Exhibit 4.A - Third Supplemental Indenture


    EXHIBIT
      4.A

     

    Execution
      Copy

     

    


     

    COLORADO
      INTERSTATE GAS COMPANY

     

    


     

    as
      Issuer

     

    


     

    and

     

    


     

    THE
      BANK OF
      NEW YORK TRUST COMPANY, N.A.

     

    


     

    as
      Trustee

     

    


     

    THIRD
      SUPPLEMENTAL INDENTURE

     

    


     

    Dated
      as of
      November 1, 2005

     

    


     

    To

     

    INDENTURE

     

    Dated
      as of
      June 27, 1997

     

    


     

    6.80%
      SENIOR NOTES
      DUE
      2015

     

    


     

    


     

    


     

    


     


    
      
        
           

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

        
        

      

    



    TABLE
      OF
      CONTENTS

     

     

    Page

    


    
      	
              ARTICLE
                1
                Relation to Indenture; Definitions

            	
              1

            
	 	
              SECTION
                1.01.

            	
              Relation
                to
                Indenture 

            	
              1

            
	 	
              SECTION
                1.02.

            	
              Definitions

            	
              1

            
	 	
              SECTION
                1.03.

            	
              General
                References

            	
              1

            
	 	 	 	 
	
              ARTICLE
                2
                The Series
                of Securities

            	
              2

            
	 	
              SECTION
                2.01.

            	
              The
                Form and
                Title of the Securities

            	
              2

            
	 	
              SECTION
                2.02.

            	
              Amount

            	
              2

            
	 	
              SECTION
                2.03.

            	
              Stated
                Maturity

            	
              2

            
	 	
              SECTION
                2.04.

            	
              Interest
                and
                Interest Rates

            	
              2

            
	 	
              SECTION
                2.05.

            	
              Place
                of
                Payment

            	
              2

            
	 	
              SECTION
                2.06.

            	
              Optional
                Redemption

            	
              2

            
	 	
              SECTION
                2.07.

            	
              Discharge

            	
              3

            
	 	
              SECTION
                2.08.

            	
              Global
                Securities; Restrictions on Transfer and Exchange

            	
              3

            
	 	
              SECTION
                2.09.

            	
              Transfer
                and
                Exchange

            	
              3

            
	 	
              SECTION
                2.10.

            	
              Legends

            	
              4

            
	 	
              SECTION
                2.11.

            	
              Registration
                Rights Agreement

            	
              5

            
	 	 
	
              ARTICLE
                3
                Covenants;
                Amendments to Indenture

            	
              5

            
	 	
              SECTION
                3.01.

            	
              Additional
                Covenant

            	
              5

            
	 	
              SECTION
                3.02.

            	
              Amendments
                to
                Indenture

            	
              6

            
	 	 	 	 
	
              ARTICLE
                4
                Miscellaneous

            	
              7

            
	 	
              SECTION
                4.01.

            	
              Certain
                Trustee Matters

            	
              7

            
	 	
              SECTION
                4.02.

            	
              Continued
                Effect

            	
              8

            
	 	
              SECTION
                4.03.

            	
              Governing
                Law

            	
              8

            
	 	
              SECTION
                4.04.

            	
              Counterparts

            	
              8

            


    

    


     

    EXHIBITS

     

    Exhibit
      A: Form
      of
      Note

     

    


     

    


     

    


     


    
      
        
          Third
            Supplemental Indenture

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

        
        

      

    



    THIRD
      SUPPLEMENTAL INDENTURE,
      dated as of
      November 1, 2005 (this “Third
      Supplemental Indenture”),
      between
COLORADO
      INTERSTATE GAS COMPANY,
      a Delaware
      corporation (the “Company”),
      and
THE
      BANK OF
      NEW YORK TRUST COMPANY, N.A.,
      a national
      banking association (successor-in-interest to Harris Trust and Savings Bank),
      as
      trustee under the Indenture referred to below (in such capacity, the
“Trustee”).

     

    RECITALS
      OF
      THE COMPANY

     

    WHEREAS,
      the
      Company and the Trustee are parties to an Indenture, dated as of June 27, 1997
      (the “Original
      Indenture”),
      as amended and
      supplemented by the First Supplemental Indenture thereto dated as of June 27,
      1997 (the “First
      Supplemental Indenture”),
      and the Second
      Supplemental Indenture thereto dated as of March 9, 2005 (the “Second
      Supplemental Indenture”)
      (the Original
      Indenture, as supplemented from time to time, including without limitation
      pursuant to the First Supplemental Indenture and the Second Supplemental
      Indenture and pursuant to this Third Supplemental Indenture being referred
      to
      herein as the “Indenture”);
      and

     

    WHEREAS,
      under the
      Original Indenture, a new series of Securities may at any time be established
      by
      the Board of Directors of the Company, in accordance with the provisions of
      the
      Original Indenture, and the terms of such series may be established by a
      supplemental indenture executed by the Company and by the Trustee;
      and

     

    WHEREAS,
      the
      Company proposes to create under the Indenture a new series of Securities;
      and

     

    WHEREAS,
      all acts
      and things necessary to make the Notes (as herein defined), when executed by
      the
      Company and authenticated and delivered by the Trustee as provided in the
      Original Indenture and this Third Supplemental Indenture, the valid and binding
      obligations of the Company and to make this Third Supplemental Indenture a
      valid
      and binding agreement in accordance with the Original Indenture have been done
      or performed; and

     

    WHEREAS,
      the
      Company has entered into a Registration Rights Agreement dated as of November
      1,
      2005 (the “Registration
      Rights Agreement”)
      relating to the
      Notes, among the Company and the initial purchasers named therein (the
“Initial
      Purchasers”);

     

    NOW,
      THEREFORE, in
      consideration of the premises, agreements and obligations set forth herein
      and
      for other good and valuable consideration, the receipt and sufficiency of which
      are hereby acknowledged, the parties hereto hereby agree, for the equal and
      proportionate benefit of all Holders of the Notes, as follows:

     

    ARTICLE
      1

    Relation
      to
      Indenture; Definitions

     

    SECTION
      1.01.   Relation
      to Indenture. 

     

    With
      respect to the
      Notes, this Third Supplemental Indenture constitutes an integral part of the
      Indenture.

     

    SECTION
      1.02.   Definitions. 

     

    For
      all purposes of
      this Third Supplemental Indenture, capitalized terms used herein and not
      otherwise defined herein shall have the meanings assigned thereto in the
      Original Indenture.

