest on, any of the Debentures as and
when

                                       43

<PAGE>   52

the same shall become due by the terms of such Debentures otherwise than by
acceleration (unless such default has been cured and a sum sufficient to pay all
matured installments of interest and principal has been deposited with the
Trustee (in accordance with Section 8.1(c)); (ii) a default in the covenants
contained in Section 6.7; or (iii) in respect of a covenant or provision hereof
which cannot be modified or amended without the consent of the holder of each
Outstanding Debenture affected; provided, however, that if the Debentures are
held by the Trust or a trustee of the Trust, such waiver or modification to such
waiver shall not be effective until the holders of a majority in liquidation
preference of Trust Securities of the Trust shall have consented to such waiver
or modification to such waiver; provided further, that if the consent of the
holder of each Outstanding Debenture is required, such waiver shall not be
effective until each holder of the Trust Securities of the Trust shall have
consented to such waiver. Upon any such waiver, the default covered thereby
shall be deemed to be cured for all purposes of this Indenture and the Company,
the Trustee and the holders of the Debentures shall be restored to their former
positions and rights hereunder, respectively; but no such waiver shall extend to
any subsequent or other default or impair any right consequent thereon.

SECTION 8.7       UNDERTAKING TO PAY COSTS.

         All parties to this Indenture agree, and each holder of any Debentures
by such holder's acceptance thereof shall be deemed to have agreed, that any
court may in its discretion require, in any suit for the enforcement of any
right or remedy under this Indenture, or in any suit against the Trustee for any
action taken or omitted by it as Trustee, the filing by any party litigant in
such suit of an undertaking to pay the costs of such suit, and that such court
may in its discretion assess reasonable costs, including reasonable attorneys'
fees, against any party litigant in such suit, having due regard to the merits
and good faith of the claims or defenses made by such party litigant; but the
provisions of this Section 8.7 shall not apply to any suit instituted by the
Trustee, to any suit instituted by any Debentureholder, or group of
Debentureholders holding more than 10% in aggregate principal amount of the
Outstanding Debentures, or to any suit instituted by any Debentureholder for the
enforcement of the payment of the principal of or interest on the Debentures, on
or after the respective due dates expressed in such Debenture or established
pursuant to this Indenture.

SECTION 8.8       DIRECT ACTION; RIGHT OF SET-OFF

         In the event that an Event of Default has occurred and is continuing
and such event is attributable to the failure of the Company to pay interest on
or principal of the Debentures on an Interest Payment Date or Maturity Date, as
applicable, then a holder of Preferred Securities may institute a legal
proceeding directly against the Company for enforcement of payment to such
holder of the principal of or interest on such Debentures having a principal
amount equal to the aggregate Liquidation Amount of the Preferred Securities of
such holders (a "Direct Action"). In connection with such Direct Action, the
Company will have a right of set-off under this Indenture to the extent of any
payment actually made by the Company to such holder of the Preferred Securities
with respect to such Direct Action.

                                       44

<PAGE>   53

                                   ARTICLE IX

                      FORM OF DEBENTURE AND ORIGINAL ISSUE

SECTION 9.1       FORM OF DEBENTURE.

         The Debenture and the Trustee's Certificate of Authentication to be
endorsed thereon are to be substantially in the forms contained as Exhibit A to
this Indenture, attached hereto and incorporated herein by reference.

SECTION 9.2       ORIGINAL ISSUE OF DEBENTURES.

         Debentures in the aggregate principal amount of $15,463,920 may, upon
execution of this Indenture, be executed by the Company and delivered to the
Trustee for authentication. If the Underwriters exercise their Option and there
is an Option Closing Date (as such terms are defined in the Underwriting
Agreement, dated November ___, 2000, by and among the Company, the Trust, and
Stifel, Nicolaus & Company, Incorporated, as Representative of the Underwriters)
then, on such Option Closing Date, Debentures in the additional aggregate
principal amount of up to $2,319,590 may be executed by the Company and
delivered to the Trustee for authentication. The Trustee shall thereupon
authenticate and deliver said Debentures to or upon the written order of the
Company, signed by its President, or any Vice President and its Chief Financial
Officer or the Treasurer or an Assistant Treasurer, without any further action
by the Company.

                                    ARTICLE X

                             CONCERNING THE TRUSTEE

SECTION 10.1      CERTAIN DUTIES AND RESPONSIBILITIES OF THE TRUSTEE.

         (a) The Trustee, prior to the occurrence of an Event of Default and
after the curing of all Events of Default that may have occurred, shall
undertake to perform with respect to the Debentures such duties and only such
duties as are specifically set forth in this Indenture, and no implied covenants
shall be read into this Indenture against the Trustee. In case an Event of
Default has occurred that has not been cured or waived, the Trustee shall
exercise such of the rights and powers vested in it by this Indenture, and use
the same degree of care and skill in its exercise, as a prudent person would
exercise or use under the circumstances in the conduct of his or her own
affairs.

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<PAGE>   54

         (b) No provision of this Indenture shall be construed to relieve the
Trustee from liability for its own negligent action, its own negligent failure
to act, or its own willful misconduct, except that:

                  (i) prior to the occurrence of an Event of Default and after
the curing or waiving of all such Events of Default that may have occurred:

                           (1) the duties and obligations of the Trustee shall
         with respect to the Debentures be determined solely by the express
         provisions of this Indenture, and the Trustee shall not be liable with
         respect to the Debentures except for the performance of such duties and
         obligations as are specifically set forth in this Indenture, and no
         implied covenants or obligations shall be read into this Indenture
         against the Trustee; and

                           (2) in the absence of bad faith on the part of the
         Trustee, the Trustee may with respect to the Debentures conclusively
         rely, as to the truth of the statements and the correctness of the
         opinions expressed therein, upon any certificates or opinions furnished
         to the Trustee and conforming to the requirements of this Indenture;
         but in the case of any such certificates or opinions that by any
         provision hereof are specifically required to be furnished to the
         Trustee, the Trustee shall be under a duty to examine the same to
         determine whether or not they conform to the requirements of this
         Indenture;

                  (ii) the Trustee shall not be liable for any error of judgment
made in good faith by a Responsible Officer or Responsible Officers of the
Trustee, unless it shall be proved that the Trustee was negligent in
ascertaining the pertinent facts;

                  (iii) the Trustee shall not be liable with respect to any
action taken or omitted to be taken by it in good faith in accordance with the
direction of the holders of not less than a majority in principal amount of the
Debentures at the time Outstanding relating to the time, method and place of
conducting any proceeding for any remedy available to the Trustee, or exercising
any trust or power conferred upon the Trustee under this Indenture with respect
to the Debentures; and

                  (iv) none of the provisions contained in this Indenture shall
require the Trustee to expend or risk its own funds or otherwise incur personal
financial liability in the performance of any of its duties or in the exercise
of any of its rights or powers, if there is reasonable ground for believing that
the repayment of such funds or liability is not reasonably assured to it under
the terms of this Indenture or adequate indemnity against such risk is not
reasonably assured to it.

SECTION 10.2      NOTICE OF DEFAULTS.

         Within 90 days after actual knowledge by a Responsible Officer of the
Trustee of the occurrence of any default hereunder with respect to the
Debentures, the Trustee shall transmit by mail to all holders of the Debentures,
as their names and addresses appear in the Debenture Register, notice of such
default,

                                       46

<PAGE>   55

unless such default shall have been cured or waived; provided, however, that,
except in the case default in the payment of the principal or interest
(including any Additional Interest) on any Debenture, the Trustee shall be
protected in withholding such notice if and so long as the board of directors,
the executive committee or a trust committee of the directors and/or Responsible
Officers of the Trustee determines in good faith that the withholding of such
notice is in the interests of the holders of such Debentures; and provided,
further, that in the case of any default of the character specified in Section
8.1(a)(3), no such notice to holders of Debentures need be sent until at least
30 days after the occurrence thereof. For the purposes of this Section 10.2, the
term "default" means any event which is, or after notice or lapse of time or
both, would become, an Event of Default with respect to the Debentures.

SECTION 10.3      CERTAIN RIGHTS OF TRUSTEE.

         Except as otherwise provided in Section 10.1:

         (a) The Trustee may rely and shall be protected in acting or refraining
from acting upon any resolution, certificate, statement, instrument, opinion,
report, notice, request, consent, order, approval, bond, security or other paper
or document believed by it to be genuine and to have been signed or presented by
the proper party or parties;

         (b) Any request, direction, order or demand of the Company mentioned
herein shall be sufficiently evidenced by a Board Resolution or an instrument
signed in the name of the Company by its President or any Vice President and by
the Secretary or an Assistant Secretary or the Treasurer or an Assistant
Treasurer thereof (unless other evidence in respect thereof is specifically
prescribed herein);

         (c) The Trustee shall not be deemed to have knowledge of a default or
an Event of Default, other than an Event of Default specified in Section
8.1(a)(i); or (ii), unless and until it receives written notification of such
Event of Default from the Company or by holders of at least 25% of the aggregate
principal amount of the Debentures at the time Outstanding;

         (d) The Trustee may consult with counsel and the written advice of such
counsel or any Opinion of Counsel shall be full and complete authorization and
protection in respect of any action taken or suffered or omitted hereunder in
good faith and in reliance thereon;

         (e) The Trustee shall be under no obligation to exercise any of the
rights or powers vested in it by this Indenture at the request, order or
direction of any of the Debentureholders, pursuant to the provisions of this
Indenture, unless such Debentureholders shall have offered to the Trustee
reasonable security or indemnity against the costs, expenses and liabilities
that may be incurred therein or thereby; nothing contained herein shall,
however, relieve the Trustee of the obligation, upon the occurrence of an Event
of Default (that has not been cured or waived) to exercise with respect to the
Debentures such of the rights and powers vested in it by this Indenture, and to
use the same degree of care and skill in its

                                       47

<PAGE>   56

exercise, as a prudent person would exercise or use under the circumstances in
the conduct of his or her own affairs;

         (f) The Trustee shall not be liable for any action taken or omitted to
be taken by it in good faith and believed by it to be authorized or within the
discretion or rights or powers conferred upon it by this Indenture;

         (g) The Trustee shall not be bound to make any investigation into the
facts or matters stated in any resolution, certificate, statement, instrument,
opinion, report, notice, request, consent, order, approval, bond, security, or
other papers or documents, unless requested in writing so to do by the holders
of not less than a majority in principal amount of the Outstanding Debentures
(determined as provided in Section 11.4); provided, however, that if the payment
within a reasonable time to the Trustee of the costs, expenses or liabilities
likely to be incurred by it in the making of such investigation is, in the
opinion of the Trustee, not reasonably assured to the Trustee by the security
afforded to it by the terms of this Indenture, the Trustee may require
reasonable indemnity against such costs, expenses or liabilities as a condition
to so proceeding. The reasonable expense of every such examination shall be paid
by the Company or, if paid by the Trustee, shall be repaid by the Company upon
demand; and

         (h) The Trustee may execute any of the trusts or powers hereunder or
perform any duties hereunder either directly or by or through agents or
attorneys and the Trustee shall not be responsible for any misconduct or
negligence on the part of any agent or attorney appointed with due care by it
hereunder.

