<PAGE>   1
                                                                     EXHIBIT 4.1









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

                           AXYS PHARMACEUTICALS, INC.

                                       TO

                     U.S. BANK TRUST NATIONAL ASSOCIATION,

                                   AS TRUSTEE

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



                                   INDENTURE

                            DATED AS OF _____, 2000





                                DEBT SECURITIES





<PAGE>   2
                           AXYS PHARMACEUTICALS, INC.
                                       TO
                      U.S. BANK TRUST NATIONAL ASSOCIATION,
                                   AS TRUSTEE

                                    Indenture
                                 Debt Securities

                                TABLE OF CONTENTS
<TABLE>
<CAPTION>
                                                                                                                  Page
<S>                                                                                                               <C>
ARTICLE ONE DEFINITIONS AND OTHER PROVISIONS OF
            GENERAL APPLICATION.....................................................................................1
     Section 101.  Definitions......................................................................................1
     Section 102.  Compliance Certificates and Opinions.............................................................8
     Section 103.  Form of Documents Delivered to Trustee...........................................................9
     Section 104.  Acts of Holders.................................................................................10
     Section 105.  Notices, Etc. to Trustee and Company............................................................12
     Section 106.  Notice to Holders; Waiver.......................................................................12
     Section 107.  Conflict with Trust Indenture Act...............................................................12
     Section 108.  Effect of Headings and Table of Contents........................................................13
     Section 109.  Successors and Assigns..........................................................................13
     Section 110.  Separability Clause.............................................................................13
     Section 111.  Benefits of Indenture...........................................................................13
     Section 112.  Governing Law...................................................................................13
     Section 113.  Legal Holidays..................................................................................13
     Section 114.  Indenture and Securities Solely Corporate Obligations...........................................13

ARTICLE TWO SECURITY FORMS 14
     Section 201.  Forms Generally.................................................................................14
     Section 202.  Form of Face of Security........................................................................14
     Section 203.  Form of Reverse of Security.....................................................................16
     Section 204.  Form of Legend for Global Securities............................................................21
     Section 205.  Form of Trustee's Certificate of Authentication............................................. ...21
     Section 206.  Form of Conversion Notice...................................................................... 21

ARTICLE THREE  THE SECURITIES 23
     Section 301.  Amount Unlimited; Issuable in Series............................................................23
     Section 302.  Denominations...................................................................................25
     Section 303.  Execution, Authentication, Delivery and Dating..................................................26
     Section 304.  Temporary Securities............................................................................27
     Section 305.  Registration;Registration of Transfer and Exchange..............................................27
     Section 306.  Mutilated, Destroyed, Lost and Stolen Securities................................................29
</TABLE>



                                       i
<PAGE>   3
<TABLE>
<CAPTION>
                                                                                                                   Page
<S>                                                                                                                <C>
     Section 307.  Payment of Interest; Interest Rights Preserved...................................................30
     Section 308.  Persons Deemed Owners............................................................................31
     Section 309.  Cancellation.....................................................................................31
     Section 310.  Computation of Interest..........................................................................32

ARTICLE FOUR SATISFACION AND DISCHARGE 32
     Section 401.  Satisfaction and Discharge of Indenture..........................................................32
     Section 402.  Application of Trust Money.......................................................................33

ARTICLE FIVE REMEDIES 33
     Section 501.  Events of Default................................................................................33
     Section 502.  Acceleration of Maturity; Rescission and Annulment...............................................34
     Section 503.  Collection of Indebtedness and Suits for
                   Enforcement by Trustee...........................................................................35
     Section 504.  Trustee May File Proofs of Claim.................................................................36
     Section 505.  Trustee May Enforce Claims without
                   Possession of Securities.........................................................................36
     Section 506.  Application of Money Collected...................................................................37
     Section 507.  Limitation on Suits..............................................................................37
     Section 508.  Unconditional Right of Holders to Receive Principal,
                   Premium and Interest and to Convert..............................................................38
     Section 509.  Restoration of Rights and Remedies...............................................................38
     Section 510.  Rights and Remedies Cumulative...................................................................38
     Section 511.  Delay or Omission not Waiver.....................................................................38
     Section 512.  Control by Holders...............................................................................38
     Section 513.  Waiver of Past Defaults..........................................................................39
     Section 514.  Undertaking for Costs............................................................................39
     Section 515.  Waiver of Usury, Stay or Extension Laws..........................................................39

ARTICLE SIX THE TRUSTEE 40
     Section 601.  Certain Duties and Responsibilities..............................................................40
     Section 602.  Notice of Defaults...............................................................................40
     Section 603.  Certain Rights of Trustee........................................................................40
     Section 604.  Not Responsible for Recitals or Issuance of Securities...........................................41
     Section 605.  May Hold Securities and Act as Trustee
                   Under Other Indentures...........................................................................41
     Section 606.  Money Held in Trust..............................................................................41
     Section 607.  Compensation and Reimbursement...................................................................42
     Section 608.  Conflicting Interests............................................................................42
     Section 609.  Corporate Trustee Required; Eligibility..........................................................42
     Section 610.  Resignation and Removal;
                   Appointment of Successor.........................................................................42
     Section 611.  Acceptance of Appointment by Successor...........................................................44
     Section 612.  Merger, Conversion, Consolidation or
                   Succession to Business...........................................................................45
</TABLE>



                                       ii
<PAGE>   4
<TABLE>
<CAPTION>
                                                                                                                   Page
<S>                                                                                                                <C>
     Section 613.  Preferential Collection of Claims Against Company................................................45
     Section 614.  Appointment of Authenticating Agent..............................................................45

ARTICLE SEVEN  HOLDERS' LISTS AND REPORTS  BY
               TRUSTEE AND COMPANY..................................................................................47
      Section 701.  Company to Furnish Trustee
                    Names and Addresses of Holders..................................................................47
      Section 702.  Preservation of Information;
                    Communications to Holders.......................................................................47
      Section 703.  Reports by Trustee .............................................................................48
      Section 704.  Reports by Company .............................................................................48

ARTICLE EIGHT  CONSOLIDATION, MERGER, CONVEYANCE,
               TRANSFER OR LEASE....................................................................................48
     Section 801.  Company May Consolidate, etc. Only on
                   Certain Terms....................................................................................48
     Section 802.  Successor Substituted ...........................................................................49

ARTICLE NINE SUPPLEMENTAL INDENTURES
     Section 901.  Supplemental Indentures without Consent of Holders...............................................49
     Section 902.  Supplemental Indentures with Consent of Holders..................................................51
     Section 903.  Execution of Supplemental Indentures.............................................................52
     Section 904.  Effect of Supplemental Indentures................................................................52
     Section 905.  Conformity with Trust Indenture Act..............................................................52
     Section 906.  Reference in Securities to Supplemental Indentures...............................................52

ARTICLE TEN COVENANTS
     Section 1001. Payment of Principal, Premium and Interest.......................................................53
     Section 1002. Maintenance of Office or Agency..................................................................53
     Section 1003. Money For Securities Payments to Be Held in Trust................................................53
     Section 1004. Statement by Officers as to Default..............................................................54
     Section 1005. Existence .......................................................................................54
     Section 1006. Opinions as to Pledged Property..................................................................55
     Section 1007. Waiver of Certain Covenants .....................................................................55

ARTICLE ELEVEN REDEMPTION OF SECURITIES ............................................................................56
     Section 1101. Applicability of Article ........................................................................56
     Section 1102. Election to Redeem; Notice to Trustee............................................................56
     Section 1103. Selection by Trustee of Securities to Be Redeemed................................................56
     Section 1104. Notice of Redemption ............................................................................57
     Section 1105. Deposit of Redemption Price .....................................................................58
     Section 1106. Securities Payable on Redemption Date............................................................58
     Section 1107. Securities Redeemed in Part .....................................................................58

ARTICLE TWELVE SINKING FUNDS .......................................................................................59
</TABLE>




                                      iii
<PAGE>   5
<TABLE>
<CAPTION>
                                                                                                                  Page
<S>                                                                                                               <C>
     Section 1201. Applicability of Article .......................................................................59
     Section 1202. Satisfaction of Sinking Fund Payments with Securities...........................................59
     Section 1203. Redemption of Securities for Sinking Fund.......................................................59

ARTICLE THIRTEEN DEFEASANCE AND COVENANT DEFEASANCE................................................................60
     Section 1301. Company's Option to Effect Defeasance or
                   Covenant Defeasance.............................................................................60
     Section 1302. Defeasance and Discharge .......................................................................60
     Section 1303. Covenant Defeasance ............................................................................60
     Section 1304. Conditions to Defeasance or Covenant Defeasance.................................................61
     Section 1305. Deposited Money and U.S. Government Obligations to
                   Be Held in Trust; Miscellaneous Provision.......................................................62
     Section 1306. Reinstatement ..................................................................................63

ARTICLE FOURTEEN CONVERSION OF SECURITIES
     Section 1401. Applicability of Article .......................................................................63
     Section 1402. Exercise of Conversion Privilege................................................................63
     Section 1403. No Fractional Shares ...........................................................................65
     Section 1404. Adjustment of Conversion Price..................................................................65
     Section 1405. Notice of Certain Corporate Actions.............................................................66
     Section 1406. Reservation of Shares of Common Stock...........................................................67
     Section 1407. Payment of Certain Taxes upon Conversion........................................................67
     Section 1408. Nonassessability ...............................................................................67
     Section 1409. Provision in Case of Consolidation, Merger or
                   Sale of Assets..................................................................................67
     Section 1410. Duties of Trustee Regarding Conversion..........................................................68
     Section 1411. Repayment of Certain Funds upon Conversion......................................................69

ARTICLE FIFTEEN COLLATERAL.........................................................................................69
     Section 1501. Releases of Collateral..........................................................................69
</TABLE>


          Certain Sections of this Indenture relating to Sections 310 through
          318, inclusive, of the Trust Indenture Act of 1939:

<TABLE>
<CAPTION>
           Trust Indenture                   Indenture
           Act Section                       Section

<S>       <C>                               <C>
           ss.310 (a)(1)                     609
                  (a)(2)                     609
                  (a)(3)                     Not Applicable
                  (a)(4)                     Not Applicable
                  (b)                        608, 610
           ss.311 (a)                        613

</TABLE>


                                       iv
<PAGE>   6
<TABLE>
<CAPTION>
           Trust Indenture                   Indenture
           Act Section                       Section

<S>                                          <C>
                  (b)                        613
           ss.312 (a)                        701, 702
                  (b)                        702
                  (c)                        702
           ss.313 (a)                        703
                  (b)                        703
                  (c)                        703
                  (d)                        703
           ss.314 (a)                        704
                  (a)(4)                     101, 1004
                  (b)                        1006
                  (c)(1)                     102
                  (c)(2)                     102
                  (c)(3)                     Not Applicable
                  (d)                        1501
                  (e)                        102
           ss.315 (a)                        601
                  (b)                        602
                  (c)                        601
                  (d)                        601
                  (e)                        514
           ss.316 (a)                        101
                  (a)(1)(A)                  502, 512
                  (a)(1)(B)                  513
                  (a)(2)                     Not Applicable
                  (b)                        508
                  (c)                        104
           ss.317 (a)(1)                     03
                  (a)(2)                     504
                  (b)                        1003
           ss.318 (a)                        107
</TABLE>



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



                                       V
<PAGE>   7
          INDENTURE, dated as of_____________________, 2000, between Axys
Pharmaceuticals, Inc., a corporation duly organized and existing under the laws
of the State of Delaware (herein called the "Company"), having its principal
executive office at 180 Kimball Way, South San Francisco, California, 94080, and
U.S. Bank Trust National Association, a national banking association duly
organized and existing under the laws of the United States of America, as
Trustee (herein called the "Trustee").

                             RECITALS OF THE COMPANY

          The Company has duly authorized the execution and delivery of this
Indenture to provide for the issuance from time to time of its secured and
unsecured debentures, notes or other evidences of indebtedness (herein called
the "Securities"), to be issued in one or more series as provided in this
Indenture.

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

                   NOW, THEREFORE, THIS INDENTURE WITNESSETH:

          For and in consideration of the premises and the purchase of the
Securities by the Holders thereof, it is mutually covenanted and agreed, for the
equal and proportionate benefit of all Holders of the Securities or of series
thereof appertaining, as follows:


                                   ARTICLE ONE

             DEFINITIONS AND OTHER PROVISIONS OF GENERAL APPLICATION

          SECTION 101. DEFINITIONS. For all purposes of this Indenture, except
as otherwise expressly provided or unless the context otherwise requires:

          (1) the terms defined in this Article have the meanings assigned to
them in this Article and include the plural as well as the singular;

          (2) all other terms used herein which are defined in the Trust
Indenture Act, either directly or by reference therein, have the meanings
assigned to them therein;

          (3) all accounting terms not otherwise defined herein have the
meanings assigned to them in accordance with generally accepted accounting
principles, and, except as otherwise herein expressly provided, the term
"generally accepted accounting principles" with respect to any computation
required orpermitted hereunder shall mean such accounting principles as are
generally accepted at the date of such computation;



                                       1
<PAGE>   8
          (4) unless the context otherwise requires, any reference to an
"Article" or a "Section" refers to an Article or a Section, as the case may be,
of this Indenture; and

          (5) the words "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.

          "Act," when used with respect to any Holder, has the meaning specified
in Section 104.

          "Affiliate" of any specified Person means any other Person directly or
indirectly controlling or controlled by or under direct or indirect common
control with such specified Person. For the purposes of this definition,
"control" when used with respect to any specified Person means the power to
direct the management and policies of such Person, directly or indirectly,
whether through the ownership of voting securities, by contract or otherwise;
and the terms "controlling" and "controlled" have meanings correlative to the
foregoing.

          "Appraiser" means a Person engaged in the business of appraising
property who (except as otherwise expressly provided in this Indenture) may be
employed by or affiliated with the Company.

          "Authenticating Agent" means any Person authorized by the Trustee
pursuant to Section 614 to act on behalf of the Trustee to authenticate
Securities of one or more series.

          "Board of Directors" means either the board of directors of the
Company or any duly authorized committee of that board empowered to act for it
with respect to this Indenture.

          "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, and delivered to the Trustee.

          "Business Day" when used with respect to any Place of Payment, means
each Monday, Tuesday, Wednesday, Thursday and Friday which is not a day on which
banking institutions in that Place of Payment are authorized or obligated by law
or executive order to close.

          "Commission" means the Securities and Exchange Commission, from time
to time constituted, created under the Exchange Act, or, if at any time after
the execution of this instrument such Commission is not existing and performing
the duties now assigned to it under the Trust Indenture Act, then the body
performing such duties



                                    -PAGE 2-
<PAGE>   9
at such time.

          "Common Stock" includes any stock of any class of the Company which
has no preference in respect of dividends or of amounts payable in the event of
any voluntary or involuntary liquidation, dissolution or winding-up of the
Company and which is not subject to redemption by the Company; provided,
however, subject to the provisions of Section 1409, shares issuable upon
conversion of Securities shall include only shares of the class designated as
Common Stock of the Company at the date of this Indenture or shares of any class
or classes resulting from any reclassification or reclassifications thereof and
which have no preference in respect of dividends or of amounts payable in the
event of any voluntary or involuntary liquidation, dissolution or winding-up of
the Company and which are not subject to redemption by the Company; provided,
further, that if at any time there shall be more than one such resulting class,
the shares of each such class then so issuable shall be substantially in the
proportion which the total number of shares of such class resulting from all
such reclassifications bears to the total number of shares of all such classes
resulting from all such reclassifications.

          "Company" means the corporation named as the "Company" in the first
paragraph of this instrument until a successor Person shall have become such
pursuant to the applicable provisions of this Indenture, and thereafter
"Company" shall mean such successor Person.

          "Company Request" or "Company Order" means a written request or order
signed in the name of the Company by its Chairman of the Board, its Vice
Chairman of the Board, its President or a Vice President, and by its principal
financial officer, its Secretary or an Assistant Secretary, and delivered to the
Trustee.

          "Corporate Trust Office" means the corporate trust office of the
Trustee at which at any particular time the trust created by this Indenture
shall be administered, which office on the date hereof is located at 550 South
Hope Street, Suite 500, Los Angeles, California, 90071.

          "corporation" means a corporation, association, company, joint-stock
company or business trust.

          "Covenant Defeasance" has the meaning specified in Section 1303.

          "Defaulted Interest" has the meaning specified in Section 307.

          "Defeasance" has the meaning specified in Section 1302.

          "Depositary" means, with respect to Securities of any series issuable
in whole or in part in the form of one or more Global Securities, a clearing
agency



                                    -PAGE 3-
<PAGE>   10
registered under the Exchange Act that is designated to act as Depositary for
such Securities as contemplated by Section 301.

          "Event of Default" has the meaning specified in Section 501.

          "Exchange Act" means the Securities Exchange Act of 1934 and any
statute successor thereto, in each case as amended from time to time.

          "Expiration Date" has the meaning specified in Section 104.

          "Global Security" means a Security that evidences all or part of the
Securities of any series and bears the legend set forth in Section 204 (or such
legend as may be specified as contemplated by Section 301 for such Securities).

          "Holder" means a Person in whose name a Security is registered in the
Security Register.

          "Fair Market Value" means, at any time with respect to any property,
the sale value of such property which could be realized in an arm's length sale
at such time between an informed and willing vendee, and an informed and willing
vendor, under no compulsion to buy or sell, respectively, all as determined in
good faith (a) in the case of any Officers' Certificate or other certificate
delivered pursuant to Section 1501, by the signer or signers thereof and (b) in
all other cases, (i) by the vendor's board of directors or (ii) in the case of
any such property of the Company or any Restricted Subsidiary, by the Chief
Executive Officer or the President of the Company, except as otherwise
specifically provided in this Indenture or any Indenture supplemental hereto.

          "Financial Advisor" shall mean an investment banking firm of national
reputation which (except as otherwise expressly provided in this Indenture) may
be employed by or affiliated with the Company.

          "Indenture" means this instrument as originally executed and as it may
from time to time be supplemented or amended by one or more indentures
supplemental hereto entered into pursuant to the applicable provisions hereof,
including, for all purposes of this instrument and any such supplemental
indenture, the provisions of the Trust Indenture Act that are deemed to be a
part of and govern this instrument and any such supplemental indenture,
respectively. The term "Indenture" shall also include the terms of particular
series of Securities established as contemplated by Section 301; provided,
however, that if at any time more than one Person is acting as Trustee under
this Indenture due to the appointment of one or more separate Trustees for any
one or more separate series of Securities, "Indenture" shall mean, with respect
to such series of Securities for which any such Person is Trustee, 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 pursuant
to the



                                    -PAGE 4-
<PAGE>   11
applicable provisions hereof and shall include the terms of particular series of
Securities for which such Person is Trustee established as contemplated by
Section 301, exclusive, however, of any provisions or terms which relate solely
to other series of Securities for which such Person is not Trustee, regardless
of when such terms or provisions were adopted, and exclusive of any provisions
or terms adopted by means of one or more indentures supplemental hereto executed
and delivered after such Person had become such Trustee, but to which such
Person, as such Trustee, was not a party; provided, further that in the event
that this Indenture is supplemented or amended by one or more indentures
supplemental hereto which are only applicable to certain series of Securities,
the term "Indenture" for a particular series of Securities shall only include
the supplemental indentures applicable thereto.

          "Independent" when used with respect to any specified Person means
such a Person who (a) is "independent" within the meaning of the Trust
Indenture Act, (b) does not have any direct financial interest or any material
indirect financial interest in the Company or in any other obligor under the
Securities or in any Affiliate of the Company or of such other obligor and (c)
is not connected with the Company or such other obligor as an officer, employee,
promoter, underwriter, trustee, partner, director or Person performing similar
functions. Whenever it is herein provided that any Independent Person's opinion
or certificate shall be furnished to the Trustee, such Person shall be appointed
by a Company Order and such opinion or certificate shall state that the signer
has read this definition and that the signer is Independent within the meaning
thereof.

          "interest," when used with respect to an Original Issue Discount
Security which by its terms bears interest only after Maturity, means interest
payable after Maturity.

          "Interest Payment Date," when used with respect to any Security, means
the Stated Maturity of an installment of interest on such Security.

          "Investment Company Act" means the Investment Company Act of 1940 and
any statute successor thereto, in each case as amended from time to time.

          "Lien" shall mean any lien, mortgage, security interest, chattel
mortgage, pledge, equity or other encumbrance (statutory or otherwise) of any
kind, including, without limitation, any agreement to give any of the foregoing,
any conditional sales or other title retention agreement, any lease in the
nature thereof, and the filing of or the agreement to give any financing
statement under the Code of any jurisdiction or similar evidence of any
encumbrance, whether within or outside the United States.

          "Maturity" when used with respect to any Security, means the date on
which the principal of such Security or an installment of principal becomes due
and payable as therein or herein provided, whether at the Stated Maturity or by
declaration of acceleration, call for redemption or otherwise.





                                    -PAGE 5-
<PAGE>   12

          "Notice of Default" means a written notice of the kind specified in
Section 501(4).

          "Officers' Certificate" means a certificate signed by the Chairman of
the Board, a Vice Chairman of the Board, the President or a Vice President, and
by the principal financial officer, the Secretary or an Assistant Secretary, of
the Company, and delivered to the Trustee. One of the officers signing an
Officers' Certificate given pursuant to Section 1004 shall be the principal
executive, financial or accounting officer of the Company.

          "Opinion of Counsel" means a written opinion of counsel, who may be
counsel for, or an employee of, the Company, and who shall be reasonably
acceptable to the Trustee.

          "Original Issue Discount Security" means any Security which provides
for an amount less than the principal amount thereof to be due and payable upon
a declaration of acceleration of the Maturity thereof pursuant to Section 502.