     

    SECTION
      1.03.   General
      References. 

     

    All
      references in
      this Third Supplemental Indenture to Articles and Sections, unless otherwise
      specified, refer to the corresponding Articles and Sections of this Third
      Supplemental Indenture; and the terms “herein”,
“hereof”,
“hereunder”
      and any other
      word of similar import refers to this Third Supplemental Indenture.

     

    ARTICLE
      2

    The
      Series
      of Securities

     

    SECTION
      2.01.   The
      Form and Title of the Securities. 

     

    There
      is hereby
      established a new series of Securities to be issued under the Indenture and
      to
      be designated as the Company’s 6.80% Senior Notes due 2015 (the “Notes”).
      The Notes shall
      be substantially in the form attached as Exhibit A
      hereto, in each
      case with such appropriate insertions, omissions, substitutions and other
      variations as are required or permitted by the Indenture, and may have such
      letters, numbers or other marks of identification and such legends or
      endorsements placed thereon as the Company may deem appropriate or as may be
      required or appropriate to comply with any laws or with any rules made pursuant
      thereto or with the rules of any securities exchange or automated quotation
      system on which the Notes may be listed or traded, or to conform to general
      usage, or as may, consistently with the Indenture, be determined by the officers
      executing such Notes, as evidenced by their execution thereof.

     

    The
      Notes shall be
      executed, authenticated and delivered in accordance with the provisions of,
      and
      shall in all respects be subject to, the terms, conditions and covenants of
      the
      Original Indenture as supplemented by this Third Supplemental Indenture
      (including the form of Note set forth as Exhibit A
      hereto (the terms
      of which are incorporated in and made a part of this Third Supplemental
      Indenture for all intents and purposes)).

     

    SECTION
      2.02.   Amount. 

     

    The
      aggregate
      principal amount of the Notes which may be authenticated and delivered pursuant
      hereto is unlimited. The Trustee shall initially authenticate and deliver Notes
      for original issue in an initial aggregate principal amount of up to
      $400,000,000 upon delivery to the Trustee of a Company Order for the
      authentication and delivery of such Notes. The Company may, from time to time,
      without notice to or the consent of the Holders of the Notes, increase the
      principal amount of the Notes under the Indenture and issue such increased
      principal amount (or any portion thereof), in which case any additional Notes
      so
      issued will have the same form and terms (other than the date of issuance and,
      under certain circumstances, the date from which interest thereon will begin
      to
      accrue), and will carry the same right to receive accrued and unpaid interest,
      as the Notes previously issued, and such additional Notes will form a single
      series with the Notes previously issued.

     

    SECTION
      2.03.   Stated
      Maturity.

     

    The
      Notes may be
      issued on any Business Day on or after November 1, 2005, and the Stated Maturity
      of the Notes shall be November 15, 2015.

     

    SECTION
      2.04.   Interest
      and Interest Rates. 

     

    The
      rate or rates
      at which the Notes shall bear interest, the date or dates from which such
      interest shall accrue, the Interest Payment Dates on which any such interest
      shall be payable and the Regular Record Date for any interest payable on any
      Interest Payment Date, in each case, shall be as set forth in the form of Note
      set forth as Exhibit A
      hereto.

     

    SECTION
      2.05.   Place
      of Payment. 

     

    As
      long as any
      Notes are outstanding, the Company shall maintain an office or agency in the
      Borough of Manhattan, The City of New York, where Notes may be presented for
      payment.

     

    SECTION
      2.06.   Optional
      Redemption.

     

    At
      its option, the
      Company may redeem the Notes, in whole or in part, in principal amounts of
      $1,000 or any integral multiple thereof, at any time or from time to time,
      at
      the applicable redemption price determined as set forth in the form of Note
      attached hereto as Exhibit
      A,
      in accordance with the terms set forth in the Notes and in accordance with
      Article 3A of the Original Indenture.

     

    SECTION
      2.07.   Discharge.

     

    Article
      8 of the
      Original Indenture shall apply to the Notes.

     

    SECTION
      2.08.   Global
      Securities; Restrictions on Transfer and Exchange. 

     

    The
      Notes shall
      initially be issued in the form of one or more Global Securities. Such Global
      Securities (i)  shall bear the legends applicable to Global Securities
      set
      forth in the Original Indenture (including without limitation in Section 2.03
      thereof), (ii) may be exchanged in whole or in part for Securities in
      definitive form upon the terms and subject to the conditions provided in
      Section 2.07 of the Original Indenture and in this Third Supplemental
      Indenture and (iii) shall otherwise be subject to the applicable provisions
      of the Indenture.

     

    (1)  Rule
      144A
      Global Notes.
      The Notes offered
      and sold to “qualified institutional buyers” (“QIBs”
      or individually,
      a “QIB”)
      (which term
      shall have the meaning assigned to it in Rule 144A under the Securities Act
      of
      1933, as amended (the “Securities
      Act”))
      in the United
      States of America in reliance on Rule 144A will initially be issued as permanent
      Global Securities (the “Rule
      144A Global Notes”),
      without
      interest coupons, substantially in the form of Exhibit
      A
      hereto. The Rule 144A Global Notes will be duly executed by the Company,
      authenticated by the Trustee, deposited with the Trustee (as custodian for
      The
      Depository Trust Company (“DTC”),
      which shall act
      as Depository with respect to the Notes constituting Global Securities) and
      registered in the name of DTC or a nominee thereof.

     

    (2)  Regulation
      S
      Global Notes.
      Notes offered and
      sold in Offshore Transactions to Non-U.S. Persons (each such term to have the
      meaning assigned to it in Regulation S under the Securities Act (“Regulation
      S”))
      in reliance on
      Regulation S will initially be issued as permanent Global Securities (the
“Regulation
      S Global Notes”),
      without
      interest coupons, substantially in the form of Exhibit
      A
      hereto. The Regulation S Global Notes will be duly executed by the Company,
      authenticated by the Trustee, deposited with the Trustee (as custodian for
      DTC)
      and registered in the name of DTC or a nominee thereof.

     

    SECTION
      2.09.   Transfer
      and Exchange. 