SECTION 10.4      TRUSTEE NOT RESPONSIBLE FOR RECITALS, ETC.

         (a) The Recitals contained herein and in the Debentures shall be taken
as the statements of the Company, and the Trustee assumes no responsibility for
the correctness of the same.

         (b) The Trustee makes no representations as to the validity or
sufficiency of this Indenture or of the Debentures.

         (c) The Trustee shall not be accountable for the use or application by
the Company of any of the Debentures or of the proceeds of such Debentures, or
for the use or application of any moneys paid over by the Trustee in accordance
with any provision of this Indenture, or for the use or application of any
moneys received by any paying agent other than the Trustee.

SECTION 10.5      MAY HOLD DEBENTURES.

         The Trustee or any paying agent or registrar for the Debentures, in its
individual or any other capacity, may become the owner or pledgee of Debentures
with the same rights it would have if it were not Trustee, paying agent or
Debenture Registrar.

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<PAGE>   57

SECTION 10.6      MONEYS HELD IN TRUST.

         Subject to the provisions of Section 14.5, all moneys received by the
Trustee shall, until used or applied as herein provided, be held in trust for
the purposes for which they were received, but need not be segregated from other
funds except to the extent required by law. The Trustee shall be under no
liability for interest on any moneys received by it hereunder except such as it
may agree with the Company to pay thereon.

SECTION 10.7      COMPENSATION AND REIMBURSEMENT.

         (a) The Company covenants and agrees to pay to the Trustee, and the
Trustee shall be entitled to, such reasonable compensation (which shall not be
limited by any provision of law in regard to the compensation of a trustee of an
express trust), as the Company and the Trustee may from time to time agree in
writing, for all services rendered by it in the execution of the trusts hereby
created and in the exercise and performance of any of the powers and duties
hereunder of the Trustee, and, except as otherwise expressly provided herein,
the Company shall pay or reimburse the Trustee upon its request for all
reasonable expenses, disbursements and advances incurred or made by the Trustee
in accordance with any of the provisions of this Indenture (including the
reasonable compensation and the expenses and disbursements of its counsel and of
all Persons not regularly in its employ) except any such expense, disbursement
or advance as may arise from its negligence or bad faith. The Company also
covenants to indemnify the Trustee (and its officers, agents, directors and
employees) for, and to hold it harmless against, any loss, liability or expense
incurred without negligence or bad faith on the part of the Trustee and arising
out of or in connection with the acceptance or administration of this trust,
including the costs and expenses of defending itself against any claim of
liability in the premises.

         (b) The obligations of the Company under this Section 10.7 to
compensate and indemnify the Trustee and to pay or reimburse the Trustee for
expenses, disbursements and advances shall constitute additional indebtedness
hereunder. Such additional indebtedness shall be secured by a lien prior to that
of the Debentures upon all property and funds held or collected by the Trustee
as such, except funds held in trust for the benefit of the holders of particular
Debentures.

SECTION 10.8      RELIANCE ON OFFICERS' CERTIFICATE.

         Except as otherwise provided in Section 10.1, whenever in the
administration of the provisions of this Indenture the Trustee shall deem it
necessary or desirable that a matter be proved or established prior to taking or
suffering or omitting to take any action hereunder, such matter (unless other
evidence in respect thereof be herein specifically prescribed) may, in the
absence of negligence or bad faith on the part of the Trustee, be deemed to be
conclusively proved and established by an Officers' Certificate delivered to the
Trustee and such certificate, in the absence of negligence or bad faith on the
part of the Trustee, shall be full warrant to the Trustee for any action taken,
suffered or omitted to be taken by it under the provisions of this Indenture
upon the faith thereof.

                                       49

<PAGE>   58

SECTION 10.9      DISQUALIFICATION: CONFLICTING INTERESTS.

         If the Trustee has or shall acquire any "conflicting interest" within
the meaning of Section 310(b) of the Trust Indenture Act, the Trustee and the
Company shall in all respects comply with the provisions of Section 310(b) of
the Trust Indenture Act.

SECTION 10.10     CORPORATE TRUSTEE REQUIRED; ELIGIBILITY.

         There shall at all times be a Trustee with respect to the Debentures
issued hereunder which shall at all times be a corporation organized and doing
business under the laws of the United States of America or any state or
territory thereof or of the District of Columbia, or a corporation or other
Person permitted to act as trustee by the Commission, authorized under such laws
to exercise corporate trust powers, having a combined capital and surplus of at
least $50,000,000, and subject to supervision or examination by federal, state,
territorial, or District of Columbia authority. If such corporation publishes
reports of condition at least annually, pursuant to law or to the requirements
of the aforesaid supervising or examining authority, then for the purposes of
this Section 10.10, the combined capital and surplus of such corporation shall
be deemed to be its combined capital and surplus as set forth in its most recent
report of condition so published. The Company may not, nor may any Person
directly or indirectly controlling, controlled by, or under common control with
the Company, serve as Trustee. In case at any time the Trustee shall cease to be
eligible in accordance with the provisions of this Section 10.10, the Trustee
shall resign immediately in the manner and with the effect specified in Section
10.11.

SECTION 10.11     RESIGNATION AND REMOVAL; APPOINTMENT OF SUCCESSOR.

         (a) The Trustee or any successor hereafter appointed, may at any time
resign by giving written notice thereof to the Company and by transmitting
notice of resignation by mail, first class postage prepaid, to the
Debentureholders, as their names and addresses appear upon the Debenture
Register. Upon receiving such notice of resignation, the Company shall promptly
appoint a successor trustee with respect to Debentures by written instrument, in
duplicate, executed by order of the Board of Directors, one copy of which
instrument shall be delivered to the resigning Trustee and one copy to the
successor trustee. If no successor trustee shall have been so appointed and have
accepted appointment within 30 days after the mailing of such notice of
resignation, the resigning Trustee may petition any court of competent
jurisdiction for the appointment of a successor trustee with respect to
Debentures, or any Debentureholder who has been a bona fide holder of a
Debenture or Debentures for at least six months may, subject to the provisions
of Sections 10.9 and 10.10, on behalf of himself and all others similarly
situated, petition any such court for the appointment of a successor trustee.
Such court may thereupon after such notice, if any, as it may deem proper and
prescribe, appoint a successor trustee.

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<PAGE>   59

         (b) In case at any time any one of the following shall occur

                  (i) the Trustee shall fail to comply with the provisions of
Section 9.9 after written request therefor by the Company or by any
Debentureholder who has been a bona fide holder of a Debenture or Debentures for
at least six months; or

                  (ii) the Trustee shall cease to be eligible in accordance with
the provisions of Section 9.10 and shall fail to resign after written request
therefor by the Company or by any such Debentureholder; or

                  (iii) the Trustee shall become incapable of acting, or shall
be adjudged a bankrupt or insolvent, or commence a voluntary bankruptcy
proceeding, or a receiver of the Trustee or of its property shall be appointed
or consented to, or any public officer shall take charge or control of the
Trustee or of its property or affairs for the purpose of rehabilitation,
conservation or liquidation, then, in any such case, the Company may remove the
Trustee with respect to all Debentures and appoint a successor trustee by
written instrument, in duplicate, executed by order of the Board of Directors,
one copy of which instrument shall be delivered to the Trustee so removed and
one copy to the successor trustee, or, subject to the provisions of Sections
10.9 and 10.10, unless the Trustee's duty to resign is stayed as provided
herein, any Debentureholder who has been a bona fide holder of a Debenture or
Debentures for at least six months may, on behalf of that holder and all others
similarly situated, petition any court of competent jurisdiction for the removal
of the Trustee and the appointment of a successor trustee. Such court may
thereupon after such notice, if any, as it may deem proper and prescribe, remove
the Trustee and appoint a successor trustee.

         (c) The holders of a majority in aggregate principal amount of the
Debentures at the time Outstanding may at any time remove the Trustee by so
notifying the Trustee and the Company and may appoint a successor Trustee with
the consent of the Company.

         (d) Any resignation or removal of the Trustee and appointment of a
successor trustee with respect to the Debentures pursuant to any of the
provisions of this Section 10.11 shall become effective upon acceptance of
appointment by the successor trustee as provided in Section 10.12.

         (e) Any successor trustee appointed pursuant to this Section 10.11 may
be appointed with respect to the Debentures, and at any time there shall be only
one Trustee with respect to the Debentures.

SECTION 10.12     ACCEPTANCE OF APPOINTMENT BY SUCCESSOR.

         (a) In case of the appointment hereunder of a successor trustee with
respect to the Debentures, every successor trustee so appointed shall execute,
acknowledge and deliver to the Company and to the retiring Trustee an instrument
accepting such appointment, and thereupon the resignation or removal of the
retiring Trustee shall become effective and such successor trustee, without any
further act, deed or

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<PAGE>   60

conveyance, shall become vested with all the rights, powers, trusts and duties
of the retiring Trustee; but, on the request of the Company or the successor
trustee, such retiring Trustee shall, upon payment of its charges, execute and
deliver an instrument transferring to such successor trustee all the rights,
powers, and trusts of the retiring Trustee and shall duly assign, transfer and
deliver to such successor trustee all property and money held by such retiring
Trustee hereunder.

         (b) Upon request of any successor trustee, the Company shall execute
any and all instruments for more fully and certainly vesting in and confirming
to such successor trustee all such rights, powers and trusts referred to in
paragraph (a) of this Section 10.12.

         (c) No successor trustee shall accept its appointment unless at the
time of such acceptance such successor trustee shall be qualified and eligible
under this Article X.

