Exhibit 4.2


  


SUPPLEMENTAL INDENTURE


 


DATED JUNE 1, 2021


 


UNION ELECTRIC COMPANY


 


TO


 


THE BANK OF NEW YORK MELLON,

AS TRUSTEE


 





 



 


(SUPPLEMENTAL TO THE INDENTURE OF MORTGAGE
AND DEED OF TRUST DATED JUNE 15, 1937, AS AMENDED, EXECUTED BY UNION ELECTRIC COMPANY TO THE BANK OF NEW YORK MELLON, AS TRUSTEE)


 





 



 


2.15% First Mortgage Bonds due 2032


 


This instrument was prepared by Chonda J.
Nwamu, Esq., Senior Vice President, General Counsel 

and Secretary of Union Electric Company, 1901 Chouteau Avenue, St. Louis, Missouri  63103, 

(314) 621-3222.


  


WHEN RECORDED MAIL TO:


 


Craig W. Stensland


Union Electric Company


1901 Chouteau Avenue


St. Louis, MO 63103


 






    


     


    

 


SUPPLEMENTAL INDENTURE, dated the 1st day
of June, Two thousand and twenty-one (2021) made by and between UNION ELECTRIC COMPANY, a corporation organized and existing under the
laws of the State of Missouri (hereinafter called the “Company”), party of the first part, and The
Bank of New York Mellon, formerly The Bank of New York (successor trustee to Bank of America, National Association, formerly Boatmen’s
Trust Company), a bank existing under the laws of the State of New York (hereinafter called the “Trustee”), as Trustee under
the Indenture of Mortgage and Deed of Trust dated June 15, 1937, hereinafter mentioned, party of the second part:


 


WHEREAS, the Company has heretofore executed
and delivered to the Trustee its Indenture of Mortgage and Deed of Trust, dated June 15, 1937, as amended May 1, 1941, April 1,
1971, February 1, 1974, July 7, 1980, February 1, 2000, August 15, 2002 and May 15, 2012 (said Indenture of
Mortgage and Deed of Trust as so amended, being hereinafter referred to as the “Original Indenture”), to secure the payment
of the principal of and the interest (and premium, if any) on all bonds at any time issued and outstanding thereunder, and indentures
supplemental thereto dated June 15, 1937, May 1, 1941, March 17, 1942, April 13, 1945, April 27, 1945, October 1,
1945, April 11, 1947, April 13, 1949, September 13, 1950, December 1, 1950, September 20, 1951, May 1,
1952, March 1, 1954, May 1, 1955, August 31, 1955, April 1, 1956, July 1, 1956, August 1, 1957, February 1,
1958, March 1, 1958, November 5, 1958, March 16, 1959, June 24, 1959, December 11, 1959, August 17, 1960,
September 1, 1960, October 24, 1960, June 30, 1961, July 1, 1961, August 9, 1962, September 30, 1963, November 1,
1963, March 12, 1965, April 1, 1965, April 14, 1966, May 1, 1966, February 17, 1967, March 1, 1967, February 19,
1968, March 15, 1968, August 21, 1968, April 7, 1969, May 1, 1969, September 12, 1969, October 1, 1969,
March 26, 1970, April 1, 1970, June 12, 1970, January 1, 1971, April 1, 1971, September 15, 1971, December 3,
1973, February 1, 1974, April 25, 1974, February 3, 1975, March 1, 1975, June 11, 1975, May 12, 1976, August 16,
1976, April 26, 1977, October 15, 1977, November 7, 1977, December 1, 1977, August 1, 1978, October 12,
1979, November 1, 1979, July 7, 1980, August 1, 1980, August 20, 1980, February 1, 1981, October 8, 1981,
August 27, 1982, September 1, 1982, December 15, 1982, March 1, 1983, June 21, 1984, December 12, 1984,
June 11, 1985, March 1, 1986, May 1, 1986, May 1, 1990, December 1, 1991, December 4, 1991, January 1,
1992, September 30, 1992, October 1, 1992, December 1, 1992, February 1, 1993, February 18, 1993, May 1,
1993, August 1, 1993, October 1, 1993, January 1, 1994, February 1, 2000, August 15, 2002, March 5, 2003,
April 1, 2003, July 15, 2003, October 1, 2003, February 1, 2004 (eight separate indentures supplemental thereto),
May 1, 2004, September 1, 2004, January 1, 2005, July 1, 2005, December 1, 2005, June 1, 2007, April 1,
2008, June 1, 2008, March 1, 2009, September 1, 2012, April 1, 2014, March 15, 2015, June 1, 2017, April
1, 2018, March 1, 2019, September 15, 2019, March 1, 2020, and October 1, 2020, respectively, have heretofore been
entered into between the Company and the Trustee; and


 


WHEREAS, the following Bonds have heretofore
been issued by the Company under the Original Indenture and remain outstanding:


 


(1)               
$184,000,000 principal amount of First Mortgage Bonds, Senior Notes Series BB, which are described in the Supplemental Indenture
dated March 5, 2003, all of which are outstanding at the date of the execution hereof;


 


(2)               
$60,000,000 principal amount of First Mortgage Bonds, Environmental Improvement Series 2004A (1998A Bonds), which are described
in the Supplemental Indenture dated February 1, 2004, all of which are outstanding at the date of the execution hereof;


 


(3)               
$50,000,000 principal amount of First Mortgage Bonds, Environmental Improvement Series 2004B (1998B Bonds), which are described
in the Supplemental Indenture dated February 1, 2004, all of which are outstanding at the date of the execution hereof;


 


