<PAGE>   1


                                                                          EX-4.4




                                    EXHIBIT A

                 (FORM OF FACE OF JUNIOR SUBORDINATED DEBENTURE)

                                              Registered Principal Amount

Registered No.                                                $
               ---------------                                 ----------
CUSIP No. 096065 AA 5

                              BLUE VALLEY BAN CORP.

                           % JUNIOR SUBORDINATED DEBENTURE
                       ----

                                DUE SEPTEMBER 30, 2030



     BLUE VALLEY BAN CORP., a Kansas corporation (the "Company," which term
includes any successor corporation under the Indenture hereinafter referred to),
for value received, hereby promises to pay to WILMINGTON TRUST COMPANY as
Property Trustee of BVBC Capital Trust I or registered assigns, the principal
sum of                      Dollars ($          ) on September 30, 2030 (which
date may be shortened as provided in the Indenture, the "Stated Maturity"), and
to pay interest on said principal sum from                 , 2000, or from the
most recent interest payment date (each such date, an "Interest Payment Date")
to which interest has been paid or duly provided for, quarterly (subject to
deferral as set forth herein) in arrears on March 31, June 30, September 30 and
December 31 of each year commencing September 30, 2000, at the rate of     % per
annum until the principal hereof shall have become due and payable, and on any
overdue principal and (without duplication and to the extent that payment of
such interest is enforceable under applicable law) on any overdue installment of
interest at the same rate per annum compounded quarterly. The amount of each
interest payment due with respect to the Junior Subordinated Debentures will
include amounts accrued through the date the interest payment is due. 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. In the event that any date on which
interest is payable on this Junior Subordinated Debenture is not a Business Day
(as defined in the Indenture), then payment of interest 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
Business Day is in the next succeeding calendar year, 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. 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 Junior
Subordinated Debenture (or one or more Predecessor Junior Subordinated
Debentures, as defined in the Indenture) is registered at the close of business
on the regular record date for such interest installment, which shall be the
close of business on the business day next preceding such Interest Payment Date
unless otherwise provided in the Indenture. The principal of and the interest on
this Junior Subordinated Debenture shall be payable at the office or agency of
the Trustee (as defined in the Indenture) 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


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option of the Company by check mailed to the Registered Holder (as defined in
the Indenture) at such address as shall appear in the Securities Register (as
defined in the Indenture). Notwithstanding the foregoing, so long as the Holder
of this Junior Subordinated Debenture is the Property Trustee (as defined in the
Indenture), the payment of the principal of and interest on this Junior
Subordinated Debenture will be made at such place and to such account as may be
designated by the Property Trustee.



     The Stated Maturity may be shortened at any time by the Company to any date
not earlier than September 30, 2005, subject to the Company having received
prior approval of the Federal Reserve (as defined in the Indenture) if then
required under applicable capital guidelines or policies of the Federal Reserve.


     The indebtedness evidenced by this Junior Subordinated 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 and Subordinated Debt (as defined in the
Indenture), and this Junior Subordinated Debenture is issued subject to the
provisions of the Indenture with respect thereto. Each Holder of this Junior
Subordinated 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 and Subordinated Debt, whether now outstanding or hereafter incurred, and
waives reliance by each such holder upon said provisions.

     This Junior Subordinated Debenture shall not be entitled to any benefit
under the Indenture, 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 Junior Subordinated Debenture are continued on the
reverse side hereof and such continued provisions shall for all purposes have
the same effect as though fully set forth at this place.

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

Dated:
       ----------------

                                            BLUE VALLEY BAN CORP.



                                            By:
                                               --------------------------------
                                               --------------------------------
                                               Chief Executive Officer

Attest:

By:
    ------------------------
    -------------, Secretary






                     [FORM OF CERTIFICATE OF AUTHENTICATION]

                          CERTIFICATE OF AUTHENTICATION

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

Dated:
      -------------------


                                        WILMINGTON TRUST COMPANY, as Trustee



                                        By:
                                           ---------------------------------
                                            Authorized Signature


<PAGE>   3


                     [FORM OF CERTIFICATE OF AUTHENTICATION]

                          CERTIFICATE OF AUTHENTICATION

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

Dated:
      -------------------


                                        WILMINGTON TRUST COMPANY, as Trustee



                                        By:
                                           ---------------------------------
                                            Authorized Signature


<PAGE>   4



               [FORM OF REVERSE OF JUNIOR SUBORDINATED DEBENTURE]

                           % JUNIOR SUBORDINATED DEBENTURE
                       ----
                                   (CONTINUED)

     This Junior Subordinated Debenture is one of the junior subordinated
debentures of the Company (herein sometimes referred to as the "Junior
Subordinated Debentures"), specified in the Indenture, all issued under and
pursuant to a Subordinated Indenture dated as of                , 2000 (the
"Indenture") duly executed and delivered between the Company and WILMINGTON
TRUST COMPANY, as Trustee (the "Trustee"), to which Indenture reference is
hereby made for a description of the rights, limitations of rights, obligations,
duties and immunities thereunder of the Trustee, the Company and the Holders of
the Junior Subordinated Debentures. The Junior Subordinated Debentures are
limited in aggregate principal amount as specified in the Indenture.

     Because of the occurrence and continuation of a Special Event (as defined
in the Indenture), in certain circumstances, this Junior Subordinated Debenture
may become due and payable at the option of the Company at the principal amount
together with any interest accrued thereon (the "Redemption Price"). The
Redemption Price shall be paid prior to 2:00 p.m. Overland Park, Kansas time, on
the date of such redemption or at such earlier time as the Company determines.