         (d) Upon acceptance of appointment by a successor trustee as provided
in this Section 10.12, the Company shall transmit notice of the succession of
such trustee hereunder by mail, first class postage prepaid, to the
Debentureholders, as their names and addresses appear upon the Debenture
Register. If the Company fails to transmit such notice within ten days after
acceptance of appointment by the successor trustee, the successor trustee shall
cause such notice to be transmitted at the expense of the Company.

SECTION 10.13     MERGER, CONVERSION, CONSOLIDATION OR SUCCESSION TO BUSINESS.

         Any corporation into which the Trustee may be merged or converted or
with which it may be consolidated, or any corporation resulting from any merger,
conversion or consolidation to which the Trustee shall be a party, or any
corporation succeeding to the corporate trust business of the Trustee, shall be
the successor of the Trustee hereunder, provided that such corporation shall be
qualified under the provisions of Section 10.9 and eligible under the provisions
of Section 9.10, without the execution or filing of any paper or any further act
on the part of any of the parties hereto, anything herein to the contrary
notwithstanding. In case any Debentures shall have been authenticated, but not
delivered, by the Trustee then in office, any successor by merger, conversion or
consolidation to such authenticating Trustee may adopt such authentication and
deliver the Debentures so authenticated with the same effect as if such
successor Trustee had itself authenticated such Debentures.

SECTION 10.14     PREFERENTIAL COLLECTION OF CLAIMS AGAINST THE COMPANY.

         The Trustee shall comply with Section 311(a) of the Trust Indenture
Act, excluding any creditor relationship described in Section 311(b) of the
Trust Indenture Act. A Trustee who has resigned or been removed shall be subject
to Section 311(a) of the Trust Indenture Act to the extent included therein.

                                       52

<PAGE>   61

                                   ARTICLE XI

                         CONCERNING THE DEBENTUREHOLDERS

SECTION 11.1      EVIDENCE OF ACTION BY HOLDERS.

         (a) Whenever in this Indenture it is provided that the holders of a
majority or specified percentage in aggregate principal amount of the Debentures
may take any action (including the making of any demand or request, the giving
of any notice, consent or waiver or the taking of any other action), the fact
that at the time of taking any such action the holders of such majority or
specified percentage have joined therein may be evidenced by any instrument or
any number of instruments of similar tenor executed by such holders of
Debentures in Person or by agent or proxy appointed in writing.

         (b) If the Company shall solicit from the Debentureholders any request,
demand, authorization, direction, notice, consent, waiver or other action, the
Company may, at its option, as evidenced by an Officers' Certificate, fix in
advance a record date for the determination of Debentureholders entitled to give
such request, demand, authorization, direction, notice, consent, waiver or other
action, but the Company shall have no obligation to do so. If such a record date
is fixed, such request, demand, authorization, direction, notice, consent,
waiver or other action may be given before or after the record date, but only
the Debentureholders of record at the close of business on the record date shall
be deemed to be Debentureholders for the purposes of determining whether
Debentureholders of the requisite proportion of Outstanding Debentures have
authorized or agreed or consented to such request, demand, authorization,
direction, notice, consent, waiver or other action, and for that purpose the
Outstanding Debentures shall be computed as of the record date; provided,
however, that no such authorization, agreement or consent by such
Debentureholders on the record date shall be deemed effective unless it shall
become effective pursuant to the provisions of this Indenture not later than six
months after the record date.

SECTION 11.2      PROOF OF EXECUTION BY DEBENTUREHOLDERS.

         Subject to the provisions of Section 10.1, proof of the execution of
any instrument by a Debentureholder (such proof shall not require notarization)
or such Debentureholder's agent or proxy and proof of the holding by any Person
of any of the Debentures shall be sufficient if made in the following manner:

         (a) The fact and date of the execution by any such Person of any
instrument may be proved in any reasonable manner acceptable to the Trustee.

         (b) The ownership of Debentures shall be proved by the Debenture
Register of such Debentures or by a certificate of the Debenture Registrar
thereof.

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<PAGE>   62

         (c) The Trustee may require such additional proof of any matter
referred to in this Section 11.2 as it shall deem necessary.

SECTION 11.3      WHO MAY BE DEEMED OWNERS.

         Prior to the due presentment for registration of transfer of any
Debenture, the Company, the Trustee, any paying agent, any Authenticating Agent
and any Debenture Registrar may deem and treat the Person in whose name such
Debenture shall be registered upon the books of the Company as the absolute
owner of such Debenture (whether or not such Debenture shall be overdue and
notwithstanding any notice of ownership or writing thereon made by anyone other
than the Debenture Registrar) for the purpose of receiving payment of or on
account of the principal of and interest on such Debenture (subject to Section
2.3) and for all other purposes; and neither the Company nor the Trustee nor any
paying agent nor any Authenticating Agent nor any Debenture Registrar shall be
affected by any notice to the contrary.

SECTION 11.4      CERTAIN DEBENTURES OWNED BY COMPANY DISREGARDED.

         In determining whether the holders of the requisite aggregate principal
amount of Debentures have concurred in any direction, consent or waiver under
this Indenture, the Debentures that are owned by the Company or any other
obligor on the Debentures or by any Person directly or indirectly controlling or
controlled by or under common control with the Company or any other obligor on
the Debentures shall be disregarded and deemed not to be Outstanding for the
purpose of any such determination, except (i) that for the purpose of
determining whether the Trustee shall be protected in relying on any such
direction, consent or waiver, only Debentures that the Trustee actually knows
are so owned shall be so disregarded; and (ii) for purposes of this Section
11.4, the Trust shall be deemed not to be controlled by the Company. The
Debentures so owned that have been pledged in good faith may be regarded as
Outstanding for the purposes of this Section 11.4, if the pledgee shall
establish to the satisfaction of the Trustee the pledgee's right so to act with
respect to such Debentures and that the pledgee is not a Person directly or
indirectly controlling or controlled by or under direct or indirect common
control with the Company or any such other obligor. In case of a dispute as to
such right, any decision by the Trustee taken upon the advice of counsel shall
be full protection to the Trustee.

SECTION 11.5      ACTIONS BINDING ON FUTURE DEBENTUREHOLDERS.

         At any time prior to (but not after) the evidencing to the Trustee, as
provided in Section 11.1, of the taking of any action by the holders of the
majority or percentage in aggregate principal amount of the Debentures specified
in this Indenture in connection with such action, any holder of a Debenture that
is shown by the evidence to be included in the Debentures the holders of which
have consented to such action may, by filing written notice with the Trustee,
and upon proof of holding as provided in Section 11.2, revoke such action so far
as concerns such Debenture. Except as aforesaid any such action taken by the
holder of any Debenture shall be conclusive and binding upon such holder and
upon all future holders and owners of such Debenture, and of any Debenture
issued in exchange therefor, on registration of transfer

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<PAGE>   63

thereof or in place thereof, irrespective of whether or not any notation in
regard thereto is made upon such Debenture. Any action taken by the holders of
the majority or percentage in aggregate principal amount of the Debentures
specified in this Indenture in connection with such action shall be conclusively
binding upon the Company, the Trustee and the holders of all the Debentures.

                                   ARTICLE XII

                             SUPPLEMENTAL INDENTURES

SECTION 12.1      SUPPLEMENTAL INDENTURES WITHOUT THE CONSENT OF
                  DEBENTUREHOLDERS.

         In addition to any supplemental indenture otherwise authorized by this
Indenture, the Company and the Trustee may from time to time and at any time
enter into an indenture or indentures supplemental hereto (which shall conform
to the provisions of the Trust Indenture Act as then in effect), without the
consent of the Debentureholders, for one or more of the following purposes:

         (a) to cure any ambiguity, defect, or inconsistency herein, or in the
Debentures;

         (b) to comply with Article XI;

         (c) to provide for uncertificated Debentures in addition to or in place
of certificated Debentures;

         (d) to add to the covenants of the Company for the benefit of the
holders of all or any of the Debentures or to surrender any right or power
herein conferred upon the Company;

         (e) to add to, delete from, or revise the conditions, limitations, and
restrictions on the authorized amount, terms, or purposes of issue,
authentication, and delivery of Debentures, only as herein set forth;

         (f) to make any change that does not adversely affect the rights of any
Debentureholder in any material respect;

         (g) to provide for the issuance of and establish the form and terms and
conditions of the Debentures, to establish the form of any certifications
required to be furnished pursuant to the terms of this Indenture or of the
Debentures, or to add to the rights of the holders of the Debentures;

         (h) to qualify or maintain the qualification of this Indenture under
the Trust Indenture Act; or

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<PAGE>   64

         (i) to evidence a consolidation or merger involving the Company as
permitted under Section 13.1.

The Trustee is hereby authorized to join with the Company in the execution of
any such supplemental indenture, and to make any further appropriate agreements
and stipulations that may be therein contained, but the Trustee shall not be
obligated to enter into any such supplemental indenture that affects the
Trustee's own rights, duties or immunities under this Indenture or otherwise.
Any supplemental indenture authorized by the provisions of this Section 12.1 may
be executed by the Company and the Trustee without the consent of the holders of
any of the Debentures at the time Outstanding, notwithstanding any of the
provisions of Section 12.2.

SECTION 12.2      SUPPLEMENTAL INDENTURES WITH CONSENT OF DEBENTUREHOLDERS.

         With the consent (evidenced as provided in Section 11.1) of the holders
of not less than a majority in aggregate principal amount of the Debentures at
the time Outstanding, the Company, when authorized by Board Resolutions, and the
Trustee may from time to time and at any time enter into an indenture or
indentures supplemental hereto (which shall conform to the provisions of the
Trust Indenture Act as then in effect) for the purpose of adding any provisions
to or changing in any manner or eliminating any of the provisions of this
Indenture or of any supplemental indenture or of modifying in any manner not
covered by Section 12.1 the rights of the holders of the Debentures under this
Indenture; provided, however, that no such supplemental indenture shall without
the consent of the holders of each Debenture then Outstanding and affected
thereby, (i) extend the fixed maturity of any Debentures, reduce the principal
amount thereof, reduce the rate or extend the time of payment of interest
thereon, or modify the provisions in Article IV with respect to the conversion
of Outstanding Debentures in a manner adverse to the holders thereof, or without
the consent of the holder of each Debenture so affected; or (ii) reduce the
aforesaid percentage of Debentures, the holders of which are required to consent
to any such supplemental indenture; provided further, that if the Debentures are
held by the Trust or a trustee of the Trust, such supplemental indenture shall
not be effective until the holders of a majority in liquidation preference of
Trust Securities of the Trust shall have consented to such supplemental
indenture; provided further, that if the consent of the holder of each
Outstanding Debenture is required, such supplemental indenture shall not be
effective until each holder of the Trust Securities of the Trust shall have
consented to such supplemental indenture. It shall not be necessary for the
consent of the Debentureholders affected thereby under this Section 12.2 to
approve the particular form of any proposed supplemental indenture, but it shall
be sufficient if such consent shall approve the substance thereof.