(4)               
$50,000,000 principal amount of First Mortgage Bonds, Environmental Improvement Series 2004C (1998C Bonds), which are described
in the Supplemental Indenture dated February 1, 2004, all of which are outstanding at the date of the execution hereof;


 


(5)               
$47,500,000 principal amount of First Mortgage Bonds, Environmental Improvement Series 2004H (1992 Bonds), which are described
in the Supplemental Indenture dated February 1, 2004, all of which are outstanding at the date of the execution hereof;


 






    


     


    

 


(6)               
 $300,000,000 principal amount of First Mortgage Bonds, Senior Notes Series II, which are described in the Supplemental Indenture
dated July 1, 2005, all of which are outstanding at the date of the execution hereof;


 


(7)               
$350,000,000 principal amount of First Mortgage Bonds, Senior Notes, Series NN, which are described in the Supplemental Indenture
dated March 1, 2009, all of which are outstanding at the date of the execution hereof;


 


(8)               
$485,000,000 principal amount of First Mortgage Bonds, Senior Notes, Series OO, which are described in the Supplemental Indenture
dated September 1, 2012, all of which are outstanding at the date of the execution hereof;


 


(9)               
$350,000,000 principal amount of First Mortgage Bonds, Senior Notes, Series PP, which are described in the Supplemental Indenture
dated April 1, 2014, all of which are outstanding at the date of the execution hereof;


 


(10)            
$400,000,000 principal amount of First Mortgage Bonds, Senior Notes, Series QQ, which are described in the Supplemental Indenture
dated March 15, 2015, all of which are outstanding at the date of the execution hereof;


 


(11)            
$400,000,000 principal amount of First Mortgage Bonds, Senior Notes, Series RR, which are described in the Supplemental Indenture
dated June 1, 2017, all of which are outstanding at the date of the execution hereof;


 


(12)            
$425,000,000 principal amount of 4.000% First Mortgage Bonds, due 2048, which are described in the Supplemental Indenture dated
April 1, 2018, all of which are outstanding at the date of the execution hereof;


 


(13)            
$450,000,000 principal amount of 3.50% First Mortgage Bonds, due 2029, which are described in the Supplemental Indenture dated
March 1, 2019, all of which are outstanding at the date of the execution hereof;


 


(14)            
$330,000,000 principal amount of 3.25% First Mortgage Bonds due 2049, which are described in the Supplemental Indenture dated
September 15, 2019, all of which are outstanding at the date of the execution hereof;


 


(15)            
$465,000,000 principal amount of 2.95% First Mortgage Bonds due 2030, which are described in the Supplemental Indenture dated
March 1, 2020, all of which are outstanding at the date of the execution hereof; and


 


(16)            
$550,000,000 principal amount of 2.625% First Mortgage Bonds due 2051, which are described in the Supplemental Indenture dated
October 1, 2020, all of which are outstanding at the date of the execution hereof;


 


WHEREAS, the Company on August 31,
1955 acquired all of the properties of Union Electric Power Company, the Subsidiary as defined in Article I of the Original Indenture,
upon the dissolution of the Subsidiary; the Company, by Supplemental Indenture dated August 31, 1955, conveyed all of the properties
so acquired (other than property of the character defined as excepted property in the granting clauses of the Original Indenture) to
the Trustee upon the terms and trusts in the Original Indenture and the indentures supplemental thereto set forth for the equal and proportionate
benefit and security of all present and future holders of the Bonds and coupons issued and to be issued thereunder, all the shares of
stock of the Subsidiary were released from the lien of the Original Indenture; and the Company became entitled to change the general
designation of the Bonds so as to omit the words “and Collateral Trust”; and


 






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WHEREAS, the Articles of Incorporation
of the Company were duly amended on April 23, 1956, to change its corporate name from “Union Electric Company of Missouri”
to “Union Electric Company”; and


 


WHEREAS, the Articles of Agreement of the
Trustee were duly amended effective on January 4, 1982 to change its corporate name from “St. Louis Union Trust Company”
to “Centerre Trust Company of St. Louis”, and further amended on December 9, 1988, to change its corporate name from
 “Centerre Trust Company of St. Louis” to “Boatmen’s Trust Company”; and


 


WHEREAS, that on March 13, 1998, Boatmen’s
Trust Company merged into NationsBank, National Association and effective July 5, 1999, changed its name to Bank of America, National
Association; and


 


WHEREAS, that on February 1, 2000,
The Bank of New York, as transferee of the corporate trust business of Bank of America, National Association (formerly known as Boatmen’s
Trust Company), Trustee under the Original Indenture, became successor Trustee under the Original Indenture; and


 


WHEREAS, that effective as of July 1,
2008, The Bank of New York changed its name to The Bank of New York Mellon; and


 


WHEREAS, the Company is entitled at this
time to have authenticated and delivered additional Bonds on the basis of “property additions” upon compliance with and pursuant
to the provisions of Section 4 of Article III of the Original Indenture or on the basis of “refundable Bonds” upon
compliance with and pursuant to the provisions of Section 6 of Article III of the Original Indenture; and


 


WHEREAS, the Company desires by this Supplemental
Indenture to provide for the creation of a new series of Bonds under the Original Indenture, to have the designation provided in Article I,
Section 1 hereof (herein called the “New Bonds”), and the Original Indenture provides that certain terms and provisions,
as determined by the Board of Directors of the Company, of the Bonds of any particular series may be expressed in and provided by the
execution of an appropriate supplemental indenture; and


 


WHEREAS, the Original Indenture provides
that the Company and the Trustee may enter into indentures supplemental to the Original Indenture specifically to convey, transfer and
assign to the Trustee and to subject to the lien of the Original Indenture additional properties acquired by the Company; and