          "Outstanding," when used with respect to Securities, means, as of the
date of determination, all Securities theretofore authenticated and delivered
under this Indenture, except:

          (1) Securities theretofore canceled by the Trustee or delivered to the
Trustee for cancellation;

          (2) Securities for whose payment or redemption money in the necessary
amount has been theretofore deposited with the Trustee or any Paying Agent
(other than the Company) in trust or set aside and segregated in trust by the
Company (if the Company shall act as its own Paying Agent) for the Holders of
such Securities; provided that, if such Securities are to be redeemed, notice of
such redemption has been duly given pursuant to this Indenture or provision
therefor satisfactory to the Trustee has been made;


          (3) Securities as to which Defeasance has been effected pursuant to
Section 1302; and

          (4) Securities which have been paid pursuant to Section 306 or in
exchange for or in lieu of which other Securities have been authenticated and
delivered pursuant to this Indenture, other than any such Securities in respect
of which there shall have been presented to the Trustee proof satisfactory to it
that such Securities are held by a bona fide purchaser in whose hands such
Securities are valid obligations of the Company; provided, however, that in
determining whether the Holders of the requisite principal amount of the
Outstanding Securities have given, made or taken any request, demand,
authorization, direction, notice, consent, waiver or other action hereunder as



                                    -PAGE 6-
<PAGE>   13
of any date, (A) the principal amount of an Original Issue Discount Security
which shall be deemed to be Outstanding shall be the amount of the principal
thereof which would be due and payable as of such date upon acceleration of the
Maturity thereof to such date pursuant to Section 502, (B) if, as of such date,
the principal amount payable at the Stated Maturity of a Security is not
determinable, the principal amount of such Security which shall be deemed to be
Outstanding shall be the amount as specified or determined as contemplated by
Section 301, (C) the principal amount of a Security denominated in one or more
foreign currencies or currency units which shall be deemed to be Outstanding
shall be the U.S. dollar equivalent, determined as of such date in the manner
provided as contemplated by Section 301, of the principal amount of such
Security (or, in the case of a Security described in Clause (A) or (B) above, of
the amount determined as provided in such Clause), and (D) Securities owned by
the Company or any other obligor upon the Securities or any Affiliate of the
Company or of such other obligor shall be disregarded and deemed not to be
Outstanding, except that, in determining whether the Trustee shall be protected
in relying upon any such request, demand, authorization, direction, notice,
consent, waiver or other action, only Securities which the Trustee knows to be
so owned shall be so disregarded. Securities so owned which have been pledged in
good faith may be regarded as Outstanding if the pledgee establishes to the
satisfaction of the Trustee the pledgee's right so to act with respect to such
Securities and that the pledgee is not the Company or any other obligor upon the
Securities or any Affiliate of the Company or of such other obligor.

          "Paying Agent" means any Person authorized by the Company to pay the
principal of or any premium or interest on any Securities on behalf of the
Company.

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

          "Place of Payment," when used with respect to the Securities of any
series, means the place or places where the principal of and any premium and
interest on the Securities of that series are payable as specified as
contemplated by Section 301.

          "Predecessor Security" of any particular Security means every previous
Security evidencing all or a portion of the same debt as that evidenced by such
particular Security; and, for the purposes of this definition, any Security
authenticated and delivered under Section 306 in exchange for or in lieu of a
mutilated, destroyed, lost or stolen Security shall be deemed to evidence the
same debt as the mutilated, destroyed, lost or stolen Security.

          "Prior Lien" means any Lien on any of the collateral securing the
Company's obligations with respect to Securities issued under this Indenture
ranking prior to or upon parity with the Lien of this Indenture.



                                    -PAGE 7-
<PAGE>   14
          "Property" means any interest in any kind of property or asset,
whether real, personal or mixed, and whether tangible or intangible.

          "Redemption Date," when used with respect to any Security to be
redeemed, means the date fixed for such redemption by or pursuant to this
Indenture.

          "Redemption Price," when used with respect to any Security to be
redeemed, means the price at which it is to be redeemed pursuant to this
Indenture.

          "Regular Record Date" for the interest payable on any Interest Payment
Date on the Securities of any series means the date specified for that purpose
as contemplated by Section 301.

          "Responsible Officer" means an officer in the Corporate Trust Office
of the Trustee.

          "Securities" has the meaning stated in the first recital of this
Indenture and more particularly means any Securities authenticated and delivered
under this Indenture.

          "Securities Act" means the Securities Act of 1933 and any statute
successor thereto, in each case as amended from time to time.

          "Security Register" and "Security Registrar" have the respective
meanings specified in Section 305.

          "Special Record Date" for the payment of any Defaulted Interest means
a date fixed by the Trustee pursuant to Section 307.

          "Stated Maturity," when used with respect to any Security or any
installment of principal thereof or interest thereon, means the date specified
in such Security as the fixed date on which the principal of such Security or
such installment of principal or interest is due and payable.

          "Subsidiary" means a corporation of which at least a majority of the
outstanding voting stock having the power to elect a majority of the board of
directors of such corporation is at the time owned, directly or indirectly, by
the Company or by one or more other Subsidiaries, or by the Company and one or
more other Subsidiaries and the accounts of which are consolidated with those of
the Company in its most recent consolidated financial statements in accordance
with generally accepted accounting principles. For the purposes of this
definition, "voting stock" means stock which ordinarily has voting power for the
election of directors, whether at all times or only so long as no senior class
of stock has such voting power by reason of any contingency.



                                    -PAGE 8-
<PAGE>   15
          "Trust Indenture Act" means the Trust Indenture Act of 1939 as in
force at the date as of which this instrument was executed; provided, however,
that in the event the Trust Indenture Act of 1939 is amended after such date,
"Trust Indenture Act" means, to the extent required by any such amendment, the
Trust Indenture Act of 1939 as so amended.

          "Trustee" means the Person named as the "Trustee" in the first
paragraph of this instrument until a successor Trustee shall have become such
pursuant to the applicable provisions of this Indenture, and thereafter
"Trustee" shall mean or include each Person who is then a Trustee hereunder, and
if at any time there is more than one such Person, "Trustee" as used with
respect to the Securities of any series shall mean the Trustee with respect to
Securities of that series.

          "U.S. Government Obligation" has the meaning specified in Section
1304.

          "Vice President," when used with respect to the Company or the
Trustee, means any vice president, whether or not designated by a number or a
word or words added before or after the title "vice president."

          SECTION 102. COMPLIANCE CERTIFICATES AND OPINIONS. Upon any
application or request by the Company to the Trustee to take any action under
any provision of this Indenture, the Company shall furnish to the Trustee such
certificates and opinions as may be required under the Trust Indenture Act. Each
such certificate or opinion shall be given in the form of an Officers'
Certificate, if to be given by an officer of the Company, or an Opinion of
Counsel, if to be given by counsel, and shall comply with the requirements of
the Trust Indenture Act and any other requirements set forth in this Indenture.

          Every certificate or opinion with respect to compliance with a
condition or covenant provided for in this Indenture shall include,

          (1) a statement that each individual signing such certificate or
opinion has read such covenant or condition and the definitions herein relating
thereto;

          (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 each such individual, he or
she has made such examination or investigation as is necessary to enable him or
her 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, in the opinion of each such individual,
such condition or covenant has been complied with.



                                    -PAGE 9-
<PAGE>   16
          SECTION 103. FORM OF DOCUMENTS DELIVERED TO TRUSTEE. In any case where
several matters are required to be certified by, or covered by an opinion of,
any specified Person, it is not necessary that all such matters be certified by,
or covered by the opinion of, only one such Person, or that they be so certified
or covered by only one document, but one such Person may certify or give an
opinion with respect to some matters and one or more other such Persons as to
other matters, and any such Person may certify or give an opinion as to such
matters in one or several documents.

          Any certificate or opinion of an officer of the Company may be based,
insofar as it relates to legal matters, upon a certificate or opinion of, or
representations by, counsel, unless such officer knows, or in the exercise of
reasonable care should know, that the certificate or opinion or representations
with respect to the matters upon which his or her certificate or opinion is
based are erroneous. Any such certificate or opinion of counsel may be based,
insofar as it relates to factual matters, upon a certificate or opinion of, or
representations by, an officer or officers of the Company stating that the
information with respect to such factual matters is in the possession of the
Company, unless such counsel knows, or in the exercise of reasonable care should
know, that the certificate or opinion or representations with respect to such
matters are erroneous.

          Where any Person is required to make, give or execute two or more
applications, requests, consents, certificates, statements, opinions or other
instruments under this Indenture, they may, but need not, be consolidated and
form one instrument.

          SECTION 104. ACTS OF HOLDERS. Any request, demand, authorization,
direction, notice, consent, waiver or other action provided or permitted by this
Indenture to be given, made or taken by Holders may be embodied in and evidenced
by one or more instruments of substantially similar tenor signed by such Holders
in person or by agent duly appointed in writing; and, except as herein otherwise
expressly provided, such action shall become effective when such instrument or
instruments are delivered to the Trustee and, where it is hereby expressly
required, to the Company. The Trustee shall promptly deliver to the Company
copies of all such instrument or instruments delivered to the Trustee. Such
instrument or instruments (and the action embodied therein and evidenced
thereby) are herein sometimes referred to as the "Act" of the Holders signing
such instrument or instruments. Proof of execution of any such instrument or of
a writing appointing any such agent shall be sufficient for any purpose of this
Indenture and (subject to Section 601) conclusive in favor of the Trustee and
the Company, if made in the manner provided in this Section.

          The fact and date of the execution by any Person of any such
instrument or writing may be proved by the affidavit of a witness of such
execution or by a certificate of a notary public or other officer authorized by
law to take acknowledgments of deeds, certifying that the individual signing
such instrument or writing acknowledged to him or her the execution thereof.
Where such execution is by a signer acting in a



                                   -PAGE 10-
<PAGE>   17
capacity other than his or her individual capacity, such certificate or
affidavit shall also constitute sufficient proof of his or her authority. The
fact and date of the execution of any such instrument or writing, or the
authority of the Person executing the same, may also be proved in any other
manner which the Trustee deems sufficient.

          The ownership of Securities shall be proved by the Security Register.

          Any request, demand, authorization, direction, notice, consent, waiver
or other Act of the Holder of any Security shall bind every future Holder of the
same Security and the Holder of every Security issued upon the registration of
transfer thereof or in exchange therefor or in lieu thereof in respect of
anything done, omitted or suffered to be done by the Trustee or the Company in
reliance thereon, whether or not notation of such action is made upon such
Security.

          The Company may set any day as a record date for the purpose of
determining the Holders of Outstanding Securities of any series entitled to
give, make or take any request, demand, authorization, direction, vote, notice,
consent, waiver or other action provided or permitted by this Indenture to be
given, made or taken by Holders of Securities of such series, provided that the
Company may not set a record date for, and the provisions of this paragraph
shall not apply with respect to, the giving or making of any notice,
declaration, request or direction referred to in the next paragraph. If any
record date is set pursuant to this paragraph, the Holders of Outstanding
Securities of the relevant series on such record date, and no other Holders,
shall be entitled to take the relevant action, whether or not such Holders
remain Holders after such record date; provided that no such action shall be
effective hereunder unless taken on or prior to the applicable Expiration Date
by Holders of the requisite principal amount of Outstanding Securities of such
series on such record date. Nothing in this paragraph shall be construed to
prevent the Company from setting a new record date for any action for which a
record date has previously been set pursuant to this paragraph (whereupon the
record date previously set shall automatically and with no action by any Person
be canceled and of no effect), and nothing in this paragraph shall be construed
to render ineffective any action taken by Holders of the requisite principal
amount of Outstanding Securities of the relevant series on the date such action
is taken. Promptly after any record date is set pursuant to this paragraph, the
Company, at its own expense, shall cause notice of such record date, the
proposed action by Holders and the applicable Expiration Date to be given to the
Trustee in writing and to each Holder of Securities of the relevant series in
the manner set forth in Section 106.

          The Trustee may set any day as a record date for the purpose of
determining the Holders of Outstanding Securities of any series entitled to join
in the giving or making of (i) any Notice of Default, (ii) any declaration of
acceleration referred to in Section 502, (iii) any request to institute
proceedings referred to in Section 507(2) or (iv) any direction referred to in
Section 512, in each case with respect to Securities of



                                   -PAGE 11-
<PAGE>   18
such series. If any record date is set pursuant to this paragraph, the Holders
of Outstanding Securities of such series on such record date, and no other
Holders, shall be entitled to join in such notice, declaration, request or
direction, whether or not such Holders remain Holders after such record date;
provided that no such action shall be effective hereunder unless taken on or
prior to the applicable Expiration Date by Holders of the requisite principal
amount of Outstanding Securities of such series on such record date. Nothing in
this paragraph shall be construed to prevent the Trustee from setting a new
record date for any action for which a record date has previously been set
pursuant to this paragraph (whereupon the record date previously set shall
automatically and with no action by any Person be canceled and of no effect),
and nothing in this paragraph shall be construed to render ineffective any
action taken by Holders of the requisite principal amount of Outstanding
Securities of the relevant series on the date such action is taken. Promptly
after any record date is set pursuant to this paragraph, the Trustee, at the
Company's expense, shall cause notice of such record date, the
proposed action by Holders and the applicable Expiration Date to be given to the
Company in writing and to each Holder of Securities of the relevant series in
the manner set forth in Section 106.

          With respect to any record date set pursuant to this Section, the
party hereto which sets such record dates may designate any day as the
"Expiration Date" and from time to time may change the Expiration Date to any
earlier or later day; provided that no such change shall be effective unless
notice of the proposed new Expiration Date is given to the other party hereto in
writing, and to each Holder of Securities of the relevant series in the manner
set forth in Section 106, on or prior to the existing Expiration Date. If an
Expiration Date is not designated with respect to any record date set pursuant
to this Section, the party hereto which set such record date shall be deemed to
have initially designated the 180th day after such record date as the Expiration
Date with respect thereto, subject to its right to change the Expiration Date as
provided in this paragraph. Notwithstanding the foregoing, no Expiration Date
shall be later than the 180th day after the applicable record date.

          Without limiting the foregoing, a Holder entitled hereunder to take
any action hereunder with regard to any particular Security may do so with
regard to all or any part of the principal amount of such Security or by one or
more duly appointed agents each of which may do so pursuant to such appointment
with regard to all or any part of such principal amount.

          SECTION 105. NOTICES, ETC. TO TRUSTEE AND COMPANY. Any request,
demand, authorization, direction, notice, consent, waiver or Act of Holders or
other document provided or permitted by this Indenture to be made upon, given or
furnished to, or filed with,

          (1) the Trustee by any Holder or by the Company shall be sufficient
for every purpose hereunder if made, given, furnished or filed in writing (or by
facsimile



                                   -PAGE 12-
<PAGE>   19
transmissions ((213) 533-8729), provided that oral confirmation of receipt shall
have been received) to or with the Trustee at its Corporate Trust Office,
Attention: Corporate Trust Department (Axys Pharmaceuticals, Inc. Debt
Securities), or

          (2) the Company by the Trustee or by any Holder shall be sufficient
for every purpose hereunder (unless otherwise herein expressly provided) if in
writing and mailed, first-class postage prepaid, to the Company addressed to it
at the address of its principal office specified in the first paragraph of this
instrument or at any other address previously furnished in writing to the
Trustee by the Company, Attention: Chief Financial Officer.

          SECTION 106. NOTICE TO HOLDERS; WAIVER. Where this Indenture provides
for notice to Holders of any event, such notice shall be sufficiently given
(unless otherwise herein expressly provided) if in writing and mailed,
first-class postage prepaid, to each Holder affected by such event, at its
address as it appears in the Security Register, not later than the latest date
(if any), and not earlier than the earliest date (if any), prescribed for the
giving of such notice. In any case where notice to Holders is given by mail,
neither the failure to mail such notice, nor any defect in any notice so mailed,
to any particular Holder shall affect the sufficiency of such notice with
respect to other Holders. Where this Indenture provides for notice in any
manner, such notice may be waived in writing by the Person entitled to receive
such notice, either before or after the event, and such waiver shall be the
equivalent of such notice. Waivers of notice by Holders shall be filed with the
Trustee, but such filing shall not be a condition precedent to the validity of
any action taken in reliance upon such waiver.

          In case by reason of the suspension of regular mail service or by
reason of any other cause it shall be impracticable to give such notice by mail,
then such notification as shall be made with the approval of the Trustee shall
constitute a sufficient notification for every purpose hereunder.

          SECTION 107. CONFLICT WITH TRUST INDENTURE ACT. If any provision
hereof limits, qualifies or conflicts with a provision of the Trust Indenture
Act which is required under such Act to be a part of and govern this Indenture,
the latter provision shall control. If any provision of this Indenture modifies
or excludes any provision of the Trust Indenture Act which may be so modified or
excluded, the latter provision shall be deemed to apply to this Indenture as so
modified or to be excluded, as the case may be.

          SECTION 108. EFFECT OF HEADINGS AND TABLE OF CONTENTS. The Article and
Section headings herein and the Table of Contents are for convenience only and
shall not affect the construction hereof.

          SECTION 109. SUCCESSORS AND ASSIGNS. All covenants and agreements in
this Indenture by the Company shall bind its successors and assigns,



                                   -PAGE 13-
<PAGE>   20
whether so expressed or not.


          SECTION 110. SEPARABILITY CLAUSE. In case any provision in this
Indenture or in the Securities shall be invalid, illegal or unenforceable, the
validity, legality and enforceability of the remaining provisions shall not in
any way be affected or impaired thereby.

          SECTION 111. BENEFITS OF INDENTURE. Nothing in this Indenture or in
the Securities, express or implied, shall give to any Person, other than the
parties hereto and their successors hereunder and the Holders, any benefit or
any legal or equitable right, remedy or claim under this Indenture.

          SECTION 112. GOVERNING LAW. THIS INDENTURE AND THE SECURITIES SHALL BE
GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAW OF THE STATE OF NEW YORK.

          SECTION 113. LEGAL HOLIDAYS. In any case where any Interest Payment
Date, Redemption Date or Stated Maturity of any Security or the last date on
which a Holder has the right to convert a Security at a particular conversion
price shall not be a Business Day at any Place of Payment, then (notwithstanding
any other provision of this Indenture or of the Securities (other than a
provision of any Security which specifically states that such provision shall
apply in lieu of this Section)) payment of interest or principal (and premium,
if any) or, if applicable to a particular series of Securities, conversion need
not be made at such Place of Payment on such date, but may be made on the next
succeeding Business Day at such Place of Payment with the same force and effect
as if made on the Interest Payment Date or Redemption Date, at the Stated
Maturity or on such last day for conversion, as the case may be.

          SECTION 114. INDENTURE AND SECURITIES SOLELY CORPORATE OBLIGATIONS. No
recourse for the payment of the principal of or premium, if any, or interest on
any Security, or for any claim based thereon or otherwise in respect thereof,
and no recourse under or upon any obligation, covenant or agreement of the
Company in this Indenture or in any supplemental indenture or in any Security,
or because of the creation of any indebtedness represented thereby, shall be had
against any incorporator, stockholder, employee, agent, officer, or director or
subsidiary, as such, past, present or future, of the Company or of any successor
corporation, either directly or through the Company or any 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 all such liability is hereby expressly waived and released as a
condition of, and as a consideration for, the execution of this Indenture and
the issue of the Securities.


                                   ARTICLE TWO



                                   -PAGE 14-
<PAGE>   21
                                 SECURITY FORMS

          SECTION 201. FORMS GENERALLY. The Securities of each series shall be
in substantially the form set forth in this Article, or in such other form as
shall be established by or pursuant to a Board Resolution or in one or more
indentures supplemental hereto, in each case with such appropriate insertions,
omissions, substitutions and other variations as are required or permitted by
this Indenture, and may have such letters, numbers or other marks of
identification and such legends or endorsements placed thereon as may be
required to comply with the rules of any securities exchange or Depositary
therefor or as may, consistently herewith, be determined by the officers
executing such Securities, as evidenced by their execution thereof. If the form
of Securities of any series is established by action taken pursuant to a Board
Resolution, a copy of an appropriate record of such action shall be certified by
the Secretary or an Assistant Secretary of the Company and delivered to the
Trustee at or prior to the delivery of the Company Order contemplated by Section
303 for the authentication and delivery of such Securities. Any such Board
Resolution or record of such action shall have attached thereto a true and
correct copy of the form of Security referred to therein approved by or pursuant
to such Board Resolution.

          The definitive Securities shall be printed, lithographed or engraved
on steel engraved borders or may be produced in any other manner, all as
determined by the officers executing such Securities, as evidenced by their
execution of such Securities.

          SECTION 202. FORM OF FACE OF SECURITY. [Insert any legend required by
the Internal Revenue Code and the regulations thereunder.]


                           AXYS PHARMACEUTICALS, INC.


No.                                                         $


          Axys Pharmaceuticals, Inc., a corporation duly organized and existing
under the laws of Delaware (herein called the "Company," which term includes any
successor Person under the Indenture hereinafter referred to), for value
received, hereby promises to pay to                , or registered assigns, the
principal sum of                Dollars on                [if the Security is to
bear interest prior to Maturity, insert--, and to pay interest thereon from or
from the most recent Interest Payment Date to which interest has been paid or
duly provided for, semi-annually on                and in each year,
commencing               , at the rate of    % per annum, until the principal
hereof is paid or made available for payment [if applicable, insert--, provided
that any principal and premium, and any such installment of interest, which is
overdue shall bear interest at the rate of



                                   -PAGE 15-
<PAGE>   22
__% per annum (to the extent that the payment of such interest shall be legally
enforceable), from the dates such amounts are due until they are paid or made
available for payment, and such interest shall be payable on demand]. The
interest so payable, and punctually paid or duly provided for, on any Interest
Payment Date will, as provided in such Indenture, be paid to the Person in whose
name this Security (or one or more Predecessor Securities) is registered at the
close of business on the Regular Record Date for such interest, which shall be
the _____ or _____ (whether or not a Business Day), as the case may be, next
preceding such Interest Payment Date. Any such interest not so punctually paid
or duly provided for will forthwith cease to be payable to the Holder on such
Regular Record Date and may either be paid to the Person in whose name this
Security (or one or more Predecessor Securities) is registered at the close of
business on a Special Record Date for the payment of such Defaulted Interest to
be fixed by the Trustee, notice whereof shall be given to Holders of Securities
of this series not less than 10 days prior to such Special Record Date, or be
paid at any time in any other lawful manner not inconsistent with the
requirements of any securities exchange on which the Securities of this series
may be listed, and upon such notice as may be required by such exchange, all as
more fully provided in said Indenture].

          [If the Security is not to bear interest prior to Maturity, insert --
The principal of this Security shall not bear interest except in the case of a
default in payment of principal upon acceleration, upon redemption or at Stated
Maturity and in such case the overdue principal and any overdue premium shall
bear interest at the rate of ___% per annum (to the extent that the payment of
such interest shall be legally enforceable), from the dates such amounts are due
until they are paid or made available for payment. Interest on any overdue
principal or premium shall be payable on demand. Any such interest on overdue
principal or premium which is not paid on demand shall bear interest at the rate
of ___% per annum (to the extent that the payment of such interest on interest
shall be legally enforceable), from the date of such demand until the amount so
demanded is paid or made available for payment. Interest on any overdue interest
shall be payable on demand.]