SECTION 12.3      EFFECT OF SUPPLEMENTAL INDENTURES.

         Upon the execution of any supplemental indenture pursuant to the
provisions of this Article XII, this Indenture shall be and be deemed to be
modified and amended in accordance therewith and the respective rights,
limitations of rights, obligations, duties and immunities under this Indenture
of the Trustee, the Company and the holders of Debentures shall thereafter be
determined, exercised and enforced

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<PAGE>   65

hereunder subject in all respects to such modifications and amendments, and all
the terms and conditions of any such supplemental indenture shall be and be
deemed to be part of the terms and conditions of this Indenture for any and all
purposes.

SECTION 12.4      DEBENTURES AFFECTED BY SUPPLEMENTAL INDENTURES.

         Debentures affected by a supplemental indenture, authenticated and
delivered after the execution of such supplemental indenture pursuant to the
provisions of this Article XII, may bear a notation in form approved by the
Company, provided such form meets the requirements of any exchange or automated
quotation system upon which the Debentures may be listed or quoted, as to any
matter provided for in such supplemental indenture. If the Company shall so
determine, new Debentures so modified as to conform, in the opinion of the Board
of Directors of the Company, to any modification of this Indenture contained in
any such supplemental indenture may be prepared by the Company, authenticated by
the Trustee and delivered in exchange for the Debentures then Outstanding.

SECTION 12.5      EXECUTION OF SUPPLEMENTAL INDENTURES.

         (a) Upon the request of the Company, accompanied by its Board
Resolutions authorizing the execution of any such supplemental indenture, and
upon the filing with the Trustee of evidence of the consent of Debentureholders
required to consent thereto as aforesaid, the Trustee shall join with the
Company in the execution of such supplemental indenture unless such supplemental
indenture affects the Trustee's own rights, duties or immunities under this
Indenture or otherwise, in which case the Trustee may in its discretion but
shall not be obligated to enter into such supplemental indenture. The Trustee,
subject to the provisions of Sections 10.1, may receive an Opinion of Counsel as
conclusive evidence that any supplemental indenture executed pursuant to this
Article XII is authorized or permitted by, and conforms to, the terms of this
Article XII and that it is proper for the Trustee under the provisions of this
Article XII to join in the execution thereof.

         (b) Promptly after the execution by the Company and the Trustee of any
supplemental indenture pursuant to the provisions of this Section 12.5, the
Trustee shall transmit by mail, first class postage prepaid, a notice, setting
forth in general terms the substance of such supplemental indenture, to the
Debentureholders as their names and addresses appear upon the Debenture
Register. Any failure of the Trustee to mail such notice, or any defect therein,
shall not, however, in any way impair or affect the validity of any such
supplemental indenture.

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                                  ARTICLE XIII

                              SUCCESSOR CORPORATION

SECTION 13.1      COMPANY MAY CONSOLIDATE, ETC.

         Nothing contained in this Indenture or in any of the Debentures shall
prevent any consolidation or merger of the Company with or into any other
corporation or corporations (whether or not affiliated with the Company, as the
case may be), or successive consolidations or mergers in which the Company, as
the case may be, or its successor or successors shall be a party or parties, or
shall prevent any sale, conveyance, transfer or other disposition of the
property of the Company, as the case may be, or its successor or successors as
an entirety, or substantially as an entirety, to any other corporation (whether
or not affiliated with the Company, as the case may be, or its successor or
successors) authorized to acquire and operate the same; provided, however, the
Company hereby covenants and agrees that, (i) upon any such consolidation,
merger, sale, conveyance, transfer or other disposition, the due and punctual
payment, in the case of the Company, of the principal of and interest on all of
the Debentures, according to their tenor and the due and punctual performance
and observance of all the covenants and conditions of this Indenture to be kept
or performed by the Company as the case may be, shall be expressly assumed, by
supplemental indenture (which shall conform to the provisions of the Trust
Indenture Act, as then in effect) satisfactory in form to the Trustee executed
and delivered to the Trustee by the entity formed by such consolidation, or into
which the Company, as the case may be, shall have been merged, or by the entity
which shall have acquired such property, and the ultimate parent entity of such
successor entity expressly assumes the obligations of the Company under the
related Preferred Securities Guarantee, to the extent the Preferred Securities
are then Otstanding; (ii) in case the Company consolidates with or merges into
another Person or conveys or transfers its properties and assets substantially
as an entirety to any Person, the successor Person is (1) organized under the
laws of the United States or any state or the District of Columbia and (2) is
the ultimate parent entity of the organization with which the Company is
engaging in such transaction; and (iii) immediately after giving effect thereto,
an Event of Default, and no event which, after notice or lapse of time or both,
would become an Event of Default, shall have occurred and be continuing.

SECTION 13.2      SUCCESSOR CORPORATION SUBSTITUTED.

         (a) In case of any such consolidation, merger, sale, conveyance,
transfer or other disposition and upon the assumption by the successor
corporation, by supplemental indenture, executed and delivered to the Trustee
and satisfactory in form to the Trustee, of, in the case of the Company, the due
and punctual payment of the principal of and interest on all of the Debentures
Outstanding and the due and punctual performance of all of the covenants and
conditions of this Indenture to be performed by the Company, as the case may be,
such successor corporation shall succeed to and be substituted for the Company,
with the same effect as if it had been named as the Company herein, and
thereupon the predecessor corporation shall be relieved of all obligations and
covenants under this Indenture and the Debentures.

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<PAGE>   67

         (b) In case of any such consolidation, merger, sale, conveyance,
transfer or other disposition such changes in phraseology and form (but not in
substance) may be made in the Debentures thereafter to be issued as may be
appropriate.

         (c) Nothing contained in this Indenture or in any of the Debentures
shall prevent the Company from merging into itself or acquiring by purchase or
otherwise all or any part of the property of any other Person (whether or not
affiliated with the Company).

SECTION 13.3      EVIDENCE OF CONSOLIDATION, ETC. TO TRUSTEE.

         The Trustee, subject to the provisions of Section 10.1, may receive an
Opinion of Counsel as conclusive evidence that any such consolidation, merger,
sale, conveyance, transfer or other disposition, and any such assumption, comply
with the provisions of this Article XIII.

                                   ARTICLE XIV

                           SATISFACTION AND DISCHARGE

SECTION 14.1      SATISFACTION AND DISCHARGE OF INDENTURE.

         If at any time: (a) the Company shall have delivered to the Trustee for
cancellation all Debentures theretofore authenticated (other than any Debentures
that shall have been destroyed, lost or stolen and that shall have been replaced
or paid as provided in Section 2.9) and all Debentures for whose payment money
or Governmental Obligations have theretofore been deposited in trust or
segregated and held in trust by the Company (and thereupon repaid to the Company
or discharged from such trust, as provided in Section 14.5); or (b) all such
Debentures not theretofore delivered to the Trustee for cancellation shall have
become due and payable, or are by their terms to become due and payable within
one year or are to be called for redemption within one year under arrangements
satisfactory to the Trustee for the giving of notice of redemption, and the
Company shall deposit or cause to be deposited with the Trustee as trust funds
the entire amount in moneys or Governmental Obligations sufficient or a
combination thereof, sufficient in the opinion of a nationally recognized firm
of independent public accountants expressed in a written certification thereof
delivered to the Trustee, to pay at maturity or upon redemption all Debentures
not theretofore delivered to the Trustee for cancellation, including principal
and interest due or to become due to such date of maturity or date fixed for
redemption, as the case may be, and if the Company shall also pay or cause to be
paid all other sums payable hereunder by the Company; then this Indenture shall
thereupon cease to be of further effect except for the provisions of Sections
2.3, 2.7, 2.9, 6.1, 6.2, 5.3, 10.7 and 10.10, that shall survive until the date
of maturity or redemption date, as the case may be, and Sections 10.7 and 14.5,
that shall survive to such date and thereafter, and the Trustee, on demand of
the Company and at the cost

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<PAGE>   68

and expense of the Company, shall execute proper instruments acknowledging
satisfaction of and discharging this Indenture.

SECTION 14.2      DISCHARGE OF OBLIGATIONS.

         If at any time all Debentures not heretofore delivered to the Trustee
for cancellation or that have not become due and payable as described in Section
14.1 shall have been paid by the Company by depositing irrevocably with the
Trustee as trust funds moneys or an amount of Governmental Obligations
sufficient in the opinion of a nationally recognized certified public accounting
firm to pay at maturity or upon redemption all Debentures not theretofore
delivered to the Trustee for cancellation, including principal and interest due
or to become due to such date of maturity or date fixed for redemption, as the
case may be, and if the Company shall also pay or cause to be paid all other
sums payable hereunder by the Company, then after the date such moneys or
Governmental Obligations, as the case may be, are deposited with the Trustee,
the obligations of the Company under this Indenture shall cease to be of further
effect except for the provisions of Sections 2.3, 2.7, 2.9, 6.1, 6.2, 6.3, 10.6,
10.7 and 14.5 hereof that shall survive until such Debentures shall mature and
be paid. Thereafter, Sections 10.7 and 14.5 shall survive.

SECTION 14.3      DEPOSITED MONEYS TO BE HELD IN TRUST.

         All monies or Governmental Obligations deposited with the Trustee
pursuant to Sections 14.1 or 14.2 shall be held in trust and shall be available
for payment as due, either directly or through any paying agent (including the
Company acting as its own paying agent), to the holders of the Debentures for
the payment or redemption of which such moneys or Governmental Obligations have
been deposited with the Trustee.

SECTION 14.4      PAYMENT OF MONIES HELD BY PAYING AGENTS.

         In connection with the satisfaction and discharge of this Indenture,
all moneys or Governmental Obligations then held by any paying agent under the
provisions of this Indenture shall, upon demand of the Company, be paid to the
Trustee and thereupon such paying agent shall be released from all further
liability with respect to such moneys or Governmental Obligations.

SECTION 14.5      REPAYMENT TO COMPANY.

