Document:

<PAGE>

                                                                     EXHIBIT 4.7

No. 1                                       Principal Amount:  $29,639,175
                                            CUSIP No.: 858907 AB 4

                           STERLING BANCSHARES, INC.

         9.20% SERIES JUNIOR SUBORDINATED DEFERRABLE INTEREST DEBENTURE

                               DUE MARCH 21, 2031

     Sterling Bancshares, Inc., a Texas corporation (the "Company", which term
includes any successor Person under the Indenture hereinafter referred to), for
value received, hereby promises to pay to Bankers Trust Company, not in its
individual capacity but solely as Property Trustee of Sterling Bancshares
Capital Trust II, or registered assigns, the principal sum of Twenty Nine
Million Six Hundred Thirty Nine Thousand Two Hundred Dollars ($29,639,175) on
March 21, 2031 (subject to no earlier date having been designated in accordance
with Article V of the First Supplemental Indenture to the Indenture, the "Stated
Maturity Date"), unless previously prepaid or redeemed, and to pay interest on
the outstanding principal amount hereof from March 21, 2001, or from the most
recent Interest Payment Date (as defined below) to which interest has been paid
or duly provided for, quarterly (subject to deferral as set forth herein) in
arrears on March 31, June 30, September 30 and December 31 of each year,
commencing June 30, 2001, and on the Stated Maturity Date (each such date, an
"Interest Payment Date") at the rate of 9.20% per annum until the principal
hereof shall have become due and payable, and on any overdue principal and
(without duplication and to the extent that payment of such interest is
enforceable under applicable law) on any overdue installment of interest at the
same rate per annum compounded quarterly.  The amount of interest payable on any
Interest Payment Date shall be computed on the basis of a 360-day year of twelve
30-day months and, for any period less than a full calendar month, the number of
days elapsed in such month.  In the event that any date on which the principal
of, or interest on this Debenture is payable is not a Business Day, then the
payment payable on such date will be made on the next succeeding day that is a
Business Day (and without any interest or other payment in respect of any such
delay), except that if such next succeeding Business Day falls in the next
calendar year, then such payment shall be made on the immediately preceding
Business Day, in each case with the same force and effect as if made on such
date. Pursuant to the First Supplemental Indenture to the Indenture, in certain
circumstances the Company will be required to pay Additional Sums and Compounded
Interest (each as defined in the First Supplemental Indenture to the Indenture)
with respect to this Debenture.

     The interest installment so payable, and punctually paid or duly provided
for, on any Interest Payment Date will, as provided in the Indenture, be paid to
the Person in whose name this Debenture (or one or more Predecessor Securities,
as defined in said Indenture) is registered at the close of business on the
regular record date for such interest installment, which shall be at the close
of business on the 15th day of the month in which the relevant Interest Payment
Date falls.  Payments of interest may be deferred by the Company pursuant to the
provisions of Article IV of the First Supplemental Indenture to the Indenture.
Any such interest installment not punctually paid or duly provided for shall
forthwith cease to be payable to the Holders on such regular record date and may
be paid to the Person in whose name this Debenture (or one or more Predecessor
Securities) is registered at the close of business on a special record date to
be fixed by the Trustee for the payment of such defaulted interest, notice
whereof shall be given to the
<PAGE>

Holders of this series of Debentures not less than 10 days prior to such special
record date, or may be paid at any time in any other lawful manner not
inconsistent with the requirements of any securities exchange on which the
Debentures may be listed, and upon such notice as may be required by such
exchange, all as more fully provided in the Indenture.

     The principal of and interest (including Compounded Interest and Additional
Sums, if any) on this Debenture shall be payable at the office or agency of the
Trustee maintained for that purpose in any coin or currency of the United States
of America that at the time of payment is legal tender for payment of public and
private debts; provided, however, that, payment of interest may be made at the
option of the Company by (i) check mailed to the Holder at such address as shall
appear in the Securities Register or (ii) by transfer to an account maintained
by the Person entitled thereto, provided that proper written transfer
instructions have been received by the relevant record date.  Notwithstanding
the foregoing, so long as the Holder of this Debenture is the Property Trustee,
the payment of the principal of and interest (including Compounded Interest and
Additional Sums, if any,) on this Debenture will be made at such place and to
such account as may be designated by the Property Trustee.