          Payment of the principal of (and premium, if any) and [if applicable,
insert -- any such] interest on this Security will be made at the office or
agency of the Company maintained for that purpose in _____, in such coin or
currency of the United States of America as at the time of payment is legal
tender for payment of public and private debts [if applicable, insert --;
provided, however, that at the option of the Company payment of interest may be
made by check mailed to the address of the Person entitled thereto as such
address shall appear in the Security Register].

          Reference is hereby made to the further provisions of this Security
set forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

          Unless the certificate of authentication hereon has been executed by
the



                                   -PAGE 16-
<PAGE>   23


Trustee referred to on the reverse hereof by manual signature, this Security
shall not be entitled to any benefit under the Indenture or be valid or
obligatory for any purpose.

          IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its corporate seal.

Dated:                                            AXYS PHARMACEUTICALS, INC.




                                                  By:

                                                  Title:


Attest:

          SECTION 203. FORM OF REVERSE OF SECURITY. This Security is one of a
duly authorized issue of securities of the Company (herein called the
"Securities"), issued and to be issued in one or more series under an Indenture,
dated as of ___, 2000 (herein called the "Indenture," which term shall have the
meaning assigned to it in such instrument), between the Company and U.S. Bank
Trust National Association, as Trustee (herein called the "Trustee," which term
includes any successor trustee under the Indenture), and reference is hereby
made to the Indenture and all indentures supplemental thereto for a statement of
the respective rights, limitations of rights, duties and immunities thereunder
of the Company, the Trustee and the Holders of the Securities and of the terms
upon which the Securities are, and are to be, authenticated and delivered. This
Security is one of the series designated on the face hereof [if applicable,
insert -- , limited in aggregate principal amount to $_____ ].

          [If applicable, insert -- The Securities of this series are subject to
redemption upon not less than [If applicable, insert -- 30] days' notice by
first class mail, [if applicable, insert -- (1) on _______ in any year
commencing with the year _______ and ending with the year _______ through
operation of the sinking fund for this series at a Redemption Price equal to
100% of the principal amount, and (2)] at any time [if applicable, insert -- on
or after ___, 2000], as a whole or in part, at the election of the Company, at
the following Redemption Prices (expressed as percentages of the principal
amount): If redeemed [if applicable, insert -- on or before _______, __%, and if
redeemed] during the 12-month period beginning _______ of the years indicated,
and thereafter at a Redemption Price equal to __% of the principal amount,
together in the case of any such redemption [if applicable, insert -- (whether
through operation of the sinking fund or otherwise)] with accrued interest to
the Redemption Date, but interest installments whose Stated Maturity is on or
prior to such Redemption Date will be payable to the Holders of such Securities,
or one or more Predecessor Securities, of record at the close of business on the
relevant Record Dates referred to on the face hereof, all as provided in the
Indenture.]



                                   -PAGE 17-
<PAGE>   24
Year          Redemption Price             Year                Redemption Price



          [If applicable, insert -- The Securities of this series are subject to
redemption upon not less than [if applicable, insert -- 30] days' notice by
first class mail, (1) on ______ in any year commencing with the year ____ and
ending with the year ____ through operation of the sinking fund for this series
at the Redemption Prices for redemption through operation of the sinking fund
(expressed as percentages of the principal amount) set forth in the table below,
and (2) at any time [if applicable, insert -- on or after ______], as a whole or
in part, at the election of the Company, at the Redemption Prices for redemption
otherwise than through operation of the sinking fund (expressed as percentages
of the principal amount) set forth in the table below: If redeemed during the
12-month period beginning ______ of the years indicated,

               Redemption Price For                    Redemption Price For
                Redemption Through                   Redemption Otherwise Than
                 Operation of the                    Through Operation of the
Year               Sinking Fund                            Sinking Fund



and thereafter at a Redemption Price equal to ___% of the principal amount,
together in the case of any such redemption (whether through operation of the
sinking fund or otherwise) with accrued interest to the Redemption Date, but
interest installments whose Stated Maturity is on or prior to such Redemption
Date will be payable to the Holders of such Securities, or one or more
Predecessor Securities, of record at the close of business on the relevant
Record Dates referred to on the face hereof, all as provided in the Indenture.]

          [If applicable, insert -- Notwithstanding the foregoing, the Company
may not, prior to _____, redeem any Securities of this series as contemplated by
[if applicable, insert -- Clause (2) of] the preceding paragraph as a part of,
or in anticipation of, any refunding operation by the application, directly or
indirectly, of moneys borrowed having an interest cost to the Company
(calculated in accordance with generally accepted financial practice) of less
than ___% per annum.]

          [If applicable, insert -- The sinking fund for this series provides
for the redemption on _______, in each year beginning with the year ____ and
ending with the year ____ of [if applicable, insert -- not less than $ ______
("mandatory sinking fund") and not more than] $______ aggregate principal amount
of Securities of this series. Securities of this series acquired or redeemed by
the Company otherwise than through [if applicable, insert -- mandatory] sinking
fund payments may be credited against subsequent [if applicable, insert --
mandatory] sinking fund payments otherwise



                                   -PAGE 18-
<PAGE>   25
required to be made [if applicable, insert --, in the inverse order in which
they become due].]

          [If the Security is subject to redemption of any kind, insert -- In
the event of redemption of this Security in part only, a new Security or
Securities of this series and of like tenor for the unredeemed portion hereof
will be issued in the name of the Holder hereof upon the cancellation hereof.]

          [If applicable, insert -- The Indenture contains provisions for
defeasance at any time of [the entire indebtedness of this Security] [or]
[certain restrictive covenants and Events of Default with respect to this
Security] [, in each case] upon compliance with certain conditions set forth in
the Indenture.]

          [If the Security is convertible into Common Stock of the Company,
insert -- Subject to the provisions of the Indenture, the Holder of this
Security is entitled, at its option, at any time on or before [insert date]
(except that, in case this Security or any portion hereof shall be called for
redemption, such right shall terminate with respect to this Security or portion
hereof, as the case may be, so called for redemption at the close of business on
the first Business Day next preceding the date fixed for redemption as provided
in the Indenture unless the Company defaults in making the payment due upon
redemption), to convert the principal amount of this Security (or any portion
hereof which is $1,000 or an integral multiple thereof), into fully paid and
non-assessable shares (calculated as to each conversion to the nearest 1/100th
of a share) of the Common Stock of the Company, as said shares shall be
constituted at the date of conversion, at the conversion price of $______
principal amount of Securities for each share of Common Stock, or at the
adjusted conversion price in effect at the date of conversion determined as
provided in the Indenture, upon surrender of this Security, together with the
conversion notice hereon duly executed, to the Company at the designated office
or agency of the Company in _______, accompanied (if so required by the Company)
by instruments of transfer, in form satisfactory to the Company and to the
Trustee, duly executed by the Holder or by its duly authorized attorney in
writing. Such surrender shall, if made during any period beginning at the close
of business on a Regular Record Date and ending at the opening of business on
the Interest Payment Date next following such Regular Record Date (unless this
Security or the portion being converted shall have been called for redemption on
a Redemption Date during the period beginning at the close of business on a
Regular Record Date and ending at the opening of business on the first Business
Day after the next succeeding Interest Payment Date, or if such Interest Payment
Date is not a Business Day, the second such Business Day), also be accompanied
by payment in funds acceptable to the Company of an amount equal to the interest
payable on such Interest Payment Date on the principal amount of this Security
then being converted. Subject to the aforesaid requirement for payment and, in
the case of a conversion after the Regular Record Date next preceding any
Interest Payment Date and on or before such Interest Payment Date, to the right
of the Holder of this Security (or any Predecessor Security) of record at such
Regular Record Date to receive an installment



                                   -PAGE 19-
<PAGE>   26
of interest (with certain exceptions provided in the Indenture), no adjustment
is to be made on conversion for interest accrued hereon or for dividends on
shares of Common Stock issued on conversion. The Company is not required to
issue fractional shares upon any such conversion, but shall make adjustment
therefor in cash on the basis of the current market value of such fractional
interest as provided in the Indenture. The conversion price is subject to
adjustment as provided in the Indenture. In addition, the Indenture provides
that in case of certain consolidations or mergers to which the Company is a
party or the sale of substantially all of the assets of the Company, the
Indenture shall be amended, without the consent of any Holders of Securities, so
that this Security, if then outstanding, will be convertible thereafter, during
the period this Security shall be convertible as specified above, only into the
kind and amount of securities, cash and other property receivable upon the
consolidation, merger or sale by a holder of the number of shares of Common
Stock into which this Security might have been converted immediately prior to
such consolidation, merger or sale (assuming such holder of Common Stock failed
to exercise any rights of election and received per share the kind and amount
received per share by a plurality of non-electing shares). In the event of
conversion of this Security in part only, a new Security or Securities for the
unconverted portion hereof shall be issued in the name of the Holder hereof upon
the cancellation hereof.]

          [If the Security is convertible into other securities of the Company,
specify the conversion features.]

          [If the Security is not an Original Issue Discount Security, insert --
If an Event of Default with respect to Securities of this series shall occur and
be continuing, the principal of the Securities of this series may be declared
due and payable in the manner and with the effect provided in the Indenture.]

          [If the Security is an Original Issue Discount Security, insert -- If
an Event of Default with respect to Securities of this series shall occur and be
continuing, an amount of principal of the Securities of this series may be
declared due and payable in the manner and with the effect provided in the
Indenture. Such amount shall be equal to -- insert formula for determining the
amount. Upon payment (i) of the amount of principal so declared due and payable
and (ii) of interest on any overdue principal, premium and interest (in each
case to the extent that the payment of such interest shall be legally
enforceable), all of the Company's obligations in respect of the payment of the
principal of and premium and interest, if any, on the Securities of this series
shall terminate.]

          The Indenture permits, with certain exceptions as therein provided,
the amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the Securities of each series to be
affected under the Indenture at any time by the Company and the Trustee with the
consent of the Holders of more than 50% in principal amount of the Securities at
the time Outstanding of each series to be affected. The Indenture also contains
provisions permitting the Holders of



                                   -PAGE 20-
<PAGE>   27
specified percentages in principal amount of the Securities of each series at
the time Outstanding, on behalf of the Holders of all Securities of such series,
to waive compliance by the Company with certain provisions of the Indenture and
certain past defaults under the Indenture and their consequences. Any such
consent or waiver by the Holder of this Security shall be conclusive and binding
upon such Holder and upon all future Holders of this Security and of any
Security issued upon the registration of transfer hereof or in exchange herefor
or in lieu hereof, whether or not notation of such consent or waiver is made
upon this Security.

          As provided in and subject to the provisions of the Indenture, the
Holder of this Security shall not have the right to institute any proceeding
with respect to the Indenture or for the appointment of a receiver or trustee or
for any other remedy thereunder, unless such Holder shall have previously given
the Trustee written notice of a continuing Event of Default with respect to the
Securities of this series, the Holders of not less than 25% in principal amount
of the Securities of this series at the time Outstanding shall have made written
request to the Trustee to institute proceedings in respect of such Event of
Default as Trustee and offered the Trustee reasonable indemnity, and the Trustee
shall not have received from the Holders of a majority in principal amount of
Securities of this series at the time Outstanding a direction inconsistent with
such request, and shall have failed to institute any such proceeding, for 60
days after receipt of such notice, request and offer of indemnity. The foregoing
shall not apply to any suit instituted by the Holder of this Security for the
enforcement of any payment of principal hereof or any premium or interest hereon
on or after the respective due dates expressed herein.

          No reference herein to the Indenture and no provision of this Security
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional, to pay the principal of and premium, if any, and
interest on this Security at the times, place and rate, and in the coin or
currency, herein prescribed.

          As provided in the Indenture and subject to certain limitations
therein set forth, the transfer of this Security is registrable in the Security
Register, upon surrender of this Security for registration of transfer at the
office or agency of the Company in any place where the principal of and any
premium and interest on this Security are payable, duly endorsed by, or
accompanied by a written instrument of transfer in form satisfactory to the
Company and the Security Registrar duly executed by, the Holder hereof or its
attorney duly authorized in writing, and thereupon one or more new Securities of
this series and of like tenor, of authorized denominations and for the same
aggregate principal amount, will be issued to the designated transferee or
transferees.

          The Securities of this series are issuable only in registered form
without coupons in denominations of $_____ and any integral multiple thereof. As
provided in the Indenture and subject to certain limitations therein set forth,
Securities of this series are exchangeable for a like aggregate principal amount
of Securities of this series and



                                   -PAGE 21-
<PAGE>   28
of like tenor of a different authorized denomination, as requested by the Holder
surrendering the same.

          No service charge shall be made to a Holder for any such registration
of transfer or exchange, but the Company may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

          Prior to due presentment of this Security for registration of
transfer, the Company, the Trustee and any agent of the Company or the Trustee
may treat the Person in whose name this Security is registered as the owner
hereof for all purposes, whether or not this Security be overdue, and neither
the Company, the Trustee nor any such agent shall be affected by notice to the
contrary.

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

          SECTION 204. FORM OF LEGEND FOR GLOBAL SECURITIES. Unless otherwise
specified as contemplated by Section 301 for the Securities evidenced thereby,
every Global Security authenticated and delivered hereunder shall bear a legend
in substantially the following form:

THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE
HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A
NOMINEE THEREOF. THIS SECURITY MAY NOT BE EXCHANGED IN WHOLE OR IN PART FOR A
SECURITY REGISTERED, AND NO TRANSFER OF THIS SECURITY IN WHOLE OR IN PART MAY BE
REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOSITARY OR A NOMINEE
THEREOF, EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE.

          SECTION 205. FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION. The
Trustee's certificates of authentication shall be in substantially the following
form:

This is one of the Securities of the series designated herein referred to in the
within-mentioned Indenture.

                                           U.S. BANK TRUST NATIONAL
                                             ASSOCIATION, as Trustee



                                            By:
                                               Authorized Officer



                                   -PAGE 22-
<PAGE>   29
          SECTION 206. FORM OF CONVERSION NOTICE.

To Axys Pharmaceuticals, Inc.:

          The owner of this Security hereby irrevocably exercises the option to
convert this Security, or portion hereof (which is $1,000 or an integral
multiple thereof) below designated, into shares of Common Stock of the Company
in accordance with the terms of the Indenture referred to in this Security, and
directs that the shares issuable and deliverable upon the conversion, together
with any check in payment for fractional shares and any Securities representing
any unconverted principal amount hereof, be issued and delivered to the
registered holder hereof unless a different name has been indicated below. If
this Notice is being delivered on a date after the close of business on a
Regular Record Date and prior to the opening of business on the related Interest
Payment Date (unless this Security or the portion thereof being converted has
been called for redemption on a Redemption Date within such period), this Notice
is accompanied by payment, in funds acceptable to the Company, of an amount
equal to the interest payable on such Interest Payment Date of the principal of
this Security to be converted. If shares are to be issued in the name of a
person other than the undersigned, the undersigned will pay all transfer taxes
payable with respect hereto. Any amount required to be paid by the undersigned
on account of interest accompanies this Security.

                        Principal Amount to be Converted
              (in an integral multiple of $1,000, if less than all)
                                     U.S. $________



Dated:

                                        Signature(s) must be guaranteed by an
                                        eligible guarantor institution (banks,
                                        stock brokerages, savings and loan
                                        associations and credit unions) with
                                        membership in an approved signature
                                        guarantee medallion program pursuant to
                                        Securities and Exchange Commission Rule
                                        17Ad-15 if shares of Common Stock are to
                                        be delivered, or Securities to be
                                        issued, other than to and in the name of
                                        the registered owner.



                                        Signature Guaranty



                                   -PAGE 23-
<PAGE>   30
          Fill in for registration of shares of Common Stock and Security if to
be issued otherwise than to the registered Holder.



(Name)                                    Social Security or Other Taxpayer
                                          Identification Number


(Address)


Please print Name and Address
(including zip code number)


[The above conversion notice is to be modified, as appropriate, for conversion
into other securities or property of the Company.]


                                  ARTICLE THREE

                                 THE SECURITIES

          SECTION 301. AMOUNT UNLIMITED; ISSUABLE IN SERIES. The aggregate
principal amount of Securities which may be authenticated and delivered under
this Indenture is unlimited.

          The Securities may be issued in one or more series. There shall be
established in or pursuant to a Board Resolution and, subject to Section 303,
set forth, or determined in the manner provided, in an Officers' Certificate, or
established in one or more indentures supplemental hereto, prior to the issuance
of Securities of any series,

          (1) the title of the Securities of the series (which shall distinguish
the Securities of the series from Securities of any other series);

          (2) any limit upon the aggregate principal amount of the Securities of
the series which may be authenticated and delivered under this Indenture (except
for Securities authenticated and delivered upon registration of transfer of, or
in exchange for, or in lieu of, other Securities of the series pursuant to
Section 304, 305, 306, 906 or 1107 and except for any Securities which, pursuant
to Section 303, are deemed never to have been authenticated and delivered
hereunder);

          (3) the Person to whom any interest on a Security of the series shall



                                   -PAGE 24-
<PAGE>   31
be payable, if other than the Person in whose name that Security (or one or more
Predecessor Securities) is registered at the close of business on the Regular
Record Date for such interest;

          (4) the date or dates on which the principal of any Securities of the
series is payable;

          (5) the rate or rates at which any Securities of the series shall bear
interest, if any, the date or dates from which any such interest shall accrue,
the Interest Payment Dates on which any such interest shall be payable, whether
and under what circumstances interest shall be payable in cash or another form
of consideration and the Regular Record Date for any such interest payable on
any Interest Payment Date;

          (6) the place or places where the principal of and any premium and
interest on any Securities of the series shall be payable;

          (7) the period or periods within which, the price or prices at which
and the terms and conditions upon which any Securities of the series may be
redeemed, in whole or in part, at the option of the Company and, if other than
by a Board Resolution, the manner in which any election by the Company to redeem
the Securities shall be evidenced;

          (8) the obligation, if any, of the Company to redeem or purchase any
Securities of the series pursuant to any sinking fund or analogous provisions or
at the option of the Holder thereof and the period or periods within which, the
price or prices at which and the terms and conditions upon which any Securities
of the series shall be redeemed or purchased, in whole or in part, pursuant to
such obligation;

          (9) if other than denominations of $1,000 and any integral multiple
thereof, the denominations in which any Securities of the series shall be
issuable;

          (10) if the amount of principal of or any premium or interest on any
Securities of the series may be determined with reference to an index or
pursuant to a formula, the manner in which such amounts shall be determined;

          (11) if other than the currency of the United States of America, the
currency, currencies or currency units in which the principal of or any premium
or interest on any Securities of the series shall be payable and the manner of
determining the equivalent thereof in the currency of the United States of
America for any purpose, including for purposes of the definition of
"Outstanding" in Section 101; provided, however, that prior to the issuance of
any such Securities, the Company shall have obtained the written consent of the
Trustee, which consent may be withheld in the sole discretion of the Trustee, to
the currency, currencies or currency units so established;



                                   -PAGE 25-
<PAGE>   32
          (12) if the principal of or premium, if any, or interest on any
Securities of the series is to be payable, at the election of the Company or the
Holder thereof, in one or more currencies or currency units other than that or
those in which such Securities are stated to be payable, the currency,
currencies or currency units in which the principal of or any premium or
interest on such Securities as to which such election is made shall be payable,
the periods within which and the terms and conditions upon which such election
is to be made and the amount so payable (or the manner in which such amount
shall be determined); provided, however, that prior to the issuance of any such
Securities, the Company shall have obtained the written consent of the Trustee,
which consent may be withheld in the sole discretion of the Trustee, to the
currency, currencies or currency units so established;

          (13) if other than the entire principal amount thereof, the portion of
the principal amount of any Securities of the series which shall be payable upon
declaration of acceleration of the Maturity thereof pursuant to Section 502;

          (14) if the principal amount payable at the Stated Maturity of any
Securities of the series will not be determinable as of any one or more dates
prior to the Stated Maturity, the amount which shall be deemed to be the
principal amount of such Securities as of any such date for any purpose
thereunder or hereunder, including the principal amount thereof which shall be
due and payable upon any Maturity other than the Stated Maturity or which shall
be deemed to be Outstanding as of any date prior to the Stated Maturity (or, in
any such case, the manner in which such amount deemed to be the principal amount
shall be determined);

          (15) if applicable, that the Securities of the series, in whole or any
specified part, shall be defeasible pursuant to Section 1302 or Section 1303 or
both such Sections and, if other than by a Board Resolution, the manner in which
any election by the Company to defease such Securities shall be evidenced;

          (16) if applicable, the terms of any right to convert Securities of
the series into shares of Common Stock of the Company or other securities or
property;

          (17) if applicable, that any Securities of the series shall be
issuable in whole or in part in the form of one or more Global Securities and,
in such case, the respective Depositaries for such Global Securities, the form
of any legend or legends which shall be borne by any such Global Security in
addition to or in lieu of that set forth in Section 204 and any circumstances in
addition to or in lieu of those set forth in Clause (2) of the last paragraph of
Section 305 in which any such Global Security may be exchanged in whole or in
part for Securities registered, and any transfer of such Global Security in
whole or in part may be registered, in the name or names of Persons other than
the Depositary for such Global Security or a nominee thereof;

          (18) any addition to or change in the Events of Default which applies
to any Securities of the series and any change in the right of the Trustee or
the requisite



                                   -PAGE 26-
<PAGE>   33
Holders of such Securities to declare the principal amount thereof due and
payable pursuant to Section 502;

          (19) any addition to or change in the covenants set forth in Article
Ten which applies to Securities of the series; and

          (20) any other terms of the series (which terms shall not be
inconsistent with the provisions of this Indenture, except as permitted by
Section 901(5)).

          All Securities of any one series shall be substantially identical
except as to denomination, certificate number and except as may otherwise be
provided in or pursuant to the Board Resolution referred to above and (subject
to Section 303) set forth, or determined in the manner provided, in the
Officers' Certificate referred to above or in any such indenture supplemental
hereto.