 


WHEREAS, the Company, in the exercise of
the powers and authority conferred upon and reserved to it under the provisions of the Original Indenture and pursuant to appropriate
resolutions of the Board of Directors, has duly resolved and determined to make, execute and deliver to the Trustee a Supplemental Indenture
in the form hereof for the purposes herein provided; and


 


WHEREAS, all conditions and requirements
necessary to make this Supplemental Indenture a valid, binding and legal instrument have been done, performed and fulfilled and the execution
and delivery hereof have been in all respects duly authorized;


 






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NOW, THEREFORE, THIS INDENTURE WITNESSETH:


 


That, in consideration of the premises and of
the mutual covenants herein contained and of the acceptance of this trust by the Trustee and of the sum of One Dollar duly paid by the
Trustee to the Company at or before the time of the execution of this Supplemental Indenture, and of other valuable considerations, the
receipt whereof is hereby acknowledged, and in order further to secure the payment of the principal of and interest (and premium, if
any) on all Bonds at any time issued and outstanding under the Original Indenture, according to their tenor and effect, the Company has
executed and delivered this Supplemental Indenture and has granted, bargained, sold, warranted, aliened, remised, released, conveyed,
assigned, transferred, mortgaged, pledged, set over and confirmed and by these presents does grant, bargain, sell, warrant, alien, remise,
release, convey, assign, transfer, mortgage, pledge, set over and confirm unto The Bank of New York Mellon, as Trustee, and to its successors
in trust under the Original Indenture forever, all and singular the following described properties (in addition to all other properties
heretofore subjected to the lien of the Original Indenture and not heretofore released from the lien thereof) - that is to say:


 


FIRST.


 


ALL (except as in the Original Indenture
expressly excepted) power houses, plants, buildings and other structures, dams, dam sites, substations, heating plants, gas works, holders
and tanks, together with all and singular the electric, heating, gas and mechanical appliances appurtenant thereto of every nature whatsoever,
now owned by the Company, including all and singular the machinery, engines, boilers, furnaces, generators, dynamos, turbines and motors,
and all and every character of mechanical appliance for generating or producing electricity, steam, gas and other agencies for light,
heat, cold, or power or other purposes, and all transmission and distribution systems used for the transmission and distribution of electricity,
steam, gas and other agencies for light, heat, cold or power or any other purpose whatsoever, whether underground or overhead, surface
or otherwise, now owned by the Company, including all poles, towers, posts, wires, cables, conduits, manholes, mains, pipes, tubes, drains,
furnaces, switchboards, transformers, conductors, insulators, supports, meters, lamps, fuses, junction boxes, regulator stations, and
other electric, steam and gas fixtures and apparatus; all of the aforementioned property being located in the City of St. Louis, the
counties of Adair, Atchison, Audrain, Benton, Bollinger, Boone, Butler, Caldwell, Callaway, Camden, Cape Girardeau, Clark, Clay, Clinton,
Cole, Cooper, Crawford, Daviess, Dunklin, Franklin, Gasconade, Howard, Iron, Jefferson, Knox, Lewis, Lincoln, Livingston, Macon, Madison,
Maries, Marion, Miller, Mississippi, Moniteau, Montgomery, Morgan, New Madrid, Osage, Pemiscot, Perry, Pettis, Phelps, Pike, Pulaski,
Ralls, Randolph, Ray, Reynolds, Ripley, St. Charles, St. Francois, Ste. Genevieve, St. Louis, Saline, Schuyler, Scott, Stoddard, Warren,
Washington, and Wayne, Missouri, the counties of Clay, Hancock, Henderson, Madison, Marion, Perry, Piatt and St. Clair, Illinois,
and the counties of Des Moines, Henry, Johnson, Lee, and Washington, Iowa, upon real estate owned by the Company, or occupied by it under
rights to so occupy, which real estate is described in, or added through the provisions of, the Indenture of Mortgage and Deed of Trust
dated June 15, 1937, the Supplemental Indentures dated May 1, 1941, March 17, 1942, April 13, 1945, April 27,
1945, October 1, 1945, April 11, 1947, April 13, 1949, September 13, 1950, December 1, 1950, September 20,
1951, May 1, 1952, March 1, 1954, May 1, 1955, August 31, 1955, April 1, 1956, July 1, 1956, August 1,
1957, February 1, 1958, March 1, 1958, November 5, 1958, March 16, 1959, June 24, 1959, December 11, 1959,
August 17, 1960, September 1, 1960, October 24, 1960, June 30, 1961, July 1, 1961, August 9, 1962, September 30,
1963, November 1, 1963, March 12, 1965, April 1, 1965, April 14, 1966, May 1, 1966, February 17, 1967,
March 1, 1967, February 19, 1968, March 15, 1968, August 21, 1968, April 7, 1969, May 1, 1969, September 12,
1969, October 1, 1969, March 26, 1970, April 1, 1970, June 12, 1970, January 1, 1971, April 1, 1971, September 15,
1971, December 3, 1973, February 1, 1974, April 25, 1974, February 3, 1975, March 1, 1975, June 11, 1975,
May 12, 1976, August 16, 1976, April 26, 1977, October 15, 1977, November 7, 1977, December 1, 1977, August 1,
1978, October 12, 1979, November 1, 1979, July 7, 1980, August 1, 1980, August 20, 1980, February 1, 1981,
October 8, 1981, August 27, 1982, September 1, 1982, December 15, 1982, March 1, 1983, June 21, 1984, December 12,
1984, June 11, 1985, March 1, 1986, May 1, 1986, May 1, 1990, December 1, 1991, December 4, 1991, January 1,
1992, September 30, 1992, October 1, 1992, December 1, 1992, February 1, 1993, February 18, 1993, May 1,
1993, August 1, 1993, October 1, 1993, January 1, 1994, February 1, 2000, August 15, 2002, March 5, 2003,
April 1, 2003, July 15, 2003, October 1, 2003, February 1, 2004 (eight separate indentures supplemental thereto),
May 1, 2004, September 1, 2004, January 1, 2005, July 1, 2005, December 1, 2005, June 1, 2007, April 1,
2008, June 1, 2008, March 1, 2009, May 15, 2012, September 1, 2012, April 1, 2014, March 15, 2015, June 1,
2017, April 1, 2018, March 1, 2019, September 15, 2019, March 1, 2020, October 1, 2020, and this Supplemental
Indenture, or attached to or connected with such real estate or transmission or distribution systems of the Company leading from or into
such real estate.