     So long as no Event of Default has occurred and is continuing, and subject
to the Company having received prior approval of the Federal Reserve if then
required under applicable capital guidelines, policies or regulations of the
Federal Reserve, the Company shall have the right, at any time, but only once,
during the term of the Debentures, to reduce the term of the Debentures by
selecting a date, not earlier than the Initial Optional Prepayment Date, as the
new "Stated Maturity Date"; provided that such new "Stated Maturity Date" is an
Interest Payment Date and provided further that such new "Stated Maturity Date"
shall not be later than March 21, 2031 or be earlier than any date that has
occurred.

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

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

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

                                       2
<PAGE>

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

     Dated: March 21, 2001.

Attest:                                  STERLING BANCSHARES, INC.

     /s/  JAMES W. GOOLSBY, JR.                 /s/  GEORGE MARTINEZ
By: __________________________________     By: _________________________________
        James W. Goolsby, Jr.
Name: ________________________________     Name:  George Martinez
        Assistant Secretary
Title: _______________________________     Title:  Chairman

                         CERTIFICATE OF AUTHENTICATION

     This is one of the Securities referred to in the within-mentioned Indenture
and First Supplemental Indenture.

BANKERS TRUST COMPANY,
as Trustee

     /s/  SUSAN JOHNSON
By: __________________________________
          Authorized Officer

                                       3
<PAGE>

     This Debenture, designated as a 9.20% Junior Subordinated Deferrable
Interest Debenture due March 21, 2031 (herein sometimes referred to as the
"Debentures"), is one of the series of Securities of the Company specified in
the Indenture, all issued or to be issued in one or more series under and
pursuant to an Indenture, dated as of March 21, 2001, duly executed and
delivered between the Company and Bankers Trust Company, as Trustee (the
"Trustee"), as supplemented by the First Supplemental Indenture dated as of
March 21, 2001 between the Company and the Trustee (the Indenture, as so
supplemented, being referred to as the "Indenture") to which Indenture reference
is hereby made for a description of the rights, limitations of rights,
obligations, duties and immunities thereunder of the Trustee, the Company and
the Holders of the Debentures.  By the terms of the Indenture, the Securities
are issuable in series that may vary as to amount, date of maturity, rate of
interest and in other respects as provided in the Indenture.  This series of
Debentures is limited in aggregate principal amount as specified in the First
Supplemental Indenture.

     Upon the occurrence and continuation of a Special Event, as defined in the
First Supplemental Indenture, prior to March 21, 2006 (the "Initial Optional
Prepayment Date"), the Company shall have the right, at any time within 180 days
following the occurrence of such Special Event, to prepay this Debenture in
whole (but not in part) at the Prepayment Price.  "Prepayment Price" shall mean
an amount in cash equal to 100% of the principal amount thereof plus accrued and
unpaid interest on the Debenture to be so prepaid (including Compounded Interest
and Additional Sums, if any) to the date of such prepayment.

     In addition, subject to the Company having received the prior approval of
the Federal Reserve System (the "Federal Reserve"), if then required under
applicable guidelines or policies of the Federal Reserve, and any other required
regulatory approvals, the Company shall have the right to prepay this Debenture,
in whole or in part, at any time on or after the Initial Optional Prepayment
Date at the Prepayment Price.

     The Prepayment Price shall be paid prior to 12:00 noon, New York City time,
on the date of such prepayment or at such earlier time as the Company
determines, provided, that the Company shall deposit with the Trustee an amount
sufficient to pay the applicable Prepayment Price by 10:00 a.m., New York City
time, on the date such Prepayment Price is to be paid.  Any prepayment pursuant
to this paragraph will be made upon not less than 30 days or more than 60 days
notice.  If the Debentures are only partially prepaid by the Company pursuant to
an Optional Prepayment, the particular Debentures to be prepaid shall be
selected on a pro rata basis not more than 60 days prior to the date fixed for
prepayment from the outstanding Debentures not previously called for prepayment,
provided, however, that any such proration may be made on the basis of the
aggregate principal amount of Debentures held by each Holder thereof and may be
made by making such adjustments as the Company deems fair and appropriate in
order that only Debentures in denominations of $25 or integral multiples thereof
shall be prepaid.