         Any monies or Governmental Obligations deposited with any paying agent
or the Trustee, or then held by the Company in trust, for payment of principal
of or interest on the Debentures that are not applied but remain unclaimed by
the holders of such Debentures for at least two years after the date upon which
the principal of or interest on such Debentures shall have respectively become
due and payable, shall be repaid to the Company, as the case may be, on
September 30 of each year or (if then held by the Company) shall be discharged
from such trust; and thereupon the paying agent and the Trustee shall be
released from all further liability with respect to such moneys or Governmental
Obligations, and the holder

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of any of the Debentures entitled to receive such payment shall thereafter, as
an unsecured general creditor, look only to the Company for the payment thereof.

                                   ARTICLE XV

                IMMUNITY OF INCORPORATORS, STOCKHOLDERS, OFFICERS
                                  AND DIRECTORS

SECTION 15.1      NO RECOURSE.

         No recourse under or upon any obligation, covenant or agreement of this
Indenture, or of the Debentures, or for any claim based thereon or otherwise in
respect thereof, shall be had against any incorporator, stockholder, officer or
director, past, present or future as such, of the Company or of any predecessor
or successor corporation, either directly or through the Company or any such
predecessor or successor corporation, whether by virtue of any constitution,
statute or rule of law, or by the enforcement of any assessment or penalty or
otherwise; it being expressly understood that this Indenture and the obligations
issued hereunder are solely corporate obligations, and that no such personal
liability whatever shall attach to, or is or shall be incurred by, the
incorporators, stockholders, officers or directors as such, of the Company or of
any predecessor or successor corporation, or any of them, because of the
creation of the indebtedness hereby authorized, or under or by reason of the
obligations, covenants or agreements contained in this Indenture or in any of
the Debentures or implied therefrom; and that any and all such personal
liability of every name and nature, either at common law or in equity or by
constitution or statute, of, and any and all such rights and claims against,
every such incorporator, stockholder, officer or director as such, because of
the creation of the indebtedness hereby authorized, or under or by reason of the
obligations, covenants or agreements contained in this Indenture or in any of
the Debentures or implied therefrom, are hereby expressly waived and released as
a condition of, and as a consideration for, the execution of this Indenture and
the issuance of such Debentures.

                                   ARTICLE XVI

                            MISCELLANEOUS PROVISIONS

SECTION 16.1      EFFECT ON SUCCESSORS AND ASSIGNS.

         All the covenants, stipulations, promises and agreements in this
Indenture contained by or on behalf of the Company shall bind its respective
successors and assigns, whether so expressed or not.

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SECTION 16.2      ACTIONS BY SUCCESSOR.

         Any act or proceeding by any provision of this Indenture authorized or
required to be done or performed by any board, committee or officer of the
Company shall and may be done and performed with like force and effect by the
corresponding board, committee or officer of any corporation that shall at the
time be the lawful sole successor of the Company.

SECTION 16.3      SURRENDER OF COMPANY POWERS.

         The Company by instrument in writing executed by appropriate authority
of its Board of Directors and delivered to the Trustee may surrender any of the
powers reserved to the Company, and thereupon such power so surrendered shall
terminate both as to the Company, as the case may be, and as to any successor
corporation.

SECTION 16.4      NOTICES.

         Except as otherwise expressly provided herein any notice or demand that
by any provision of this Indenture is required or permitted to be given or
served by the Trustee or by the holders of Debentures to or on the Company may
be given or served by being deposited first class postage prepaid in a post-
office letterbox addressed (until another address is filed in writing by the
Company with the Trustee), as follows: Southside Bancshares, Inc., 1201 S.
Beckham, Tyler, Texas 75701, Attention: Chief Financial Officer. Any notice,
election, request or demand by the Company or any Debentureholder to or upon the
Trustee shall be deemed to have been sufficiently given or made, for all
purposes, if given or made in writing at the Corporate Trust Office of the
Trustee.

SECTION 16.5      GOVERNING LAW.

         This Indenture and each Debenture shall be deemed to be a contract made
under the internal laws of the State of Texas and for all purposes shall be
construed in accordance with the laws of said State.

SECTION 16.6      TREATMENT OF DEBENTURES AS DEBT.

         It is intended that the Debentures shall be treated as indebtedness and
not as equity for federal income tax purposes. The provisions of this Indenture
shall be interpreted to further this intention.

SECTION 16.7      COMPLIANCE CERTIFICATES AND OPINIONS.

         (a) Upon any application or demand by the Company to the Trustee to
take any action under any of the provisions of this Indenture, the Company shall
furnish to the Trustee an Officers' Certificate stating that all conditions
precedent provided for in this Indenture relating to the proposed action have
been complied with and an Opinion of Counsel stating that in the opinion of such
counsel all such conditions

                                       62

<PAGE>   71

precedent have been complied with, except that in the case of any such
application or demand as to which the furnishing of such documents is
specifically required by any provision of this Indenture relating to such
particular application or demand, no additional certificate or opinion need be
furnished.

         (b) Each certificate or opinion of the Company provided for in this
Indenture and delivered to the Trustee with respect to compliance with a
condition or covenant in this Indenture shall include (1) a statement that the
Person making such certificate or opinion has read such covenant or condition;
(2) a brief statement as to the nature and scope of the examination or
investigation upon which the statements or opinions contained in such
certificate or opinion are based; (3) a statement that, in the opinion of such
Person, he has made such examination or investigation as, in the opinion of such
Person, is necessary to enable him to express an informed opinion as to whether
or not such covenant or condition has been complied with; and (4) a statement as
to whether or not, in the opinion of such Person, such condition or covenant has
been complied with; provided, however, that each such certificate shall comply
with the provisions of Section 314 of the Trust Indenture Act.

SECTION 16.8      PAYMENTS ON BUSINESS DAYS.

         In any case where the date of maturity of interest or principal of any
Debenture or the date of redemption of any Debenture shall not be a Business
Day, then payment of interest or principal may be made on the next succeeding
Business Day with the same force and effect as if made on the nominal date of
maturity or redemption, and no interest shall accrue for the period after such
nominal date.

SECTION 16.9      CONFLICT WITH TRUST INDENTURE ACT.

         If and to the extent that any provision of this Indenture limits,
qualifies or conflicts with the duties imposed by Sections 310 to 317,
inclusive, of the Trust Indenture Act, such imposed duties shall control.

SECTION 16.10     COUNTERPARTS.

         This Indenture may be executed in any number of counterparts, each of
which shall be an original, but such counterparts shall together constitute but
one and the same instrument.

SECTION 16.11     SEPARABILITY.

         In case any one or more of the provisions contained in this Indenture
or in the Debentures shall for any reason be held to be invalid, illegal or
unenforceable in any respect, such invalidity, illegality or unenforceability
shall not affect any other provisions of this Indenture or of the Debentures,
but this Indenture and the Debentures shall be construed as if such invalid or
illegal or unenforceable provision had never been contained herein or therein.

                                       63

<PAGE>   72

SECTION 16.12     ASSIGNMENT.

         The Company shall have the right at all times to assign any of its
respective rights or obligations under this Indenture to a direct or indirect
wholly owned Subsidiary of the Company, provided that, in the event of any such
assignment, the Company shall remain liable for all such obligations. Subject to
the foregoing, this Indenture is binding upon and inures to the benefit of the
parties thereto and their respective successors and assigns. This Indenture may
not otherwise be assigned by the parties thereto.

SECTION 16.13     ACKNOWLEDGMENT OF RIGHTS.

         The Company acknowledges that, with respect to any Debentures held by
the Trust or a trustee of the Trust, if the Property Trustee fails to enforce
its rights under this Indenture as the holder of the Debentures held as the
assets of the Trust, any holder of Preferred Securities may institute legal
proceedings directly against the Company to enforce such Property Trustee's
rights under this Indenture without first instituting any legal proceedings
against such Property Trustee or any other person or entity. Notwithstanding the
foregoing, if an Event of Default has occurred and is continuing and such event
is attributable to the failure of the Company to pay interest or principal on
the Debentures on the date such interest or principal is otherwise payable (or
in the case of redemption, on the redemption date), the Company acknowledges
that a holder of Preferred Securities may directly institute a proceeding for
enforcement of payment to such holder of the principal of or interest on the
Debentures having a principal amount equal to the aggregate liquidation amount
of the Preferred Securities of such holder on or after the respective due date
specified in the Debentures.

                                  ARTICLE XVII

                           SUBORDINATION OF DEBENTURES

SECTION 17.1      AGREEMENT TO SUBORDINATE.

         The Company covenants and agrees, and each holder of Debentures issued
hereunder by such holder's acceptance thereof likewise covenants and agrees,
that all Debentures shall be issued subject to the provisions of this Article
XVII; and each holder of a Debenture, whether upon original issue or upon
transfer or assignment thereof, accepts and agrees to be bound by such
provisions. The payment by the Company of the principal of and interest on all
Debentures issued hereunder shall, to the extent and in the manner hereinafter
set forth, be subordinated and junior in right of payment to the prior payment
in full of all Senior Debt, Subordinated Debt and Additional Senior Obligations
(collectively, "Senior Indebtedness") to the extent provided herein, whether
outstanding at the date of this Indenture or thereafter incurred; provided
however, that the Debentures shall rank pari passu in right of payment with the
Company's 8.50% Junior Subordinated Debentures due 2028, issued pursuant to the
Indenture dated as of May 18, 1998, with respect to such debentures by and
between the Company and U.S. Trust Company of Texas,

                                       64

<PAGE>   73

N.A., as trustee thereunder. No provision of this Article XVII shall prevent the
occurrence of any default or Event of Default hereunder.

SECTION 17.2      DEFAULT ON SENIOR DEBT, SUBORDINATED DEBT OR ADDITIONAL SENIOR
                  OBLIGATIONS.

         In the event and during the continuation of any default by the Company
in the payment of principal, premium, interest or any other payment due on any
Senior Indebtedness of the Company, or in the event that the maturity of any
Senior Indebtedness of the Company has been accelerated because of a default,
then, in either case, no payment shall be made by the Company with respect to
the principal (including redemption payments) of or interest on the Debentures.
In the event that, notwithstanding the foregoing, any payment shall be received
by the Trustee when such payment is prohibited by the preceding sentence of this
Section 17.2, such payment shall be held in trust for the benefit of, and shall
be paid over or delivered to, the holders of Senior Indebtedness or their
respective representatives, or to the trustee or trustees under any indenture
pursuant to which any of such Senior Indebtedness may have been issued, as their
respective interests may appear, but only to the extent that the holders of the
Senior Indebtedness (or their representative or representatives or a trustee)
notify the Trustee in writing within 90 days of such payment of the amounts then
due and owing on the Senior Indebtedness and only the amounts specified in such
notice to the Trustee shall be paid to the holders of Senior Indebtedness.

