Exhibit 4.3


 





SECOND SUPPLEMENTAL INDENTURE (as defined
herein) (this “Second Supplemental Indenture”), dated as of May 21, 2015, between Macquarie Infrastructure Corporation,
a Delaware corporation (the “Company”), and Wells Fargo Bank, National Association, as trustee under the Indenture
referred to below (the “Trustee”).


 


WITNESSETH:


 


WHEREAS, the predecessor to the Company,
Macquarie Infrastructure Company LLC, a Delaware limited liability company (“MIC LLC”), has heretofore executed
and delivered to the Trustee a Senior Debt Securities Indenture dated July 15, 2014 (the “Base Indenture”) and
a First Supplemental Indenture to the Base Indenture, dated as of July 15, 2014 (the “ First Supplemental Indenture,”
and together with the Base Indenture, the “Indenture”), providing for the issuance of its 2.875% Convertible
Senior Notes due 2019 (the “Notes”);


 


WHEREAS, on May 21, 2015, MIC LLC converted
(the “Conversion”) from a Delaware limited liability company to a Delaware corporation named Macquarie Infrastructure
Corporation (“MIC Corp”));


 


WHEREAS, at the effective time of the Conversion
(the “Effective Time”) each limited liability company interest (“LLC Interest”) of MIC LLC
issued and outstanding immediately prior to the Effective Time, by virtue of the Conversion and without any action on the part
of MIC LLC, the Company or the holders of the LLC Interests, was automatically converted into a share of common stock, par value
$0.001 per share (the “Common Stock”) of MIC Corp;


 


WHEREAS, Section 8.07 of the First Supplemental
Indenture provides that, in connection with, among other things, any recapitalization, reclassification or change of the LLC Interests
of MIC LLC, as a result of which LLC Interests would be converted into, or exchanged for, stock, other securities, other property
or assets (including cash or any combination thereof) with respect to or in exchange for such LLC Interests, then the Company shall
execute with the Trustee a supplemental indenture providing that the right to convert each $1,000 principal amount of Notes shall
be changed into a right to convert such principal amount of Notes for the kind and amount of shares of stock, other securities
or other property or assets (including cash or any combination thereof) receivable upon such recapitalization, reclassification
or change of the LLC Interests by a holder of a number of LLC Interests issuable upon conversion of such Notes immediately prior
to such recapitalization, reclassification or change of the LLC Interests;


 


WHEREAS, Section 7.02(a) of the Indenture
provides that the Company, when authorized by the resolutions of the Board of Directors, and the Trustee may enter into a supplemental
indenture, without the consent of the holders of any of the Notes at the time outstanding, to make provision with respect to the
conversion rights of the holders of Notes pursuant to the requirements of Section 8.07 of the Indenture;


 


WHEREAS, immediately prior to the Effective
Time, each $1,000 principal amount of Notes was convertible into approximately 11.7942 shares of LLC Interests;


 


WHEREAS, the Company has heretofore delivered
or is delivering contemporaneously herewith to the Trustee the Officers’ Certificate and the Opinion of Counsel described
in Sections 1.02 of the Base Indenture and 8.07(b) of the First Supplemental Indenture; and


 






    	 



    	 



    

 


 


WHEREAS, all other acts and proceedings
required by applicable law and the Indenture necessary to authorize the execution and delivery of this Second Supplemental Indenture
and to make this Second Supplemental Indenture a valid and binding agreement for the purposes expressed herein, in accordance with
its terms, have been complied with or have been duly done or performed.


 


NOW, THEREFORE, in consideration of the
foregoing and notwithstanding any provision of the Indenture which, absent this Second Supplemental Indenture, might operate to
limit such action, the parties hereto, intending to be legally bound hereby, agree as follows:


 


Article 1


AMENDMENTS


 


Section 1.01. Settlement Upon
Conversion. In accordance with Section 7.02(a) of the First Supplemental Indenture, from and after the date of this Second
Supplemental Indenture, the right to convert each $1,000 principal amount of Notes into LLC Interests is hereby changed, to a right
to convert such $1,000 principal amount of Notes into Common Stock, calculated so that a holder will be entitled to receive a number
of shares of Common Stock equal to the number of LLC Interests such holder would have been entitled to receive prior to the Conversion.
The provisions of the Indenture, as modified herein, shall continue to apply, mutatis mutandis, to the Holders’ right
to convert each Note into the Common Stock.


 


Section 1.02. Effectiveness. This
Second Supplemental Indenture will become effective and operative and binding upon each of the Company, the Trustee and the Holders
as of the Effective Time.


 


Article 2


MISCELLANEOUS PROVISIONS


 


Section 2.01. Capitalized Terms. Capitalized
terms used herein without definition shall have the meanings assigned to them in the Indenture.


 


Section 2.20. Indenture Remains in Full
Force and Effect. Except as supplemented hereby, all provisions of the Indenture shall remain in full force and effect.


 


Section 2.03. Governing Law. The
laws of the State of New York shall govern this Second Supplemental Indenture.


 


Section 2.04. Headings, Etc. The
titles and headings of the articles and sections of this Second Supplemental Indenture have been inserted for convenience of reference
only, are not to be considered a part hereof, and shall in no way modify or restrict any of the terms or provisions hereof.


 


Section 2.05. Separability. In
case any provision in the Indenture, as modified by this Second Supplemental Indenture, or in the Notes shall be invalid, illegal
or unenforceable, the validity, legality and enforceability of the remaining provisions shall not in any way be affected or impaired
thereby.


 






    	 



    	 



    

 


 


Section 2.06. Execution in
Counterparts. This Second Supplemental Indenture may be executed in any number of counterparts, each of which shall be
an original, but such counterparts shall together constitute but one and the same instrument.


 


[Signature Page Follows]


 






    	 



    	 



    

 


 


IN WITNESS WHEREOF, the parties hereto have
caused this Second Supplemental Indenture to be duly executed as of the date first above written.


 


	MACQUARIE INFRASTRUCTURE CORPORATION
	 	 	 
	By:	 	
        /s/ James Hooke

	Name:	 	James Hooke
	Title:	 	Chief Executive Officer
	 	 	 
	 	 	 
	By:	 	
        /s/ Michael Kernan

	Name:	 	Michael Kernan
	Title:	 	General Counsel
	 
	
        WELLS FARGO BANK, NATIONAL ASSOCIATION

        as Trustee

         

	 	 
	By:	 	
/s/ Stefan Victory
	Name:	 	Stefan Victory




	Title:	 	Vice President



 


 


 


 


[Signature Page to
Second Supplemental Indenture]