     In the event of prepayment of this Debenture in part only, a new Debenture
or Debentures for the portion hereof that has not been prepaid will be issued in
the name of the Holder hereof upon the cancellation hereof.

     Notwithstanding the foregoing, any prepayment of Debentures by the Company
shall be subject to the prior approval of the Federal Reserve, if such approval
is then required under

                                       4
<PAGE>

applicable capital guidelines or policies of the Federal Reserve, and the
receipt of any other required regulatory approvals.

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

     The Indenture contains provisions permitting the Company and the Trustee,
with the consent of the Holders of a majority in aggregate principal amount of
the Securities of each series affected at the time outstanding, as defined in
the Indenture, to execute supplemental indentures for the purpose of adding any
provisions to or changing in any manner or eliminating any of the provisions of
the Indenture or of any supplemental indenture or of modifying in any manner the
rights of the Holders of the Securities; provided, however, that no such
supplemental indenture shall, without the consent of each Holder of Securities
then outstanding and affected thereby, (i) extend or change the Stated Maturity
Date of any Securities (except as expressly permitted in accordance with the
terms of any supplemental indenture establishing such series of Securities in
accordance with Section 2.2 of the Indenture), or reduce the principal amount
thereof, or reduce any amount payable on redemption thereof, or reduce the rate
of interest thereon, or extend the time of payment of interest thereon (except
as expressly permitted in accordance with the terms of any supplemental
indenture establishing such series of Securities in accordance with Section 2.2
of the Indenture), or make the principal of, or interest on, the Securities
payable in any coin or currency other than U.S. dollars, or impair or affect the
right of any holder of Securities to institute suit for the payment thereof, or
(ii) reduce the aforesaid percentage amount of Securities, the Holders of which
are required to consent to any such supplemental indenture.  The Indenture also
contains provisions permitting the Holders of a majority in aggregate principal
amount of the Securities of any series at the time outstanding affected thereby,
on behalf of all of the Holders of the Securities of such series, to waive any
past default in the performance of any of the covenants contained in the
Indenture, or established pursuant to the Indenture with respect to such series,
and its consequences, except a default in the payment of the principal of or
interest on any of the Securities or a default in respect of any covenant or
provision under which the Indenture cannot be modified or amended without the
consent of each Holder of Securities affected thereby.  Any such consent or
waiver by the holder of this Debenture (unless revoked as provided in the
Indenture) shall be conclusive and binding upon such Holder and upon all future
holders and owners of this Debenture and of any Debenture issued in exchange
herefor or in place hereof, irrespective of whether or not any notation of such
consent or waiver is made upon this Debenture.

     No reference herein to the Indenture and no provision of this Debenture or
of the Indenture shall alter or impair the obligation of the Company, which is
absolute and unconditional, to pay the principal of and interest (including
Compounded Interest and Additional Sums, if any) on this Debenture at the time
and place and at the rate and in the money herein prescribed.

     So long as no Event of Default shall have occurred and be continuing, the
Company shall have the right, at any time and from time to time during the term
of the Debentures, to defer payments of interest by extending the interest
payment period of such Debentures for a period

                                       5
<PAGE>

not exceeding 20 consecutive quarterly periods, including the first such
quarterly period during such extension period, and not extending beyond the
Stated Maturity Date of the Securities (an "Extended Interest Payment Period")
or ending on a date other than an Interest Payment Date, at the end of which
period the Company shall pay all interest then accrued and unpaid (together with
interest thereon at the rate specified for the Debentures to the extent that
payment of such interest is enforceable under applicable law). Before the
termination of any such Extended Interest Payment Period, the Company may
further defer payments of interest by further extending such Extended Interest
Payment Period, provided that such Extended Interest Payment Period, together
with all such previous and further extensions within such Extended Interest
Payment Period, (i) shall not exceed 20 consecutive quarterly periods, including
the first quarterly period during such Extended Interest Payment Period, (ii)
shall not end on any date other than an Interest Payment Date, and (iii) shall
not extend beyond the Stated Maturity Date of the Debentures. Upon the
termination of any such Extended Interest Payment Period and the payment of all
accrued and unpaid interest and any additional amounts then due, the Company may
commence a new Extended Interest Payment Period, subject to the foregoing
requirements.