     The Company shall have the right to redeem this Junior Subordinated
Debenture at the option of the Company, in whole or in part, from time to time,
on or after September 30, 2005, at a redemption price equal to 100% of the
principal amount to be redeemed plus any accrued but unpaid interest thereon to
the date of such redemption. Any redemption pursuant to this paragraph will be
made upon not less than 30 days' nor more than 60 days' notice. If the Junior
Subordinated Debentures are only partially redeemed by the Company pursuant to
this paragraph, the Junior Subordinated Debentures will be redeemed pro rata or
by lot or by any other method utilized by the Trustee; provided that if, at the
time of redemption, the Junior Subordinated Debentures are registered as a
Global Subordinated Debenture (as defined in the Indenture), the Depositary (as
defined in the Indenture) shall determine the principal amount of such Junior
Subordinated Debentures held by each Junior Subordinated Debenture Holder to be
redeemed in accordance with its procedures.


     In the event of redemption of this Junior Subordinated Debenture in part
only, a new Junior Subordinated Debenture for the unredeemed portion hereof will
be issued in the name of the Holder hereof upon the cancellation hereof.

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

     The Indenture contains provisions permitting the Company and the Trustee,
with the consent of the Holders of not less than a majority in aggregate
principal amount of the Junior Subordinated Debentures at the time Outstanding,
as defined in the Indenture, to execute supplemental indentures for the purpose
of adding any provisions to or changing in any manner



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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 Junior
Subordinated Debentures; provided, however, that no such supplemental indenture
shall (i) change the stated maturity of the Junior Subordinated Debentures
except as provided in the Indenture, or reduce the principal amount thereof, or
reduce the rate or extend the time of payment of interest thereon, without the
consent of the Holder of each Junior Subordinated Debenture so affected, or (ii)
reduce the aforesaid percentage of Junior Subordinated Debentures, the Holders
of which are required to consent to any such supplemental indenture, without the
consent of the Holders of each Junior Subordinated Debenture then Outstanding
and affected thereby. The Indenture also contains provisions permitting the
Holders of a majority in aggregate principal amount of the Junior Subordinated
Debentures at the time Outstanding, on behalf of all of the Holders of the
Junior Subordinated Debentures, to waive any past default in the performance of
any of the covenants contained in the Indenture, or established pursuant to the
Indenture, and its consequences, except a default in the payment of the
principal of or interest on any of the Junior Subordinated Debentures. Any such
consent or waiver by the registered Holder of this Junior Subordinated 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 Junior
Subordinated Debenture and of any Junior Subordinated Debenture issued in
exchange herefor or in place hereof (whether by registration of transfer or
otherwise), irrespective of whether or not any notation of such consent or
waiver is made upon this Junior Subordinated Debenture.

     No reference herein to the Indenture and no provision of this Junior
Subordinated 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 on this Junior Subordinated Debenture at the time and place and at the
rate and in the money herein prescribed.

     The Company shall have the right at any time during the term of the Junior
Subordinated Debentures and from time to time to extend the interest payment
period of such Junior Subordinated Debentures for up to 20 consecutive quarters
(an "Extended Interest Payment Period"), at the end of which period the Company
shall pay all interest then accrued and unpaid (together with interest thereon
at the rate specified for the Junior Subordinated 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 extend such Extended Interest Payment Period, provided that such
Extended Interest Payment Period together with all such further extensions
thereof shall not exceed 20 consecutive quarters or extend beyond the Stated
Maturity. At the termination of any such Extended Interest Payment Period and
upon the payment of all accrued and unpaid interest and any additional amounts
then due, the Company may commence a new Extended Interest Payment Period.

     The Company has agreed that if at any time (a) there shall have occurred
any event of which the Company has actual knowledge that (i) with the giving of
notice or the lapse of time, or both, would constitute an Event of Default and
(ii) in respect to which the Company shall not have taken reasonable steps to
cure, or (b) the Company shall have given notice of its election of an Extended
Interest Payment Period as provided herein and shall not have rescinded such
notice, or such Extended Interest Payment Period, or any extension thereof,
shall be continuing; or (c) while the Junior Subordinated Debentures are held by
the Trust, the Company shall be in default with respect to its payment of any
obligation under the Preferred Securities Guarantee, then the Company 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 or (ii) make any payment of principal, interest or premium, if
any, on or repay, repurchase or redeem any debt securities of the Company
(including the Junior Subordinated Debentures) that rank pari passu with or
junior in interest to the Junior Subordinated Debentures or make any guarantee
payments with respect to any guarantee by the Company of the debt securities of
any subsidiary of the Company if such guarantee ranks pari passu or junior in
interest to the Junior Subordinated Debentures (other than (A) dividends or
distributions in common stock, (B) any declaration of a dividend in connection
with the implementation of a shareholders' 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) payments under the Preferred Securities Guarantee
and (D) 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).

<PAGE>   6


     As provided in the Indenture and subject to certain limitations therein set
forth, this Junior Subordinated Debenture is transferable by the registered
Holder hereof on the Securities Register of the Company, upon surrender of this
Junior Subordinated Debenture for registration of transfer at the office or
agency of the Trustee accompanied by a written instrument or instruments of
transfer in form satisfactory to the Company or the Trustee duly executed by the
registered Holder hereof or such Holder's attorney duly authorized in writing,
and thereupon one or more new Junior Subordinated Debentures of authorized
denominations and for the same aggregate principal amount will be issued to the
designated transferee or transferees. No service charge will be made for any
such transfer, but the Company may require payment of a sum sufficient to cover
any tax or other governmental charge payable in relation thereto.

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

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

     The Junior Subordinated Debentures are issuable only in registered form
without coupons in denominations of $8 and any integral multiple thereof.

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