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                                                                     EXHIBIT 4.3

                          JUNIOR SUBORDINATED DEBENTURE

                               [FACE OF SECURITY]


         THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
AS AMENDED (THE "SECURITIES ACT"), ANY STATE SECURITIES LAWS OR ANY OTHER
APPLICABLE SECURITIES LAW. NEITHER THIS SECURITY NOR ANY INTEREST OR
PARTICIPATION HEREIN MAY BE REOFFERED, SOLD, ASSIGNED, TRANSFERRED, PLEDGED,
ENCUMBERED OR OTHERWISE DISPOSED OF IN THE ABSENCE OF SUCH REGISTRATION OR
UNLESS SUCH TRANSACTION IS EXEMPT FROM, OR NOT SUBJECT TO, THE REGISTRATION
REQUIREMENTS OF THE SECURITIES ACT AND ANY APPLICABLE STATE SECURITIES LAWS. THE
HOLDER OF THIS SECURITY BY ITS ACCEPTANCE HEREOF AGREES TO OFFER, SELL OR
OTHERWISE TRANSFER THIS SECURITY ONLY (A) TO THE COMPANY, (B) PURSUANT TO A
REGISTRATION STATEMENT THAT HAS BEEN DECLARED EFFECTIVE UNDER THE SECURITIES
ACT, (C) TO A PERSON WHOM THE SELLER REASONABLY BELIEVES IS A QUALIFIED
INSTITUTIONAL BUYER IN A TRANSACTION MEETING THE REQUIREMENTS OF RULE 144A SO
LONG AS THIS SECURITY IS ELIGIBLE FOR RESALE PURSUANT TO RULE 144A IN ACCORDANCE
WITH RULE 144A, (D) TO A NON-U.S. PERSON IN AN OFFSHORE TRANSACTION IN
ACCORDANCE WITH RULE 903 OR RULE 904 (AS APPLICABLE) OF REGULATION S UNDER THE
SECURITIES ACT, (E) TO AN INSTITUTIONAL "ACCREDITED INVESTOR" WITHIN THE MEANING
OF SUBPARAGRAPH (A) OF RULE 501 UNDER THE SECURITIES ACT THAT IS ACQUIRING THIS
SECURITY FOR ITS OWN ACCOUNT, OR FOR THE ACCOUNT OF SUCH INSTITUTIONAL
ACCREDITED INVESTOR, FOR INVESTMENT PURPOSES AND NOT WITH A VIEW TO, OR FOR
OFFER OR SALE IN CONNECTION WITH, ANY DISTRIBUTION IN VIOLATION OF THE
SECURITIES ACT, OR (F) PURSUANT TO ANY OTHER AVAILABLE EXEMPTION FROM THE
REGISTRATION REQUIREMENTS OF THE SECURITIES ACT, SUBJECT TO THE COMPANY'S RIGHT
PRIOR TO ANY SUCH OFFER, SALE OR TRANSFER TO REQUIRE THE DELIVERY OF AN OPINION
OF COUNSEL, CERTIFICATION AND/OR OTHER INFORMATION SATISFACTORY TO IT IN
ACCORDANCE WITH THE INDENTURE, A COPY OF WHICH MAY BE OBTAINED FROM THE COMPANY.

         THE HOLDER OF THIS SECURITY BY ITS ACCEPTANCE HEREOF ALSO AGREES,
REPRESENTS AND WARRANTS THAT IT IS NOT AN EMPLOYEE BENEFIT, INDIVIDUAL
RETIREMENT ACCOUNT OR OTHER PLAN OR ARRANGEMENT SUBJECT TO TITLE I OF THE
EMPLOYMENT RETIREMENT INCOME SECURITY ACT OF 1974, AS AMENDED ("ERISA"), OR
SECTION 4975 OF THE INTERNAL REVENUE- CODE OF 1986, AS AMENDED (THE "CODE")
(EACH A "PLAN"), OR AN ENTITY WHOSE UNDERLYING ASSETS INCLUDE "PLAN ASSETS" BY
REASON OF ANY PLAN'S INVESTMENT IN THE ENTITY,