 


SECOND.


 


ALSO, (except as in the Original Indenture
expressly excepted) all franchises and all permits, ordinances, easements, privileges, immunities and licenses, all rights to construct,
maintain and operate overhead, surface and underground systems for the distribution and transmission of electricity, steam, gas or other
agencies for the supply to itself or others of light, heat, cold or power, all rights-of-way, all waters, water rights and flowage rights
and all grants and consents, now owned or, subject to the provisions of Article XII of the Original Indenture, which it may hereafter
acquire.


 






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ALSO, (except as in the Original Indenture
expressly excepted) all inventions, patent rights and licenses of every kind now owned by the Company or, subject to the provisions of
Article XII of the Original Indenture, which it may hereafter acquire.


 


THIRD.


 


ALSO, subject to the provisions of Article XII
of the Original Indenture, all other property, real, personal and mixed (except as therein or herein expressly excepted) of every nature
and kind and wheresoever situated now or hereafter possessed by or belonging to the Company, or to which it is now, or may at any time
hereafter be, in any manner entitled at law or in equity.


 


EXPRESSLY EXCEPTING AND EXCLUDING, HOWEVER,
from this Supplemental Indenture and from the lien and operation hereof:


 


(a)       all
property expressly excepted and excluded from the Original Indenture, and from the lien and operation thereof; and


 


(b)       when
the amendment set forth in Section 2 of Article III of the Supplemental Indenture dated May 15, 2012 becomes effective, all Excepted
Property as defined in such Section.


 


TO HAVE AND TO HOLD all said properties,
real, personal and mixed, mortgaged, pledged and conveyed by the Company as aforesaid, or intended so to be, unto the Trustee and its
successors and assigns forever.


 


SUBJECT, HOWEVER, to the exceptions and
reservations and matters hereinabove recited, to existing leases, to existing liens upon rights of way for transmission or distribution
line purposes, as defined in Article I of the Original Indenture, and any extensions thereof, and subject to existing easements
for streets, alleys, highways, rights-of-way and railroad purposes over, upon and across certain of the property hereinbefore described,
and subject also to all the terms, conditions, agreements, covenants, exceptions and reservations expressed or provided in the deeds
or other instruments respectively under and by virtue of which the Company acquired the properties hereinabove described, and to undetermined
liens and charges, if any, incidental to construction or other existing permitted liens as defined in Article I of the Original
Indenture.


 


IN TRUST, NEVERTHELESS, upon the terms
and trusts in the Original Indenture and the indentures supplemental thereto, including this Supplemental Indenture, set forth, for the
equal and proportionate benefit and security of all present and future holders of the Bonds and coupons issued and to be issued thereunder,
or any of them, without preference of any of said Bonds and coupons of any particular series over the Bonds and coupons of any other
series, by reason of priority in the time of the issue, sale or negotiation thereof, or by reason of the purpose of issue or otherwise
howsoever, except as otherwise provided in Section 2 of Article IV of the Original Indenture.


 


AND IT IS HEREBY COVENANTED, DECLARED AND AGREED,
by and between the parties hereto, for the benefit of those who shall hold the Bonds and coupons, or any of them to be issued under the
Original Indenture, as follows:


 


ARTICLE
I



DESCRIPTION OF THE NEW BONDS


 


Section 1.         
There is hereby created a new series of Bonds to be executed, authenticated and delivered under and secured by the Original Indenture
which shall, subject to the provisions of Section 1 of Article II of the Original Indenture, be designated as “2.15%
First Mortgage Bonds due 2032” (the “New Bonds”) of the Company. The New Bonds shall be executed, authenticated and
delivered in accordance with the provisions of, and shall in all respects be subject to all of the terms, conditions and covenants of,
the Original Indenture.


 






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The New Bonds shall mature on March 15, 2032,
and shall bear interest at the rate per annum set forth in the form of the New Bond contained in Section 3 of this Article I,
payable semi-annually in arrears on the 15th day of March and the 15th day of September in each year (each, an “Interest Payment
Date”), commencing on March 15, 2022, and at maturity. The New Bonds shall be payable as to principal and interest in any
coin or currency of the United States of America which at the time of payment is legal tender for public and private debts, and shall
be payable, in immediately available funds, at the office of the Trustee.


 


Section 2.         
The New Bonds will be initially issued in global form registered in the name of CEDE & CO. (as nominee for The Depository
Trust Company). The New Bonds will bear the depository legend in substantially the form set forth in Section 3 of this Article I.
Any transfer shall be effected at the principal office or place of business of the Trustee. The New Bonds are exchangeable for the New
Bonds of other denominations, as in the Original Indenture provided, except that payment of a service charge therefor will not be required
by the Company.