          If any of the terms of the series are established by action taken
pursuant to a Board Resolution, a copy of an appropriate record of such action
shall be certified by the Secretary or an Assistant Secretary of the Company and
delivered to the Trustee at or prior to the delivery of the Officers'
Certificate setting forth the terms of the series.

          SECTION 302. DENOMINATIONS. The Securities of each series shall be
issuable only in registered form without coupons and only in such denominations
as shall be specified as contemplated by Section 301. In the absence of any such
specified denomination with respect to the Securities of any series, the
Securities of such series shall be issuable in denominations of $1,000 and any
integral multiple thereof.

          SECTION 303. EXECUTION, AUTHENTICATION, DELIVERY AND DATING. The
Securities shall be executed on behalf of the Company by its Chairman of the
Board, its Vice Chairman of the Board, its principal financial officer, its
President or one of its Vice Presidents, under its corporate seal reproduced
thereon attested by its Secretary or one of its Assistant Secretaries. The
signature of any of these officers on the Securities may be manual or facsimile.

          Securities bearing the manual or facsimile signatures of individuals
who were at any time the proper officers of the Company shall bind the Company,
notwithstanding that such individuals or any of them have ceased to hold such
offices prior to the authentication and delivery of such Securities or did not
hold such offices at the date of such Securities.

          At any time and from time to time after the execution and delivery of
this Indenture, the Company may deliver Securities of any series executed by the
Company to the Trustee for authentication, together with a Company Order for the
authentication and delivery of such Securities, and the Trustee in accordance
with the Company Order



                                   -PAGE 27-
<PAGE>   34
shall authenticate and deliver such Securities. If the form or terms of the
Securities of the series have been established by or pursuant to one or more
Board Resolutions as permitted by Sections 201 and 301, in authenticating such
Securities, and accepting the additional responsibilities under this Indenture
in relation to such Securities, the Trustee shall be entitled to receive, and
(subject to Section 601) shall be fully protected in relying upon, an Opinion of
Counsel stating,

          (1) if the form of such Securities has been established by or pursuant
to Board Resolution as permitted by Section 201, that such form has been
established in conformity with the provisions of this Indenture;

          (2) if the terms of such Securities have been established by or
pursuant to Board Resolution as permitted by Section 301, that such terms have
been established in conformity with the provisions of this Indenture; and

          (3) that such Securities, when authenticated and delivered by the
Trustee and issued by the Company in the manner and subject to any conditions
specified in such Opinion of Counsel, will constitute valid and legally binding
obligations of the Company enforceable in accordance with their terms, subject
to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and
similar laws of general applicability relating to or affecting creditors' rights
and to general equity principles.


          If such form or terms have been so established, the Trustee shall not
be required to authenticate such Securities if the issue of such Securities
pursuant to this Indenture will affect the Trustee's own rights, duties or
immunities under the Securities and this Indenture or otherwise in a manner
which is not reasonably acceptable to the Trustee.

          Notwithstanding the provisions of Section 301 and of the preceding
paragraph, if all Securities of a series are not to be originally issued at one
time, it shall not be necessary to deliver the Officers' Certificate otherwise
required pursuant to Section 301 or the Company Order and Opinion of Counsel
otherwise required pursuant to such preceding paragraph at or prior to the
authentication of each Security of such series if such documents are delivered
at or prior to the authentication upon original issuance of the first Security
of such series to be issued.

          Each Security shall be dated the date of its authentication.

          No Security shall be entitled to any benefit under this Indenture or
be valid or obligatory for any purpose unless there appears on such Security a
certificate of authentication substantially in the form provided for herein
executed by the Trustee by manual signature, and such certificate upon any
Security shall be conclusive evidence, and the only evidence, that such Security
has been duly authenticated and delivered hereunder. Notwithstanding the
foregoing, if any Security shall have been authenticated



                                   -PAGE 28-
<PAGE>   35
and delivered hereunder but never issued and sold by the Company, and the
Company shall deliver such Security to the Trustee for cancellation as provided
in Section 309, for all purposes of this Indenture such Security shall be deemed
never to have been authenticated and delivered hereunder and shall never be
entitled to the benefits of this Indenture.

          SECTION 304. TEMPORARY SECURITIES. Pending the preparation of
definitive Securities of any series, the Company may execute, and upon Company
Order the Trustee shall authenticate and deliver, temporary Securities which are
printed, lithographed, typewritten, mimeographed or otherwise produced, in any
authorized denomination, substantially of the tenor of the definitive Securities
in lieu of which they are issued and with such appropriate insertions,
omissions, substitutions and other variations as the officers executing such
Securities may determine, as evidenced by their execution of such Securities.

          If temporary Securities of any series are issued, the Company will
cause definitive Securities of that series to be prepared without unreasonable
delay. After the preparation of definitive Securities of such series, the
temporary Securities of such series shall be exchangeable for definitive
Securities of such series upon surrender of the temporary Securities of such
series at the office or agency of the Company in a Place of Payment for that
series, without charge to the Holder. Upon surrender for cancellation of any one
or more temporary Securities of any series, the Company shall execute and the
Trustee shall authenticate and deliver in exchange therefor one or more
definitive Securities of the same series, of any authorized denominations and of
like tenor and aggregate principal amount. Until so exchanged, the temporary
Securities of any series shall in all respects be entitled to the same benefits
under this Indenture as definitive Securities of such series and tenor.

          SECTION 305. REGISTRATION; REGISTRATION OF TRANSFER AND EXCHANGE. The
Company shall cause to be kept at the Corporate Trust Office of the Trustee a
register (the register maintained in such office and in any other office or
agency of the Company in a Place of Payment being herein sometimes collectively
referred to as the "Security Register") in which, subject to such reasonable
regulations as it may prescribe, the Company shall provide for the registration
of Securities and of transfers of Securities. The Trustee is hereby appointed
"Security Registrar" for the purpose of registering Securities and transfers of
Securities as herein provided.

          Upon surrender for registration of transfer of any Security of a
series at the office or agency of the Company in a Place of Payment for that
series, the Company shall execute, and the Trustee shall authenticate and
deliver, in the name of the designated transferee or transferees, one or more
new Securities of the same series, of any authorized denominations and of like
tenor and aggregate principal amount.



                                   -PAGE 29-
<PAGE>   36
          At the option of the Holder, Securities of any series may be exchanged
for other Securities of the same series, of any authorized denominations and of
like tenor and aggregate principal amount, upon surrender of the Securities to
be exchanged at such office or agency. Whenever any Securities are so
surrendered for exchange, the Company shall execute, and the Trustee shall
authenticate and deliver, the Securities which the Holder making the exchange is
entitled to receive.

          All Securities issued upon any registration of transfer or exchange of
Securities shall be the valid obligations of the Company, evidencing the same
debt, and entitled to the same benefits under this Indenture, as the Securities
surrendered upon such registration of transfer or exchange.

          Every Security presented or surrendered for registration of transfer
or for exchange shall (if so required by the Company or the Trustee) be duly
endorsed, or be accompanied by a written instrument of transfer in form
satisfactory to the Company and the Security Registrar duly executed, by the
Holder thereof or its attorney duly authorized in writing.

          No service charge shall be made for any registration of transfer or
exchange of Securities, but the Company may require payment of a sum sufficient
to cover any tax or other governmental charge that may be imposed in connection
with any registration of transfer or exchange of Securities, other than
exchanges pursuant to Section 304, 906 or 1107 not involving any transfer.

          If the Securities of any series (or of any series and specified tenor)
are to be redeemed in part, the Company shall not be required (A) to issue,
register the transfer of or exchange any Securities of that series (or of that
series and specified tenor, as the case may be) during a period beginning at the
opening of business 15 days before the day of the mailing of a notice of
redemption of any such Securities selected for redemption under Section 1103 and
ending at the close of business on the day of such mailing, or (B) to register
the transfer of or exchange any Security so selected for redemption in whole or
in part, except the unredeemed portion of any Security being redeemed in part.

          The provisions of Clauses (1), (2), (3) and (4) below shall apply only
to Global Securities:

          (1) Each Global Security authenticated under this Indenture shall be
registered in the name of the Depositary designated for such Global Security or
a nominee thereof and delivered to such Depositary or a nominee thereof or
custodian therefor, and each such Global Security shall constitute a single
Security for all purposes of this Indenture.

          (2) Notwithstanding any other provision in this Indenture, no Global
Security may be exchanged in whole or in part for Securities registered, and no
transfer



                                   -PAGE 30-
<PAGE>   37
of a Global Security in whole or in part may be registered, in the name
of any Person other than the Depositary for such Global Security or a nominee
thereof unless (A) such Depositary (i) has notified the Company that it is
unwilling or unable to continue as Depositary for such Global Security or (ii)
has ceased to be a clearing agency registered under the Exchange Act, (B) there
shall have occurred and be continuing an Event of Default with respect to such
Global Security or (C) there shall exist such circumstances, if any, in addition
to or in lieu of the foregoing as have been specified for this purpose as
contemplated by Section 301.

          (3) Subject to Clause (2) above, any exchange of a Global Security for
other Securities may be made in whole or in part, and all Securities issued in
exchange for a Global Security or any portion thereof shall be registered in
such names as the Depositary for such Global Security shall direct.

          (4) Every Security authenticated and delivered upon registration of
transfer of, or in exchange for or in lieu of, a Global Security or any portion
thereof, whether pursuant to this Section, Section 304, 306, 906 or 1107 or
otherwise, shall be authenticated and delivered in the form of, and shall be, a
Global Security, unless such Security is registered in the name of a Person
other than the Depositary for such Global Security or a nominee thereof.

          SECTION 306. MUTILATED, DESTROYED, LOST AND STOLEN SECURITIES. If any
mutilated Security is surrendered to the Trustee, the Company shall execute and
the Trustee shall authenticate and deliver in exchange therefor a new Security
of the same series and of like tenor and principal amount and bearing a number
not contemporaneously outstanding.

          If there shall be delivered to the Company and the Trustee (i)
evidence to their satisfaction of the destruction, loss or theft of any Security
and (ii) such security or indemnity as may be required by them to save each of
them and any agent of either of them harmless, then, in the absence of notice to
the Company or the Trustee that such Security has been acquired by a bona fide
purchaser, the Company shall execute and the Trustee shall authenticate and
deliver, in lieu of any such destroyed, lost or stolen Security, a new Security
of the same series and of like tenor and principal amount and bearing a number
not contemporaneously outstanding.

          In case any such mutilated, destroyed, lost or stolen Security has
become or is about to become due and payable, the Company in its discretion may,
instead of issuing a new Security, pay such Security.

          Upon the issuance of any new Security under this Section, 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.



                                   -PAGE 31-
<PAGE>   38
          Every new Security of any series issued pursuant to this Section in
lieu of any destroyed, lost or stolen Security shall constitute an original
additional contractual obligation of the Company, whether or not the destroyed,
lost or stolen Security shall be at any time enforceable by anyone, and shall be
entitled to all the benefits of this Indenture equally and proportionately with
any and all other Securities of that series duly issued hereunder.

          The provisions of this Section are exclusive and shall preclude (to
the extent lawful) all other rights and remedies with respect to the replacement
or payment of mutilated, destroyed, lost or stolen Securities.

          SECTION 307. PAYMENT OF INTEREST; INTEREST RIGHTS PRESERVED. Except as
otherwise provided as contemplated by Section 301 with respect to any series of
Securities, interest on any Security which is payable, and is punctually paid or
duly provided for, on any Interest Payment Date shall be paid to the Person in
whose name that Security (or one or more Predecessor Securities) is registered
at the close of business on the Regular Record Date for such interest.

          Any interest on any Security of any series which is payable, but is
not punctually paid or duly provided for, on any Interest Payment Date (herein
called "Defaulted Interest") shall forthwith cease to be payable to the Holder
on the relevant Regular Record Date by virtue of having been such Holder, and
such Defaulted Interest may be paid by the Company, at its election in each
case, as provided in Clause (1) or (2) below:

          (1) The Company may elect to make payment of any Defaulted Interest to
the Persons in whose names the Securities of such series (or their respective
Predecessor Securities) are registered at the close of business on a Special
Record Date for the payment of such Defaulted Interest, which shall be fixed in
the following manner. The Company shall notify the Trustee in writing of the
amount of Defaulted Interest proposed to be paid on each Security of such series
and the date of the proposed payment, and at the same time the Company shall
deposit with the Trustee an amount of money equal to the aggregate amount
proposed to be paid in respect of such Defaulted Interest or shall make
arrangements satisfactory to the Trustee for such deposit prior to the date of
the proposed payment, such money when deposited to be held in trust for the
benefit of the Persons entitled to such Defaulted Interest as in this Clause
provided. Thereupon the Trustee shall fix a Special Record Date for the payment
of such Defaulted Interest which shall be not more than 15 days and not less
than 10 days prior to the date of the proposed payment and not less than 10 days
after the receipt by the Trustee of the notice of the proposed payment. The
Trustee shall promptly notify the Company of such Special Record Date and, in
the name and at the expense of the Company, shall cause notice of the proposed
payment of such Defaulted Interest and the Special Record Date therefor to be
given to each Holder of Securities of such series in the manner set forth in
Section 106, not less than



                                   -PAGE 32-
<PAGE>   39
10 days prior to such Special Record Date. Notice of the proposed payment of
such Defaulted Interest and the Special Record Date therefor having been so
mailed, such Defaulted Interest shall be paid to the Persons in whose names the
Securities of such series (or their respective Predecessor Securities) are
registered at the close of business on such Special Record Date and shall no
longer be payable pursuant to the following Clause (2).

          (2) The Company may make payment of any Defaulted Interest on the
Securities of any series in any other lawful manner not inconsistent with the
requirements of any securities exchange on which such Securities may be listed,
and upon such notice as may be required by such exchange, if, after notice given
by the Company to the Trustee of the proposed payment pursuant to this Clause,
such manner of payment shall be deemed practicable by the Trustee.


          Subject to the foregoing provisions of this Section, each Security
delivered under this Indenture upon registration of transfer of or in exchange
for or in lieu of any other Security shall carry the rights to interest accrued
and unpaid, and to accrue, which were carried by such other Security.

          Subject to the provisions of Section 1402, in the case of any Security
(or any part thereof) which is converted after any Regular Record Date and on or
prior to the next succeeding Interest Payment Date (other than any Security the
principal of (or premium, if any, on) which shall become due and payable,
whether at Stated Maturity or by declaration of acceleration prior to such
Interest Payment Date), interest whose Stated Maturity is on such Interest
Payment Date shall be payable on such Interest Payment Date notwithstanding such
conversion and such interest (whether or not punctually paid or duly provided
for) shall be paid to the Person in whose name that Security (or any one or more
Predecessor Securities) is registered at the close of business on such Regular
Record Date. Except as otherwise expressly provided in the immediately preceding
sentence or in Section 1402, in the case of any Security (or any part thereof)
which is converted, interest whose Stated Maturity is after the date of
conversion of such Security (or such part thereof) shall not be payable.

          SECTION 308. PERSONS DEEMED OWNERS. Prior to due presentment of a
Security for registration of transfer, the Company, the Trustee and any agent of
the Company or the Trustee may treat the Person in whose name such Security is
registered as the owner of such Security for the purpose of receiving payment of
principal of and any premium and (subject to Section 307) any interest on such
Security and for all other purposes whatsoever, whether or not such Security be
overdue, and neither the Company, the Trustee nor any agent of the Company or
the Trustee shall be affected by notice to the contrary.

          SECTION 309. CANCELLATION. All Securities surrendered for payment,
redemption, registration of transfer or exchange or for credit against any
sinking fund payment shall, if surrendered to any Person other than the Trustee,
be



                                   -PAGE 33-
<PAGE>   40
delivered to the Trustee and shall be promptly canceled by it. The Company may
at any time deliver to the Trustee for cancellation any Securities previously
authenticated and delivered hereunder which the Company may have acquired in any
manner whatsoever, and may deliver to the Trustee (or to any other Person for
delivery to the Trustee) for cancellation any Securities previously
authenticated hereunder which the Company has not issued and sold, and all
Securities so delivered shall be promptly canceled by the Trustee. No Securities
shall be authenticated in lieu of or in exchange for any Securities canceled as
provided in this Section, except as expressly permitted by this Indenture. All
canceled Securities held by the Trustee shall be disposed of as directed by a
Company Order.

          SECTION 310. COMPUTATION OF INTEREST. Except as otherwise specified as
contemplated by Section 301 for Securities of any series, interest on the
Securities of each series shall be computed on the basis of a 360-day year of
twelve 30-day months.


                                  ARTICLE FOUR

                           SATISFACTION AND DISCHARGE

          SECTION 401. SATISFACTION AND DISCHARGE OF INDENTURE. This Indenture
shall upon Company Request cease to be of further effect (except as to any
surviving rights of registration of transfer or exchange of Securities herein
expressly provided for), and the Trustee, at the expense of the Company, shall
execute proper instruments acknowledging satisfaction and discharge of this
Indenture, when

          (1) either

          (A) all Securities theretofore authenticated and delivered (other than
(i) Securities which have been destroyed, lost or stolen and which have been
replaced or paid as provided in Section 306 and (ii) Securities for whose
payment money has theretofore been deposited in trust or segregated and held in
trust by the Company and thereafter repaid to the Company or discharged from
such trust, as provided in Section 1003) have been delivered to the Trustee for
cancellation; or

          (B) all such Securities not theretofore delivered to the Trustee for
cancellation

          (i) have become due and payable, or

          (ii) will become due and payable at their Stated Maturity within one
      year, or



                                   -PAGE 34-
<PAGE>   41
          (iii) are to be called for redemption within one year under
      arrangements satisfactory to the Trustee for the giving of notice of
      redemption by the Trustee in the name, and at the expense, of the Company,
      and the Company, in the case of (i), (ii) or (iii) above, has deposited or
      caused to be deposited with the Trustee as trust funds in trust for the
      purpose money in an amount sufficient to pay and discharge the entire
      indebtedness on such Securities not theretofore delivered to the Trustee
      for cancellation, for principal and any premium and interest to the date
      of such deposit (in the case of Securities which have become due and
      payable) or to the Stated Maturity or Redemption Date, as the case may be;

          (2) the Company has paid or caused to be paid all other sums payable
hereunder by the Company; and

          (3) the Company has delivered to the Trustee an Officers' Certificate
and an Opinion of Counsel, each stating that all conditions precedent herein
provided for relating to the satisfaction and discharge of this Indenture have
been complied with.

          Notwithstanding the satisfaction and discharge of this Indenture, the
obligations of the Company to the Trustee under Section 607, the obligations of
the Trustee to any Authenticating Agent under Section 614 and, if money shall
have been deposited with the Trustee pursuant to subclause (B) of Clause (1) of
this Section, the obligations of the Trustee under Section 402 and the last
paragraph of Section 1003 shall survive.

          SECTION 402. APPLICATION OF TRUST MONEY. Subject to the provisions of
the last paragraph of Section 1003, all money deposited with the Trustee
pursuant to Section 401 shall be held in trust and applied by it, in accordance
with the provisions of the Securities and this Indenture, to the payment, either
directly or through any Paying Agent (including the Company acting as its own
Paying Agent) as the Trustee may determine, to the Persons entitled thereto, of
the principal and any premium and interest for whose payment such money has been
deposited with the Trustee.


                                  ARTICLE FIVE

                                    REMEDIES

          SECTION 501. EVENTS OF DEFAULT. "Event of Default," wherever used
herein with respect to Securities of any series, means any one of the following
events (whatever the reason for such Event of Default and whether it shall be
voluntary or involuntary or be effected by operation of law or pursuant to any
judgment, decree or order of any court or any order, rule or regulation of any
administrative or governmental body):



                                   -PAGE 35-
<PAGE>   42
          (1) default in the payment of any interest upon any Security of that
series when it becomes due and payable, and continuance of such default for a
period of 30 days; or

          (2) default in the payment of the principal of or any premium on any
Security of that series at its Maturity; or

          (3) default in the deposit of any sinking fund payment, when and as
due by the terms of a Security of that series; or

          (4) default in the performance, or breach, of any covenant or warranty
of the Company in this Indenture (other than a covenant or warranty a default in
whose performance or whose breach is elsewhere in this Section specifically
dealt with or which has expressly been included in this Indenture solely for the
benefit of series of Securities other than that series), and continuance of such
default or breach for a period of 60 days after there has been given, by
registered or certified mail, to the Company by the Trustee or to the Company
and the Trustee by the Holders of at least 25% in principal amount of the
Outstanding Securities of that series a written notice specifying such default
or breach and requiring it to be remedied and stating that such notice is a
"Notice of Default" hereunder; or

          (5) the entry by a court having jurisdiction in the premises of (A) a
decree or order for relief in respect of the Company in an involuntary case or
proceeding under any applicable Federal or State bankruptcy, insolvency,
reorganization or other similar law or (B) a decree or order adjudging the
Company a bankrupt or insolvent, or approving as properly filed a petition
seeking reorganization, arrangement, adjustment or composition of or in respect
of the Company under any applicable Federal or State law, or appointing a
custodian, receiver, liquidator, assignee, trustee, sequestrator or other
similar official of the Company or of any substantial part of its property, or
ordering the winding up or liquidation of its affairs, and the continuance of
any such decree or order for relief or any such other decree or order unstayed
and in effect for a period of 90 consecutive days; or

          (6) the commencement by the Company of a voluntary case or proceeding
under any applicable Federal or State bankruptcy, insolvency, reorganization or
other similar law or of any other case or proceeding to be adjudicated a
bankrupt or insolvent, or the consent by it to the entry of a decree or order
for relief in respect of the Company in an involuntary case or proceeding under
any applicable Federal or State bankruptcy, insolvency, reorganization or other
similar law or to the commencement of any bankruptcy or insolvency case or
proceeding against it, or the filing by it of a petition or answer or consent
seeking reorganization or relief under any applicable Federal or State law, or
the consent by it to the filing of such petition or to the appointment of or
taking possession by a custodian, receiver, liquidator, assignee, trustee,
sequestrator or other similar official of the Company or of any substantial part
of its property, or the making by it of an assignment for the benefit of
creditors, or the



                                   -PAGE 36-
<PAGE>   43
admission by it in writing of its inability to pay its debts
generally as they become due, or the taking of corporate action by the Company
in furtherance of any such action; or

          (7) any other Event of Default provided with respect to Securities of
that series.