     

    (1)  Transfer
      and
      Exchange of Notes in Certificated Form.
      In addition to
      the requirements set forth in Section 2.07 of the Original Indenture, the Notes
      in certificated form that are Registrable Securities under the Registration
      Rights Agreement (the “Transfer
      Restricted Securities”)
      presented or
      surrendered for registration of transfer or exchange pursuant to Section 2.07
      of
      the Original Indenture shall be accompanied by the following additional
      information and documents, as applicable, upon which the Registrar may
      conclusively rely:

     

    (a)  if
      such Transfer
      Restricted Securities are being delivered to the Registrar by a Holder for
      registration in the name of such Holder, without transfer, a certification
      from
      such Holder to that effect (in substantially the form of the Exchange/Transfer
      Certificate included in Exhibit
      A
      hereto); or

     

    (b)  if
      such Transfer
      Restricted Securities are being transferred (1) to a QIB in accordance with
      Rule
      144A under the Securities Act or (2) pursuant to an exemption from registration
      in accordance with Rule 144 under the Securities Act (and based upon an opinion
      of counsel if the Company or the Trustee so requests) or (3) pursuant to an
      effective registration statement under the Securities Act, a certification
      to
      that effect from such holder (in substantially the form of the Exchange/Transfer
      Certificate included in Exhibit
      A
      hereto); or

     

    (c)  if
      such Transfer
      Restricted Securities are being transferred pursuant to an exemption from
      registration in accordance with Rule 904 of Regulation S under the Securities
      Act, certifications to that effect from such Holder (in substantially the form
      of both (i) the Exchange/Transfer Certificate included in Exhibit
      A
      hereto and (ii) the Regulation S Certificate included in Exhibit
      A
      hereto) and an opinion of counsel to that effect if the Company or the Trustee
      so requests; or

     

    (d)  if
      such Transfer
      Restricted Securities are being transferred in reliance on and in compliance
      with another exemption from the registration requirements of the Securities
      Act,
      a certification to that effect from such Holder (in substantially the form
      of
      the Exchange/Transfer Certificate included in Exhibit
      A
      hereto) and an opinion of counsel to that effect if the Company or the Trustee
      so requests.

     

    (2)  Transfer
      and
      Exchange of Global Notes.
      The transfer and
      exchange of the Global Notes (as defined below) or beneficial interests therein
      shall be effected through the Depository, upon the terms and subject to the
      conditions provided in Section 2.07 of the Original Indenture and Article 2
      of
      this Third Supplemental Indenture (including the restrictions on transfer set
      forth therein and herein) and the rules and procedures of the Depository
      therefor, which shall include restrictions on transfer comparable to those
      set
      forth therein and herein to the extent required by the Securities
      Act.

     

    SECTION
      2.10.   Legends. 

     

    (1)  Except
      as permitted
      by the following paragraphs (2) and (3) immediately below, each certificate
      evidencing the Rule 144A Global Notes or Regulation S Global Notes (each a
      “Global
      Note”)
      or any other
      Notes in certificated form (and all Notes issued in exchange therefor or
      substitution thereof other than the Exchange Notes (as defined below)) shall
      bear a legend in substantially the following form:

     

    THIS
      NOTE HAS NOT
      BEEN REGISTERED UNDER THE U.S. SECURITIES ACT OF 1933, AS AMENDED (THE
“SECURITIES ACT”) AND, ACCORDINGLY, MAY NOT BE OFFERED, SOLD, PLEDGED OR
      OTHERWISE TRANSFERRED WITHIN THE UNITED STATES OR TO, OR FOR THE ACCOUNT OR
      BENEFIT OF, U.S. PERSONS, EXCEPT AS SET FORTH IN THE FOLLOWING SENTENCE. BY
      ITS
      ACQUISITION HEREOF OR OF A BENEFICIAL INTEREST HEREIN, THE HOLDER (1) REPRESENTS
      THAT (A) IT IS A “QUALIFIED INSTITUTIONAL BUYER” (AS DEFINED IN RULE 144A UNDER
      THE SECURITIES ACT) (A “QIB”), (B) IT IS NOT A U.S. PERSON, IS NOT ACQUIRING
      THIS NOTE FOR THE ACCOUNT OR BENEFIT OF A U.S. PERSON AND IS ACQUIRING THIS
      NOTE
      IN AN OFFSHORE TRANSACTION IN COMPLIANCE WITH REGULATION S UNDER THE SECURITIES
      ACT OR (C) IT IS AN INSTITUTIONAL “ACCREDITED INVESTOR” (AS DEFINED IN RULE
      501(A)(1), (2), (3) OR (7) OF REGULATION D UNDER THE SECURITIES ACT) (AN “IAI”),
      (2) AGREES THAT IT WILL NOT, WITHIN THE TIME PERIOD REFERRED TO UNDER RULE
      144(k) (TAKING INTO ACCOUNT THE PROVISIONS OF RULE 144(d) UNDER THE SECURITIES
      ACT, IF APPLICABLE) UNDER THE SECURITIES ACT AS IN EFFECT ON THE DATE OF THE
      TRANSFER OF THIS NOTE, RESELL OR OTHERWISE TRANSFER THIS NOTE EXCEPT (A) TO
      THE
      ISSUER OR ANY SUBSIDIARY THEREOF, (B) TO A PERSON WHOM THE HOLDER REASONABLY
      BELIEVES IS A QIB PURCHASING FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A QIB
      IN
      COMPLIANCE WITH RULE 144A UNDER THE SECURITIES ACT, (C) OUTSIDE THE UNITED
      STATES IN AN OFFSHORE TRANSACTION IN COMPLIANCE WITH RULE 904 UNDER THE
      SECURITIES ACT, (D) PURSUANT TO THE EXEMPTION FROM REGISTRATION PROVIDED BY
      RULE
      144 UNDER THE SECURITIES ACT (IF AVAILABLE), (E) TO AN IAI THAT, PRIOR TO SUCH
      TRANSFER, FURNISHES TO THE TRUSTEE A SIGNED LETTER CONTAINING CERTAIN
      REPRESENTATIONS AND AGREEMENTS RELATING TO THE REGISTRATION OF TRANSFER OF
      THIS
      NOTE (THE FORM OF WHICH LETTER CAN BE OBTAINED FROM THE TRUSTEE) AND, IF SUCH
      TRANSFER IS IN RESPECT OF AN AGGREGATE PRINCIPAL AMOUNT OF NOTES AT THE TIME
      OF
      TRANSFER OF LESS THAN $250,000, AN OPINION OF COUNSEL ACCEPTABLE TO THE ISSUER
      THAT SUCH TRANSFER IS IN COMPLIANCE WITH THE SECURITIES ACT OR (F) PURSUANT
      TO
      AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT AND, IN EACH CASE,
      IN ACCORDANCE WITH APPLICABLE STATE SECURITIES LAWS, AND (3) AGREES THAT IT
      WILL
      DELIVER TO EACH PERSON TO WHOM THIS NOTE OR AN INTEREST HEREIN IS TRANSFERRED
      A
      NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND. IN CONNECTION WITH ANY
      TRANSFER OF THIS NOTE OR ANY INTEREST HEREIN WITHIN THE TIME PERIOD REFERRED
      TO
      ABOVE, THE HOLDER MUST CHECK THE APPROPRIATE BOX SET FORTH ON THE REVERSE HEREOF
      RELATING TO THE MANNER OF SUCH TRANSFER AND SUBMIT THIS CERTIFICATE TO THE
      TRUSTEE. AS USED HEREIN, THE TERMS “OFFSHORE TRANSACTION,”“UNITED STATES” AND
“U.S. PERSON” HAVE THE MEANINGS GIVEN TO THEM BY RULE 902 OF REGULATION S UNDER
      THE SECURITIES ACT. THE INDENTURE CONTAINS A PROVISION REQUIRING THE TRUSTEE
      TO
      REFUSE TO REGISTER ANY TRANSFER OF THIS NOTE IN VIOLATION OF THE FOREGOING
      RESTRICTIONS.

