SUPPLEMENTAL INDENTURE

EXHIBIT 4.1

SOUTHERN CALIFORNIA GAS

COMPANY

TO

U.S. BANK NATIONAL ASSOCIATION

(successor by merger to U.S. Bank Trust National Association,

formerly known as First Trust of California, National Association)

TRUSTEE

SUPPLEMENTAL INDENTURE

To Base Indenture dated October 1, 1940

Dated as of November 21, 2008

TABLE OF CONTENTS

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THIS SUPPLEMENTAL INDENTURE, dated as of November 21, 2008 (this “ Supplemental Indenture ”), is made and entered into in the City of Los Angeles, State of California by and between SOUTHERN CALIFORNIA GAS COMPANY, a corporation duly organized and existing under the laws of the State of California, and having its principal place of business in the City of Los Angeles, State of California (hereinafter sometimes called the “ Corporation ”) and U.S. BANK NATIONAL ASSOCIATION (successor by merger to U.S. Bank Trust National Association, formerly known as First Trust of California, National Association), an association duly organized and existing under the laws of the United States of America and having a corporate trust office in the City and County of Los Angeles, State of California (hereinafter, together with its predecessors as trustees under the Indenture referred to below, sometimes called the “ Trustee ”).

WITNESSETH:

WHEREAS, the Corporation has executed and delivered to the Trustee a certain Indenture (hereinafter referred to as the “ Base Indenture ”) dated October 1, 1940, to secure bonds of the Corporation designated generally as its “ First Mortgage Bonds ” to be issued from time to time in one or more series, any of which series may vary from any other as to certain particulars specified in Section 2.01 of the Base Indenture, and the Corporation has executed and delivered to the Trustee supplemental indentures dated, respectively, as of July 1, 1947, May 1, 1948, June 1, 1950, April 1, 1952, August 1, 1955, June 1, 1956, December 1, 1956, July 1, 1957, October 1, 1959, July 1, 1963, September 1, 1964, June 1, 1965, December 1, 1966, October 1, 1970, August 1, 1972, September 1, 1972, October 1, 1974, May 1, 1976, October 1, 1977, November 1, 1979, February 1, 1981, September 15, 1981, April 1, 1982, August 15, 1983, May 18, 1984, December 16, 1985, March 1, 1986, November 15, 1986, December 1, 1986, January 15, 1988, June 15, 1988, November 1, 1988, December 1, 1990, October 1, 1991, August 15, 1992, December 15, 1992, March 1, 1993, June 15, 1993, November 1, 1993, November 15, 1993, October 1, 2002, October 17, 2003, December 15, 2003, December 10, 2004 and November 18, 2005 supplementing and amending the Base Indenture (each, a “ Prior Supplemental Indenture ,” and the Base Indenture together with all Prior Supplemental Indentures and this Supplemental Indenture being herein collectively referred to as the “ Indenture ”); and

WHEREAS, the Base Indenture and the Prior Supplemental Indentures dated, respectively, as of July 1, 1947, May 1, 1948, June 1, 1950, April 1, 1952 and August 1, 1955, are recorded in the office of the County Recorder of each of the Counties listed below in the Official Records thereof, as stated in the Prior Supplemental Indenture dated as of June 1, 1956; the Prior Supplemental Indentures dated, respectively, as of June 1, 1956 and December 1, 1956, are so recorded as stated in the Prior Supplemental Indenture dated as of July 1, 1957; the Prior Supplemental Indenture dated as of July 1, 1957 and each subsequently dated Prior Supplemental Indenture (other than the Prior Supplemental Indenture dated November 18, 2005) is so recorded as stated in the Prior Supplemental Indenture dated as of the next succeeding date; and the Prior Supplemental Indenture dated as of November 18, 2005 is recorded in the offices of the County Recorders in the Counties of the State of California, as follows:

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WHEREAS, bonds of the Corporation of five (5) series designated, respectively, as its “First Mortgage Bonds, Series GG, Due 2012,” “First Mortgage Bonds, Series HH, due 2018,” “First Mortgage Bonds, Series II, Due 2011,” “First Mortgage Bonds, Series JJ, Due 2009” and “First Mortgage Bonds, Series KK, due 2035” are outstanding as a part of the First Mortgage Bonds referred to in the Indenture, each such series of bonds, unless and until the taking of further appropriate action by the Board of Directors of the Corporation, being without limitation as to aggregate authorized principal amount; and

WHEREAS, pursuant to the provisions of Sections 2.01 and 2.02 of the Indenture, the Board of Directors has, by resolution duly adopted and delivered to the Trustee, authorized the creation, as a part of the First Mortgage Bonds referred to in the Indenture, a new series of bonds designated “First Mortgage Bonds, Series LL, due 2014” (the “ Series LL Bonds ”), of the form, terms and provisions provided herein, which new series of bonds, unless and until the taking of further appropriate action by the Board of Directors, is to be without limitation as to aggregate authorized principal amount and of which series of bonds in the aggregate principal amount of $250,000,000 are to be presently issued; and

WHEREAS, under the provisions of Sections 2.02 and 16.01 of the Indenture, the Corporation and the Trustee may execute and deliver a Supplemental Indenture (i) to set forth the particulars, permitted by Section 2.01 of the Indenture, as to which the Series LL Bonds may vary from the bonds of the other series of the First Mortgage Bonds, and (ii) for any purpose not inconsistent with the terms of the Indenture; and

WHEREAS, the making, executing, delivering and recording of this Supplemental Indenture have been duly authorized by proper corporate action of the Corporation; and

WHEREAS, the issuance of the Series LL Bonds and the encumbrance of the Corporation’s property to secure the Series LL Bonds pursuant to this Supplemental Indenture have been authorized by the Public Utilities Commission of the State of California:

NOW, THEREFORE, in consideration of the foregoing premises and of other good and valuable consideration, receipt of which is hereby acknowledged, and in order: (a) to set forth or

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specify (i) the form of the fully registered Series LL Bonds, and the form of the certificate to be endorsed on all Series LL Bonds, and (ii) the terms and provisions of the Series LL Bonds, including the particulars thereof which vary from the bonds of the other series of the First Mortgage Bonds; and (b) further to secure the payment of both the principal of and interest on the bonds of the Corporation now or at any time hereafter outstanding under the Indenture, including specifically, but without limitation, all of the First Mortgage Bonds now outstanding and the $250,000,000 aggregate principal amount of Series LL Bonds and further to secure the observance and performance of all of the covenants, agreements and conditions contained in the Indenture, and without in any way limiting the generality or effect of the Indenture insofar as by any provision thereof any of the property therein or hereafter described or referred to is now subject or intended to be subject to the lien and operation thereof, but to such extent confirming such lien and operation, the Corporation has executed and delivered this Supplemental Indenture and has granted, bargained, sold, released, conveyed, mortgaged, assigned, transferred, pledged, set over and confirmed, and does hereby grant, bargain, sell, release, convey, mortgage, assign, transfer, pledge, set over and confirm unto U.S. Bank National Association, the Trustee, and to its successors or successors in the trust created by the Indenture, and to its and their assigns, forever, with power of sale, subject, to the extent applicable by the terms of the Indenture to any of the properties hereinafter referred to or described, to the exceptions (other than as expressly provided in the granting clauses of the Prior Supplemental Indentures dated respectively as of June 1, 1956, July 1, 1957, October 1, 1959, July 1, 1963, September 1, 1964 and December 1, 1966 with respect to exception (f) set forth on page 67 of the Base Indenture and reading as follows: “(f) Any gas and/or oil acreage, gas and/or oil wells, gas and/or oil reserves, or gas and/or oil leaseholds hereafter acquired by the Corporation, or any property or equipment now or hereafter owned by the Corporation and used for the development of gas and/or oil acreage or for the drilling for or production of gas and/or oil from such acreage;” which exception (f) is by said granting clauses expressly made inapplicable to certain therein specified parcels of property), reservations, conditions, terms and provisions provided in the Indenture with respect to properties subject or intended to be subject thereto, all of the properties and assets of the Corporation, real, personal and mixed, of every kind and character, whether now or hereafter owned by the Corporation and wheresoever situated, including, without in any way limiting or modifying the generality or effect of the foregoing, all and singular, the following properties:

FIRST: All and singular the plants, properties, equipment, real and personal property, estates, interests, goodwill, generating, transmission, feeding, storing, and distribution systems, and utilities of the Corporation situated in the Counties of Fresno, Imperial, Kern, Kings, Los Angeles, Orange, Riverside, San Bernardino, San Diego, San Luis Obispo, Santa Barbara, Tulare and Ventura, and elsewhere, in the State of California, with all and singular the franchises, ordinances, grants, easements, licenses, powers, immunities, permits, privileges, appurtenances, tenements and other rights and property thereunto appertaining or belonging, as the same now exist and as the same and any and all parts thereof may hereafter exist or be improved, added to, enlarged, extended or acquired in said counties or elsewhere in said state or any other state or states.

SECOND: All other property, real, personal and mixed, of every kind, nature and description (including, without in any way limiting the effect or the generality hereof, all facilities; all stocks, bonds and other securities from time to time conveyed, assigned, transferred, mortgaged or pledged on behalf of the Corporation, or with its consent, to the

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Trustee in the manner and for the purposes as provided in the Indenture; all gas manufacturing plants, boilers, engines, compressors, motors, pumps, generators, gasholders, tanks, appliances, oil storage facilities, gas storage facilities, wells, buildings, structures, plants, works and other improvements; all gas transmission and distributing lines and systems; all meters and regulators and all other apparatus, machinery, appliances, tools, furniture, fixtures, supplies, facilities and utilities and other personal property; or any right or interest in any thereof; all business and goodwill, rights, consents, franchises, ordinances, licenses, agreements, contracts, permits, easements, rights of way, leases and leasehold interests; powers, grants, privileges and immunities to construct, operate and maintain lines and other facilities or properties for conveying gas or other commodity or utility for any purpose or purposes through, under and over public streets or highways, or public or private places or property; all reversions, remainders, tolls, incomes, revenues, earnings, rents, issues and profits of any property, real, personal and mixed; and all other classes and types of property described or referred to in the Indenture), now or hereafter owned, held, possessed, acquired or enjoyed by or in any manner conferred upon or appertaining to the Corporation, including the interest of the Corporation in all leases now or hereafter owned by it, together with all and singular the tenements, hereditaments, and appurtenances belonging or in any way appertaining to each and every part of any and all property subject or intended to be subject to the lien and operation of the Indenture, and the reversion and reversions, remainder and remainders, tolls, incomes, revenues, earnings, rents, issues and profits thereof.

SAVING AND EXCEPTING, however, from the property hereby mortgaged, conveyed in trust and/or pledged, all property, whether now owned by the Corporation or hereafter acquired by it, expressly saved and excepted from the lien of the Indenture and therein referred to as the “excepted property” (except as otherwise expressly provided in any Prior Supplemental Indenture hereinabove mentioned with respect to exception (f) of said “excepted property”), unless and until, upon the occurrence of an event of default under the Indenture, the Trustee, or any receiver appointed thereunder, shall take possession of any or all of such excepted property.