          SECTION 502. ACCELERATION OF MATURITY; RESCISSION AND ANNULMENT. If an
Event of Default (other than an Event of Default specified in Section 501(5) or
501(6)) with respect to Securities of any series at the time Outstanding occurs
and is continuing, then in every such case the Trustee or the Holders of not
less than 25% in principal amount of the Outstanding Securities of that series
may declare the principal amount of all the Securities of that series (or, if
any Securities of that series are Original Issue Discount Securities, such
portion of the principal amount of such Securities as may be specified by the
terms thereof) to be due and payable immediately, by a notice in writing to the
Company (and to the Trustee if given by Holders), and upon any such declaration
such principal amount (or specified amount) shall become immediately due and
payable. If an Event of Default specified in Section 501(5) or 501(6) with
respect to Securities of any series at the time Outstanding occurs, the
principal amount of all the Securities of that series (or, if any Securities of
that series are Original Issue Discount Securities, such portion of the
principal amount of such Securities as may be specified by the terms thereof)
shall automatically, and without any declaration or other action on the part of
the Trustee or any Holder, become immediately due and payable.

          At any time after such a declaration of acceleration with respect to
Securities of any series has been made and before a judgment or decree for
payment of the money due has been obtained by the Trustee as hereinafter in this
Article provided, the Holders of a majority in principal amount of the
Outstanding Securities of that series, by written notice to the Company and the
Trustee, may rescind and annul such declaration and its consequences if

          (1) the Company has paid or deposited with the Trustee a sum
sufficient to pay

          (A) all overdue interest on all Securities of that series,

          (B) the principal (or other specified amount in the case of Original
Issue Discount Securities) of (and premium, if any, on) any Securities of that
series which have become due otherwise than by such declaration of acceleration
and any interest thereon at the rate or rates prescribed therefor in such
Securities,

          (C) to the extent that payment of such interest is lawful, interest
upon overdue interest at the rate or rates prescribed therefor in such
Securities, and



                                   -PAGE 37-
<PAGE>   44
          (D) all sums paid or advanced by the Trustee hereunder and the
reasonable compensation, expenses, disbursements and advances of the Trustee,
its agents and counsel; and

          (2) all Events of Default with respect to Securities of that series,
other than the non-payment of the principal of Securities of that series which
have become due solely by such declaration of acceleration, have been cured or
waived as provided in Section 513.

          No such rescission shall affect any subsequent default or impair any
right consequent thereon.

          SECTION 503. COLLECTION OF INDEBTEDNESS AND SUITS FOR ENFORCEMENT BY
TRUSTEE. The Company covenants that if

          (1) default is made in the payment of any interest on any Security
when such interest becomes due and payable and such default continues for a
period of 30 days, or

          (2) default is made in the payment of the principal of (or premium, if
any, on) any Security at the Maturity thereof, the Company will, upon demand of
the Trustee, pay to it, for the benefit of the Holders of such Securities, the
whole amount then due and payable on such Securities for principal and any
premium and interest and, to the extent that payment of such interest shall be
legally enforceable, interest on any overdue principal and premium and on any
overdue interest, at the rate or rates prescribed therefor in such Securities,
and, in addition thereto, such further amount as shall be sufficient to cover
the costs and expenses of collection, including the reasonable compensation,
expenses, disbursements and advances of the Trustee, its agents and counsel.

          If an Event of Default with respect to Securities of any series occurs
and is continuing, the Trustee may in its discretion proceed to protect and
enforce its rights and the rights of the Holders of Securities of such series by
such appropriate judicial proceedings as the Trustee shall deem most effectual
to protect and enforce any such rights, whether for the specific enforcement of
any covenant or agreement in this Indenture or in aid of the exercise of any
power granted herein, or to enforce any other proper remedy.

          SECTION 504. TRUSTEE MAY FILE PROOFS OF CLAIM. In case of any judicial
proceeding relative to the Company (or any other obligor upon the Securities),
its property or its creditors, the Trustee shall be entitled and empowered, by
intervention in such proceeding or otherwise, to take any and all actions
authorized under the Trust Indenture Act in order to have claims of the Holders
and the Trustee allowed in any such proceeding. In particular, the Trustee shall
be authorized to collect and receive any moneys or other property payable or
deliverable on any such claims and to



                                   -PAGE 38-
<PAGE>   45
distribute the same; and any custodian, receiver, assignee, trustee, liquidator,
sequestrator or other similar official in any such judicial proceeding is hereby
authorized by each Holder to make such payments to the Trustee and, in the event
that the Trustee shall consent to the making of such payments directly to the
Holders, to pay to the Trustee any amount due it for the reasonable
compensation, expenses, disbursements and advances of the Trustee, its agents
and counsel, and any other amounts due the Trustee under Section 607.

          No provision of this Indenture shall be deemed to authorize the
Trustee to authorize or consent to or accept or adopt on behalf of any Holder
any plan of reorganization, arrangement, adjustment or composition affecting the
Securities or the rights of any Holder thereof or to authorize the Trustee to
vote in respect of the claim of any Holder in any such proceeding; provided,
however, that the Trustee may, on behalf of the Holders, vote for the election
of a trustee in bankruptcy or similar official and be a member of a creditors'
or other similar committee.

          SECTION 505. TRUSTEE MAY ENFORCE CLAIMS WITHOUT POSSESSION OF
SECURITIES. All rights of action and claims under this Indenture or the
Securities may be prosecuted and enforced by the Trustee without the possession
of any of the Securities or the production thereof in any proceeding relating
thereto, and any such 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 the payment of the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel, be for the
ratable benefit of the Holders of the Securities in respect of which such
judgment has been recovered.

          SECTION 506. APPLICATION OF MONEY COLLECTED. Any money collected by
the Trustee pursuant to this Article shall be applied in the following order, at
the date or dates fixed by the Trustee and, in case of the distribution of such
money on account of principal or any premium or interest, upon presentation of
the Securities and the notation thereon of the payment if only partially paid
and upon surrender thereof if fully paid:

          FIRST: To the payment of all amounts due the Trustee under Section
607; and

          SECOND: To the payment of the amounts then due and unpaid for
principal of and any premium, if any, and interest on the Securities 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 Securities for principal and premium, if any, and interest,
respectively.

          SECTION 507. LIMITATION ON SUITS. No Holder of any Security of any
series shall have any right to institute any proceeding, judicial or otherwise,
with



                                   -PAGE 39-
<PAGE>   46
respect to this Indenture, or for the appointment of a receiver or trustee,
or for any other remedy hereunder, unless

          (1) such Holder has previously given written notice to the Trustee of
a continuing Event of Default with respect to the Securities of that series;

          (2) the Holders of not less than 25% in principal amount of the
Outstanding Securities of that series shall have made written request to the
Trustee to institute proceedings in respect of such Event of Default in its own
name as Trustee hereunder;

          (3) such Holder or Holders have offered to the Trustee reasonable
indemnity against the costs, expenses and liabilities to be incurred in
compliance with such request;

          (4) the Trustee for 60 days after its receipt of such notice, request
and offer of indemnity has failed to institute any such proceeding; and

          (5) no direction inconsistent with such written request has been given
to the Trustee during such 60-day period by the Holders of a majority in
principal amount of the Outstanding Securities of that series;

it being understood and intended that no one or more of such Holders shall have
any right in any manner whatever by virtue of, or by availing of, any provision
of this Indenture to affect, disturb or prejudice the rights of any other of
such Holders, or to obtain or to seek to obtain priority or preference over any
other of such Holders or to enforce any right under this Indenture, except in
the manner herein provided and for the equal and ratable benefit of all of such
Holders.

          SECTION 508. UNCONDITIONAL RIGHT OF HOLDERS TO RECEIVE PRINCIPAL,
PREMIUM AND INTEREST AND TO CONVERT. Notwithstanding any other provision in this
Indenture, the Holder of any Security shall have the right, which is absolute
and unconditional, to receive payment of the principal of and any premium and
(subject to Section 307) interest on such Security on the respective Stated
Maturities expressed in such Security (or, in the case of redemption, on the
Redemption Date), to convert such Securities in accordance with Article Fourteen
and to institute suit for the enforcement of any such payment, and such rights
shall not be impaired without the consent of such Holder.

          SECTION 509. RESTORATION OF RIGHTS AND REMEDIES. If the Trustee or any
Holder has instituted any proceeding to enforce any right or remedy under this
Indenture and such proceeding has been discontinued or abandoned for any reason,
or has been determined adversely to the Trustee or to such Holder, then and in
every such case, subject to any determination in such proceeding, the Company,
the



                                   -PAGE 40-
<PAGE>   47
Trustee and the Holders shall be restored severally and respectively to
their former positions hereunder and thereafter all rights and remedies of the
Trustee and the Holders shall continue as though no such proceeding had been
instituted.

          SECTION 510. RIGHTS AND REMEDIES CUMULATIVE. Except as otherwise
provided with respect to the replacement or payment of mutilated, destroyed,
lost or stolen Securities in the last paragraph of Section 306, no right or
remedy herein conferred upon or reserved to the Trustee or to the Holders is
intended to be exclusive of any other right or remedy, and every right and
remedy shall, to the extent permitted by law, be cumulative and in addition to
every other right and remedy given hereunder or now or hereafter existing at law
or in equity or otherwise. The assertion or employment of any right or remedy
hereunder, or otherwise, shall not prevent the concurrent assertion or
employment of any other appropriate right or remedy.

          SECTION 511. DELAY OR OMISSION NOT WAIVER. No delay or omission of the
Trustee or of any Holder of any Securities to exercise any right or remedy
accruing upon any Event of Default shall impair any such right or remedy or
constitute a waiver of any such Event of Default or an acquiescence therein.
Every right and remedy given by this Article or by law to the Trustee or to the
Holders may be exercised from time to time, and as often as may be deemed
expedient, by the Trustee (subject to the limitations contained in this
Indenture) or by the Holders, as the case may be.

          SECTION 512. CONTROL BY HOLDERS. The Holders of a majority in
principal amount of the Outstanding Securities of any series 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, with respect to the Securities of such series, provided that

          (1) such direction shall not be in conflict with any rule of law or
with this Indenture and the Trustee shall not have determined that the action so
directed would be unjustly prejudicial to Holders of Securities of that series,
or any other series, not taking part in such direction, and

          (2) the Trustee may take any other action deemed proper by the Trustee
which is not inconsistent with such direction or this Indenture.

          SECTION 513. WAIVER OF PAST DEFAULTS. The Holders of not less than a
majority in principal amount of the Outstanding Securities of any series may on
behalf of the Holders of all the Securities of such series waive any past
default hereunder with respect to such series and its consequences, except a
default

          (1) in the payment of the principal of or any premium or interest on
any Security of such series, or



                                   -PAGE 41-
<PAGE>   48
          (2) in respect of a covenant or provision hereof which under Article
Nine cannot be modified or amended without the consent of the Holder of each
Outstanding Security of such series affected.

          Upon any such waiver, such default shall cease to exist, and any Event
of Default arising therefrom shall be deemed to have been cured, for every
purpose of this Indenture; but no such waiver shall extend to any subsequent or
other default or impair any right consequent thereon.

          SECTION 514. UNDERTAKING FOR COSTS. 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, suffered or omitted by it as Trustee, a court may require any
party litigant in such suit to file an undertaking to pay the costs of such
suit, and may assess costs against any such party litigant, in the manner and to
the extent provided in the Trust Indenture Act; provided that neither this
Section nor the Trust Indenture Act shall be deemed to authorize any court to
require such an undertaking or to make such an assessment in any suit instituted
by the Company or in any suit for the enforcement of the right to convert any
Security in accordance with Article Fourteen.

          SECTION 515. WAIVER OF USURY, STAY OR EXTENSION LAWS. The Company
covenants (to the extent that it may lawfully do so) that it will 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
performance 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.


                                   ARTICLE SIX

                                   THE TRUSTEE

          SECTION 601. CERTAIN DUTIES AND RESPONSIBILITIES. The duties and
responsibilities of the Trustee shall be as provided by the Trust Indenture Act.
Notwithstanding the foregoing, no provision of this Indenture shall require the
Trustee to expend or risk its own funds or otherwise incur any financial
liability in the performance of any of its duties hereunder, or in the exercise
of any of its rights or powers, if it shall have reasonable grounds for
believing that repayment of such funds or adequate indemnity against such risk
or liability is not reasonably assured to it. Whether or not therein expressly
so provided, every provision of this Indenture relating to the conduct or
affecting the liability of or affording protection to the Trustee shall be
subject to the provisions of this Section.



                                   -PAGE 42-
<PAGE>   49
          SECTION 602. NOTICE OF DEFAULTS. If a default occurs hereunder with
respect to Securities of any series which default is known to the Trustee, the
Trustee shall give the Holders of Securities of such series notice of such
default as and to the extent provided by the Trust Indenture Act; provided,
however, that in the case of any default of the character specified in Section
501(4) with respect to Securities of such series, no such notice to Holders
shall be given until at least 30 days after the occurrence thereof. For the
purpose of this Section, 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 Securities of such series.

          SECTION 603. CERTAIN RIGHTS OF TRUSTEE. Subject to the provisions of
Section 601:

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

          (2) any request or direction of the Company mentioned herein shall be
sufficiently evidenced by a Company Request or Company Order, and any resolution
of the Board of Directors shall be sufficiently evidenced by a Board Resolution;

          (3) whenever in the administration of this Indenture the Trustee shall
deem it desirable that a matter be proved or established prior to taking,
suffering or omitting any action hereunder, the Trustee (unless other evidence
be herein specifically prescribed) may, in the absence of bad faith on its part,
rely upon an Officers' Certificate;

          (4) 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, suffered or omitted by it
hereunder in good faith and in reliance thereon;

          (5) the Trustee shall be under no obligation to exercise any of the
rights or powers vested in it by this Indenture at the request or direction of
any of the Holders pursuant to this Indenture, unless such Holders shall have
offered to the Trustee reasonable security or indemnity against the costs,
expenses and liabilities which might be incurred by it in compliance with such
request or direction;

          (6) 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, direction, consent, order, bond, debenture,
note, other evidence of indebtedness or other paper or document, but the
Trustee, in its discretion, may



                                   -PAGE 43-
<PAGE>   50
make such further inquiry or investigation into such facts or matters as it may
see fit, and, if the Trustee shall determine to make such further inquiry or
investigation, it shall be entitled to examine the books, records and premises
of the Company upon reasonable advance notice during normal business hours,
personally or by agent or attorney; and

          (7) 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 604. NOT RESPONSIBLE FOR RECITALS OR ISSUANCE OF SECURITIES.
The recitals contained herein and in the Securities, except the Trustee's
certificates of authentication, shall be taken as the statements of the Company,
and neither the Trustee nor any Authenticating Agent assumes any responsibility
for their correctness. The Trustee makes no representations as to the validity
or sufficiency of this Indenture or of the Securities. Neither the Trustee nor
any Authenticating Agent shall be accountable for the use or application by the
Company of Securities or the proceeds thereof.

          SECTION 605. MAY HOLD SECURITIES AND ACT AS TRUSTEE UNDER OTHER
INDENTURES. The Trustee, any Authenticating Agent, any Paying Agent, any
Security Registrar or any other agent of the Company, in its individual or any
other capacity, may become the owner or pledgee of Securities and, subject to
Sections 608 and 613, may otherwise deal with the Company with the same rights
it would have if it were not Trustee, Authenticating Agent, Paying Agent,
Security Registrar or such other agent.

          Subject to the limitations imposed by the Trust Indenture Act, nothing
in this Indenture shall prohibit the Trustee from becoming and acting as trustee
under other indentures under which other securities, or certificates of interest
of participation in other securities, of the Company are outstanding in the same
manner as if it were not Trustee hereunder.

          SECTION 606. MONEY HELD IN TRUST. Money held by the Trustee in trust
hereunder 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 money
received by it hereunder except as otherwise agreed with the Company.

          SECTION 607. COMPENSATION AND REIMBURSEMENT. The Company agrees

          (1) to pay to the Trustee from time to time reasonable compensation
for all services rendered by it hereunder (which compensation shall not be
limited by any provision of law in regard to the compensation of a trustee of an
express trust);



                                   -PAGE 44-
<PAGE>   51
          (2) except as otherwise expressly provided herein, to reimburse the
Trustee upon its request for all reasonable expenses, disbursements and advances
incurred or made by the Trustee in accordance with any provision of this
Indenture (including the reasonable compensation and the expenses and
disbursements of its agents and counsel), except any such expense, disbursement
or advance as may be attributable to its negligence or bad faith; and

          (3) to indemnify the Trustee for, and to hold it harmless against, any
loss, liability or expense incurred without negligence or bad faith on its part,
arising out of or in connection with the acceptance or administration of the
trust or trusts hereunder, including the costs and expenses of defending itself
against any claim or liability in connection with the exercise or performance of
any of its powers or duties hereunder.

          SECTION 608. CONFLICTING INTERESTS. If the Trustee has or shall
acquire a conflicting interest within the meaning of the Trust Indenture Act,
the Trustee shall either eliminate such interest or resign, to the extent and in
the manner provided by, and subject to the provisions of, the Trust Indenture
Act and this Indenture. To the extent permitted by such Act, the Trustee shall
not be deemed to have a conflicting interest by virtue of being a trustee under
this Indenture with respect to Securities of more than one series.

          SECTION 609. CORPORATE TRUSTEE REQUIRED; ELIGIBILITY. There shall at
all times be one (and only one) Trustee hereunder with respect to the Securities
of each series, which may be Trustee hereunder for Securities of one or more
other series. Each Trustee shall be a Person that is eligible pursuant to the
Trust Indenture Act to act as such and has (or if the Trustee is a subsidiary of
a bank holding company its parent shall have) a combined capital and surplus of
at least $100,000,000. If any such Person publishes reports of condition at
least annually, pursuant to law or to the requirements of its supervising or
examining authority, then for the purposes of this Section and to the extent
permitted by the Trust Indenture Act, the combined capital and surplus of such
Person shall be deemed to be its combined capital and surplus as set forth in
its most recent report of condition so published. If at any time the Trustee
with respect to the Securities of any series shall cease to be eligible in
accordance with the provisions of this Section, it shall resign immediately in
the manner and with the effect hereinafter specified in this Article.

          SECTION 610. RESIGNATION AND REMOVAL; APPOINTMENT OF SUCCESSOR. No
resignation or removal of the Trustee and no appointment of a successor Trustee
pursuant to this Article shall become effective until the acceptance of
appointment by the successor Trustee in accordance with the applicable
requirements of Section 611.

          The Trustee may resign at any time with respect to the Securities of
one



                                   -PAGE 45-
<PAGE>   52
or more series by giving written notice thereof to the Company. If the
instrument of acceptance by a successor Trustee required by Section 611 shall
not have been delivered to the Trustee within 30 days after the giving 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 the
Securities of such series.

          The Trustee may be removed at any time with respect to the Securities
of any series by Act of the Holders of a majority in principal amount of the
Outstanding Securities of such series, delivered to the Trustee and to the
Company.

          If at any time:

          (1) the Trustee shall fail to comply with Section 608 after written
request therefor by the Company or by any Holder who has been a bona fide Holder
of a Security for at least six months, or

          (2) the Trustee shall cease to be eligible under Section 609 and shall
fail to resign after written request therefor by the Company or by any such
Holder, or

          (3) the Trustee shall become incapable of acting or shall be adjudged
a bankrupt or insolvent or a receiver of the Trustee or of its property shall be
appointed 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, (A) the Company by a Board Resolution may
remove the Trustee with respect to all Securities, or (B) subject to Section
514, any Holder who has been a bona fide Holder of a Security for at least six
months may, on behalf of himself and all others similarly situated, petition any
court of competent jurisdiction for the removal of the Trustee with respect to
all Securities and the appointment of a successor Trustee or Trustees.

          If the Trustee shall resign, be removed or become incapable of acting,
or if a vacancy shall occur in the office of Trustee for any cause, with respect
to the Securities of one or more series, the Company, by a Board Resolution,
shall promptly appoint a successor Trustee or Trustees with respect to the
Securities of that or those series (it being understood that any such successor
Trustee may be appointed with respect to the Securities of one or more or all of
such series and that at any time there shall be only one Trustee with respect to
the Securities of any particular series) and shall comply with the applicable
requirements of Section 611. If, within one year after such resignation, removal
or incapability, or the occurrence of such vacancy, a successor Trustee with
respect to the Securities of any series shall be appointed by Act of the Holders
of a majority in principal amount of the Outstanding Securities of such series
delivered to the Company and the retiring Trustee, the successor Trustee so
appointed shall, forthwith upon its acceptance of such appointment in accordance
with the applicable requirements of Section 611, become the successor Trustee
with respect



                                   -PAGE 46-
<PAGE>   53
to the Securities of such series and to that extent supersede the successor
Trustee appointed by the Company. If no successor Trustee with respect to the
Securities of any series shall have been so appointed by the Company or the
Holders and accepted appointment in the manner required by Section 611, the
retiring Trustee may petition, or any Holder who has been a bona fide Holder of
a Security of such series for at least six months may, on behalf of himself and
all others similarly situated, petition, any court of competent jurisdiction for
the appointment of a successor Trustee with respect to the Securities of such
series.

          The Company shall give notice of each resignation and each removal of
the Trustee with respect to the Securities of any series and each appointment of
a successor Trustee with respect to the Securities of any series to all Holders
of Securities of such series in the manner provided in Section 106. Each notice
shall include the name of the successor Trustee with respect to the Securities
of such series and the address of its Corporate Trust Office.

          SECTION 611. ACCEPTANCE OF APPOINTMENT BY SUCCESSOR. In case of the
appointment hereunder of a successor Trustee with respect to all Securities,
every such 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 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.