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AND NO PERSON INVESTING "PLAN ASSETS" OF ANY PLAN MAY ACQUIRE OR HOLD THE
SECURITIES OR ANY INTEREST THEREIN, UNLESS SUCH PURCHASER OR HOLDER IS ELIGIBLE
FOR EXEMPTIVE RELIEF AVAILABLE UNDER U.S. DEPARTMENT OF LABOR PROHIBITED
TRANSACTION CLASS EXEMPTION 96-23, 95-60, 91-38, 90-1 OR 84-14 OR ANOTHER
APPLICABLE EXEMPTION OR ITS PURCHASE AND HOLDING OF THIS SECURITY IS NOT
PROHIBITED BY SECTION 406 OF ERISA OR SECTION 4975 OF THE CODE WITH RESPECT TO
SUCH PURCHASE OR HOLDING. ANY PURCHASER OR HOLDER OF THE SECURITIES OR ANY
INTEREST THEREIN WILL BE DEEMED TO HAVE REPRESENTED BY ITS PURCHASE AND HOLDING
THEREOF THAT EITHER (i) IT IS NOT AN EMPLOYEE BENEFIT PLAN WITHIN THE MEANING OF
SECTION 3(3) OF ERISA, OR A PLAN TO WHICH SECTION 4975 OF THE CODE IS
APPLICABLE, A TRUSTEE OR OTHER PERSON ACTING ON BEHALF OF AN EMPLOYEE BENEFIT
PLAN OR PLAN, OR ANY OTHER PERSON OR ENTITY USING THE ASSETS OF ANY EMPLOYEE
BENEFIT PLAN OR PLAN TO FINANCE SUCH PURCHASE, OR (ii) SUCH PURCHASE WILL NOT
RESULT IN A PROHIBITED TRANSACTION UNDER SECTION 406 OR ERISA OR SECTION 4975 OF
THE CODE FOR WHICH THERE IS NO APPLICABLE STATUTORY OR ADMINISTRATIVE EXEMPTION.

         THIS SECURITY WILL BE ISSUED AND MAY BE TRANSFERRED ONLY IN BLOCKS
HAVING AN AGGREGATE PRINCIPAL AMOUNT OF NOT LESS THAN $500,000.00 AND MULTIPLES
OF $1,000.00 IN EXCESS THEREOF. ANY ATTEMPTED TRANSFER OF THIS SECURITY IN A
BLOCK HAVING AN AGGREGATE PRINCIPAL AMOUNT OF LESS THAN $500,000.00 SHALL BE
DEEMED TO BE VOID AND OF NO LEGAL EFFECT WHATSOEVER.

        THE HOLDER OF THIS SECURITY AGREES THAT IT WILL COMPLY WITH THE
FOREGOING RESTRICTIONS.

        IN CONNECTION WITH ANY TRANSFER, THE HOLDER WILL DELIVER TO THE
REGISTRAR AND TRANSFER AGENT SUCH CERTIFICATES AND OTHER INFORMATION AS MAY BE
REQUIRED BY THE INDENTURE TO CONFIRM THAT THE TRANSFER COMPLIES WITH THE
FOREGOING RESTRICTIONS.

        Floating Rate Junior Subordinated Deferrable Interest Debenture

                                       of

                         TEXAS CAPITAL BANCSHARES, INC.

                                November 19, 2002

         Texas Capital Bancshares, Inc., a Delaware corporation (the "Company"
which term includes any successor Person under the Indenture hereinafter
referred to), for value received promises to pay to State Street Bank and Trust
Company of Connecticut,

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National Association, not in its individual capacity but solely as Institutional
Trustee for Texas Capital Bancshares Statutory Trust I (the "Holder") or
registered assigns, the principal sum of TEN MILLION THREE HUNDRED TEN THOUSAND
DOLLARS ($10,310,000) on November 19, 2032, and to pay interest on said
principal sum from December 31, 2002, or from the most recent interest payment
date (each such date, an "Interest Payment Date") to which interest has been
paid or duly provided for, quarterly (subject to deferral as set forth herein)
in arrears on March 31, June 30, September 30 and December 31 of each year
commencing December 31, 2002, at an annual rate equal to 4.77% beginning on (and
including) the date of original issuance and ending on (but excluding) December
31, 2002 and at an annual rate for each successive period beginning on (and
including) December 31, 2002, and each succeeding Interest Payment Date, and
ending on (but excluding) the next succeeding Interest Payment Date (each a
"Distribution Period"), equal to 3-Month LIBOR, determined as described below,
plus 3.35% (the "Coupon Rate"), applied to the principal amount hereof, until
the principal hereof is paid or duly provided for or made available for payment,
and on any overdue principal and (without duplication) on any overdue
installment of interest at the same rate per annum, compounded quarterly, from
the dates such amounts are due until they are paid or made available for
payment. The amount of interest payable for any period will be computed on the
basis of the actual number of days in the Distribution Period concerned divided
by 360. In the event that any date on which interest is payable on this
Debenture is not a Business Day, then a payment of the interest payable on such
date will be made on the next succeeding day which is a Business Day (and
without any interest or other payment in respect of any such delay), with the
same force and effect as if made on the date the payment was originally payable.
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) is
registered at the close of business on the regular record date for such interest
installment, which shall be fifteen days prior to the day on which the relevant
Interest Payment Date occurs. Any such interest installment not so punctually
paid or duly provided for shall forthwith cease to be payable to the Holder 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.