     

    (2)  Upon
      any sale or
      transfer of a Transfer Restricted Security (including any Transfer Restricted
      Security represented by a Global Note) pursuant to Rule 144 under the Securities
      Act or an effective registration statement under the Securities Act, which
      effectiveness shall be certified by the Company to the Trustee and Registrar
      upon which each may conclusively rely:

     

    (a)  in
      the case of any
      Transfer Restricted Security in definitive form, the Registrar shall permit
      the
      Holder thereof to exchange such Transfer Restricted Security for a Note in
      definitive form that does not bear the legend set forth in (1) above and rescind
      any restriction on the transfer of such Transfer Restricted Security;
      and

     

    (b)  in
      the case of any
      Transfer Restricted Security represented by a Global Note, such Transfer
      Restricted Security shall not be required to bear the legend(s) set forth in
      (1)
      above if all other interests in such Global Note have been or are concurrently
      being sold or transferred pursuant to Rule 144 under the Securities Act or
      pursuant to an effective registration statement under the Securities Act, but
      such Transfer Restricted Security shall continue to be subject to the provisions
      of Section 2.07 of the Original Indenture and this Section 2.10 of this Third
      Supplemental Indenture.

     

    (3)  Notwithstanding
      the
      foregoing, upon consummation of the Exchange Offer (as defined in the
      Registration Rights Agreement), the Company shall issue and, upon receipt of
      a
      Company Order in accordance with Section 2.03 of the Original Indenture, the
      Trustee shall authenticate Notes (“Exchange
      Notes”)
      in exchange for
      Notes accepted for exchange in the Exchange Offer, which Exchange Notes shall
      not bear the legend set forth in (1) above, and the Registrar shall rescind
      any
      restriction on the transfer of the Exchange Notes, in each case unless the
      Holder of Notes being transferred in the Exchange Offer is either (A) a
      broker-dealer tendering Notes acquired directly from the Company, (B) a person
      participating in the Exchange Offer for purposes of distributing the Exchange
      Notes or (C) a person who is an “affiliate” (as defined in Rule 144 under the
      Securities Act) of the Company. The Company shall identify to the Trustee such
      Holders of the Notes in a written certification signed by an Officer of the
      Company and, absent receipt of a certificate from the Company to such effect,
      the Trustee shall assume that there are no such Holders.

     

    SECTION
      2.11.   Registration
      Rights Agreement. 

     

    Holders
      of the
      Notes shall have the benefit of the Company’s registration obligations with
      respect to the Notes, and such Holders shall also have certain obligations
      to
      indemnify the Company under certain circumstances, all as more fully set forth
      in the Registration Rights Agreement.

     

    ARTICLE
      3

    Covenants;
      Amendments to Indenture

     

    SECTION
      3.01.   Additional
      Covenant

     

    The
      covenant
      contained in this Section 3.01 shall apply to the Notes only and not to any
      other series of Securities issued under the Indenture, and is being included
      solely for the benefit of the Notes and the Holders thereof. This covenant
      shall
      be effective only for so long as there remain outstanding any
      Notes.

     

    SEC
      Reports;
      Financial Statements.
      In addition to
      the requirements of Section 4.05 of the Original Indenture:

     

    (1) whether
      or not the
      Company is then subject to Section 13 or 15(d) of the Exchange Act, from and
      after the Original Issue Date of the Notes, the Company shall electronically
      file with the SEC, so long as the Notes are outstanding, the annual, quarterly
      and other periodic reports that the Company is required to file (or would
      otherwise be required to file) with the SEC pursuant to Sections 13 and 15(d)
      of
      the Exchange Act, and such documents shall be filed with the SEC on or prior
      to
      the respective dates (the “Required
      Filing Dates”)
      by which the
      Company is required to file (or would otherwise be required to file) such
      documents, unless, in each case, such filings are not then permitted by the
      SEC;

     

    (2) from
      and after the
      Original Issue Date of the Notes, the Company shall provide the Trustee with,
      and the Trustee will mail to any Holder of Notes requesting in writing to the
      Trustee copies of, such annual, quarterly and other periodic reports specified
      in Sections 13 and 15(d) of the Exchange Act within 15 days after its Required
      Filing Date;

     

    (3) in
      addition, for so
      long as the Notes are not freely transferable under the Securities Act, the
      Company shall furnish to the Holders of Notes and to prospective investors
      in
      the Notes, the information required to be delivered pursuant to Rule 144A(d)(4)
      under the Securities Act;

     

    (4) the
      Company shall
      provide the Trustee with a sufficient number of copies of all reports and other
      documents and information that the Trustee may be required to deliver to Holders
      of Notes under clause (2) of this Section 3.01; and

     

    (5) delivery
      of such
      reports, information and documents to the Trustee is for informational purposes
      only and the Trustee’s receipt of such shall not constitute constructive notice
      of any information contained therein or determinable from information contained
      therein, including the Company’s compliance with any of its covenants hereunder
      (as to which the Trustee is entitled to rely exclusively on Officers’
      Certificates).