 


Notwithstanding the provisions of Section 6
of Article II of the Original Indenture, the New Bonds shall be dated the date of authentication and shall bear interest from the
Interest Payment Date to which interest on the New Bonds has been paid next preceding the date thereof, unless such date is an Interest
Payment Date to which interest has been paid, in which case they shall bear interest from the date thereof, or unless the date thereof
is prior to March 15, 2022, in which case they shall bear interest from June 22, 2021; provided, however, that, subject to the provisions
of this Section with respect to failure by the Company to pay any interest on an Interest Payment Date, the holder of any New Bond
dated after a record date (as hereinafter defined) for the payment of interest and prior to the date of payment of such interest shall
not be entitled to payment of such interest and shall have no claim against the Company with respect thereto.


 


The person in whose name any New Bond is registered
at the close of business on any record date with respect to any Interest Payment Date shall be entitled to receive the interest payable
on such Interest Payment Date notwithstanding the cancellation of such Bond upon any transfer or exchange thereof subsequent to the record
date and prior to such Interest Payment Date, except if and to the extent the Company shall default in the payment of the interest due
on such Interest Payment Date, in which case such defaulted interest shall be paid to the person in whose name such Bond is registered
on the date of payment of such defaulted interest or on a subsequent record date for such payment if one shall have been established
as hereinafter provided. A subsequent record date may be established by the Company by notice mailed to the holders of the New Bonds
not less than ten days preceding such record date, which record date shall be not more than thirty days prior to the subsequent Interest
Payment Date. The term “record date” as used in this Section with respect to any regular interest payment date
shall mean the March 1 or September 1, as the case may be, next preceding such Interest Payment Date, or, if such March 1 or September
1 shall be a legal holiday in the State of New York or in the State of Missouri or a day on which banking institutions in the Borough
of Manhattan, The City of New York, or the City of St. Louis, Missouri, are authorized by law to close, the next preceding day which
shall not be a legal holiday or a day on which such institutions are so authorized to close.





 


Section 3.         
The New Bonds and the Trustee’s certificate on the New Bonds shall be substantially in the following forms respectively:


 






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[FORM OF FACE OF NEW BOND]


 


	REGISTERED	REGISTERED




 


[DTC Legend


 


THIS BOND IS A GLOBAL BOND 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 BONDS REPRESENTED
HEREBY AS PROVIDED IN THE AMENDED INDENTURE REFERRED TO BELOW, THIS BOND 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 BOND 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

(Incorporated under the laws of the State of Missouri)


  


2.15% FIRST MORTGAGE BOND DUE 2032


 


	CUSIP:	NUMBER:
	ISIN:	 




 


	ORIGINAL ISSUE DATE:	PRINCIPAL AMOUNT: $
	 	 
	INTEREST RATE: 2.15%	MATURITY DATE: March 15, 2032




  


UNION ELECTRIC COMPANY, a corporation organized
and existing under the laws of the State of Missouri (hereinafter called the “Company”, which term shall include any successor
corporation as defined in the Amended Indenture referred to on the reverse hereof), for value received, hereby promises to pay to ________________,
or registered assigns, the sum of ____________________________________ Dollars ($___________), on the Maturity Date set forth above in
any coin or currency of the United States of America which at the time of payment is legal tender for public and private debts, and to
pay interest thereon, in like coin or currency, at the Interest Rate set forth above, payable semi-annually in arrears, on March 15 and
September 15 in each year (each, an “Interest Payment Date”) until the Maturity Date, commencing March 15, 2022, and on the
Maturity Date or, if the Company shall default in the payment of the principal hereof, until the Company’s obligation with respect
to the payment of such principal shall be discharged as provided in the Amended Indenture referred to on the reverse hereof. Such interest
shall be payable from the March 15 or September 15, as the case may be, next preceding the date hereof to which interest has not been
paid, unless the date hereof is a March 15 or September 15 to which interest has been paid, in which case from the date hereof, or unless
the date hereof is prior to the first payment of interest, in which case from the Original Issue Date set forth above. The interest so
payable will be paid to the person in whose name this Bond, or the Bond in exchange or substitution for which this Bond shall have been
issued, shall have been registered at the close of business on the March 1 or September 1, as the case may be (each, a “Record
Date”), next preceding the date of payment, subject to certain exceptions set forth in the Amended Indenture. The principal of,
premium, if any, and interest on, this Bond are payable, in immediately available funds, at the office of the Trustee hereinafter referred
to; provided, however, that at the option of the Company, interest on this Bond may be paid by check mailed to the registered holder
of this Bond at such holder’s address as it shall appear on the books of the Company to be kept for that purpose or by a wire transfer
to an account designated by the registered holder of this Bond entitled thereto.


 


This Bond shall not be entitled to any benefit
under the Amended Indenture or any indenture supplemental thereto, or become valid or obligatory for any purpose, until The Bank of New
York Mellon, the Trustee under the Amended Indenture, or a successor trustee thereto under the Amended Indenture, or an agent therefor,
shall have signed the form of certificate endorsed hereon.


 


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


 






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IN WITNESS WHEREOF, Union Electric Company has
caused this Bond to be signed in its name by its Chairman of the Board or President or a Vice President by manual signature or a facsimile
thereof, and its corporate seal (or a facsimile thereof) to be hereto affixed and attested by its Secretary or an Assistant Secretary
by manual signature or a facsimile thereof.


 


 


	Dated	 
	 	 
	 	UNION ELECTRIC COMPANY
	 	 	 
	 	By	 
	 	 	 
	 	 
	[CORPORATE SEAL]	 
	 	 
	Attest:	 
	 	 
	 	 


 


[FORM OF TRUSTEE’S CERTIFICATE]


 


This Bond is one of the Bonds, of the series designated
therein, described in the within-mentioned Amended Indenture and Supplemental Indenture of June 1, 2021.