        "3-Month LIBOR" as used herein, means the London interbank offered rate
for three-month U.S. dollar deposits determined by the Trustee in the following
order of priority: provided, however, that prior to November 19, 2007, the
3-Month LIBOR shall not exceed 8.5%: (i) the rate (expressed as a percentage per
annum) for U.S. dollar deposits of an amount equal or comparable to the
aggregate liquidation amount of the Debentures having a three-month maturity
that appears on Telerate Page 3750 as of 11:00 a.m. (London time) on the
particular Determination Date ("Telerate Page 3750" means the display designated
as "Page 3750" on the Dow Jones Telerate Service or such other page as may
replace Page 3750 on that service or such other service or services as may be
nominated by the British Bankers' Association as the information vendor for the
purpose of displaying London interbank offered rates for U.S. dollars deposits);
(ii) if such rate does not appear on Telerate Page 3750 as of 11:00 a.m. (London
time) on the

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Determination Date, 3-Month LIBOR will be the arithmetic mean of the rates
(expressed as percentages per annum) for U.S. dollar deposits of an amount equal
or comparable to the aggregate liquidation amount of the Debentures having a
three-month maturity that appear on Reuters Monitor Money Rates Page LIBOR
("Reuters Page LIBO") as of 11:00 a.m. (London time) on such Determination Date;
(iii) if such rate does not appear on Reuters Page LIBO as of 11:00 a.m. (London
time) on the related Determination Date, the Trustee will request the principal
London offices of four leading banks in the London interbank market to provide
such banks' offered quotations (expressed as percentages per annum) to prime
banks in the London interbank market for U.S. dollar deposits of an amount equal
or comparable to the aggregate liquidation amount of the Debentures having a
three-month maturity as of 11:00 a.m. (London time) on such Determination Date,
and if at least two quotations are provided, 3-Month LIBOR will be the
arithmetic mean of such quotations; and (iv) if fewer than two such quotations
are provided as requested in clause (iii) above, the Trustee will request four
major New York City banks to provide such banks' offered quotations (expressed
as percentages per annum) to leading European banks for loans in U.S. dollars of
an amount equal or comparable to the aggregate liquidation amount of the
Debentures as of 11:00 a.m. (London time) on such Determination Date, and if at
least two such quotations are provided, 3-Month LIBOR will be the arithmetic
mean of such quotations. If the rate for U.S. dollar deposits of an amount equal
or comparable to the aggregate liquidation amount of the Debentures having a
three-month maturity that initially appears on Telerate Page 3750 or Reuters
Page LIBO, as the case may be, as of 11:00 a.m. (London time) on the related
Determination Date is superseded on the Telerate Page 3750 or Reuters Page LIBO,
as the case may be, by a corrected rate by 12:00 noon (London time) on such
Determination Date, then the corrected rate as so substituted on the applicable
page will be the applicable 3-Month LIBOR for such Determination Date. As used
herein, "Determination Date" means the date that is two London Banking Days
(i.e., a day in which dealings in deposits in U.S. dollars are transacted in the
London interbank market) preceding the commencement of the relevant Distribution
Period.

         In the event that the 3-Month LIBOR is indeterminable by the methods
described above, the Coupon Rate shall equal the 3-Month LIBOR in effect on the
most recent Determination Date (whether or not 3-Month LIBOR for such period was
in fact determined on such Determination Date) plus 3.35%.

        The Coupon Rate for any Distribution Period will at no time be higher
than the maximum rate then permitted by New York law as the same may be modified
by United States law.

        All percentages resulting from any calculations on the Debentures will
be rounded, if necessary, to the nearest one hundred-thousandth of a percentage
point, with five one-millionths of a percentage point rounded upward (e.g.,
9.876545% or .09876545 being rounded to 9.87655% or .0987655), and all dollar
amounts used in or resulting from such calculation will be rounded to the
nearest cent (with one-half cent being rounded upward).

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        The principal of and interest on this Debenture shall be payable at the
office or agency of the Trustee (or other paying agent appointed by the Company)
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 by check
mailed to the registered holder at such address as shall appear in the Debenture
Register if a request for a wire transfer by such holder has not been received
by the Company or by wire transfer to an account appropriately designated by the
holder hereof. Notwithstanding the foregoing, so long as the holder of this
Debenture is the Institutional Trustee, the payment of the principal of and
interest on this Debenture will be made in immediately available funds at such
place and to such account as may be designated by the Trustee.