     

    SECTION
      3.02.   Amendments
      to Indenture

     

    The
      amendments
      contained in this Section 3.02 shall apply to the Notes only and not to any
      other series of Securities issued under the Indenture. Such amendments shall
      be
      effective only for so long as there remain outstanding any Notes.

     

    (a) Section
      1.01 of the
      Original Indenture is hereby amended, subject to the preamble of this Section
      3.02 and with respect to the Notes only, by inserting the following definition
      in the appropriate alphabetical position:

     

    “Permitted
      Liens”
      means

     

    (1) Liens
      upon
      rights-of-way for pipeline purposes;

     

    (2) any
      governmental
      Lien, mechanics’, materialmen’s, carriers’ or similar Lien incurred in the
      ordinary course of business which is not yet due or which is being contested
      in
      good faith by appropriate proceedings and any undetermined Lien which is
      incidental to construction;

     

    (3) the
      right reserved
      to, or vested in, any municipality or public authority by the terms of any
      right, power, franchise, grant, license, permit or by any provision of law,
      to
      purchase or recapture or to designate a purchase of, any property;

     

    (4) Liens
      of taxes and
      assessments which are (A) for the then current year, (B) not at the time
      delinquent or (C) delinquent but the validity of which is being contested at
      the
      time by the Company or any Subsidiary in good faith;

     

    (5) Liens
      of, or to
      secure performance of leases;

     

    (6) any
      Lien upon, or
      deposits of, any assets in favor of any surety company or clerk of court for
      the
      purposes of obtaining indemnity or stay of judicial proceedings;

     

    (7) any
      Lien upon
      property or assets acquired or sold by the Company or any Subsidiary resulting
      from the exercise of any rights arising out of defaults on
      receivables;

     

    (8) any
      Lien incurred
      in the ordinary course of business in connection with workmen’s compensation,
      unemployment insurance, temporary disability, social security, retiree health
      or
      similar laws or regulations or to secure obligations imposed by statute or
      governmental regulations;

     

    (9) any
      Lien upon any
      property or assets in accordance with customary banking practice to secure
      any
      Indebtedness incurred by the Company or any Subsidiary in connection with the
      exporting of goods to, or between, or the marketing of goods in, or the
      importing of goods from, foreign countries;

     

    (10) any
      Lien securing
      industrial development, pollution control, or similar revenue
      bonds;

     

    (11) Liens
      to secure
      Indebtedness owing to the Company or its Subsidiaries;

     

    (12) Liens
      contemplated
      by the Indenture relating to compensation and other payments to the Trustee;
      and

     

    (13) Liens
      deemed to
      exist by reason of negative pledges in respect of Indebtedness.

     

    (b) Section
      2.03 of the
      Original Indenture is hereby amended, subject to the preamble of this Section
      3.02 and with respect to the Notes only, by deleting the second sentence of
      the
      first paragraph of such Section 2.03.

     

    (c) Section
      4.08 of the
      Original Indenture is hereby amended, subject to the preamble of this Section
      3.02 and with respect to the Notes only, by:

     

    (i) deleting
      the word
“and” immediately following the semicolon appearing in clause (5) of such
      Section 4.08;

     

    (ii) inserting
      the
      following new clause (6) immediately below clause (5) of such Section
      4.08:

     

    (6) Permitted
      Liens;
      and

     

    ;
      and

     

    (iii) renumbering
      and
      restating the former clause (6) of such Section 4.08 to read in its entirety
      as
      follows:

     

    (7) any
      extension,
      renewal or replacement (or successive extensions, renewals or replacements),
      as
      a whole or in part, of any Lien referred to in the foregoing clauses (1) through
      (6) inclusive; provided that such extension, renewal or replacement of such
      Lien
      is limited to all or any part of the same property, shares of stock or
      Indebtedness that secured the Lien extended, renewed or replaced (plus
      improvements on such property), and that such secured Indebtedness at such
      time
      is not increased.

     

    ARTICLE
      4

    Miscellaneous

     

    SECTION
      4.01.   Certain
      Trustee Matters. 

     

    The
      recitals
      contained herein shall be taken as the statements of the Company, and the
      Trustee assumes no responsibility for their correctness.

     

    The
      Trustee makes
      no representations as to the validity or sufficiency of this Third Supplemental
      Indenture or the Notes or the proper authorization or the due execution hereof
      or thereof by the Company.

     

    SECTION
      4.02.   Continued
      Effect. 

     

    Except
      as expressly
      supplemented and amended by this Third Supplemental Indenture, the Original
      Indenture (as supplemented and amended by the First Supplemental Indenture)
      shall continue in full force and effect in accordance with the provisions
      thereof, and the Original Indenture (as supplemented and amended by the First
      Supplemental Indenture and by this Third Supplemental Indenture) is in all
      respects hereby ratified and confirmed. This Third Supplemental Indenture and
      all its provisions shall be deemed a part of the Original Indenture in the
      manner and to the extent herein and therein provided.

     

    SECTION
      4.03.   Governing
      Law. 

     

    This
      Third
      Supplemental Indenture and the Notes shall be governed by and construed in
      accordance with the laws of the State of New York without regard to principles
      of conflicts of law.

     

    SECTION
      4.04.   Counterparts. 

     

    This
      instrument may
      be executed in any number of counterparts, each of which shall be deemed to
      be
      an original, but all such counterparts shall together constitute but one and
      the
      same instrument.

     

    (Signature
      Pages Follow)

     

    


     

    


     

    


     

    


     

     

    


     

    


     


    
      
        
          Third
            Supplemental Indenture

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

        
        

      

    



    IN
      WITNESS WHEREOF,
      the parties hereto have caused this Third Supplemental Indenture to be duly
      executed and delivered, all as of the day and year first above
      written.