TO HAVE AND TO HOLD in trust with power of sale for the equal and proportionate benefit and security of all holders of bonds of the Corporation, now or hereafter outstanding under the Indenture as from time to time in effect, and for the enforcement and payment of said bonds and interest thereon when payable, and the performance of and compliance with the covenants and conditions of the Indenture as from time to time in effect, without any preference, distinction or priority as to lien or otherwise of any of said bonds over any others thereof by reason of the difference in the time of the actual issue, sale or negotiation thereof, or for any other reason whatsoever, except as otherwise expressly provided in the Indenture as from time to time in effect, so that each and every such bond shall have the same lien and so that the principal and interest of every such bond shall, subject to the terms thereof, be equally and proportionately secured by said lien, as if such bond had been made, executed, delivered, sold and negotiated simultaneously with the execution and delivery of the Base Indenture.

IT IS HEREBY COVENANTED, DECLARED, AND AGREED by and between the parties hereto that all such bonds are issued, authenticated and delivered, or are to be issued, authenticated and delivered, and that all property subject, or to become subject, to the Indenture is to be held, subject to the covenants, conditions, uses and trusts therein set forth.

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ARTICLE I

AMOUNT, FORM, NUMBERING, DENOMINATION,

TRANSFER AND EXCHANGE OF

SERIES LL BONDS, DUE 2014

Section 1.01. The Series LL Bonds may be issued at any time or from time to time upon and subject to the terms and provisions of the Indenture. Unless and until the taking of further appropriate action by the Board of Directors of the Corporation the Series LL Bonds shall be without limitation as to aggregate authorized principal amount.

Section 1.02. The Series LL Bonds shall be issued only as fully registered bonds without coupons. In addition, the Series LL Bonds may be issuable in whole or in part in the form of one or more securities that evidences all or part of the bonds of such series which is issued to a depository or a nominee thereof for such series (a “ Global Security ”) and, in such case, the Board of Directors shall appoint a clearing agency registered under the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), designated to act as depositary (a “ depositary ”) for such Global Securities.

Section 1.03. In the event the Series LL Bonds are issued as a Global Security the following provisions, in addition to the provisions of the Indenture, shall apply:

(a) Each Global Security authenticated under the Indenture shall be registered in the name of the depositary designated for such Global Security or a nominee thereof and delivered to such depositary or a nominee thereof or custodian therefor, and each such Global Security shall constitute a single bond for all purposes of this Supplemental Indenture.

(b) Notwithstanding any other provision in this Supplemental Indenture, no Global Security may be exchanged in whole or in part for bonds registered, and no transfer of a Global Security in whole or in part may be registered, in the name of any person other than the depositary for such Global Security or a nominee thereof unless (A) such depositary has notified the Corporation that it is unwilling or unable to continue as depositary for such Global Security and a successor depositary has not been appointed by the Corporation within 90 days of receipt by the Corporation of such notification, (B) if at any time the depositary ceases to be a clearing agency registered under the Exchange Act at a time when the depositary is required to be so registered to act as such depositary and no successor depositary shall have been appointed by the Corporation within 90 days after it became aware of such cessation, (C) the Corporation, in its sole discretion, executes and delivers to the Trustee a written order signed in the name of the Corporation by its Chairman of the Board, its President or a Vice President, and by its Treasurer, an Assistant Treasurer, its Secretary or an Assistant Secretary to the effect that such Global Security, together with all other Global Securities of the same series, shall be exchangeable as described below, or (D) an Event of Default (as defined in Section 1.02 of the Indenture) has occurred and is continuing with respect to the Series LL Bonds. If any of the events described in clauses (A) through (D) of the preceding sentence occur, the beneficial owners of interests in the relevant Global Securities will be entitled to

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exchange those interests for definitive bonds and, without unnecessary delay but in any event not later than the earliest date on which those interests may be so exchanged, the Corporation will deliver to the Trustee definitive bonds in such form and denominations as are required by or pursuant to this Indenture, and of the same series, containing identical terms and in an aggregate principal amount equal to the principal amount of such Global Securities, such bonds to be duly executed by the Corporation. On or after the earliest date on which such beneficial interests may be so exchanged, such Global Securities shall be surrendered from time to time by the depositary as shall be specified in the order from th