          In case of the appointment hereunder of a successor Trustee with
respect to the Securities of one or more (but not all) series, the Company, the
retiring Trustee and each successor Trustee with respect to the Securities of
one or more series shall execute and deliver an indenture supplemental hereto
wherein each successor Trustee shall accept such appointment and which (1) shall
contain such provisions as shall be necessary or desirable to transfer and
confirm to, and to vest in, each successor Trustee all the rights, powers,
trusts and duties of the retiring Trustee with respect to the Securities of that
or those series to which the appointment of such successor Trustee relates, (2)
if the retiring Trustee is not retiring with respect to all Securities, shall
contain such provisions as shall be deemed necessary or desirable to confirm
that all the rights, powers, trusts and duties of the retiring Trustee with
respect to the Securities of that or those series as to which the retiring
Trustee is not retiring shall continue to be vested in the retiring Trustee, and
(3) shall add to or change any of the provisions of this Indenture as shall be
necessary to provide for or facilitate the administration of the trusts
hereunder by more than one Trustee, it being understood



                                   -PAGE 47-
<PAGE>   54
that nothing herein or in such supplemental indenture shall constitute such
Trustees co-trustees of the same trust and that each such Trustee shall be
trustee of a trust or trusts hereunder separate and apart from any trust or
trusts hereunder administered by any other such Trustee; and upon the execution
and delivery of such supplemental indenture the resignation or removal of the
retiring Trustee shall become effective to the extent provided therein and each
such successor Trustee, without any further act, deed or conveyance, shall
become vested with all the rights, powers, trusts and duties of the retiring
Trustee with respect to the Securities of that or those series to which the
appointment of such successor Trustee relates; but, on request of the Company or
any successor Trustee, such retiring Trustee shall duly assign, transfer and
deliver to such successor Trustee all property and money held by such retiring
Trustee hereunder with respect to the Securities of that or those series to
which the appointment of such successor Trustee relates.

          Upon request of any such 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 the
first or second preceding paragraph, as the case may be.

          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.

          SECTION 612. 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 all or substantially all the corporate trust business
of the Trustee (including the trust created by this Indenture), shall be the
successor of the Trustee hereunder, provided such corporation shall be otherwise
qualified and eligible under this Article, without the execution or filing of
any paper or any further act on the part of any of the parties hereto. In case
any Securities 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 Securities
so authenticated with the same effect as if such successor Trustee had itself
authenticated such Securities.

          SECTION 613. PREFERENTIAL COLLECTION OF CLAIMS AGAINST COMPANY. If and
when the Trustee shall be or become a creditor of the Company (or any other
obligor upon the Securities), the Trustee shall be subject to the provisions of
the Trust Indenture Act regarding the collection of claims against the Company
(or any such other obligor).

          SECTION 614. APPOINTMENT OF AUTHENTICATING AGENT. The



                                   -PAGE 48-
<PAGE>   55
Trustee may appoint an Authenticating Agent or Agents with respect to one or
more series of Securities which shall be authorized to act on behalf of the
Trustee to authenticate Securities of such series issued upon original issue and
upon exchange, registration of transfer or partial redemption thereof or
pursuant to Section 306, and Securities 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. Wherever reference is
made in this Indenture to the authentication and delivery of Securities by the
Trustee or the Trustee's certificate of authentication, such reference shall be
deemed to include authentication and delivery on behalf of the Trustee by an
Authenticating Agent and a certificate of authentication executed on behalf of
the Trustee by an Authenticating Agent. Each Authenticating Agent shall be
acceptable to the Company and shall at all times be a corporation organized and
doing business under the laws of the United States of America, any State thereof
or the District of Columbia, authorized under such laws to act as Authenticating
Agent, having (or if the Authenticating Agent is a subsidiary of a bank holding
company its parent shall have) a combined capital and surplus of not less than
$100,000,000 and subject to supervision or examination by Federal or State
authority. If such Authenticating Agent publishes reports of condition at least
annually, pursuant to law or to the requirements of said supervising or
examining authority, then for the purposes of this Section, the combined capital
and surplus of such Authenticating Agent shall be deemed to be its combined
capital and surplus as set forth in its most recent report of condition so
published. If at any time an Authenticating Agent shall cease to be eligible in
accordance with the provisions of this Section, such Authenticating Agent shall
resign immediately in the manner and with the effect specified in this Section.

          Any corporation into which an Authenticating Agent may be merged or
converted or with which it may be consolidated, or any corporation resulting
from any merger, conversion or consolidation to which such Authenticating Agent
shall be a party, or any corporation succeeding to the corporate agency or
corporate trust business of an Authenticating Agent (including the
authenticating agency contemplated by this Indenture), shall continue to be an
Authenticating Agent, provided such corporation shall be otherwise eligible
under this Section, without the execution or filing of any paper or any further
act on the part of the Trustee or the Authenticating Agent.

          An Authenticating Agent may resign at any time by giving written
notice thereof to the Trustee and to the Company. The Trustee may at any time
terminate the agency of an Authenticating Agent by giving written notice thereof
to such Authenticating Agent and to the Company. Upon receiving such a notice of
resignation or upon such a termination, or in case at any time such
Authenticating Agent shall cease to be eligible in accordance with the
provisions of this Section, the Trustee may appoint a successor Authenticating
Agent which shall be acceptable to the Company and shall give notice of such
appointment in the manner provided in Section 106 to all Holders of Securities
of the series with respect to which such Authenticating Agent will serve. Any
successor Authenticating Agent upon acceptance of its appointment



                                   -PAGE 49-
<PAGE>   56
hereunder shall become vested with all the rights, powers and duties of its
predecessor hereunder, with like effect as if originally named as an
Authenticating Agent. No successor Authenticating Agent shall be appointed
unless eligible under the provisions of this Section.

          The Trustee agrees to pay to each Authenticating Agent from time to
time reasonable compensation for its services under this Section, and the
Trustee shall be entitled to be reimbursed for such payments, subject to the
provisions of Section 607.

          If an appointment with respect to one or more series is made pursuant
to this Section 614, the Securities of such series may have endorsed thereon, in
addition to the Trustee's certificate of authentication, an alternative
certificate of authentication in the following form:

          This is one of the Securities of the series designated therein
referred to in the within-mentioned Indenture.

                                         U.S. BANK TRUST NATIONAL
                                           ASSOCIATION, as Trustee



                                         By:
                                            As Authenticating Agent



                                         By:
                                            Authorized Officer


                                  ARTICLE SEVEN

                HOLDERS' LISTS AND REPORTS BY TRUSTEE AND COMPANY

          SECTION 701. COMPANY TO FURNISH TRUSTEE NAMES AND ADDRESSES OF
HOLDERS. The Company will furnish or cause to be furnished to the Trustee

          (1) semi-annually, not later than 15 days after the Regular Record
Date, a list, in such form as the Trustee may reasonably require, of the names
and addresses of the Holders of Securities of each series as of such Regular
Record Date, as the case may be, and



                                   -PAGE 50-
<PAGE>   57
          (2) 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 that no such list need be furnished by the Company to the Trustee so
long as the Trustee is acting as Security Registrar.

          SECTION 702. PRESERVATION OF INFORMATION; COMMUNICATIONS TO HOLDERS.
The Trustee shall preserve, in as current a form as is reasonably practicable,
the names and addresses of Holders contained in the most recent list furnished
to the Trustee as provided in Section 701, if any, and the names and addresses
of Holders received by the Trustee in its capacity as Security Registrar. The
Trustee may destroy any list furnished to it as provided in Section 701 upon
receipt of a new list so furnished.

          The rights of Holders to communicate with other Holders with respect
to their rights under this Indenture or under the Securities, and the
corresponding rights and privileges of the Trustee, shall be as provided by the
Trust Indenture Act.

          Every Holder of Securities, by receiving and holding the same, agrees
with the Company and the Trustee that neither the Company nor the Trustee nor
any agent of either of them shall be held accountable by reason of any
disclosure of information as to names and addresses of Holders made pursuant to
the Trust Indenture Act.

          SECTION 703. REPORTS BY TRUSTEE. The Trustee shall transmit to Holders
such reports concerning the Trustee and its actions under this Indenture as may
be required pursuant to the Trust Indenture Act at the times and in the manner
provided pursuant thereto.

          Reports so required to be transmitted at stated intervals of not more
than 12 months shall be transmitted no later than July 1 in each calendar year,
commencing with the first July 1 after the first issuance of Securities pursuant
to this Indenture.

          A copy of each such report shall, at the time of such transmission to
Holders, be filed by the Trustee with each stock exchange upon which any
Securities are listed, with the Commission and with the Company. The Company
will notify the Trustee when any Securities are listed on any stock exchange.

          SECTION 704. REPORTS BY COMPANY. The Company shall file with the
Trustee and the Commission, and transmit to Holders, such information, documents
and other reports, and such summaries thereof, as may be required pursuant to
the Trust Indenture Act at the times and in the manner provided pursuant to the
Trust Indenture Act; provided that any such information, documents or reports
required to be filed by the Company with the Commission pursuant to Section 13
or 15(d) of the Exchange Act shall be filed with the Trustee within 15 days
after the same is so



                                   -PAGE 51-
<PAGE>   58
required to be filed with the Commission.


                                  ARTICLE EIGHT

              CONSOLIDATION, MERGER, CONVEYANCE, TRANSFER OR LEASE

          SECTION 801. COMPANY MAY CONSOLIDATE, ETC. ONLY ON CERTAIN TERMS. The
Company shall not consolidate with or merge into any other Person (in a
transaction in which the Company is not the surviving corporation) or convey,
transfer or lease its properties and assets substantially as an entirety to any
Person, unless:

          (1) in case the Company shall consolidate with or merge into another
Person (in any transaction in which the Company is not the surviving
corporation) or convey, transfer or lease its properties and assets
substantially as an entirety to any Person, the Person formed by such
consolidation or into which the Company is merged or the Person which acquires
by conveyance or transfer, or which leases, the properties and assets of the
Company substantially as an entirety shall be a corporation, limited liability
company, partnership or trust, shall be organized and validly existing under the
laws of the United States of America, any State thereof or the District of
Columbia and shall expressly assume, by an indenture supplemental hereto,
executed and delivered to the Trustee, in form satisfactory to the Trustee, the
due and punctual payment of the principal of and any premium and interest on all
the Securities and the performance or observance of every covenant of this
Indenture on the part of the Company to be performed or observed and the
conversion rights shall be provided for in accordance with Article Fourteen, if
applicable, or as otherwise specified pursuant to Section 301, by supplemental
indenture satisfactory in form to the Trustee, executed and delivered to the
Trustee, by the Person (if other than the Company) formed by such consolidation
or into which the Company shall have been merged or by the Person which shall
have acquired the Company's assets;

          (2) immediately after giving effect to such transaction and treating
any indebtedness which becomes an obligation of the Company or any Subsidiary as
a result of such transaction as having been incurred by the Company or such
Subsidiary at the time of such transaction, no Event of Default, and no event
which, after notice or lapse of time or both, would become an Event of Default,
shall have happened and be continuing; and

          (3) the Company has delivered to the Trustee an Officers' Certificate
and an Opinion of Counsel, each stating that such consolidation, merger,
conveyance, transfer or lease and, if a supplemental indenture is required in
connection with such transaction, such supplemental indenture comply with this
Article and that all conditions precedent herein provided for relating to such
transaction have been complied with.



                                   -PAGE 52-
<PAGE>   59
          SECTION 802. SUCCESSOR SUBSTITUTED. Upon any consolidation of the
Company with, or merger of the Company into, any other Person or any conveyance,
transfer or lease of the properties and assets of the Company substantially as
an entirety in accordance with Section 801, the successor Person formed by such
consolidation or into which the Company is merged or to which such conveyance,
transfer or lease is made shall succeed to, and be substituted for, and may
exercise every right and power of, the Company under this Indenture with the
same effect as if such successor Person had been named as the Company herein,
and thereafter, except in the case of a lease, the predecessor Person shall be
relieved of all obligations and covenants under this Indenture and the
Securities.

                                  ARTICLE NINE

                             SUPPLEMENTAL INDENTURES

          SECTION 901. SUPPLEMENTAL INDENTURES WITHOUT CONSENT OF HOLDERS.
Without the consent of any Holders, the Company, when authorized by a Board
Resolution, and the Trustee, at any time and from time to time, may enter into
one or more indentures supplemental hereto, in form satisfactory to the Trustee,
for any of the following purposes:

          (1) to evidence the succession of another Person to the Company, or
successive successions, and the assumption by any such successor of the
covenants of the Company herein and in the Securities; or

          (2) to add to the covenants of the Company for the benefit of the
Holders of all or any series of Securities (and if such covenants are to be for
the benefit of less than all series of Securities, stating that such covenants
are expressly being included solely for the benefit of such series) or to
surrender any right or power herein conferred upon the Company; or

          (3) to add any additional Events of Default for the benefit of the
Holders of all or any series of Securities (and if such additional Events of
Default are to be for the benefit of less than all series of Securities, stating
that such additional Events of Default are expressly being included solely for
the benefit of such series); or

          (4) to add to or change any of the provisions of this Indenture to
such extent as shall be necessary to permit or facilitate the issuance of
Securities in bearer form, registrable or not registrable as to principal, and
with or without interest coupons, or to permit or facilitate the issuance of
Securities in uncertificated form; or

          (5) to add to, change or eliminate any of the provisions of this
Indenture in respect of one or more series of Securities, provided that any such
addition, change or elimination (A) shall neither (i) apply to any Security of
any series



                                   -PAGE 53-
<PAGE>   60
created prior to the execution of such supplemental indenture and entitled to
the benefit of such provision nor (ii) modify the rights of the Holder of any
such Security with respect to such provision or (B) shall become effective only
when there is no such Security Outstanding; or

          (6) to secure the Securities of any one or more series; or

          (7) to establish the form or terms of Securities of any series as
permitted by Sections 201 and 301; or

          (8) to evidence and provide for the acceptance of appointment
hereunder by a successor Trustee with respect to the Securities of one or more
series and to add to or change any of the provisions of this Indenture as shall
be necessary to provide for or facilitate the administration of the trusts
hereunder by more than one Trustee, pursuant to the requirements of Section 611;
or

          (9) to make provision with respect to the conversion rights of Holders
or Holders of Securities of one or more series, pursuant to the requirements of
Article Fourteen, including providing for the conversion of the securities into
any security (other than the Common Stock of the Company) or property of the
Company; or

          (10) to cure any ambiguity, to correct or supplement any provision
herein which may be defective or inconsistent with any other provision herein,
or to make any other provisions with respect to matters or questions arising
under this Indenture, provided that such action pursuant to this Clause (10)
shall not adversely affect the interests of the Holders of Securities of any
series in any material respect; or

          (11) to supplement any of the provisions of the Indenture to such
extent as shall be necessary to permit or facilitate the defeasance and
discharge of any series of Securities pursuant to Articles Four and Thirteen,
provided that any such action shall not adversely affect the interests of the
Holders of Securities of such series or any other series of Securities in any
material respect.

          SECTION 902. SUPPLEMENTAL INDENTURES WITH CONSENT OF HOLDERS. With the
consent of the Holders of a majority in principal amount of the Outstanding
Securities of each series affected by such supplemental indenture, by Act of
said Holders delivered to the Company and the Trustee, the Company, when
authorized by a Board Resolution, and the Trustee may enter into an indenture or
indentures supplemental hereto for the purpose of adding any provisions to or
changing in any manner or eliminating any of the provisions of this Indenture or
of modifying in any manner the rights of the Holders of Securities of such
series under this Indenture; provided, however, that no such supplemental
indenture shall, without the consent of the Holder of each Outstanding Security
affected thereby,



                                   -PAGE 54-
<PAGE>   61
          (1) change the Stated Maturity of the principal of, or any installment
of principal of or interest on, any Security, or reduce the principal amount
thereof or the rate of interest thereon or any premium payable upon the
redemption thereof, or reduce the amount of the principal of an Original Issue
Discount Security or any other Security which would be due and payable upon a
declaration of acceleration of the Maturity thereof pursuant to Section 502, or
change any Place of Payment where, or the coin or currency in which, any
Security or any premium or interest thereon is payable, or impair the right to
institute suit for the enforcement of any such payment on or after the Stated
Maturity thereof (or, in the case of redemption, on or after the Redemption
Date), or modify the provisions of this Indenture with respect to the
subordination of such series of Securities in a manner adverse to the Holders of
Securities of such series, or

          (2) reduce the percentage in principal amount of the Outstanding
Securities of any series, the consent of whose Holders is required for any such
supplemental indenture, or the consent of whose Holders is required for any
waiver (of compliance with certain provisions of this Indenture or certain
defaults hereunder and their consequences) provided for in this Indenture, or

          (3) modify any of the provisions of this Section, Section 513 or
Section 1007, except to increase any percentage provided for herein or therein
or to provide that certain other provisions of this Indenture cannot be modified
or waived without the consent of the Holder of each Outstanding Security
affected thereby; provided, however, that this clause shall not be deemed to
require the consent of any Holder with respect to changes in the references to
"the Trustee" and concomitant changes in this Section and Section 1007, or the
deletion of this proviso, in accordance with the requirements of Sections 611
and 901(8), or

          (4) if applicable, make any change that adversely affects the right to
convert any security as provided in Article Fourteen or pursuant to Section 301
(except as permitted by Section 901(9)) or decrease the conversion rate or
increase the conversion price of any such security.

          A supplemental indenture which changes or eliminates any covenant or
other provision of this Indenture which has expressly been included solely for
the benefit of one or more particular series of Securities, or which modifies
the rights of the Holders of Securities of such series with respect to such
covenant or other provision, shall be deemed not to affect the rights under this
Indenture of the Holders of Securities of any other series.

          It shall not be necessary for any Act of Holders under this Section to
approve the particular form of any proposed supplemental indenture, but it shall
be sufficient if such Act shall approve the substance thereof.

          SECTION 903. EXECUTION OF SUPPLEMENTAL INDENTURES. In executing, or
accepting the additional trusts created by, any supplemental indenture



                                   -PAGE 55-
<PAGE>   62
permitted by this Article or the modifications thereby of the trusts created by
this Indenture, the Trustee shall be entitled to receive, and (subject to
Sections 601 and 603) shall be fully protected in relying upon, an Opinion of
Counsel stating that the execution of such supplemental indenture is authorized
or permitted by this Indenture. The Trustee may, but shall not be obligated to,
enter into any such supplemental indenture which affects the Trustee's own
rights, duties or immunities under this Indenture or otherwise.

          SECTION 904. EFFECT OF SUPPLEMENTAL INDENTURES. Upon the execution of
any supplemental indenture under this Article, this Indenture shall be modified
in accordance therewith, and such supplemental indenture shall form a part of
this Indenture for all purposes; and every Holder of Securities theretofore or
thereafter authenticated and delivered hereunder shall be bound thereby.

          SECTION 905. CONFORMITY WITH TRUST INDENTURE ACT. Every supplemental
indenture executed pursuant to this Article shall conform to the requirements of
the Trust Indenture Act.

          SECTION 906. REFERENCE IN SECURITIES TO SUPPLEMENTAL INDENTURES.
Securities of any series authenticated and delivered after the execution of any
supplemental indenture pursuant to this Article may, and shall if required by
the Trustee, bear a notation in form approved by the Trustee as to any matter
provided for in such supplemental indenture. If the Company shall so determine,
new Securities of any series so modified as to conform, in the opinion of the
Trustee and the Company, to any such supplemental indenture may be prepared and
executed by the Company and authenticated and delivered by the Trustee in
exchange for Outstanding Securities of such series.


                                   ARTICLE TEN

                                    COVENANTS

          SECTION 1001. PAYMENT OF PRINCIPAL, PREMIUM AND INTEREST. The Company
covenants and agrees for the benefit of each series of Securities that it will
duly and punctually pay the principal of and any premium and interest on the
Securities of that series in accordance with the terms of the Securities and
this Indenture.

          SECTION 1002. MAINTENANCE OF OFFICE OR AGENCY. The Company will
maintain in each Place of Payment for any series of Securities an office or
agency where Securities of that series may be presented or surrendered for
payment, where Securities of that series may be surrendered for registration of
transfer or exchange, where Securities of that series may be surrendered for
conversion and where notices and demands to or upon the Company in respect of
the Securities of that series and



                                   -PAGE 56-
<PAGE>   63
this Indenture may be served. The Company will give prompt written notice to the
Trustee of the location, and any change in the location, of such office or
agency. 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, surrenders, 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, surrenders, notices and
demands.

          The Company may also from time to time designate one or more other
offices or agencies where the Securities of one or more series may be presented
or surrendered for any or all such purposes and may from time to time rescind
such designations; provided, however, that no such designation or rescission
shall in any manner relieve the Company of its obligation to maintain an office
or agency in each Place of Payment for Securities of any series for such
purposes. The Company will give prompt written notice to the Trustee of any such
designation or rescission and of any change in the location of any such other
office or agency.

          SECTION 1003. MONEY FOR SECURITIES PAYMENTS TO BE HELD IN TRUST. If
the Company shall at any time act as its own Paying Agent with respect to any
series of Securities, it will, on or before each due date of the principal of or
any premium or interest on any of the Securities of that series, segregate and
hold in trust for the benefit of the Persons entitled thereto a sum sufficient
to pay the principal and any premium and interest so becoming due until such
sums shall be paid to such Persons or otherwise disposed of as herein provided
and will promptly notify the Trustee of its action or failure so to act.

          Whenever the Company shall have one or more Paying Agents for any
series of Securities, it will, on or prior to each due date of the principal of
or any premium or interest on any Securities of that series, deposit with a
Paying Agent a sum sufficient to pay such amount, such sum to be held as
provided by the Trust Indenture Act, and (unless such Paying Agent is the
Trustee) the Company will promptly notify the Trustee of its action or failure
so to act.

          The Company will cause each Paying Agent for any series of Securities
other than the Trustee to execute and deliver to the Trustee an instrument in
which such Paying Agent shall agree with the Trustee, subject to the provisions
of this Section, that such Paying Agent will (1) comply with the provisions of
the Trust Indenture Act applicable to it as a Paying Agent and (2) during the
continuance of any default by the Company (or any other obligor upon the
Securities of that series) in the making of any payment in respect of the
Securities of that series, upon the written request of the Trustee, forthwith
pay to the Trustee all sums held in trust by such Paying Agent for payment in
respect of the Securities of that series.

          The Company may at any time, for the purpose of obtaining the



                                   -PAGE 57-
<PAGE>   64
satisfaction and discharge of this Indenture or for any other purpose, pay, or
by Company Order 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 trusts 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.

          Any money deposited with the Trustee or any Paying Agent, or then held
by the Company, in trust for the payment of the principal of or any premium or
interest on any Security of any series and remaining unclaimed for a period
ending on the earlier of the date that is ten Business Days prior to the date
such money would escheat to the State or two years after such principal, premium
or interest has become due and payable shall be paid to the Company on Company
Request, or (if then held by the Company) shall be discharged from such trust;
and the Holder of such Security shall thereafter, as an unsecured general
creditor, look only to the Company for payment thereof, and all liability of the
Trustee or such Paying Agent with respect to such trust money, and all liability
of the Company as trustee thereof, shall thereupon cease; provided, however,
that the Trustee or such Paying Agent, before being required to make any such
repayment, may at the expense of the Company cause to be published once, in a
newspaper published in the English language, customarily published on each
Business Day and of general circulation in each Place of Payment, notice that
such money remains unclaimed and that, after a date specified therein, which
shall not be less than 30 days from the date of such publication, any unclaimed
balance of such money then remaining will be repaid to the Company.