SECTION 17.3      LIQUIDATION; DISSOLUTION; BANKRUPTCY.

         (a) Upon any payment by the Company or distribution of assets of the
Company of any kind or character, whether in cash, property or securities, to
creditors upon any dissolution or winding-up or liquidation or reorganization of
the Company, whether voluntary or involuntary or in bankruptcy, insolvency,
receivership or other proceedings, all amounts due upon all Senior Indebtedness
of the Company shall first be paid in full, or payment thereof provided for in
money in accordance with its terms, before any payment is made by the Company on
account of the principal or interest on the Debentures; and upon any such
dissolution or winding-up or liquidation or reorganization, any payment by the
Company, or distribution of assets of the Company of any kind or character,
whether in cash, property or securities, to which the holders of the Debentures
or the Trustee would be entitled to receive from the Company, except for the
provisions of this Article XVII, shall be paid by the Company or by any
receiver, trustee in bankruptcy, liquidating trustee, agent or other Person
making such payment or distribution, or by the holders of the Debentures or by
the Trustee under this Indenture if received by them or it, directly to the
holders of Senior Indebtedness of the Company (pro rata to such holders on the
basis of the respective amounts of Senior Indebtedness held by such holders, as
calculated by the Company) or their representative or representatives, or to the
trustee or trustees under any indenture pursuant to which any instruments
evidencing such Senior Indebtedness may have been issued, as their respective
interests may appear, to the extent necessary to pay such Senior Indebtedness in
full, in money or money's worth, after giving effect to any concurrent payment
or distribution to or for the holders of such Senior Indebtedness, before any
payment or distribution is made to the holders of Debentures or to the Trustee.

                                       65

<PAGE>   74

         (b) In the event that, notwithstanding the foregoing, any payment or
distribution of assets of the Company of any kind or character, whether in cash,
property or securities, prohibited by the foregoing, shall be received by the
Trustee before all Senior Indebtedness of the Company is paid in full, or
provision is made for such payment in money in accordance with its terms, such
payment or distribution shall be held in trust for the benefit of and shall be
paid over or delivered to the holders of such Senior Indebtedness or their
representative or representatives, or to the trustee or trustees under any
indenture pursuant to which any instruments evidencing such Senior Indebtedness
may have been issued, and their respective interests may appear, as calculated
by the Company, for application to the payment of all Senior Indebtedness of the
Company, as the case may be, remaining unpaid to the extent necessary to pay
such Senior Indebtedness in full in money in accordance with its terms, after
giving effect to any concurrent payment or distribution to or for the benefit of
the holders of such Senior Indebtedness.

         (c) For purposes of this Article XVII, the words "cash, property or
securities" shall not be deemed to include shares of stock of the Company as
reorganized or readjusted, or securities of the Company or any other corporation
provided for by a plan of reorganization or readjustment, the payment of which
is subordinated at least to the extent provided in this Article XVII with
respect to the Debentures to the payment of all Senior Indebtedness of the
Company, as the case may be, that may at the time be outstanding, provided that
(i) such Senior Indebtedness is assumed by the new corporation, if any,
resulting from any such reorganization or readjustment; and (ii) the rights of
the holders of such Senior Indebtedness are not, without the consent of such
holders, altered by such reorganization or readjustment. The consolidation of
the Company with, or the merger of the Company into, another corporation or the
liquidation or dissolution of the Company following the conveyance or transfer
of its property as an entirety, or substantially as an entirety, to another
corporation upon the terms and conditions provided for in Article XIII shall not
be deemed a dissolution, winding-up, liquidation or reorganization for the
purposes of this Section 17.3 if such other corporation shall, as a part of such
consolidation, merger, conveyance or transfer, comply with the conditions stated
in Article XIII. Nothing in Section 17.2 or in this Section 17.3 shall apply to
claims of, or payments to, the Trustee under or pursuant to Section 10.7.

SECTION 17.4      SUBROGATION.

         (a) Subject to the payment in full of all Senior Indebtedness of the
Company, the rights of the holders of the Debentures shall be subrogated to the
rights of the holders of such Senior Indebtedness to receive payments or
distributions of cash, property or securities of the Company, as the case may
be, applicable to such Senior Indebtedness until the principal of and interest
on the Debentures shall be paid in full; and, for the purposes of such
subrogation, no payments or distributions to the holders of such Senior
Indebtedness of any cash, property or securities to which the holders of the
Debentures or the Trustee would be entitled except for the provisions of this
Article XVII, and no payment over pursuant to the provisions of this Article
XVII to or for the benefit of the holders of such Senior Indebtedness by holders
of the Debentures or the Trustee, shall, as between the Company, its creditors
other than holders of Senior Indebtedness of the Company, and the holders of the
Debentures, be deemed to be a payment by the Company to or on account of such
Senior Indebtedness. It is understood that the provisions of this

                                       66

<PAGE>   75

Article XVII are and are intended solely for the purposes of defining the
relative rights of the holders of the Debentures, on the one hand, and the
holders of such Senior Indebtedness on the other hand.

         (b) Nothing contained in this Article XVII or elsewhere in this
Indenture or in the Debentures is intended to or shall impair, as between the
Company, its creditors (other than the holders of Senior Indebtedness of the
Company), and the holders of the Debentures, the obligation of the Company,
which is absolute and unconditional, to pay to the holders of the Debentures the
principal of and interest on the Debentures as and when the same shall become
due and payable in accordance with their terms, or is intended to or shall
affect the relative rights of the holders of the Debentures and creditors of the
Company, as the case may be, other than the holders of Senior Indebtedness of
the Company, as the case may be, nor shall anything herein or therein prevent
the Trustee or the holder of any Debenture from exercising all remedies
otherwise permitted by applicable law upon default under this Indenture, subject
to the rights, if any, under this Article XVII of the holders of such Senior
Indebtedness in respect of cash, property or securities of the Company, as the
case may be, received upon the exercise of any such remedy.

         (c) Upon any payment or distribution of assets of the Company referred
to in this Article XVII, the Trustee, subject to the provisions of Article X,
and the holders of the Debentures shall be entitled to conclusively rely upon
any order or decree made by any court of competent jurisdiction in which such
dissolution, winding-up, liquidation or reorganization proceedings are pending,
or a certificate of the receiver, trustee in bankruptcy, liquidation trustee,
agent or other Person making such payment or distribution, delivered to the
Trustee or to the holders of the Debentures, for the purposes of ascertaining
the Persons entitled to participate in such distribution, the holders of Senior
Indebtedness and other indebtedness of the Company, as the case may be, the
amount thereof or payable thereon, the amount or amounts paid or distributed
thereon and all other facts pertinent thereto or to this Article XVII.

SECTION 17.5      TRUSTEE TO EFFECTUATE SUBORDINATION.

         Each holder of Debentures by such holder's acceptance thereof
authorizes and directs the Trustee on such holder's behalf to take such action
as may be necessary or appropriate to effectuate the subordination provided in
this Article XVII and appoints the Trustee such holder's attorney-in-fact for
any and all such purposes.

SECTION 17.6      NOTICE BY THE COMPANY.

         (a) The Company shall give prompt written notice to a Responsible
Officer of the Trustee of any fact known to the Company that would prohibit the
making of any payment of monies to or by the Trustee in respect of the
Debentures pursuant to the provisions of this Article XVII. Notwithstanding the
provisions of this Article XVII or any other provision of this Indenture, the
Trustee shall not be charged with knowledge of the existence of any facts that
would prohibit the making of any payment of monies to or by the Trustee in
respect of the Debentures pursuant to the provisions of this Article XVII,
unless and until a Responsible Officer of the Trustee shall have received
written notice thereof from the Company or

                                       67

<PAGE>   76

a holder or holders of Senior Indebtedness or from any trustee therefor; and
before the receipt of any such written notice, the Trustee, subject to the
provisions of Section 10.1, shall be entitled in all respects to assume that no
such facts exist; provided, however, that if the Trustee shall not have received
the notice provided for in this Section 17.6 at least two Business Days prior to
the date upon which by the terms hereof any money may become payable for any
purpose (including, without limitation, the payment of the principal of or
interest on any Debenture), then, anything herein contained to the contrary
notwithstanding, the Trustee shall have full power and authority to receive such
money and to apply the same to the purposes for which they were received, and
shall not be affected by any notice to the contrary that may be received by it
within two Business Days prior to such date.

         (b) The Trustee, subject to the provisions of Section 10.1, shall be
entitled to conclusively rely on the delivery to it of a written notice by a
Person representing himself to be a holder of Senior Indebtedness of the Company
(or a trustee on behalf of such holder) to establish that such notice has been
given by a holder of such Senior Indebtedness or a trustee on behalf of any such
holder or holders. In the event that the Trustee determines in good faith that
further evidence is required with respect to the right of any Person as a holder
of such Senior Indebtedness to participate in any payment or distribution
pursuant to this Article XVII, the Trustee may request such Person to furnish
evidence to the reasonable satisfaction of the Trustee as to the amount of such
Senior Indebtedness held by such Person, the extent to which such Person is
entitled to participate in such payment or distribution and any other facts
pertinent to the rights of such Person under this Article XVII, and, if such
evidence is not furnished, the Trustee may defer any payment to such Person
pending judicial determination as to the right of such Person to receive such
payment.

SECTION 17.7      RIGHTS OF THE TRUSTEE; HOLDERS OF SENIOR INDEBTEDNESS.

         (a) The Trustee in its individual capacity shall be entitled to all the
rights set forth in this Article XVII in respect of any Senior Indebtedness at
any time held by it, to the same extent as any other holder of Senior
Indebtedness, and nothing in this Indenture shall deprive the Trustee of any of
its rights as such holder. The Trustee's right to compensation and reimbursement
of expenses as set forth in Section 10.7 shall not be subject to the
subordination provisions of the Article XVII.

         (b) With respect to the holders of Senior Indebtedness of the Company,
the Trustee undertakes to perform or to observe only such of its covenants and
obligations as are specifically set forth in this Article XVII, and no implied
covenants or obligations with respect to the holders of such Senior Indebtedness
shall be read into this Indenture against the Trustee. The Trustee shall not be
deemed to owe any fiduciary duty to the holders of such Senior Indebtedness and,
subject to the provisions of Section 10.1, the Trustee shall not be liable to
any holder of such Senior Indebtedness if it shall pay over or deliver to
holders of Debentures, the Company or any other Person money or assets to which
any holder of such Senior Indebtedness shall be entitled by virtue of this
Article XVII or otherwise.