         So long as no Event of Default has occurred and is continuing, the
Company shall have the right, from time to time, and without causing an Event of
Default, to defer payments of interest on the Debentures by extending the
interest payment period on the Debentures at any time and from time to time
during the term of the Debentures, for up to 20 consecutive quarterly periods
(each such extended interest payment period, an "Extension Period"), during
which Extension Period no interest (including Additional Interest) shall be due
and payable. No Extension Period may end on a date other than an Interest
Payment Date. At the end of any such Extension Period the Company shall pay all
interest then accrued and unpaid on the Debentures (together with Additional
Interest thereon); provided, however, that no Extension Period may extend beyond
the Maturity Date; provided further, however, that during any such Extension
Period, the Company shall not and shall not permit any Affiliate to (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 or such Affiliate's
capital stock (other than payments of dividends or distributions to the Company)
or make any guarantee payments with respect to the foregoing or (ii) make any
payment of principal of or interest or premium, if any, on or repay, repurchase
or redeem any debt securities of the Company or any Affiliate that rank pari
passu in all respects with or junior in interest to the Debentures (other than,
with respect to clauses (i) and (ii) above, (a) repurchases, redemptions or
other acquisitions of shares of capital stock of the Company in connection with
any employment contract, benefit plan or other similar arrangement with or for
the benefit of one or more employees, officers, directors or consultants, in
connection with a dividend reinvestment or stockholder stock purchase plan or in
connection with the issuance of capital stock of the Company (or securities
convertible into or exercisable for such capital stock) as consideration in an
acquisition transaction entered into prior to the applicable Extension Period,
(b) as a result of any exchange or conversion of any class or series of the
Company's capital stock (or any capital stock of a subsidiary of the Company)
for any class or series of the Company's capital stock or of any class or series
of the Company's indebtedness for any class or series of the Company's capital
stock, (c) the purchase of fractional interests in shares of the Company's
capital stock pursuant to the conversion or exchange provisions of such capital
stock or the security being converted or exchanged, (d) any declaration of a
dividend in connection with any stockholders' rights plan, or the issuance of
rights, stock or other property under any stockholders' rights plan, or the
redemption or repurchase of rights pursuant thereto, (e) any dividend in

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the form of stock, warrants, options or other rights where the dividend stock or
the stock issuable upon exercise of such warrants, options or other rights is
the same stock as that on which the dividend is being paid or ranks pari passu
with or junior to such stock and any cash payments in lieu of fractional shares
issued in connection therewith, or (f) payments under the Capital Securities
Guarantee). Prior to the termination of any Extension Period, the Company may
further extend such period, provided that such period together with all such
previous and further consecutive extensions thereof shall not exceed 20
consecutive quarterly periods, or extend beyond the Maturity Date. Upon the
termination of any Extension Period and upon the payment of all accrued and
unpaid interest and Additional Interest, the Company may commence a new
Extension Period, subject to the foregoing requirements. No interest or
Additional Interest shall be due and payable during an Extension Period, except
at the end thereof, but each installment of interest that would otherwise have
been due and payable during such Extension Period shall bear Additional
Interest. The Company must give the Trustee notice of its election to begin or
extend such Extension Period at least five (5) Business Days prior to the
earlier of (i) the date interest on the Debentures would have been payable
except for the election to begin such Extension Period or (ii) the date such
interest is payable, but in any event not less than five (5) Business Days prior
to such record date.

         Subject to the Company having received prior approval of the Federal
Reserve if then required under applicable capital guidelines or policies of the
Federal Reserve, the Company may redeem this Debenture prior to the Maturity
Date in the manner and at the times set forth in the Indenture.

        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 be deemed to be a contract made under the law of
the State of New York, and for all purposes shall be governed by and construed
with the law of said State, without regard to conflict of laws principles
thereof.

        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.

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        Capitalized terms used and not defined in this Debenture shall have the
meanings assigned in the Indenture duly executed and dated as of the date of
original issuance of this Debenture between the Trustee and the Company. The
Indenture contains a description of the rights, limitations of rights,
obligations, duties and immunities thereunder of the Trustee, the Company and
the holders of the Debentures and of the terms upon which the Debentures are,
and are to be, authenticated and delivered.

                                   (continued)


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         IN WITNESS WHEREOF, the Company has duly executed this certificate.

                                       TEXAS CAPITAL BANCSHARES, INC.


                                       By:  /s/ RALEIGH HORTENSTINE III
                                          --------------------------------------

                                       Name:    Raleigh Hortenstine III
                                            ------------------------------------

                                       Title:   President
                                             -----------------------------------



                          CERTIFICATE OF AUTHENTICATION

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

                                       State Street Bank and Trust Company of
                                       Connecticut, National Association, as
                                       Trustee


                                       By:      /s/ EARL W. DENNISON, JR.
                                          --------------------------------------
                                                     Authorized Officer



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