          SECTION 1004. STATEMENT BY OFFICERS AS TO DEFAULT. The Company will
deliver to the Trustee, within 120 days after the end of each fiscal year of the
Company ending after the date hereof, an Officers' Certificate, stating whether
or not to the best knowledge of the signers thereof the Company is in default in
the performance and observance of any of the terms, provisions and conditions of
this Indenture (without regard to any period of grace or requirement of notice
provided hereunder) and, if the Company shall be in default, specifying all such
defaults and the nature and status thereof of which they may have knowledge.

          SECTION 1005. EXISTENCE. Subject to Article Eight, the Company will do
or cause to be done all things necessary to preserve and keep in full force and
effect its existence.

          SECTION 1006. OPINIONS AS TO PLEDGED PROPERTY. Promptly after the
execution and delivery of this Indenture and of each supplemental indenture or
other instrument of further assurance, the Company shall furnish to the Trustee
an Opinion of Counsel stating that, in the opinion of such counsel, this
Indenture and all such supplemental indentures have been properly recorded
and filed so as to make effective the



                                   -PAGE 58-
<PAGE>   65
lien intended to be created by this Indenture and such indenture supplemental
hereto, and reciting the details of such action or referring to prior Opinions
of Counsel in which such details are given, or stating that, in the opinion of
such counsel, no such action is necessary to make such lien effective.

          On or before May 1, in each calendar year, beginning with the first
calendar year commencing more than three months after the date of authentication
and delivery of any Securities of any series that are secured by any lien on
property, the Company shall furnish to the Trustee an Opinion of Counsel either
stating that, in the opinion of such counsel, such action has been taken with
respect to the recording, filing, re-recording and re-filing of this Indenture,
any indentures supplemental hereto and any other requisite documents and with
respect to the execution and filing of any financing statements and continuation
statements as is necessary to maintain the lien and security interest created by
this Indenture and any such indentures supplemental hereto with respect to the
property pledged to secure such Securities and reciting the details of such
action or stating that in the opinion of such counsel no such action is
necessary to maintain such lien and security interest. Such Opinion of Counsel
shall also describe the recording, filing, re-recording and re-filing of this
Indenture, any indentures supplemental hereto and any other requisite documents
and the execution and filing of any financing statements and any other requisite
documents and the execution and filing of any financing statements and
continuation statements that will, in the opinion of such counsel, be required
to maintain the lien and security interest of this Indenture and any such
indentures supplemental hereto with respect to such property until May 1 in the
following calendar year.

          SECTION 1007. WAIVER OF CERTAIN COVENANTS. Except as otherwise
specified as contemplated by Section 301 for Securities of such series, the
Company may, with respect to the Securities of any series, omit in any
particular instance to comply with any term, provision or condition set forth in
any covenant provided pursuant to Section 301(19), 901(2) or 901(7) for the
benefit of the Holders of such series if before the time for such compliance the
Holders of at least 50% in principal amount of the Outstanding Securities of
such series shall, by Act of such Holders, either waive such compliance in such
instance or generally waive compliance with such term, provision or condition,
but no such waiver shall extend to or affect such term, provision or condition
except to the extent so expressly waived, and, until such waiver shall become
effective, the obligations of the Company and the duties of the Trustee in
respect of any such term, provision or condition shall remain in full force and
effect.

                                 ARTICLE ELEVEN



                                   -PAGE 59-
<PAGE>   66
                            REDEMPTION OF SECURITIES

          SECTION 1101. APPLICABILITY OF ARTICLE. Securities of any series which
are redeemable before their Stated Maturity shall be redeemable in accordance
with their terms and (except as otherwise specified as contemplated by Section
301 for such Securities) in accordance with this Article.

          SECTION 1102. ELECTION TO REDEEM; NOTICE TO TRUSTEE. The election of
the Company to redeem any Securities shall be evidenced by a Board Resolution or
in another manner specified as contemplated by Section 301 for such Securities.
In case of any redemption at the election of the Company of less than all the
Securities of any series (including any such redemption affecting only a single
Security), the Company shall, at least 60 days prior to the Redemption Date
fixed by the Company (unless a shorter notice shall be satisfactory to the
Trustee), notify the Trustee of such Redemption Date, of the principal amount of
Securities of such series to be redeemed and, if applicable, of the tenor of the
Securities to be redeemed. In the case of any redemption of Securities prior to
the expiration of any restriction on such redemption provided in the terms of
such Securities or elsewhere in this Indenture, the Company shall furnish the
Trustee with an Officers' Certificate evidencing compliance with such
restriction.

          SECTION 1103. SELECTION BY TRUSTEE OF SECURITIES TO BE REDEEMED. If
less than all the Securities of any series are to be redeemed (unless all the
Securities of such series and of a specified tenor are to be redeemed or unless
such redemption affects only a single Security), the particular Securities to be
redeemed shall be selected not more than 60 days prior to the Redemption Date by
the Trustee, from the Outstanding Securities of such series not previously
called for redemption, by such method as the Trustee shall deem fair and
appropriate and which may provide for the selection for redemption of a portion
of the principal amount of any Security of such series, provided that the
unredeemed portion of the principal amount of any Security shall be in an
authorized denomination (which shall not be less than the minimum authorized
denomination) for such Security. If less than all the Securities of such series
and of a specified tenor are to be redeemed (unless such redemption affects only
a single Security), the particular Securities to be redeemed shall be selected
not more than 60 days prior to the Redemption Date by the Trustee, from the
Outstanding Securities of such series and specified tenor not previously called
for redemption in accordance with the preceding sentence.

          If any Security selected for partial redemption is converted in part
before termination of the conversion right with respect to the portion of the
Security so selected, the converted portion of such Security shall be deemed (so
far as may be) to be the portion selected for redemption. Securities which have
been converted during a selection of Securities to be redeemed shall be treated
by the Trustee as Outstanding for the purpose of such selection.



                                   -PAGE 60-
<PAGE>   67
          The Trustee shall promptly notify the Company in writing of the
Securities selected for redemption as aforesaid and, in case of any Securities
selected for partial redemption as aforesaid, the principal amount thereof to be
redeemed.

          The provisions of the two preceding paragraphs shall not apply with
respect to any redemption affecting only a single Security, whether such
Security is to be redeemed in whole or in part. In the case of any such
redemption in part, the unredeemed portion of the principal amount of the
Security shall be in an authorized denomination (which shall not be less than
the minimum authorized denomination) for such Security.

          For all purposes of this Indenture, unless the context otherwise
requires, all provisions relating to the redemption of Securities shall relate,
in the case of any Securities redeemed or to be redeemed only in part, to the
portion of the principal amount of such Securities which has been or is to be
redeemed.

          SECTION 1104. NOTICE OF REDEMPTION. Notice of redemption shall be
given by first-class mail, postage prepaid, mailed not less than 30 nor more
than 60 days prior to the Redemption Date, to each Holder of Securities to be
redeemed, at its address appearing in the Security Register.

          All notices of redemption shall state:

          (1) the Redemption Date,

          (2) the Redemption Price (including accrued interest, if any),

          (3) if less than all the Outstanding Securities of any series
consisting of more than a single Security are to be redeemed, the identification
(and, in the case of partial redemption of any such Securities, the principal
amounts) of the particular Securities to be redeemed and, if less than all the
Outstanding Securities of any series consisting of a single Security are to be
redeemed, the principal amount of the particular Security to be redeemed,

          (4) that on the Redemption Date the Redemption Price will become due
and payable upon each such Security to be redeemed and, if applicable, that
interest thereon will cease to accrue on and after said date,

          (5) the place or places where each such Security is to be surrendered
for payment of the Redemption Price,

          (6) if applicable, the conversion price, that the date on which the
right to convert the principal of the Securities or the portions thereof to be
redeemed will terminate will be the Redemption Date and the place or places
where such Securities may be surrendered for conversion, and



                                   -PAGE 61-
<PAGE>   68
          (7) that the redemption is for a sinking fund, if such is the case.

          Notice of redemption of Securities to be redeemed at the election of
the Company shall be given by the Company or, at the Company's request, by the
Trustee in the name and at the expense of the Company and shall be irrevocable.

          SECTION 1105. DEPOSIT OF REDEMPTION PRICE. On or prior to any
Redemption Date, the Company shall deposit with the Trustee or with a Paying
Agent (or, if the Company is acting as its own Paying Agent, segregate and hold
in trust as provided in Section 1003) an amount of money sufficient to pay the
Redemption Price of, and (except if the Redemption Date shall be an Interest
Payment Date) accrued interest on, all the Securities which are to be redeemed
on that date.

          If any Security called for redemption is converted, any money
deposited with the Trustee or with a Paying Agent or so segregated and held in
trust for the redemption of such Security shall (subject to the right of any
Holder of such Security to receive interest as provided in the last paragraph of
Section 307) be paid to the Company on Company Request, or if then held by the
Company, shall be discharged from such trust.

          SECTION 1106. SECURITIES PAYABLE ON REDEMPTION DATE. Notice of
redemption having been given as aforesaid, the Securities so to be redeemed
shall, on the Redemption Date, become due and payable at the Redemption Price
therein specified, and from and after such date (unless the Company shall
default in the payment of the Redemption Price and accrued interest) such
Securities shall cease to bear interest. Upon surrender of any such Security for
redemption in accordance with said notice, such Security shall be paid by the
Company at the Redemption Price, together with accrued interest to the
Redemption Date; provided, however, that, unless otherwise specified as
contemplated by Section 301, installments of interest whose Stated Maturity is
on or prior to the Redemption Date will be payable to the Holders of such
Securities, or one or more Predecessor Securities, registered as such at the
close of business on the relevant Record Dates according to their terms and the
provisions of Section 307.

          If any Security called for redemption shall not be so paid upon
surrender thereof for redemption, the principal and any premium shall, until
paid, bear interest from the Redemption Date at the rate prescribed therefor in
the Security.

          SECTION 1107. SECURITIES REDEEMED IN PART. Any Security which is to be
redeemed only in part shall be surrendered at a Place of Payment therefor (with,
if the Company or the Trustee so requires, due endorsement by, or a written
instrument of transfer in form satisfactory to the Company and the Trustee duly
executed by, the Holder thereof or its attorney duly authorized in writing), and
the Company shall execute, and the Trustee shall authenticate and deliver to the
Holder of such Security



                                   -PAGE 62-
<PAGE>   69

without service charge, a new Security or Securities of the same series and of
like tenor, of any authorized denomination as requested by such Holder, in
aggregate principal amount equal to and in exchange for the unredeemed portion
of the principal of the Security so surrendered.


                                 ARTICLE TWELVE

                                  SINKING FUNDS

          SECTION 1201. APPLICABILITY OF ARTICLE. The provisions of this Article
shall be applicable to any sinking fund for the retirement of Securities of any
series except as otherwise specified as contemplated by Section 301 for such
Securities.

          The minimum amount of any sinking fund payment provided for by the
terms of any Securities is herein referred to as a "mandatory sinking fund
payment," and any payment in excess of such minimum amount provided for by the
terms of such Securities is herein referred to as an "optional sinking fund
payment." If provided for by the terms of any Securities, the cash amount of any
sinking fund payment may be subject to reduction as provided in Section 1202.
Each sinking fund payment shall be applied to the redemption of Securities as
provided for by the terms of such Securities.

          SECTION 1202. SATISFACTION OF SINKING FUND PAYMENTS WITH SECURITIES.
The Company (1) may deliver Outstanding Securities of a series (other than any
previously called for redemption) and (2) may apply as a credit Securities of a
series which have been redeemed either at the election of the Company pursuant
to the terms of such Securities or through the application of permitted optional
sinking fund payments pursuant to the terms of such Securities, in each case in
satisfaction of all or any part of any sinking fund payment with respect to any
Securities of such series required to be made pursuant to the terms of such
Securities as and to the extent provided for by the terms of such Securities;
provided that the Securities to be so credited have not been previously so
credited. The Securities to be so credited shall be received and credited for
such purpose by the Trustee at the Redemption Price, as specified in the
Securities so to be redeemed, for redemption through operation of the sinking
fund and the amount of such sinking fund payment shall be reduced accordingly.

          SECTION 1203. REDEMPTION OF SECURITIES FOR SINKING FUND. Not less than
60 days prior to each sinking fund payment date for any Securities, the Company
will deliver to the Trustee an Officers' Certificate specifying the amount of
the next ensuing sinking fund payment for such Securities pursuant to the terms
of such Securities, the portion thereof, if any, which is to be satisfied by
payment of cash and the portion thereof, if any, which is to be satisfied by
delivering and crediting Securities pursuant to Section 1202 and will also
deliver to the Trustee any Securities to be so



                                   -PAGE 63-
<PAGE>   70

delivered. Not less than 30 days prior to each such sinking fund payment date,
the Trustee shall select the Securities to be redeemed upon such sinking fund
payment date in the manner specified in Section 1103 and cause notice of the
redemption thereof to be given in the name of and at the expense of the Company
in the manner provided in Section 1104. Such notice having been duly given, the
redemption of such Securities shall be made upon the terms and in the manner
stated in Sections 1106 and 1107.


                                ARTICLE THIRTEEN

                       DEFEASANCE AND COVENANT DEFEASANCE

          SECTION 1301. COMPANY'S OPTION TO EFFECT DEFEASANCE OR COVENANT
DEFEASANCE. The Company may elect, at its option at any time, to have Section
1302 or Section 1303 applied to any Securities or any series of Securities, as
the case may be, designated pursuant to Section 301 as being defeasible pursuant
to such Section 1302 or 1303, in accordance with any applicable requirements
provided pursuant to Section 301 and upon compliance with the conditions set
forth below in this Article. Any such election shall be evidenced by a Board
Resolution or in another manner specified as contemplated by Section 301 for
such Securities.

          SECTION 1302. DEFEASANCE AND DISCHARGE. Upon the Company's exercise of
its option (if any) to have this Section applied to any Securities or any series
of Securities, as the case may be, the Company shall be deemed to have been
discharged from its obligations with respect to such Securities as provided in
this Section on and after the date the conditions set forth in Section 1304 are
satisfied (hereinafter called "Defeasance"). For this purpose, such Defeasance
means that the Company shall be deemed to have paid and discharged the entire
indebtedness represented by such Securities and to have satisfied all its other
obligations under such Securities and this Indenture insofar as such Securities
are concerned (and the Trustee, at the expense of the Company, shall execute
proper instruments acknowledging the same), subject to the following which shall
survive until otherwise terminated or discharged hereunder: (1) the rights of
Holders of such Securities to receive, solely from the trust fund described in
Section 1304 and as more fully set forth in such Section, payments in respect of
the principal of and any premium and interest on such Securities when payments
are due, (2) the Company's obligations with respect to such Securities under
Sections 304, 305, 306, 1002 and 1003, and, if applicable, Article Fourteen, (3)
the rights, powers, trusts, duties and immunities of the Trustee hereunder and
(4) this Article. Subject to compliance with this Article, the Company may
exercise its option (if any) to have this Section applied to any Securities
notwithstanding the prior exercise of its option (if any) to have Section 1303
applied to such Securities.

          SECTION 1303. COVENANT DEFEASANCE. Upon the Company's exercise of its
option (if any) to have this Section applied to any Securities or any series



                                   -PAGE 64-
<PAGE>   71

of Securities, as the case may be, (1) the Company shall be released from its
obligations under any covenants provided pursuant to Section 301(19), 901(2) or
901(7) for the benefit of the Holders of such Securities and (2) the occurrence
of any event specified in Section 501(4) (with respect to any such covenants
provided pursuant to Section 301(19), 901(2) or 901(7)), shall be deemed not to
be or result in an Event of Default, in each case with respect to such
Securities as provided in this Section on and after the date the conditions set
forth in Section 1304 are satisfied (hereinafter called "Covenant Defeasance").
For this purpose, such Covenant Defeasance means that, with respect to such
Securities, the Company may omit to comply with and shall have no liability in
respect of any term, condition or limitation set forth in any such specified
Section (to the extent so specified in the case of Section 501(4)), whether
directly or indirectly by reason of any reference elsewhere herein to any such
Section or Article or by reason of any reference in any such Section or Article
to any other provision herein or in any other document, but the remainder of
this Indenture and such Securities shall be unaffected thereby.

          SECTION 1304. CONDITIONS TO DEFEASANCE OR COVENANT DEFEASANCE. The
following shall be the conditions to the application of Section 1302 or Section
1303 to any Securities or any series of Securities, as the case may be:

          (1) The Company shall irrevocably have deposited or caused to be
deposited with the Trustee (or another trustee which satisfies the requirements
contemplated by Section 609 and agrees to comply with the provisions of this
Article applicable to it) as trust funds in trust for the purpose of making the
following payments, specifically pledged as security for, and dedicated solely
to, the benefits of the Holders of such Securities, (A) money in an amount, or
(B) U.S. Government Obligations which through the scheduled payment of principal
and interest in respect thereof in accordance with their terms will provide, not
later than one day before the due date of any payment, money in an amount, or
(C) a combination thereof, in each case 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 and discharge,
and which shall be applied by the Trustee (or any such other qualifying trustee)
to pay and discharge, the principal of and any premium and interest on such
Securities on the respective Stated Maturities, in accordance with the terms of
this Indenture and such Securities. As used herein, "U.S. Government Obligation"
means (x) any security which is (i) a direct obligation of the United States of
America for the payment of which the full faith and credit of the United States
of America is pledged or (ii) an obligation 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, which, in either case (i) or (ii),
is not callable or redeemable at the option of the issuer thereof, and (y) any
depositary receipt issued by a bank (as defined in Section 3(a)(2) of the
Securities Act) as custodian with respect to any U.S. Government Obligation
which is specified in Clause (x) above and held by such bank for the account of
the holder of



                                   -PAGE 65-
<PAGE>   72

such depositary receipt, or with respect to any specific payment of principal of
or interest on any U.S. Government Obligation which is so specified and held,
provided 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 U.S.
Government Obligation or the specific payment of principal or interest evidenced
by such depositary receipt.

          (2) In the event of an election to have Section 1302 apply to any
Securities or any series of Securities, as the case may be, the Company shall
have delivered to the Trustee an Opinion of Counsel stating that (A) the Company
has received from, or there has been published by, the Internal Revenue Service
a ruling or (B) since the date of this instrument, there has been a change in
the applicable Federal income tax law, in either case (A) or (B) to the effect
that, and based thereon such opinion shall confirm that, the Holders of such
Securities will not recognize gain or loss for Federal income tax purposes as a
result of the deposit, Defeasance and discharge to be effected with respect to
such Securities and will be subject to Federal income tax on the same amount, in
the same manner and at the same times as would be the case if such deposit,
Defeasance and discharge were not to occur.

          (3) In the event of an election to have Section 1303 apply to any
Securities or any series of Securities, as the case may be, the Company shall
have delivered to the Trustee an Opinion of Counsel to the effect that the
Holders of such Securities will not recognize gain or loss for Federal income
tax purposes as a result of the deposit and Covenant Defeasance to be effected
with respect to such Securities and will be subject to Federal income tax on the
same amount, in the same manner and at the same times as would be the case if
such deposit and Covenant Defeasance were not to occur.

          (4) The Company shall have delivered to the Trustee an Officers'
Certificate to the effect that neither such Securities nor any other Securities
of the same series, if then listed on any securities exchange, will be delisted
as a result of such deposit.

          (5) No event which is, or after notice or lapse of time or both would
become, an Event of Default with respect to such Securities or any other
Securities shall have occurred and be continuing at the time of such deposit or,
with regard to any such event specified in Sections 501(5) and (6), at any time
on or prior to the 90th day after the date of such deposit (it being understood
that this condition shall not be deemed satisfied until after such 90th day).

          (6) Such Defeasance or Covenant Defeasance shall not cause the Trustee
to have a conflicting interest within the meaning of the Trust Indenture Act
(assuming all Securities are in default within the meaning of such Act).



                                   -PAGE 66-
<PAGE>   73

          (7) Such Defeasance or Covenant Defeasance shall not result in a
breach or violation of, or constitute a default under, any other agreement or
instrument to which the Company is a party or by which it is bound.

          (8) Such Defeasance or Covenant Defeasance shall not result in the
trust arising from such deposit constituting an investment company within the
meaning of the Investment Company Act unless such trust shall be registered
under such Act or exempt from registration thereunder.

          (9) The Company shall have delivered to the Trustee an Officers'
Certificate and an Opinion of Counsel, each stating that all conditions
precedent with respect to such Defeasance or Covenant Defeasance have been
complied with.

          SECTION 1305. DEPOSITED MONEY AND U.S. GOVERNMENT OBLIGATIONS TO BE
HELD IN TRUST; MISCELLANEOUS PROVISIONS. Subject to the provisions of the last
paragraph of Section 1003, all money and U.S. Government Obligations (including
the proceeds thereof) deposited with the Trustee or other qualifying trustee
(solely for purposes of this Section and Section 1306, the Trustee and any such
other trustee are referred to collectively as the "Trustee") pursuant to Section
1304 in respect of any Securities shall be held in trust and applied by the
Trustee, in accordance with the provisions of such Securities and this
Indenture, to the payment, either directly or through any such Paying Agent
(including the Company acting as its own Paying Agent) as the Trustee may
determine, to the Holders of such Securities, of all sums due and to become due
thereon in respect of principal and any premium and interest, but money so held
in trust need not be segregated from other funds except to the extent required
by law.

          The Company shall pay and indemnify the Trustee against any tax, fee
or other charge imposed on or assessed against the U.S. Government Obligations
deposited pursuant to Section 1304 or the principal and interest received in
respect thereof other than any such tax, fee or other charge which by law is for
the account of the Holders of Outstanding Securities.

          Anything in this Article to the contrary notwithstanding, the Trustee
shall deliver or pay to the Company from time to time upon Company Request any
money or U.S. Government Obligations held by it as provided in Section 1304 with
respect to any Securities which, in the opinion of a nationally recognized firm
of independent public accountants expressed in a written certification thereof
delivered to the Trustee, are in excess of the amount thereof which would then
be required to be deposited to effect the Defeasance or Covenant Defeasance, as
the case may be, with respect to such Securities.