     

    COLORADO
      INTERSTATE
      GAS COMPANY

    


    


    By:/s/
      Daniel
      B. Martin        

    Name:
      Daniel B.
      Martin

    Title:
      Senior Vice
      President

    


    


    ATTEST:

    


    By:/s/
      Stacy J.
      James             

    Name:
      Stacy J.
      James

    Title:
      Corporate
      Secretary

    


    


    



    
      
        
          HOU:2509545.3
            

           

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            Supplemental Indenture

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

        
        

      

    



    THE
      BANK OF NEW
      YORK TRUST COMPANY, N.A.

    as
      Trustee

    


    


    By: /s/John
      Stohlmann        

    Authorized
      Signatory

    


    


    ATTEST:

    


    By:
/s/
      Patrick
      T. Giordano         

    Name:
Patrick
      T.
      Giordano     

    Title:
      Vice
      President         

    


    


     


    
      
        
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            Supplemental Indenture

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

        
        

      

    



    EXHIBIT
      A

     

    [FORM
      OF
      FACE OF NOTE]

     

    [If
      a
      Global Security, insert—UNLESS THIS NOTE IS PRESENTED BY AN AUTHORIZED
      REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY (“DTC”) (55 WATER STREET, NEW
      YORK, NEW YORK) TO THE ISSUER OR ITS AGENT FOR REGISTRATION OF TRANSFER,
      EXCHANGE OR PAYMENT AND ANY NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE &
      CO., OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF
      DTC,
      AND ANY PAYMENT IS MADE TO CEDE & CO., OR TO SUCH OTHER ENTITY AS IS
      REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC, ANY TRANSFER, PLEDGE OR OTHER
      USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL, INASMUCH
      AS
      THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST
      HEREIN.]

     

    [If
      a
      Global Security, insert—UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR
      THE INDIVIDUAL NOTES REGISTERED HEREBY, THIS GLOBAL NOTE MAY NOT BE TRANSFERRED
      EXCEPT AS A WHOLE BY DTC TO A NOMINEE OF DTC OR BY A NOMINEE OF DTC TO DTC
      OR
      ANOTHER NOMINEE OF DTC OR BY DTC OR ANY SUCH NOMINEE TO A SUCCESSOR OF DTC
      OR A
      NOMINEE OF SUCH SUCCESSOR.]

     

    [If
      a
      Transfer Restricted Security, insert—THIS NOTE HAS NOT BEEN REGISTERED UNDER THE
      U.S. SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”) AND, ACCORDINGLY,
      MAY NOT BE OFFERED, SOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHIN THE UNITED
      STATES OR TO, OR FOR THE ACCOUNT OR BENEFIT OF, U.S. PERSONS, EXCEPT AS SET
      FORTH IN THE FOLLOWING SENTENCE. BY ITS ACQUISITION HEREOF OR OF A BENEFICIAL
      INTEREST HEREIN, THE HOLDER (1) REPRESENTS THAT (A) IT IS A “QUALIFIED
      INSTITUTIONAL BUYER” (AS DEFINED IN RULE 144A UNDER THE SECURITIES ACT) (A
“QIB”), (B) IT IS NOT A U.S. PERSON, IS NOT ACQUIRING THIS NOTE FOR THE ACCOUNT
      OR BENEFIT OF A U.S. PERSON AND IS ACQUIRING THIS NOTE IN AN OFFSHORE
      TRANSACTION IN COMPLIANCE WITH REGULATION S UNDER THE SECURITIES ACT OR (C)
      IT
      IS AN INSTITUTIONAL “ACCREDITED INVESTOR” (AS DEFINED IN RULE 501(A)(1), (2),
      (3) OR (7) OF REGULATION D UNDER THE SECURITIES ACT) (AN “IAI”), (2) AGREES THAT
      IT WILL NOT, WITHIN THE TIME PERIOD REFERRED TO UNDER RULE 144(k) (TAKING INTO
      ACCOUNT THE PROVISIONS OF RULE 144(d) UNDER THE SECURITIES ACT, IF APPLICABLE)
      UNDER THE SECURITIES ACT AS IN EFFECT ON THE DATE OF THE TRANSFER OF THIS NOTE,
      RESELL OR OTHERWISE TRANSFER THIS NOTE EXCEPT (A) TO THE ISSUER OR ANY
      SUBSIDIARY THEREOF, (B) TO A PERSON WHOM THE HOLDER REASONABLY BELIEVES IS
      A QIB
      PURCHASING FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A QIB IN COMPLIANCE WITH
      RULE 144A UNDER THE SECURITIES ACT, (C) OUTSIDE THE UNITED STATES IN AN OFFSHORE
      TRANSACTION IN COMPLIANCE WITH RULE 904 UNDER THE SECURITIES ACT, (D) PURSUANT
      TO THE EXEMPTION FROM REGISTRATION PROVIDED BY RULE 144 UNDER THE SECURITIES
      ACT
      (IF AVAILABLE), (E) TO AN IAI THAT, PRIOR TO SUCH TRANSFER, FURNISHES TO THE
      TRUSTEE A SIGNED LETTER CONTAINING CERTAIN REPRESENTATIONS AND AGREEMENTS
      RELATING TO THE REGISTRATION OF TRANSFER OF THIS NOTE (THE FORM OF WHICH LETTER
      CAN BE OBTAINED FROM THE TRUSTEE) AND, IF SUCH TRANSFER IS IN RESPECT OF AN
      AGGREGATE PRINCIPAL AMOUNT OF NOTES AT THE TIME OF TRANSFER OF LESS THAN
      $250,000, AN OPINION OF COUNSEL ACCEPTABLE TO THE ISSUER THAT SUCH TRANSFER
      IS
      IN COMPLIANCE WITH THE SECURITIES ACT OR (F) PURSUANT TO AN EFFECTIVE
      REGISTRATION STATEMENT UNDER THE SECURITIES ACT AND, IN EACH CASE, IN ACCORDANCE
      WITH APPLICABLE STATE SECURITIES LAWS, AND (3) AGREES THAT IT WILL DELIVER
      TO
      EACH PERSON TO WHOM THIS NOTE OR AN INTEREST HEREIN IS TRANSFERRED A NOTICE
      SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND. IN CONNECTION WITH ANY TRANSFER
      OF
      THIS NOTE OR ANY INTEREST HEREIN WITHIN THE TIME PERIOD REFERRED TO ABOVE,
      THE
      HOLDER MUST CHECK THE APPROPRIATE BOX SET FORTH ON THE REVERSE HEREOF RELATING
      TO THE MANNER OF SUCH TRANSFER AND SUBMIT THIS CERTIFICATE TO THE TRUSTEE.
      AS
      USED HEREIN, THE TERMS “OFFSHORE TRANSACTION,”“UNITED STATES” AND “U.S. PERSON”
      HAVE THE MEANINGS GIVEN TO THEM BY RULE 902 OF REGULATION S UNDER THE SECURITIES
      ACT. THE INDENTURE CONTAINS A PROVISION REQUIRING THE TRUSTEE TO REFUSE TO
      REGISTER ANY TRANSFER OF THIS NOTE IN VIOLATION OF THE FOREGOING
      RESTRICTIONS.]

