AMENDMENT NO. 2 TO JOINT FILING AGREEMENT

Exhibit 4

AMENDMENT NO. 2 TO JOINT FILING AGREEMENT

     In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, AEI and each of the Xxxxxxx Entities (as such term is defined in the Statement on Schedule 13D originally filed with the Securities and Exchange Commission on October 5, 2009, as amended by Amendment No. 1 to the Statement on Schedule 13D filed with the Securities and Exchange Commission on October 13, 2009 (as amended, the “Statement”)) entered into a Joint Filing Agreement, dated October 2, 2009, as amended by Amendment No. 1 to Joint Filing Agreement, dated as of October 8, 2009 (as amended, the “Joint Filing Agreement”) in connection with the Statement relating to the 12,642,668 American Depositary Receipts, representing 63,213,340 Class “B” Shares, par value Ps.1, of Transportadora de Gas del Sur S.A. and this Joint Filing Agreement was included as Exhibits to the Statement.

          AEI and the Xxxxxxx Entities hereby wish to amend the Joint Filing Agreement to provide for AEI LLC, AEI (Luxembourg) S.àr.l. and AEI Utilities, S.L. to be joined as additional parties to the Joint Filing Agreement and each of AEI LLC, AEI (Luxembourg) S.àr.l. and AEI Utilities, S.L. hereby agree to be joined as an additional party to the Joint Filing Agreement and be bound by each and all of the provisions thereof.

          This Amendment may be executed in any number of counterparts all of which taken together shall constitute one and the same instrument.

          In witness whereof, the undersigned hereby execute this Amendment this 2nd day of November, 2009.

	AEI
	By:	/s/ Xxxxxxx X. Xxxx
		Name:	Xxxxxxx X. Xxxx
		Title:	EVP, General Counsel
	AEI LLC
	By:	AEI, as its sole member
	By:	/s/ Xxxxx X. Xxxxxx
		Name:	Xxxxx X. Xxxxxx
		Title:	CEO
	AEI (LUXEMBOURG) S.ÀR.L.
	By:	/s/ Xxxxx X. Xxxxxx
		Name:	Xxxxx X. Xxxxxx
		Title:	Manager

	AEI UTILITIES, S.L.
	By:	/s/ Xxxxx Xxxxxxx
		Name:	Xxxxx Xxxxxxx
		Title:	Director
	XXXXXXX INVESTMENT MANAGEMENT LIMITED
	By:	/s/ Xxxxx Xxxxxxx
		Name:	Xxxxx Xxxxxxx
		Title:	Head of Legal

	XXXXXXX GROUP PLC XXXXXXX INVESTMENTS (UK) LIMITED XXXXXXX MANAGEMENT COMPANY LIMITED XXXXXXX GLOBAL SPECIAL SITUATIONS FUND 2 LIMITED XXXXXXX GLOBAL SPECIAL SITUATIONS FUND 3 LIMITED PARTNERSHIP XXXXXXX GLOBAL SPECIAL SITUATIONS FUND 4 LIMITED PARTNERSHIP XXXXXXX GLOBAL SPECIAL SITUATIONS FUND 5 LIMITED PARTNERSHIP XXXXXXX EMERGING MARKETS LIQUID INVESTMENT PORTFOLIO XXXXXXX EMERGING MARKETS GLOBAL INVESTMENT PORTFOLIO LIMITED XXXXXXX GROWING MULTI STRATEGY FUND LIMITED XXXXXXX SICAV EMERGING MARKETS DEBT FUND EMDCD LTD. FCI LTD. XXXXXXX CAYMAN SPC NO. 3 LIMITED ON BEHALF OF AND FOR THE ACCOUNT OF AEI SEGREGATED PORTFOLIO XXXXXXX EMERGING MARKETS DEBT AND CURRENCY FUND
	By:	Xxxxxxx Investment Management Limited, as
	By:	/s/ Xxxxx Xxxxxxx
		Name:	Xxxxx Xxxxxxx
		Title:	Head of Legal