 


	 	THE BANK OF NEW YORK MELLON, as TRUSTEE
	 	
	 	By	 
	 	 	Authorized Officer	 


 






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[FORM OF REVERSE OF NEW BOND]


 


This Bond is one of a duly authorized issue of
Bonds of the Company (herein called the “Bonds”), in unlimited aggregate principal amount, of the series hereinafter specified,
all issued and to be issued under and equally secured by the Indenture of Mortgage and Deed of Trust, dated June 15, 1937, executed
by the Company to The Bank of New York Mellon, formerly The Bank of New York (successor trustee to Bank of America, National Association,
formerly Boatmen’s Trust Company), as trustee (herein called the “Trustee”), as amended by indentures supplemental
thereto dated May 1, 1941, April 1, 1971, February 1, 1974, July 7, 1980, February 1, 2000, August 15,
2002 and May 15, 2012, between the Company and the Trustee (said mortgage and deed of trust, as so amended, being herein called
the “Amended Indenture”), to which Amended Indenture and all indentures supplemental thereto reference is hereby made for
a description of the properties mortgaged and pledged, the nature and extent of the security, the rights of the bearers or registered
owners of the Bonds and of the Trustee in respect thereto, and the terms and conditions upon which the Bonds are, and are to be, secured.
To the extent permitted by, and as provided in, the Amended Indenture, modifications or alterations of the Amended Indenture, or of any
indenture supplemental thereto, and of the rights and obligations of the Company and of the holders of the Bonds may be made with the
consent of the Company by an affirmative vote or consent of the holders of the Bonds then outstanding as are specified in the Amended
Indenture. No such modification or alteration shall be made which will affect the terms of payment of the principal of, or interest or
premium on, this Bond, which are unconditional. The Bonds may be issued in series, for various principal sums, may mature at different
times, may bear interest at different rates and may otherwise vary as in the Amended Indenture provided. This Bond is one of a series
designated as the “2.15% First Mortgage Bonds due 2032” (herein called the “Bonds of this Series”) of the Company,
issued under and secured by the Amended Indenture and described in the indenture (hereinafter called the “New Supplemental Indenture”)
dated June 1, 2021, between the Company and the Trustee, supplemental to the Amended Indenture.


 


The Bonds of this Series are not entitled to the
benefit of any improvement, maintenance or analogous fund.


 


All or a portion of the Bonds 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 Bonds of this Series to be redeemed
on any redemption date prior to December 15, 2031 (three months prior to the Maturity Date) (the “Par Call Date”) will
be equal to the greater of the following amounts: (a) 100% of the principal amount of the Bonds of this Series being redeemed on
that redemption date; or (b) the sum of the present values of the remaining scheduled payments of principal and interest on the
Bonds of this Series being redeemed on that redemption date that would be payable if such Bonds matured on the Par Call Date (not including
any portion of any payments of interest accrued to the redemption date) discounted to the redemption date on a semiannual basis (assuming
a 360 day year consisting of twelve 30 day months) at the Adjusted Treasury Rate (as defined below), plus 10 basis points, as determined
by the Reference Treasury Dealer (as defined below), plus, in each case, accrued and unpaid interest thereon to the redemption date.
The redemption price for the Bonds of this Series to be redeemed on any redemption date on or after the Par Call Date will be equal to
100% of the principal amount of the Bonds of this Series being redeemed on that redemption date plus accrued and unpaid interest thereon
to the redemption date. Notwithstanding the foregoing, installments of interest on Bonds of this Series that are due and payable
on Interest Payment Dates falling on or prior to a redemption date will be payable on the Interest Payment Date to the holder of this
Bond as of the close of business on the relevant Record Date.


 


With respect to a redemption occurring prior to
the Par Call Date, the Company shall give the Trustee written notice of the redemption price promptly after the calculation thereof and
the Trustee shall not be responsible for such calculation.


 


The Company shall send notice of any redemption
at least 10 days but not more than 60 days before the redemption date to each holder of the Bonds of this Series to be
redeemed, and, if less than all Bonds of this Series are to be redeemed, the particular Bonds of this Series to be redeemed will be selected
by the Trustee by lot; provided that as long as the Bonds of this Series are represented by global certificates registered in the name
of The Depository Trust Company, or its nominee, beneficial interests in such global certificates will be selected for redemption by
The Depository Trust Company in accordance with its standard procedures therefor. Unless the Company defaults in payment of the
redemption price, on and after the redemption date, interest will cease to accrue on the Bonds of this Series or portions thereof
called for redemption.


 






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Any notice of redemption at the Company’s
option may state that such redemption will be conditional upon receipt by the Trustee, on or prior to the redemption date, of money sufficient
to pay the principal of and premium, if any, and interest on, the Bonds of this Series or portions thereof called for redemption, and
that if such money has not been so received, such notice will be of no force and effect and the Company will not be required to redeem
such Bonds or portions thereof.


 


“ADJUSTED TREASURY RATE” means, with
respect to any redemption date, the rate per annum equal to the semiannual equivalent yield to maturity of the Comparable Treasury Issue,
assuming a price for the Comparable Treasury Issue (expressed as a percentage of its principal amount) equal to the Comparable Treasury
Price for such redemption date.