                                       68

<PAGE>   77

SECTION 17.8      SUBORDINATION MAY NOT BE IMPAIRED.

         (a) No right of any present or future holder of any Senior Indebtedness
of the Company to enforce subordination as herein provided shall at any time in
any way be prejudiced or impaired by any act or failure to act on the part of
the Company or by any act or failure to act, in good faith, by any such holder,
or by any noncompliance by the Company with the terms, provisions and covenants
of this Indenture, regardless of any knowledge thereof that any such holder may
have or otherwise be charged with.

         (b) Without in any way limiting the generality of the foregoing
paragraph, the holders of Senior Indebtedness of the Company may, at any time
and from time to time, without the consent of or notice to the Trustee or the
holders of the Debentures, without incurring responsibility to the holders of
the Debentures and without impairing or releasing the subordination provided in
this Article XVII or the obligations hereunder of the holders of the Debentures
to the holders of such Senior Indebtedness, do any one or more of the following:
(i) change the manner, place or terms of payment or extend the time of payment
of, or renew or alter, such Senior Indebtedness, or otherwise amend or
supplement in any manner such Senior Indebtedness or any instrument evidencing
the same or any agreement under which such Senior Indebtedness is outstanding;
(ii) sell, exchange, release or otherwise deal with any property pledged,
mortgaged or otherwise securing such Senior Indebtedness; (iii) release any
Person liable in any manner for the collection of such Senior Indebtedness; and
(iv) exercise or refrain from exercising any rights against the Company and any
other Person.

         IN WITNESS WHEREOF, the parties hereto have caused this Indenture to be
duly executed, all as of the day and year first above written.

                                                     SOUTHSIDE BANCSHARES, INC.

                                                     By:
                                                        ------------------------
                                                     Name:
                                                          ----------------------
                                                     Title:
                                                           ---------------------

                                                     WILMINGTON TRUST COMPANY,
                                                          AS TRUSTEE

                                                     By:
                                                        ------------------------
                                                     Name:
                                                          ----------------------
                                                     Title:
                                                           ---------------------

                                       69
<PAGE>   78

STATE OF TEXAS                      )
                                    ) ss:
COUNTY OF                           )
          ---------------------

         On the __th day of ____, 2000, before me personally came
____________________to me known, who, being by me duly sworn, did depose and say
that he is the ______________________ of Company, one of the corporations
described in and which executed the above instrument; that he knows the
corporate seal of said corporation; that the seal affixed to the said instrument
is such corporation seal; that it was so affixed by authority of the Board of
Directors of said corporation, and that he signed his name thereto by like
authority.

                                                --------------------------------
                                                Notary Public,
                                                              ------------------

[seal]                                          My Commission expires:
                                                                      ----------

                                       70
<PAGE>   79

                                    EXHIBIT A

                           (FORM OF FACE OF DEBENTURE)

                           SOUTHSIDE BANCSHARES, INC.

                   ______% CONVERTIBLE SUBORDINATED DEBENTURE

                              DUE DECEMBER 31, 2030

NO. ___                                                             $___________

                                                        CUSIP NO. ______________

         Southside Bancshares, Inc., a Texas corporation (the "Company," which
term includes any successor corporation under the Indenture hereinafter referred
to), for value received, hereby promises to pay to, _______________ or
registered assigns, the principal sum of _________________________
($___________) on December 31, 2030, (the "Stated Maturity"), and to pay
interest on said principal sum from December 31, 2000, or from the most recent
interest payment date (each such date, an "Interest Payment Date") to which
interest has been paid or duly provided for, quarterly (subject to deferral as
set forth herein) in arrears on the last day of March, June, September and
December of each year commencing December 31, 2000, at the rate of _____% per
annum until the principal hereof shall have become due and payable, and on any
overdue principal and (without duplication and to the extent that payment of
such interest is enforceable under applicable law) on any overdue installment of
interest at the same rate per annum compounded quarterly. The amount of interest
payable on any Interest Payment Date shall be computed on the basis of a 360-day
year of twelve 30-day months. The amount of interest for any partial period
shall be computed on the basis of the number of days elapsed in a 360-day year
of twelve 30-day months. In the event that any date on which interest is payable
on this Debenture is not a business day, then payment of interest payable on
such date shall be made on the next succeeding day that is a business day (and
without any interest or other payment in respect of any such delay) except that,
if such business day is in the next succeeding calendar year, payment of such
interest will be made on the immediately preceding business day, in each case,
with the same force and effect as if made on such date. The interest installment
so payable, and punctually paid or duly provided for, on any Interest Payment
Date shall, as provided in the Indenture, be paid to the person in whose name
this Debenture (or one or more Predecessor Debentures, as defined in said
Indenture) is registered at the close of business on the regular record date for
such interest installment, which shall be the close of business on the business
day next preceding such Interest Payment Date unless otherwise provided in the
Indenture. Any such interest installment not punctually paid or duly provided
for shall forthwith cease to be payable to the registered holders on such
regular record date and may be paid to the Person in whose name this Debenture
(or one or more Predecessor Debentures) is registered at the close of business
on a special record date to be fixed by the

                                       A-1

<PAGE>   80

Trustee for the payment of such defaulted interest, notice thereof shall be
fixed by the Trustee for the payment of such defaulted interest, notice thereof
shall be given to the registered holders of the Debentures not less than 10 days
prior to such special record date, or may be paid at any time in any other
lawful manner not inconsistent with the requirements of any securities exchange
or quotation system on or in which the Debentures may be listed or quoted, and
upon such notice as may be required by such exchange, all as more fully provided
in the Indenture. The principal of and the interest on this Debenture shall be
payable at the office or agency of the Trustee maintained for that purpose in
any coin or currency of the United States of America that at the time of payment
is legal tender for payment of public and private debts; provided, however, that
payment of interest may be made at the option of the Company by check mailed to
the registered holder at such address as shall appear in the Debenture Register.
Notwithstanding the foregoing, so long as the holder of this Debenture is the
Property Trustee, the payment of the principal of and interest on this Debenture
shall be made at such place and to such account as may be designated by the
Trustee.

         The Stated Maturity may be shortened at any time by the Company to any
date not earlier than December 31, 2005, subject to the Company having received
prior approval of the Federal Reserve if then required under applicable capital
guidelines, policies or regulations of the Federal Reserve.

         The indebtedness evidenced by this Debenture is, to the extent provided
in the Indenture, subordinate and junior in right of payment to the prior
payment in full of all Senior Indebtedness, and this Debenture is issued subject
to the provisions of the Indenture with respect thereto. Each holder of this
Debenture, by accepting the same, (a) agrees to and shall be bound by such
provisions; (b) authorizes and directs the Trustee on his or her behalf to take
such action as may be necessary or appropriate to acknowledge or effectuate the
subordination so provided; and (c) appoints the Trustee his or her attorney-
in-fact for any and all such purposes. Each holder hereof, by his or her
acceptance hereof, hereby waives all notice of the acceptance of the
subordination provisions contained herein and in the Indenture by each holder of
Senior Indebtedness, whether now outstanding or hereafter incurred, and waives
reliance by each such holder upon said provisions.

         This Debenture shall not be entitled to any benefit under the Indenture
hereinafter referred to, be valid or become obligatory for any purpose until the
Certificate of Authentication hereon shall have been signed by or on behalf of
the Trustee.

         The provisions of this Debenture are continued on the reverse side
hereof and such continued provisions shall for all purposes have the same effect
as though fully set forth at this place.

                                       A-2

<PAGE>   81

         IN WITNESS WHEREOF, the Company has caused this instrument to be
executed.

Dated                       , 20  .
     -----------------------    --
                                                     SOUTHSIDE BANCSHARES, INC.

                                                     By:
                                                        ------------------------
                                                     Name:
                                                          ----------------------
                                                     Title:
                                                           ---------------------

Attest:

By:
   ------------------------
Name:
     ----------------------
Title:
      ---------------------

                                       A-3

<PAGE>   82

                     [FORM OF CERTIFICATE OF AUTHENTICATION]

                          CERTIFICATE OF AUTHENTICATION

         This is one of the Debentures described in the within-mentioned
Indenture.

Dated:             , 20
         ----------    --
Wilmington Trust Company,                        -------------------------------
as Trustee                                         or       Authentication Agent

By                                                        By
  ----------------------------                              --------------------
      Authorized Signatory

                                       A-4

<PAGE>   83

                         [FORM OF REVERSE OF DEBENTURE]

              _______% CONVERTIBLE SUBORDINATED DEBENTURE DUE 2030
                                   (CONTINUED)

         This Debenture is one of the subordinated debentures of the Company
(herein sometimes referred to as the "Debentures"), all issued or to be issued
under and pursuant to an Indenture dated as of November ___, 2000, (the
"Indenture") duly executed and delivered between the Company and Wilmington
Trust Company, as Trustee (the "Trustee"), to which Indenture reference is
hereby made for a description of the rights, limitations of rights, obligations,
duties and immunities thereunder of the Trustee, the Company and the holders of
the Debentures. The Debentures are limited in aggregate principal amount as
specified in the Indenture.

         Because of the occurrence and continuation of a Special Event (as
defined in the Indenture), in certain circumstances, this Debenture may become
due and payable at the principal amount together with any interest accrued
thereon (the "Redemption Price"). The Redemption Price shall be paid prior to
12:00 noon, Eastern Standard Time, on the date of such redemption or at such
earlier time as the Company determines. The Company shall have the right as set
forth in the Indenture to redeem this Debenture at the option of the Company, as
set forth in the Indenture, in whole or in part (i) at any time on or after
December 31, 2003, at a Redemption Price equal to ____% of the principal amount
so redeemed until December 31, 2003, and equal to ____% of the principal amount
so redeemed on or after December 31, 2004, plus in each case accrued but unpaid
interest hereon to the date of redemption (an "Early Redemption"); provided,
however, the Company shall have no right to an Early Redemption unless the stock
price for the Company's common stock has been at least 125% of the Conversion
Price for a period of twenty consecutive business days ending within five days
of the date of notice of redemption; (ii) at any time on or after December 31,
2005 at a Redemption Price equal to 100% of the principal amount so redeemed
plus any accrued but unpaid interest hereon to the date of redemption ("Optional
Redemption"); or (iii) at any time in certain circumstances upon the occurrence
of a Special Event, at a Redemption Price equal to 100% of the principal amount
hereof plus any accrued but unpaid interest hereon, to the date of such
redemption. Any redemption pursuant to this paragraph shall be made upon not
less than 30 days nor more than 60 days notice, at the Redemption Price. The
Redemption Price shall be paid at the time and in the manner provided therefor
in the Indenture. If the Debentures are only partially redeemed by the Company
pursuant to an Early Redemption or an Optional Redemption, the Debentures shall
be redeemed pro rata or by lot or by any other method utilized by the Trustee as
described in the Indenture.