     

    COLORADO
      INTERSTATE GAS COMPANY

     

    6.80%
      Senior Note due 2015

     

    
      	
              Rate
                of Interest

               

            	
              Maturity
                Date

               

            	
              Original
                Issue Date

               

            
	
              6.80%

               

            	
              November
                15,
                2015

               

            	
              ________
                __,
                20__

               

            


    

    


     

    
      	
              No.
                _________

               

            	
              U.S.$_____________

               

            
	
              CUSIP
                No.
                ___________

               

            	 


    

    Colorado
      Interstate
      Gas Company, a corporation duly organized and existing under the laws of the
      State of Delaware (herein called the “Company”),
      for value
      received, hereby promises to pay to ___________________________________ or
      registered assigns, the principal sum of __________________________ on the
      maturity date shown above, and to pay interest thereon, at the annual rate
      of
      interest shown above, from the Original Issue Date shown above or from the
      most
      recent Interest Payment Date (as hereinafter defined) to which interest has
      been
      paid or duly provided for, payable semi-annually on May 15 and November 15
      of
      each year (each, an “Interest
      Payment Date”)
      and at such
      maturity date, commencing on the first such date after the Original Issue Date,
      except that if the Original Issue Date is on or after a Regular Record Date
      (as
      defined below) but before the next Interest Payment Date, interest payments
      will
      commence on the second Interest Payment Date following the Original Issue
      Date.

     

    The
      interest so
      payable, and punctually paid or duly provided for, on any Interest Payment
      Date
      will, as provided in the Indenture, be paid to the person in whose name this
      Note is registered at the close of business on the “Regular
      Record Date”
      for any such
      Interest Payment Date, which shall be the fifteenth calendar day (whether or
      not
      a Business Day) preceding the applicable Interest Payment Date. Any such
      interest not so punctually paid or duly provided for, and any interest payable
      on such defaulted interest (to the extent lawful), will 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 Company, notice of which shall be given to Holders of Notes not less than
      15
      days prior to such special record date. Payment of the principal of and interest
      on this Note will be made at the agency of the Company maintained for that
      purpose in New York, New York and at any other office or agency maintained
      by
      the Company for such purpose, in United States dollars; provided,
however,
      that at the
      option of the Company payment of interest, other than interest due on the
      maturity date shown above, may be made by check mailed to the address of the
      person entitled thereto as such address shall appear in the Security
      Register.

     

    Reference
      is hereby
      made to the further provisions of this Note set forth on the reverse hereof,
      which further provisions shall for all purposes have the same effect as if
      set
      forth at this place.

     

    Unless
      the
      certificate of authentication hereon has been executed by the Trustee referred
      to on the reverse hereof by manual signature, this Note shall not be entitled
      to
      any benefit under the Indenture or be valid or obligatory for any
      purpose.

     

    (Signature
      Page
      Follows)

     


    
      
        
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    IN
      WITNESS WHEREOF,
      COLORADO INTERSTATE GAS COMPANY
      has caused this
      instrument to be executed in its corporate name by the signature of its duly
      authorized officers.

     

    COLORADO
      INTERSTATE
      GAS COMPANY

     

    


     

    By: /s/
      Daniel B. Martin                  

                            Name:  Daniel
      B. Martin 

                            Title:    
      Senior Vice President      

     

    ATTEST:

     

    


    By:
/s/
      Stacy J.
      James        

    Name: 
      Stacy J.
      James

    Title:    
      Corporate Secretary

    


     

    


     

    DATED:
     

     

    


     

    TRUSTEE’S
      CERTIFICATE OF AUTHENTICATION

     

    This
      is one of the
      6.80% Senior Notes due 2015 referred to in the within-mentioned
      Indenture.

     

    THE
      BANK OF NEW
      YORK TRUST COMPANY, N.A.

     

    as
      Trustee

     

    


     

    By:       

     

    Authorized
      Signatory

     

    


     

    [REVERSE
      OF
      NOTE]

     


    
      
        
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          A-Third
            Supplemental Indenture

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

      

    


     

    COLORADO
      INTERSTATE GAS COMPANY

     

    6.80%
      Senior Note due 2015

     

    This
      Note is one of
      a duly authorized issue of securities of the Company (which term includes any
      successor corporation under the Indenture hereinafter referred to) designated
      as
      its 6.80% Senior Notes due 2015 (the “Notes”),
      issued or to be
      issued pursuant to an Indenture, dated as of June 27, 1997, between the Company
      and The Bank of New York Trust Company, N.A. (successor-in-interest to Harris
      Trust and Savings Bank), as Trustee (the “Trustee,”
      which term
      includes any successor trustee under such Indenture), as amended and
      supplemented by the First Supplemental Indenture thereto dated as of June 27,
      1997 and the Second Supplemental Indenture thereto dated as of March 9, 2005
      and
      as further amended and supplemented by the Third Supplemental Indenture thereto
      dated as of November 1, 2005 (such Indenture, as so amended and supplemented
      being referred to herein as the “Indenture”).
      The terms of
      this Note include those stated in the Indenture and those made part of the
      Indenture by reference to the Trust Indenture Act of 1939, as amended. Reference
      is hereby made to the Indenture and all further supplemental indentures thereto
      for a statement of the respective rights, limitation of rights, duties and
      immunities thereunder of the Company, the Trustee and the Holders and of the
      terms upon which the Notes are, and are to be, authenticated and delivered.
      

     

    This
      Note is a
      Series of Securities issued or to be issued by the Company under the Indenture.
      The Indenture provides that the Securities of the Company referred to therein
      (“Securities”),
      including the
      Notes, may be issued in one or more Series, which different Series may be issued
      in such aggregate principal amounts and on such terms (including, but not
      limited to, terms relating to interest rate or rates, provisions for determining
      such interest rate or rates and adjustments thereto, maturity, redemption
      (optional and mandatory), sinking fund, covenants and Events of Default) as
      may
      be provided in or pursuant to the Authorizing Resolutions and/or supplemental
      indenture (if any) relating to the several Series.