     The Company has agreed that it will not: (i) declare or pay any dividends
or distributions on, or redeem, purchase, acquire, or make a liquidation payment
with respect to, any of the Company's capital stock (which includes common and
preferred stock) (other than (a) dividends or distributions in shares of, or
options, warrants or rights to subscribe for or purchase shares of, Common Stock
of the Company, (b) any declaration of a dividend in connection with the
implementation of a stockholder's rights plan, or the issuance of stock under
any such plan in the future, or the redemption or repurchase of any such rights
pursuant thereto, (c) as a result of a reclassification of any class or series
of the Company's capital stock solely into another class or series of the
Company's capital stock, (d) the purchase of fractional shares resulting from
such a reclassification or pursuant to the conversion or exchange provisions of
such capital stock or any security convertible or exchangeable into shares of
the Company's capital stock, and (e) purchases of Common Stock related to the
issuance of Common Stock or rights under any of the Company's benefit plans for
its directors, officers or employees or any of the Company's dividend
reinvestment plans); (ii) make any payment of principal, interest on or repay or
prepay or repurchase or redeem any debt securities of the Company that rank pari
passu with or junior in right of payment to the Debentures; or (iii) make any
guarantee payments with respect to any guarantee (other than payments under the
Preferred Securities Guarantee) by the Company of the debt securities of any
Subsidiary of the Company if such guarantee ranks pari passu or junior in right
of payment to the Debentures, if at such time (1) there shall have occurred any
event of which the Company has actual knowledge that (a) is or, with the giving
of notice or the lapse of time, or both, would be, an Event of Default and (b)
in respect of which the Company shall not have taken reasonable steps to cure,
(2) the Company shall be in default with respect to its payment obligations
under the Preferred Securities Guarantee or (3) the Company shall have given
notice of its election of the exercise of its right to extend the interest
payment period and any such extension shall be continuing.

     Subject to (i) the prior approval of the Federal Reserve, if such approval
is then required under applicable capital guidelines or policies of the Federal
Reserve and the receipt of any other required regulatory approval, and (ii) the
receipt by the Company of an opinion of counsel to the effect that such
distribution will not be a taxable event to holders of Preferred Securities, the

                                       6
<PAGE>

Company will have the right at any time to liquidate the Trust and cause the
Debentures to be distributed to the holders of the Trust Securities in
liquidation of the Trust.

     The Debentures of this series are issuable only in registered form without
coupons in denominations of $25 and any integral multiple thereof.  As provided
in the Indenture and subject to the transfer restrictions limitations as may be
contained herein and therein from time to time, this Debenture is transferable
by the holder hereof on the Securities Register of the Company, upon surrender
of this Debenture for registration of transfer at the office or agency of the
Company in the City and State of New York accompanied by a written instrument or
instruments of transfer in form satisfactory to the Company or the Trustee duly
executed by the holder hereof or his attorney duly authorized in writing, and
thereupon one or more new Debentures of authorized denominations and for the
same aggregate principal amount and series will be issued to the designated
transferee or transferees. No service charge will be made for any such
registration of transfer, but the Company may require payment of a sum
sufficient to cover any tax or other governmental charge payable in relation
thereto.

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

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

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

     THE INDENTURE AND THE DEBENTURES SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

                                       7<PAGE>
<TABLE>
<S>                                   <C>                                    <C>
NUMBER                                              INTRUSION                              SHARES
 C                                                      .COM
INCORPORATED UNDER THE LAWS           SECURITY SOLUTIONS FOR A .COM WORLD (TM)          COMMON STOCK
OF THE STATE OF DELAWARE
                                                                                      CUSIP 46121E 10 6
THIS CERTIFICATE IS TRANSFERABLE IN                                          SEE REVERSE FOR CERTAIN DEFINITIONS
RIDGEFIELD PARK, NJ OR NEW YORK, NY             INTRUSION.COM, INC.              AND RESTRICTIONS ON TRANSFER

THIS CERTIFIES THAT

is the OWNER of

               FULLY PAID AND NON-ASSESSABLE SHARES OF COMMON STOCK, $.01 PAR VALUE PER SHARE, OF

                                                INTRUSION.COM, INC.