          SECTION 1306. REINSTATEMENT. If the Trustee or the Paying Agent is
unable to apply any money in accordance with this Article with respect to any
Securities by reason of any order or judgment of any court or governmental
authority enjoining,



                                   -PAGE 67-
<PAGE>   74

restraining or otherwise prohibiting such application, then the obligations
under this Indenture and such Securities from which the Company has been
discharged or released pursuant to Section 1302 or 1303 shall be revived and
reinstated as though no deposit had occurred pursuant to this Article with
respect to such Securities, until such time as the Trustee or Paying Agent is
permitted to apply all money held in trust pursuant to Section 1305 with respect
to such Securities in accordance with this Article; provided, however, that if
the Company makes any payment of principal of or any premium or interest on any
such Security following such reinstatement of its obligations, the Company shall
be subrogated to the rights (if any) of the Holders of such Securities to
receive such payment from the money so held in trust.


                                ARTICLE FOURTEEN

                            CONVERSION OF SECURITIES

          SECTION 1401. APPLICABILITY OF ARTICLE. The provisions of this Article
shall be applicable to the Securities of any series which are convertible into
shares of Common Stock of the Company, and the issuance of such shares of Common
Stock upon the conversion of such Securities, except as otherwise specified as
contemplated by Section 301 for the Securities of such series.

          SECTION 1402. EXERCISE OF CONVERSION PRIVILEGE. In order to exercise a
conversion privilege, the Holder of a Security of a series with such a privilege
shall surrender such Security to the Company at the office or agency maintained
for that purpose pursuant to Section 1002, accompanied by a duly executed
conversion notice to the Company substantially in the form set forth in Section
206 stating that the Holder elects to convert such Security or a specified
portion thereof. Such notice shall also state, if different from the name and
address of such Holder, the name or names (with address) in which the
certificate or certificates for shares of Common Stock which shall be issuable
on such conversion shall be issued. Securities surrendered for conversion shall
(if so required by the Company or the Trustee) be duly endorsed by or
accompanied by instruments of transfer in forms satisfactory to the Company and
the Trustee duly executed by the registered Holder or its attorney duly
authorized in writing; and Securities so surrendered for conversion (in whole or
in part) during the period from the close of business on any Regular Record Date
to the opening of business on the next succeeding Interest Payment Date
(excluding Securities or portions thereof called for redemption during the
period beginning at the close of business on a Regular Record Date and ending at
the opening of business on the first Business Day after the next succeeding
Interest Payment Date, or if such Interest Payment Date is not a Business Day,
the second such Business Day) shall also be accompanied by payment in funds
acceptable to the Company of an amount equal to the interest payable on such
Interest Payment Date on the principal amount of such Security then being
converted, and such interest shall be payable to such registered Holder
notwithstanding the



                                   -PAGE 68-
<PAGE>   75

conversion of such Security, subject to the provisions of Section 307 relating
to the payment of Defaulted Interest by the Company. As promptly as practicable
after the receipt of such notice and of any payment required pursuant to a Board
Resolution and, subject to Section 303, set forth, or determined in the manner
provided, in an Officers' Certificate, or established in one or more indentures
supplemental hereto setting forth the terms of such series of Security, and the
surrender of such Security in accordance with such reasonable regulations as the
Company may prescribe, the Company shall issue and shall deliver, at the office
or agency at which such Security is surrendered, to such Holder or on its
written order, a certificate or certificates for the number of full shares of
Common Stock issuable upon the conversion of such Security (or specified portion
thereof), in accordance with the provisions of such Board Resolution, Officers'
Certificate or supplemental indenture, and cash as provided therein in respect
of any fractional share of such Common Stock otherwise issuable upon such
conversion. Such conversion shall be deemed to have been effected immediately
prior to the close of business on the date on which such notice and such
payment, if required, shall have been received in proper order for conversion by
the Company and such Security shall have been surrendered as aforesaid (unless
such Holder shall have so surrendered such Security and shall have instructed
the Company to effect the conversion on a particular date following such
surrender and such Holder shall be entitled to convert such Security on such
date, in which case such conversion shall be deemed to be effected immediately
prior to the close of business on such date) and at such time the rights of the
Holder of such Security as such Security Holder shall cease and the Person or
Persons in whose name or names any certificate or certificates for shares of
Common Stock of the Company shall be issuable upon such conversion shall be
deemed to have become the Holder or Holders of record of the shares represented
thereby. Except as set forth above and subject to the final paragraph of Section
307, no payment or adjustment shall be made upon any conversion on account of
any interest accrued on the Securities (or any part thereof) surrendered for
conversion or on account of any dividends on the Common Stock of the Company
issued upon such conversion.

          In the case of any Security which is converted in part only, upon such
conversion the Company shall execute and the Trustee shall authenticate and
deliver to or on the order of the Holder thereof, at the expense of the Company,
a new Security or Securities of the same series, of authorized denominations, in
aggregate principal amount equal to the unconverted portion of such Security.

          SECTION 1403. NO FRACTIONAL SHARES. No fractional share of Common
Stock of the Company shall be issued upon conversions of Securities of any
series. If more than one Security shall be surrendered for conversion at one
time by the same Holder, the number of full shares which shall be issuable upon
conversion shall be computed on the basis of the aggregate principal amount of
the Securities (or specified portions thereof to the extent permitted hereby) so
surrendered. If, except for the provisions of this Section 1403, any Holder of a
Security or Securities would be



                                   -PAGE 69-
<PAGE>   76

entitled to a fractional share of Common Stock of the Company upon the
conversion of such Security or Securities, or specified portions thereof, the
Company shall pay to such Holder an amount in cash equal to the current market
value of such fractional share computed, (i) if such Common Stock is listed or
admitted to unlisted trading privileges on a national securities exchange or
market, on the basis of the last reported sale price regular way on such
exchange or market on the last trading day prior to the date of conversion upon
which such a sale shall have been effected, or (ii) if such Common Stock is not
at the time so listed or admitted to unlisted trading privileges on a national
securities exchange or market, on the basis of the average of the bid and asked
prices of such Common Stock in the over-the-counter market, on the last trading
day prior to the date of conversion, as reported by the National Quotation
Bureau, Incorporated or similar organization if the National Quotation Bureau,
Incorporated is no longer reporting such information, or if not so available,
the fair market price as determined by the Board of Directors. For purposes of
this Section, "trading day" shall mean each Monday, Tuesday, Wednesday, Thursday
and Friday other than any day on which the Common Stock is not traded on the
Nasdaq National Market, or if the Common Stock is not traded on the Nasdaq
National Market, on the principal exchange or market on which the Common Stock
is traded or quoted.

          SECTION 1404. ADJUSTMENT OF CONVERSION PRICE. The conversion price of
Securities of any series that is convertible into Common Stock of the Company
shall be adjusted for any stock dividends, stock splits, reclassifications,
combinations or similar transactions in accordance with the terms of the
supplemental indenture or Board Resolutions setting forth the terms of the
Securities of such series.

          Whenever the conversion price is adjusted, the Company shall compute
the adjusted conversion price in accordance with terms of the applicable Board
Resolution or supplemental indenture and shall prepare an Officers' Certificate
setting forth the adjusted conversion price and showing in reasonable detail the
facts upon which such adjustment is based, and such certificate shall forthwith
be filed at each office or agency maintained for the purpose of conversion of
Securities pursuant to Section 1002 and, if different, with the Trustee. The
Company shall forthwith cause a notice setting forth the adjusted conversion
price to be mailed, first class postage prepaid, to each Holder of Securities of
such series at its address appearing on the Security Register and to any
conversion agent other than the Trustee. Unless and until a Responsible Officer
of the Trustee shall have received an Officers' Certificate setting forth an
adjustment of the conversion price, the Trustee may assume that no such
adjustment has been made and that the last conversion price of which it has
knowledge remains in effect.

          SECTION 1405. NOTICE OF CERTAIN CORPORATE ACTIONS. In case:

          (1) the Company shall declare a dividend (or any other distribution)
on its Common Stock payable otherwise than in cash out of its retained earnings
(other



                                   -PAGE 70-
<PAGE>   77

than a dividend for which approval of any shareholders of the Company is
required) that would require an adjustment pursuant to Section 1404; or

          (2) the Company shall authorize the granting to all or substantially
all of the holders of its Common Stock of rights, options or warrants to
subscribe for or purchase any shares of capital stock of any class or of any
other rights (other than any such grant for which approval of any shareholders
of the Company is required); or

          (3) of any reclassification of the Common Stock of the Company (other
than a subdivision or combination of its outstanding shares of Common Stock, or
of any consolidation, merger or share exchange to which the Company is a party
and for which approval of any shareholders of the Company is required), or of
the sale of all or substantially all of the assets of the Company; or

          (4) of the voluntary or involuntary dissolution, liquidation or
winding up of the Company;

then the Company shall cause to be filed with the Trustee, and shall cause to be
mailed to all Holders at their last addresses as they shall appear in the
Security Register, at least 20 days (or 10 days in any case specified in Clause
(1) or (2) above) prior to the applicable record date hereinafter specified, a
notice in the form of an Officers' Certificate stating (i) the date on which a
record is to be taken for the purpose of such dividend, distribution, rights,
options 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, options or warrants are to be determined, or (ii) the date
on which such reclassification, consolidation, merger, share exchange, sale,
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, share
exchange, sale, dissolution, liquidation or winding up. If at any time the
Trustee shall not be the conversion agent, a copy of such notice shall also
forthwith be filed by the Company with the Trustee. Unless and until a
Responsible Officer of the Trustee shall have received such Officers'
Certificate, the Trustee shall not be charged with knowledge of any event
described in this Section 1405.

          SECTION 1406. RESERVATION OF SHARES OF COMMON STOCK. The Company shall
at all times reserve and keep available, free from preemptive rights, out of its
authorized but unissued Common Stock, for the purpose of effecting the
conversion of Securities, the full number of shares of Common Stock of the
Company then issuable upon the conversion of all outstanding Securities of any
series that has conversion rights.

          SECTION 1407. PAYMENT OF CERTAIN TAXES UPON CONVERSION.



                                   -PAGE 71-
<PAGE>   78

Except as provided in the next sentence, the Company will pay any and all taxes
that may be payable in respect of the issue or delivery of shares of its Common
Stock on conversion of Securities pursuant hereto. The Company shall not,
however, be required to pay any tax which may be payable in respect of any
transfer involved in the issue and delivery of shares of its Common Stock in a
name other than that of the Holder of the Security or Securities to be
converted, and no such issue or delivery shall be made unless and until the
Person requesting such issue has paid to the Company the amount of any such tax,
or has established, to the satisfaction of the Company, that such tax has been
paid.

          SECTION 1408. NONASSESSABILITY. The Company covenants that all shares
of its Common Stock which may be issued upon conversion of Securities will upon
issue in accordance with the terms hereof be duly and validly issued and fully
paid and nonassessable.

          SECTION 1409. PROVISION IN CASE OF CONSOLIDATION, MERGER OR SALE OF
ASSETS. In case of any consolidation or merger of the Company with or into any
other Person, any merger of another Person with or into the Company (other than
a merger which does not result in any reclassification, conversion, exchange or
cancellation of outstanding shares of Common Stock of the Company) or any
conveyance, sale, transfer or lease of all or substantially all of the assets of
the Company, the Person formed by such consolidation or resulting from such
merger or which acquires such assets, as the case may be, shall execute and
deliver to the Trustee a supplemental indenture providing that the Holder of
each Security of a series then Outstanding that is convertible into Common Stock
of the Company shall have the right thereafter (which right shall be the
exclusive conversion right thereafter available to said Holder), during the
period such Security shall be convertible, to convert such Security only into
the kind and amount of securities, cash and other property receivable upon such
consolidation, merger, conveyance, sale, transfer or lease by a holder of the
number of shares of Common Stock of the Company into which such Security might
have been converted immediately prior to such consolidation, merger, conveyance,
sale, transfer or lease, assuming such holder of Common Stock of the Company (i)
is not a Person with which the Company consolidated or merged with or into or
which merged into or with the Company or to which such conveyance, sale,
transfer or lease was made, as the case may be (a "Constituent Person"), or an
Affiliate of a Constituent Person and (ii) failed to exercise his rights of
election, if any, as to the kind or amount of securities, cash and other
property receivable upon such consolidation, merger, conveyance, sale, transfer
or lease (provided that if the kind or amount of securities, cash and other
property receivable upon such consolidation, merger, conveyance, sale, transfer,
or lease is not the same for each share of Common Stock of the Company held
immediately prior to such consolidation, merger, conveyance, sale, transfer or
lease by others than a Constituent Person or an Affiliate thereof and in respect
of which such rights of election shall not have been exercised ("Non-electing
Share"), then for the purpose of this Section 1409 the kind and amount of
securities, cash and other



                                   -PAGE 72-
<PAGE>   79

property receivable upon such consolidation, merger, conveyance, sale, transfer
or lease by the holders of each Non-electing Share shall be deemed to be the
kind and amount so receivable per share by a plurality of the Non-electing
Shares). Such supplemental indenture shall provide for adjustments which, for
events subsequent to the effective date of such supplemental indenture, shall be
as nearly equivalent as may be practicable to the adjustments provided for in
this Article or in accordance with the terms of the supplemental indenture or
Board Resolutions setting forth the terms of such adjustments. The above
provisions of this Section 1409 shall similarly apply to successive
consolidations, mergers, conveyances, sales, transfers or leases. Notice of the
execution of such a supplemental indenture shall be given by the Company to the
Holder of each Security of a series that is convertible into Common Stock of the
Company as provided in Section 106 promptly upon such execution.

          Neither the Trustee nor any conversion agent, if any, shall be under
any responsibility to determine the correctness of any provisions contained in
any such supplemental indenture relating either to the kind or amount of shares
of stock or other securities or property or cash receivable by Holders of
Securities of a series convertible into Common Stock of the Company upon the
conversion of their Securities after any such consolidation, merger, conveyance,
transfer, sale or lease or to any such adjustment, but may accept as conclusive
evidence of the correctness of any such provisions, and shall be protected in
relying upon, an Opinion of Counsel with respect thereto, which the Company
shall cause to be furnished to the Trustee upon request.

          SECTION 1410. DUTIES OF TRUSTEE REGARDING CONVERSION. Neither the
Trustee nor any conversion agent shall at any time be under any duty or
responsibility to any Holder of Securities of any series that is convertible
into Common Stock of the Company to determine whether any facts exist which may
require any adjustment of the conversion price, or with respect to the nature or
extent of any such adjustment when made, or with respect to the method employed,
whether herein or in any supplemental indenture, any resolutions of the Board of
Directors or written instrument executed by one or more officers of the Company
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 or amount) of any shares of Common Stock of the Company, or of any
securities or property, which may at any time be issued or delivered upon the
conversion of any Securities and neither the Trustee nor any conversion agent
makes any representation with respect thereto. Subject to the provisions of
Section 601, neither the Trustee nor any conversion agent shall be responsible
for any failure of the Company to issue, transfer or deliver any shares of its
Common Stock or stock certificates or other securities or property upon the
surrender of any Security for the purpose of conversion or to comply with any of
the covenants of the Company contained in this Article Fourteen or in the
applicable supplemental indenture, resolutions of the Board of Directors or
written instrument executed by one or more duly authorized officers of the
Company.



                                   -PAGE 73-
<PAGE>   80

          SECTION 1411. REPAYMENT OF CERTAIN FUNDS UPON CONVERSION. Any funds
which at any time shall have been deposited by the Company or on its behalf with
the Trustee or any other paying agent for the purpose of paying the principal
of, and premium, if any, and interest, if any, on any of the Securities
(including, but not limited to, funds deposited for the sinking fund referred to
in Article Twelve hereof and funds deposited pursuant to Article Thirteen
hereof) and which shall not be required for such purposes because of the
conversion of such Securities as provided in this Article Fourteen shall after
such conversion be repaid to the Company by the Trustee upon the Company's
written request.


                                 ARTICLE FIFTEEN

                                   COLLATERAL

          SECTION 1501. RELEASES OF COLLATERAL. In case this Indenture or any
indenture supplemental hereto shall provide for the release of any property from
the lien hereof or thereof in favor of the Holders of Securities of any series
the Trustee shall release the same from the Lien of this Indenture or such
indenture supplemental hereto upon receipt by the Trustee of an application of
the Company requesting such release and describing the Property to be so
released, together with:

          (a) a Board Resolution requesting such release and authorizing an
application to the Trustee therefor;

          (b) an Officers' Certificate, dated not more than 30 days prior to the
date of the application for such release stating in substance as follows:

                (i) the Company has sold or disposed of or has contracted to
          sell or dispose of the Property so requested to be released or the
          Company is otherwise entitled to the release of such Property;

                (ii) that, in the opinion of the signer, the security afforded
          by this Indenture and such indenture supplemental hereto will not be
          impaired by such release in contravention of the provisions hereof,
          and, unless the Property (or comparable Property) is to be leased or
          rented by the Company, the Property to be released is not necessary
          for the efficient operation of its remaining Property that is used or
          useful in connection with its business;

                (iii) either (1) that the Company has disposed of or will
          dispose of, the Property so to be released for a consideration
          representing, in the opinion of the signers, its Fair Market Value,
          which consideration may consist of any one or



                                   -PAGE 74-
<PAGE>   81

          more of the following: (A) cash, (B) obligations secured by a purchase
          money Lien upon the Property so to be released, and (C) any other
          Property that, upon acquisition thereof by the Company, would be
          subject to the Lien of this Indenture, and such indenture supplemental
          hereto subject to no Lien other than Liens permitted hereby and
          thereby, all of such consideration to be briefly described in the
          certificate, or (2) that the Property so to be released has been or is
          to be disposed of without consideration (or for consideration less
          than Fair Market Value), in which event such certificate shall state
          the reason for its disposition at less than Fair Market Value;

                (iv) that no Default exists;

                (v) the Fair Market Value, in the opinion of the signers, of the
          Property to be released; provided, however, that it shall not be
          necessary under this clause (v) to state the Fair Market Value of any
          Property whose Fair Market Value is certified in a certificate of an
          Independent Appraiser or Independent Financial Advisor under
          subdivision (c) of this Section;

                (vi) that all conditions precedent herein provided relating to
          the release of the Property in question have been complied with; and

                (vii) whether the aggregate of the Fair Market Value of the
          Property to be released and the Fair Market Value of all other
          Property released since the commencement of the then current calendar
          year (as previously certified to the Trustee in connection with
          releases) is 10% or more of the aggregate principal amount of all
          Securities of such series then outstanding and whether the Fair Market
          Value of the Property to be released is at least $25,000 and at least
          1% of the aggregate principal amount of all Securities of such series
          at the time outstanding and if all the facts specified in this clause
          (vii) are present, that a certificate of an Independent Appraiser or
          Independent Financial Advisor as to the Fair Market Value of the
          Property to be released will be furnished under subdivision (c) of
          this Section;

          (c) in case it shall be stated pursuant to clause (b)(vii) that the
same shall be furnished, a certificate of an Independent Appraiser, or if such
Property consists of securities being pledged as collateral, a certificate of an
Independent Financial Advisor, dated not more that 30 days prior to the
application for such release, stating:

                (1) the Fair Market Value, in the opinion of the signer, of the
          Property to be released; and

                (2) that such release, in the opinion of the signer, will not
          impair the security under this Indenture in contravention of its
          terms;



                                   -PAGE 75-
<PAGE>   82
          (d) except as may be provided in a supplemental indenture, any cash or
obligations received or, if such amounts have not yet been received, an
undertaking to deliver any cash or other obligations as and when received, as
consideration for any Property so to be released or, if the Property so to be
released is subject to a Prior Lien, a certificate of the trustee, mortgagee or
other holder of such Prior Lien that it has received such money or obligations
and has been irrevocably authorized by the Company to pay over to the Trustee
any balance of such money or obligation, remaining after the discharge of such
Prior Lien; and, if any Property other than cash or obligations is included in
the consideration for any Property so to be released, such instruments of
conveyance, assignment and transfer, if any, as may be necessary, in the Opinion
of Counsel hereinafter referred to, to subject to the Lien of this Indenture and
any such indenture supplemental hereto all the right, title and interest of the
Company in and to such Property;

          (e) in case the consideration for a proposed release includes Property
other than cash or obligations, a certificate of an Appraiser, or if such
Property consists of securities being pledged as collateral, a certificate of a
Financial Advisor, stating, in the opinion of the signor, the Fair Market Value
thereof; and the Appraiser or the Financial Advisor shall be an Independent
Appraiser or an Independent Financial Advisor if

                (1) within six months prior to the date of acquisition by the
          Company, such Property has been used or operated, by a Person or
          Persons other than the Company, in a business similar to that in which
          it has been or is to be used or operated by the Company, and

                (2) the Fair Market Value of such Property as set forth in the
          certificate required by this subdivision (e) is not less than $25,000
          and not less than 1% of the aggregate principal amount of the
          Securities of such series outstanding;

          (f) an Opinion of Counsel substantially to the effect (i) either (1)
that such instruments of conveyance, assignment and transfer as have been or are
then delivered to the Trustee are sufficient to subject to the Lien of this
Indenture and any such indenture supplemental hereto all the right, title and
interest of the Company in and to any Property, other than cash and obligations,
that is included in the consideration for the Property so to be released, or (2)
that no instruments of conveyance, assignment or transfer are necessary for such
purpose, (ii) that the Company has corporate power to own all Property included
in the consideration for such release, (iii) in case any part of the money or
obligations referred to in subdivision (d) of this Section 10.03 has been
deposited with a third party trustee, mortgagee or other holder (specifying the
trustee or other holder of the Lien) an opinion that such third party is
entitled to receive the same, and (iv) that all conditions precedent herein
provided relating to the release of the Property in question have been complied
with.



                                   -PAGE 76-
<PAGE>   83

          All cash received by the Trustee pursuant to the provisions of this
Section shall be held by the Trustee in trust and as collateral as provided in
this Indenture and any such indenture supplemental hereto.



                                   -PAGE 77-
<PAGE>   84

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

                                        AXYS PHARMACEUTICALS, INC.



                                        By:
                                             Title:


                                        U.S. BANK TRUST NATIONAL
                                            ASSOCIATION, AS TRUSTEE



                                        By:
                                             Title:



                                   -PAGE 78-