UNION ELECTRIC COMPANY 6.70% SENIOR SECURED NOTE DUE 2019

Exhibit 4.3

THIS NOTE IS A GLOBAL NOTE REGISTERED IN THE NAME OF THE DEPOSITARY (REFERRED TO HEREIN) OR A NOMINEE THEREOF AND, UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE FOR THE INDIVIDUAL NOTES REPRESENTED HEREBY AS PROVIDED IN THE INDENTURE REFERRED TO BELOW, THIS NOTE MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY. UNLESS THIS NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY (55 WATER STREET, NEW YORK, NEW YORK), TO THE TRUSTEE FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY AND ANY PAYMENT IS MADE TO CEDE & CO., ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

UNION ELECTRIC COMPANY

6.70% SENIOR SECURED NOTE DUE 2019

UNION ELECTRIC COMPANY, a corporation of the State of Missouri (the “COMPANY”), for value received hereby promises to pay to CEDE & CO. or registered assigns, the principal sum of FOUR HUNDRED FIFTY MILLION DOLLARS ($450,000,000) on the Maturity Date set forth above, and to pay interest thereon from June 19, 2008 or from the most recent Interest Payment Date to which interest has been paid or duly provided for, semi-annually in arrears on the February 1 and August 1 in each year, commencing February 1, 2009, at the per annum Interest Rate set forth above, until the principal hereof is paid or made available for payment, subject to certain interest rate increase provisions described below.  No interest shall accrue on the Maturity Date, so long as the principal amount of this Note is paid on the Maturity Date.  The interest so payable and punctually paid or duly provided for on any such Interest Payment Date (except for interest payable on the Maturity Date set forth above or, if applicable, upon redemption or acceleration) will, as provided in the Indenture (as defined below), be paid to the Person in whose name this Note is registered at the close of business on the Regular Record Date for such interest, which shall be the January 15 or July 15 as the case may be, next preceding such Interest Payment Date; provided that the first Interest Payment Date for any part of this Note, the Original Issue Date of which is after a Regular Record Date but prior to the applicable Interest Payment Date, shall be the Interest Payment Date following the next succeeding Regular Record Date; and provided that interest payable on the Maturity Date set forth above or, if applicable, upon redemption or acceleration, shall be payable to the Person to whom principal shall be payable.  Except as otherwise provided in the Indenture, any such interest not so punctually paid or duly provided for shall forthwith cease to be payable to the Holder on such Regular Record Date and shall be paid to the Person in whose name this Note 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 Noteholders not more than fifteen days or fewer than ten days prior to such Special Record Date.  Payment of the principal of and interest and premium on this Note shall be payable pursuant to Section 2.12(a) of the Indenture.

This Note is a Global Note in respect of a duly authorized issue of 6.70% Senior Secured Notes due 2019 (the “NOTES OF THIS SERIES”, which term includes any Global Notes representing such Notes) of the Company issued and to be issued under an Indenture dated as of August 15, 2002, between the Company and The Bank of New York, as trustee (the “TRUSTEE”, which term includes any successor Trustee under the Indenture) and indentures supplemental thereto (collectively, the “INDENTURE”). Under the Indenture, one or more series of notes may be issued and, as used herein, the term “Notes” refers to the Notes of this Series and any other outstanding series of Notes.  Reference is hereby made to the Indenture for a more

complete statement of the respective rights, limitations of rights, duties and immunities thereunder of the Company, the Trustee and the Noteholders and of the terms upon which the Notes are and are to be authenticated and delivered.  This Note has been issued in respect of the series designated on the first page hereof in the aggregate principal amount of $450,000,000.

The Notes will be secured by first mortgage bonds (the “SENIOR NOTE FIRST MORTGAGE BONDS”) delivered by the Company to the Trustee for the benefit of the Holders of the Notes, issued under the Indenture of Mortgage or Deed of Trust, dated June 15, 1937, from the Company to The Bank of New York, as successor trustee (the “MORTGAGE TRUSTEE”), as supplemented and modified (collectively, the “FIRST MORTGAGE”).  Reference is made to the First Mortgage and the Indenture for a description of the rights of the Trustee as holder of the Senior Note First Mortgage Bonds, the property mortgaged and pledged, the nature and extent of the security and the rights of the holders of first mortgage bonds, under the First Mortgage and the rights of the Company and of the Mortgage Trustee in respect thereof, the duties and immunities of the Mortgage Trustee and the terms and conditions upon which the Senior Note First Mortgage Bonds are secured and the circumstances under which additional first mortgage bonds may be issued.

So long as any of the Notes of this Series are outstanding, the Company will not optionally redeem, purchase or otherwise retire in full its outstanding First Mortgage Bonds, and, therefore, the Release Date will not occur.

Each Note of this Series shall be dated and issued as of the date of its authentication by the Trustee and shall bear an Original Issue Date. Each Note issued upon transfer, exchange or substitution of such Note shall bear the Original Issue Date of such transferred, exchanged or substituted Note, as the case may be.

All or a portion of the Notes of this Series may be redeemed at the option of the Company at any time or from time to time.  The redemption price for the Notes of this Series to be redeemed on any redemption date will be equal to the greater of: (a) 100% of the principal amount of the Notes of this Series being redeemed on the redemption date; or (b) the sum of the present values of the remaining scheduled payments of principal and interest on the Notes of this Series being redeemed on that redemption date (not including any portion of any payments of interest accrued to and including the redemption date) discounted to the re