(herein called the "Corporation") transferable on the books of the Corporation by the holder hereof, in person
or by duly authorized attorney, upon surrender of this Certificate properly endorsed or accompanied by a proper
assignment. This Certificate and the shares represented hereby are issued under and shall be held subject to all
of the provisions of the Certificate of Incorporation and the By-laws of the Corporation, and all amendments
thereto, copies of which are on file at the principal offices of the Corporation and the Transfer Agent, to all
of which the holder of this Certificate, by acceptance hereof, assents. This Certificate is not valid unless
countersigned by the Transfer Agent and registered by the Registrar of the Corporation.

        IN WITNESS WHEREOF, the Corporation has caused the facsimile signatures of its duly authorized officers
and its facsimile seal to be hereunto affixed.

        /s/ TIMOTHY W. KINNEAR          INTRUSION.COM, INC.     DATED:
PRESIDENT AND CHIEF EXECUTIVE OFFICER        CORPORATE          COUNTERSIGNED AND REGISTERED:
          /s/ JAY R. WIDDIG                    SEAL                     CHASEMELLON SHAREHOLDER SERVICES, L.L.C.
              SECRETARY                      DELAWARE                                                   TRANSFER AGENT
                                                                                                         AND REGISTRAR
                                                                BY
                                                                                                  AUTHORIZED SIGNATURE
</TABLE>
<PAGE>

                               INTRUSION.COM, INC.

        The Certificate of Incorporation of the Corporation on file in the
Office of the Secretary of State of Delaware sets forth a full statement of
(i) all of the designations, preferences, limitations and relative rights of
the shares of each class of capital stock authorized to be issued, (ii) the
authority of the Board of Directors to fix and determine the relative rights
and preferences of the shares of preferred stock which the Corporation is
authorized to issue in series and, if and to the extent fixed and determined,
the relative rights and preferences of any such series, (iii) the denial to
stockholders of preemptive rights to acquire unissued or treasury shares or
other securities of the Corporation and (iv) the denial to stockholders of the
right to cumulate votes in any election of directors of the Corporation. The
Corporation will furnish a copy of such statement to the record holder of this
Certificate without charge on written request to the Corporation at its
principal place of business or to the Transfer Agent and Registrar.

        The following abbreviations, when used in the inscription on the face
of this certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

<TABLE>
<S>                                             <C>
TEN COM--as tenants in common                   UNIF GIFT MIN ACT--.......Custodian........
TEN ENT--as tenants by the entireties                               (Cust)         (Minor)
JT TEN--as joint tenants with right of                            under Uniform Gifts to Minors
        survivorship and not as tenants                           Act..........................
        in common                                                              (State)

    Additional abbreviations may also be used though not in the above list.

        For Value Received,_______________________hereby sell(s), assign(s) and transfer(s) unto

PLEASE INSERT SOCIAL SECURITY OR OTHER
IDENTIFYING NUMBER OF ASSIGNEE
______________________________________

___________________________________________________________________________________________________________
            PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING POSTAL ZIP CODE, OF ASSIGNEE

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

_____________________________________________________________________________________________________Shares
of the Common Stock represented by the within Certificate and do(es) hereby irrevocably constitute and
appoint____________________________________________________________________________________________Attorney
to transfer the said stock on the books of the within-named Corporation with full power of substitution in
the premises.

Dated _____________________________
                                                X ____________________________________________
                     NOTICE:                                      (SIGNATURE)
              THE SIGNATURE(S) TO THIS
              ASSIGNMENT MUST
              CORRESPOND WITH
              THE NAME(S) AS WRITTEN
              UPON THE FACE OF THE
              CERTIFICATE IN EVERY
              PARTICULAR, WITHOUT
              ALTERATION OR
              ENLARGEMENT OR ANY               X ____________________________________________
              CHANGE WHATEVER.                                    (SIGNATURE)

                                                ________________________________________________
                                                THE SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE
                                                GUARANTOR INSTITUTION (BANKS, STOCKBROKERS,
                                                SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS
                                                WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE
                                                MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15.
                                                ________________________________________________
                                                SIGNATURE(S) GUARANTEED BY:

                                                ________________________________________________
</TABLE>

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