         In the event of redemption of this Debenture in part only, a new
Debenture or Debentures for the unredeemed portion hereof shall be issued in the
name of the holder hereof upon the cancellation hereof.

                                       A-5

<PAGE>   84

         In case an Event of Default (as defined in the Indenture) shall have
occurred and be continuing, the principal of all of the Debentures may be
declared, and upon such declaration shall become, due and payable, in the
manner, with the effect and subject to the conditions provided in the Indenture.

         The Indenture contains provisions permitting the Company and the
Trustee, with the consent of the holders of not less than a majority in
aggregate principal amount of the Debentures at the time Outstanding (as defined
in the Indenture) to execute supplemental indentures for the purpose of adding
any provisions to or changing in any manner or eliminating any of the provisions
of the Indenture or of any supplemental indenture or of modifying in any manner
the rights of the holders of the Debentures; provided, however, that no such
supplemental indenture shall (i) extend the fixed maturity of the Debentures
except as provided in the Indenture, or reduce the principal amount thereof, or
reduce the rate or extend the time of payment of interest thereon, without the
consent of the holder of each Debenture so affected; or (ii) reduce the
aforesaid percentage of Debentures, the holders of which are required to consent
to any such supplemental indenture, without the consent of the holders of each
Debenture then Outstanding and affected thereby. The Indenture also contains
provisions permitting the holders of a majority in aggregate principal amount of
the Debentures at the time Outstanding, on behalf of all of the holders of the
Debentures, to waive any past default in the performance of any of the covenants
contained in the Indenture, or established pursuant to the Indenture, and its
consequences, except a default in the payment of the principal of or interest on
any of the Debentures. Any such consent or waiver by the registered holder of
this Debenture (unless revoked as provided in the Indenture) shall be conclusive
and binding upon such holder and upon all future holders and owners of this
Debenture and of any Debenture issued in exchange herefor or in place hereof
(whether by registration of transfer or otherwise), irrespective of whether or
not any notation of such consent or waiver is made upon this Debenture.

         Any Debentureholder has the right, exercisable at any time after
__________, 2000 and on or before the close of business on the Business Day
immediately preceding the date of repayment of the Debentures, whether at
maturity or upon redemption (either at the option of the Company or pursuant to
a Special Event), to convert the principal amount thereof (or any portion
thereof that is an integral multiple of $10) into fully paid and nonassessable
shares of Common Stock of the Company at an initial conversion ratio of _____
shares of Common Stock for each $10 in aggregate principal amount of Debentures
(equal to an initial conversion price of $_____ per share of Common Stock),
subject to adjustment under certain circumstances (the "Conversion Ratio"). The
number of shares issuable upon conversion of a principal amount of Debentures
shall be determined by dividing such principal amount by 10 and multiplying the
quotient so obtained by the Conversion Ratio in effect on the Conversion Date.
No fractional shares of Common Stock shall be issued upon conversion and, in
lieu thereof, a cash payment shall be made for any fractional interest. The
outstanding principal amount of any Debenture shall be reduced by the portion of
the principal amount thereof converted into shares of Common Stock.

         To convert a Debenture, a Debentureholder must (i) complete and sign a
Conversion Request substantially in the form attached hereto, (ii) surrender the
Debenture to the Conversion Agent, (iii) furnish appropriate endorsements or
transfer documents if required by the Debenture Registrar or Conversion

                                       A-6

<PAGE>   85

Agent, and (iv) pay any transfer or similar tax, if required. If a Conversion
Request is delivered on or after the regular record date and prior to the
subsequent Interest Payment Date, the Debentureholder shall be required to pay
to the Company the interest payment to be made on the subsequent Interest
Payment Date, and shall be entitled to receive the interest payable on the
subsequent Interest Payment Date, on the portion of Debentures to be converted
notwithstanding the conversion thereof prior to such Interest Payment Date.
Notwithstanding the foregoing, if, during an Extended Interest Payment Period, a
notice of redemption is mailed pursuant to Section 3.4 of the Indenture and a
Debenture is converted after such mailing but prior to the relevant redemption
date, all accrued but unpaid interest (including Additional Payments, if any)
through the date of conversion shall be paid to the Debentureholder of such
Debenture on the redemption date. Except as otherwise provided in the
immediately preceding two sentences, in the case of any Debenture which is
converted, interest with a Stated Maturity which is after the date of conversion
of such Debenture shall not be payable, and the Company shall not make or be
required to make any other payment, adjustment or allowance with respect to
accrued but unpaid interest (including Additional Payments, if any) on the
Debentures being converted, which shall be deemed to be paid in full. If any
Debenture called for redemption is converted, any money deposited with the
Trustee or with any Paying Agent or so segregated and held in trust for the
redemption of such Debenture shall be paid to the Company upon Company request
or, if then held by the Company, shall be discharged from such trust.

         No reference herein to the Indenture and no provision of this Debenture
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional, to pay the principal and interest on this
Debenture at the time and place and at the rate and in the money herein
prescribed.

         Provided certain conditions are met, the Company shall have the right
at any time during the term of the Debentures and from time to time to extend
the interest payment period of such Debentures for up to 20 consecutive quarters
(each, an "Extended Interest Payment Period"), at the end of which period the
Company shall pay all interest then accrued and unpaid (together with interest
thereon at the rate specified for the Debentures to the extent that payment of
such interest is enforceable under applicable law). Before the termination of
any such Extended Interest Payment Period, so long as no Event of Default shall
have occurred and be continuing, the Company may further extend such Extended
Interest Payment Period, provided that such Extended Interest Payment Period
together with all such further extensions thereof shall not exceed 20
consecutive quarters, extend beyond the Stated Maturity or end on a date other
than an Interest Payment Date. At the termination of any such Extended Interest
Payment Period and upon the payment of all accrued and unpaid interest and any
additional amounts then due and subject to the foregoing conditions, the Company
may commence a new Extended Interest Payment Period.

         As provided in the Indenture and subject to certain limitations therein
set forth, this Debenture is transferable by the registered holder hereof on the
Debenture Register of the Company, upon surrender of this Debenture for
registration of transfer at the office or agency of the Trustee accompanied by a
written instrument or instruments of transfer in form satisfactory to the
Company or the Trustee duly executed by the registered holder hereof or his
attorney duly authorized in writing, and thereupon one or more new Debentures of
authorized denominations and for the same aggregate principal amount shall be
issued to the

                                       A-7

<PAGE>   86

designated transferee or transferees. No service charge shall be made for any
such transfer, but the Company may require payment of a sum sufficient to cover
any tax or other governmental charge payable in relation thereto.

         Prior to due presentment for registration of transfer of this
Debenture, the Company, the Trustee, any paying agent and the Debenture
Registrar may deem and treat the registered holder hereof as the absolute owner
hereof (whether or not this Debenture shall be overdue and notwithstanding any
notice of ownership or writing hereon made by anyone other than the Debenture
Registrar) for the purpose of receiving payment of or on account of the
principal hereof and interest due hereon and for all other purposes, and neither
the Company nor the Trustee nor any paying agent nor any Debenture Registrar
shall be affected by any notice to the contrary.

         No recourse shall be had for the payment of the principal of or the
interest on this Debenture, or for any claim based hereon, or otherwise in
respect hereof, or based on or in respect of the Indenture, against any
incorporator, stockholder, officer or director, past, present or future, as
such, of the Company or of any predecessor or successor corporation, whether by
virtue of any constitution, statute or rule of law, or by the enforcement of any
assessment or penalty or otherwise, all such liability being, by the acceptance
hereof and as part of the consideration for the issuance hereof, expressly
waived and released.

         The Debentures are issuable only in registered form without coupons in
denominations of $10 and any integral multiple thereof.

         All terms used in this Debenture that are defined in the Indenture
shall have the meanings assigned to them in the Indenture.

                                       A-8

<PAGE>   87

                           FORM OF CONVERSION REQUEST

To:      Southside Bancshares, Inc.

         The undersigned owner of these Preferred Securities hereby irrevocably
elects to convert these Preferred Securities, or the portion below designated,
into Common Stock of the Company (the "Common Stock") in accordance with the
terms of the Indenture (the "Indenture"), dated as of __________, 2000, between
Southside Bancshares, Inc., and Wilmington Trust Company.

         The undersigned owner of these Preferred Securities hereby directs the
Conversion Agent to convert such Preferred Securities on behalf of the
undersigned, into Common Stock (at the Conversion Ratio specified in the
Indenture). The undersigned owner of these Preferred Securities also hereby
notifies the Conversion Agent that the shares issuable and deliverable upon
conversion, together with any check in payment for fractional shares, should be
issued in the name of and delivered to the undersigned, unless a different name
has been indicated in the assignment below. (if shares are to be issued in the
name of a person other than the undersigned, the undersigned shall pay all
transfer taxes payable with respect thereto.)

Date:
     ------------------

Principal Amount of Securities to be converted ($10 or integral multiples
thereof): $
           ----------------

If a name of names other than the undersigned, please indicate in the spaces
below the name or names in which the shares of Common Stock are to be issued,
along with the address or addresses of such person or persons:

--------------------

--------------------

--------------------

(Sign exactly as your name appears on the other side of this Preferred Security)
(for conversion only)

Please print or type name and address, including zip code, and social security
or other identifying number:

--------------------

--------------------

--------------------

Signature Guarantee:*
                     -----------------------

------------

         *Signature must be guaranteed by an "eligible guarantor institution"
that is a bank, stockbroker, savings and loan association or credit union
meeting the requirements of the Registrar, which requirements include membership
or participation in the Securities Transfer Agents Medallion Program ("STAMP")
or such other "signature guarantee program" as may be determined by the
Registrar in addition to, or in substitution for, STAMP, all in accordance with
the Securities and Exchange Act of 1934, as amended.

                                       A-9

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