 


“COMPARABLE TREASURY ISSUE” means
the United States Treasury security selected by the Reference Treasury Dealer as having a maturity comparable to the remaining term of
the Bonds of this Series to be redeemed (assuming, for this purpose, that the Bonds matured on the Par Call Date) that would be
utilized, at the time of selection and in accordance with customary financial practice, in pricing new issues of corporate debt securities
of comparable maturity to the Par Call Date.


 


“COMPARABLE TREASURY PRICE” means,
with respect to any redemption date, (A) the average of the Reference Treasury Dealer Quotations for such redemption date, after
excluding the highest and lowest of such Reference Treasury Dealer Quotations, or (B) if the Company obtains fewer than four such
Reference Treasury Dealer Quotations, the average of all such quotations, or (C) if only one Reference Treasury Dealer Quotation
is received, such quotation.


 


“REFERENCE TREASURY DEALER” means
each of (A) BofA Securities, Inc., Goldman Sachs & Co. LLC, Mizuho Securities USA LLC and a Primary Treasury Dealer (as defined
below) selected by SMBC Nikko Securities America, Inc. or, in each case, an affiliate thereof, which are primary U.S. Government securities
dealers in the United States (each, a “Primary Treasury Dealer”), and their respective successors; provided, however, that
if any of the foregoing shall cease to be a Primary Treasury Dealer, the Company will substitute therefor another Primary Treasury Dealer;
and (B) any other Primary Treasury Dealer(s) selected by the Company.


 


“REFERENCE TREASURY DEALER QUOTATIONS”
means, with respect to each Reference Treasury Dealer and any redemption date, the average, as determined by the Company, of the bid
and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) quoted in writing
to the Company by such Reference Treasury Dealer at 5:00 p.m. (New York City time) on the third Business Day preceding such redemption
date.


 


In case an event of default, as defined in the
Amended Indenture, shall occur, the principal of all the Bonds at any such time outstanding under the Amended Indenture may be declared
or may become due and payable, upon the conditions and in the manner and with the effect provided in the Amended Indenture. The Amended
Indenture provides that such declaration may in certain events be waived by the holders of a majority in principal amount of the Bonds
outstanding.


 


This Bond is exchangeable by the registered owner
hereof, in person or by duly authorized attorney, on the books of the Company to be kept for that purpose at the office of the Company
in the City of St. Louis, Missouri, upon surrender and cancellation of this Bond and on presentation of a duly executed written
instrument of transfer, and thereupon a new Bond or Bonds of the same series, of the same aggregate principal amount and in authorized
denominations will be issued to the transferee or transferees in exchange herefor, without payment of any charge other than stamp taxes
and other governmental charges incident thereto; and this Bond with or without others of like series, may in like manner be exchanged
for one or more new Bonds of the same series of other authorized denominations but of the same aggregate principal amount; all subject
to the terms and conditions set forth in the Amended Indenture.


 






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Each initial and future holder of this Bond, by
its acquisition of an interest in this Bond, irrevocably (a) consents to the amendments set forth in Article III of the Supplemental
Indenture dated as of May 15, 2012, supplemental to the Amended Indenture, without any other or further action by any holder of
this Bond, and (b) designates the Trustee, and its successors, as its proxy with irrevocable instructions to vote and deliver written
consents on behalf of such holder in favor of such amendments at any meeting of holders, in lieu of any meeting of holders, in response
to any consent solicitation or otherwise.


 


No recourse shall be had for the payment of the
principal of, premium, if any, or the interest on, this Bond, or for any claim based hereon or on the Amended Indenture or any indenture
supplemental thereto, against any incorporator, or against any stockholder, director or officer, past, present or future, of the Company,
or of any predecessor or successor corporation, either directly or through the Company or any such predecessor or successor corporation,
whether for amounts unpaid on stock subscriptions or by virtue of any constitution, statute or rule of law, or by the enforcement of
any assessment or penalty or otherwise, all such liability, whether at common law, in equity, by any constitution, statute or otherwise,
of incorporators, stockholders, directors or officers being released by every owner hereof by the acceptance of this Bond and as part
of the consideration for the issue hereof, and being likewise released by the terms of the Amended Indenture.


 


[END OF FORM OF REVERSE OF NEW BOND]


 


Section 4.      Until
New Bonds in definitive form are ready for delivery, the Company may execute, and upon its request in writing the Trustee shall authenticate
and deliver, in lieu thereof, New Bonds in temporary form, as provided in Section 9 of Article II of the Original Indenture.


 


ARTICLE
II



ISSUE OF THE NEW BONDS


 


Section 1.      The
principal amount of the New Bonds which may be authenticated and delivered hereunder is not limited.


 


Section 2.      The
New Bonds in the aggregate principal amount of Five Hundred Twenty-Five Million Dollars ($525,000,000), being the initial issue of the
New Bonds, may forthwith at any time or from time to time be executed by the Company and delivered to the Trustee and shall be authenticated
by the Trustee and delivered (either before or after the filing or recording hereof) to or upon the order of the Company, upon compliance
by the Company with the applicable provisions of Article III and Article XVIII of the Original Indenture.


 


Section 3.      After
the authentication of the New Bonds, without the consent of any existing holder of the New Bonds, the Company may thereafter obtain from
time to time the authentication of additional New Bonds pursuant to the terms of the Original Indenture by the order of the Company referring
to this Supplemental Indenture having the same terms and conditions as the Outstanding New Bonds in all respects (including the same
CUSIP number), except for the date of original issuance, the offering price and, if applicable, the initial interest accrual date and
the initial Interest Payment Date.


 


ARTICLE
III



REDEMPTION OF THE NEW BONDS AND CONSENT TO AMENDMENTS


 


Section 1.      The
New Bonds are redeemable as set forth in the form of such Bonds set forth in Section 3 of Article I hereof. If the Company
elects to redeem any New Bonds, it shall notify the Trustee of the redemption date and the principal amount of such Bonds to be redeemed
not less than 15 days nor more than 90 days before such redemption date.


 


Section 2.      Each
initial and future holder of the New Bonds, by its acquisition of an interest in such Bonds, irrevocably (a) consents to the amendments
set forth in Article III of the Supplemental Indenture dated as of May 15, 2012, supplemental to the Original Indenture, without
any other or further action by any holder of such bonds, and (b) designates the Trustee, and its successors, as its proxy with
irrevocable instructions to vote and deliver written consents on behalf of such holder in favor of such amendments at any meeting of
holders, in lieu of any meeting of holders, in response to any consent solicitation or otherwise.


 






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ARTICLE
IV



COVENANTS


 


The Company hereby covenants, warrants and agrees:


 


Section 1.      That
the Company is lawfully seized and possessed of all of the mortgaged property described in the granting clauses of this Supplemental
Indenture to the extent shown on its books and records as of the date hereof; that it has good right and lawful authority to mortgage
the same as provided in this Supplemental Indenture; and that such mortgaged property will be, at the actual date of the issue of the
New Bonds, free and clear of any deed of trust, mortgage, lien, charge or encumbrance thereon or affecting the title thereto prior to
the lien of the Original Indenture, except for permitted liens and as set forth in the granting clauses of the Original Indenture and
this Supplemental Indenture.


 


ARTICLE
V



THE TRUSTEE


 


The Trustee hereby accepts the trusts hereby declared
and provided, and agrees to perform the same upon the terms and conditions in the Original Indenture and in this Supplemental Indenture
set forth, and upon the following terms and conditions:


 


The Trustee shall not be responsible in any manner
whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or the due execution hereof by the Company
or for or in respect of the recitals contained herein, all of which recitals are made by the Company solely.


 


ARTICLE
VI



MISCELLANEOUS PROVISIONS.


 


Section 1.      Except
as otherwise defined herein, all terms contained in this Supplemental Indenture shall, for all purposes thereof, have the meanings given
to such terms in Article I of the Original Indenture.


 


Section 2.      This
Supplemental Indenture may be simultaneously executed in any number of counterparts, each of which when so executed shall be deemed to
be an original; but such counterparts shall together constitute but one and the same instrument.



 






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IN WITNESS WHEREOF, said Union Electric
Company has caused this Supplemental Indenture to be executed on its behalf by its Chairman of the Board or President or one of its Vice
Presidents and this Supplemental Indenture to be attested by its Secretary or one of its Assistant Secretaries; and said The Bank of
New York Mellon, in evidence of its acceptance of the trust hereby created, has caused this Supplemental Indenture to be executed on
its behalf by its President or one of its Vice Presidents, and this Supplemental Indenture to be attested by one of its Vice Presidents,
its Secretary, or one of its Assistant Secretaries; all as of the 1st day of June, Two thousand and twenty-one.


 


 


	Attested:	 	UNION ELECTRIC COMPANY,

    1901 Chouteau Avenue

    St. Louis, Missouri 63103
	 	 	 
	/s/ Craig W. Stensland	 	By:	/s/ Darryl T. Sagel
	Craig W. Stensland	 	Name:	Darryl T. Sagel
	Assistant Secretary	 	Title:	Vice President and Treasurer
	 	 	 	 



 






     


     


    

 


	Attested:	 	THE BANK OF NEW YORK MELLON,
	 	 	 
	/s/ Christine S. Conway	 	By:	/s/ Rita Duggan
	Name: 	Christine S. Conway	 	Name:
	Rita
                           Duggan

    

	Title:   	Vice President	 	Title:	Vice President
	 	 	 	 







     


     


    

 


	STATE OF MISSOURI	 	}
	 	 	} SS.:
	CITY OF ST. LOUIS	 	}


 


On this 11th day of June, 2021, before me appeared
Darryl T. Sagel and Craig W. Stensland, to me personally known, who, being by me duly sworn, did say that they are the Vice President
and Treasurer, and an Assistant Secretary of UNION ELECTRIC COMPANY, a corporation, and that said instrument was signed on behalf
of said corporation by authority of its Board of Directors, and said Vice President and Treasurer, and Assistant Secretary acknowledged
said instrument to be the free act and deed of said corporation.


 


IN TESTIMONY WHEREOF, I have hereto set
my hand and affixed my official seal at my office, in the City and State aforesaid, the day and year last above written.


 


 


	 	/s/ Stephanie A. Gifford
	 	Notary Public – Notary Seal
	 	State of Missouri
	 	My Commission: Expires January 30, 2024
	 	St. Louis County
	 	Commission #11479771



 






     


     


    

 


	STATE OF NEW YORK	 	}
	 	 	} SS.:
	COUNTY OF NEW YORK	 	}


 


On this 9th day of June, 2021, before me appeared
Rita Duggan, to me personally known, who, being by me duly sworn, did say that she is a Vice President of THE BANK OF NEW YORK MELLON,
a corporation, and that said instrument was signed on behalf of said corporation, as the trustee thereunder by authority of its Board
of Directors, and said Vice President, acknowledged said instrument to be the free act and deed of said corporation as the trustee under
said instrument.


 


IN TESTIMONY WHEREOF, I have hereto set
my hand and affixed my official seal at my office, in the City and State aforesaid, the day and year last above written.


  


	 	/s/ Helen Choi
	 	Helen Choi

    Notary Public, State of New York

    No. 01CH6291290

    Qualified in New York County

    Commission Expires October 15, 2021