     

    This
      Note is
      redeemable, in whole or in part, at the Company’s option at any time prior to
      its Stated Maturity at a redemption price equal to the greater of (a) 100%
      of
      the principal amount of this Note, and (b) as determined by the Quotation Agent
      (as defined below), the sum of the present values of the remaining scheduled
      payments of principal and interest (not including any portion of those payments
      of interest accrued as of the date of redemption) discounted to the date of
      redemption on a semi-annual basis (assuming 360-day years, each consisting
      of
      twelve 30-day months), at the Adjusted Treasury Rate (as defined below) plus
      45
      basis points plus, in each case, accrued interest to the date of
      redemption.

     

    For
      purposes of
      determining any redemption price, the following definitions shall
      apply:

     

    “Adjusted
      Treasury Rate”
      means, with
      respect to any date of redemption, the rate per annum equal to the semi-annual
      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 the date of
      redemption.

     

    “Comparable
      Treasury Issue”
      means the United
      States Treasury security selected by the Quotation Agent as having a maturity
      comparable to the remaining term of this Note 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
      remaining term of this Note.

     

    “Comparable
      Treasury Price”
      means, with
      respect to any date of redemption, (a) the average of the Reference Treasury
      Dealer Quotations for the date of redemption, after excluding the highest and
      lowest Reference Treasury Dealer Quotations, or (b) if the Trustee obtains
      fewer
      than three Reference Treasury Dealer Quotations, the average of all such
      Reference Treasury Dealer Quotations.

     

    “Quotation
      Agent”
      means Citigroup
      Global Markets Inc. or another Reference Treasury Dealer appointed by the
      Company.

     

    “Reference
      Treasury Dealer”
      means (a)
      Citigroup Global Markets Inc. and its respective successors; provided,
however,
      that if the
      foregoing shall cease to be a primary U.S. Government securities dealer in
      New
      York City (a “Primary
      Treasury Dealer”),
      the Company
      shall substitute another Primary Treasury Dealer; and (b) any other Primary
      Treasury Dealers selected by the Company.

     

    “Reference
      Treasury Dealer Quotations”
      means, with
      respect to each Reference Treasury Dealer and any date of redemption, the
      average, as determined by the Trustee, 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 Trustee by that Reference Treasury
      Dealer at 5:00 p.m., New York City time, on the third business day preceding
      that date of redemption.

     

    Unless
      the Company
      defaults in payment of the redemption price, on and after the date of
      redemption, interest will cease to accrue on this Note or the portions hereof
      called for redemption.

     

    In
      the event of
      redemption of this Note in part only, a new Note or Notes for the unredeemed
      portion hereof shall be issued in the name of the Holder hereof upon the
      surrender hereof.

     

    If
      an Event of
      Default, as defined in the Indenture and in the Authorizing Resolution and/or
      supplemental indenture (if any) relating to the Notes (if there shall be any
      additional Events of Default specified in respect of the Notes), shall occur
      and
      be continuing, the principal of all the Notes may be declared due and payable
      in
      the manner and with the effect provided in the Indenture.

     

    The
      Indenture
      permits, with certain exceptions as therein provided, the amendment thereof
      and
      the modification of the rights and obligations of the Company and the rights
      of
      the Holders of the Notes under the Indenture at any time by the Company and
      the
      Trustee with the consent of the Holders of a majority in aggregate principal
      amount of the Securities affected thereby, voting as a single class (which
      may
      include the Notes), at the time outstanding. The Indenture also contains
      provisions permitting the Holders of specified percentages in aggregate
      principal amount of the Securities at the time outstanding to waive compliance
      by the Company with certain provisions of the Indenture and certain past
      defaults under the Indenture and their consequences. Any such consent or waiver
      by the Holder of this Note shall be conclusive and binding upon such Holder
      and
      upon all future Holders of this Note and of any Note issued upon the
      registration of transfer hereof or in exchange herefor in lieu hereof, whether
      or not notation of such consent or waiver is made upon this Note.

     

    The
      Indenture
      provides that no Holder may pursue any remedy under the Indenture unless the
      Trustee shall have failed to act after notice of an Event of Default and written
      request by Holders of at least 25% in principal amount of the Securities of
      the
      applicable Series and the offer to the Trustee of indemnity satisfactory to
      it;
      however, such provision does not affect the right to sue for enforcement of
      any
      overdue payment on any Security.

     

    No
      reference herein
      to the Indenture and no provision of this Note or of the Indenture shall alter
      or impair the obligation of the Company, which is absolute and unconditional,
      to
      pay the principal of and interest on this Note at the times, places and rates,
      and in the coin or currency, herein prescribed.

     

    As
      provided in the
      Indenture and subject to certain limitations therein set forth, the transfer
      of
      this Note is registrable in the Security Register upon surrender of this Note
      for registration of transfer at the agency of the Company provided for that
      purpose duly endorsed by, or accompanied by a written instrument of transfer
      in
      substantially the form accompanying this Note duly executed by, the Holder
      hereof or his attorney duly authorized in writing, and thereupon one or more
      new
      Notes, of authorized denominations and for the same aggregate principal amount,
      will be issued to the designated transferee or transferees.

     

    The
      Notes are
      issuable only in registered form without coupons in denominations of $1,000
      and
      any integral multiple thereof. As provided in the Indenture and subject to
      certain limitations therein set forth, the Notes are exchangeable for a like
      aggregate principal amount of Notes of a different authorized denomination,
      as
      requested by the Holder surrendering the same.

     

    No
      service charge
      shall be made for any such registration of transfer or exchange, but the Company
      may require payment of a sum sufficient to cover any transfer tax or similar
      governmental charge payable in connection therewith (other than any such
      transfer taxes or similar governmental charge payable upon exchanges pursuant
      to
      Sections 2.11, 3A.08 or 9.05 of the Indenture, in which case such transfer
      taxes
      or similar governmental charges shall be paid by the Company).

     

    Prior
      to due
      presentment of this Note for registration of transfer, the Company, the Trustee
      and any agent of the Company or the Trustee may treat the person in whose name
      this Note is registered as the owner hereof for all purposes, whether or not
      this Note be overdue, and neither the Company, the Trustee nor any such agent
      shall be affected by notice to the contrary.

     

    All
      terms used in
      this Note which are defined in the Indenture shall have the meanings assigned
      to
      them in the Indenture.

     

    Customary
      abbreviations may be used in the name of a Note holder or any assignee, such
      as:
      TEN COM ( = tenants in common), TEN ENT ( = tenants by the entireties), JT
      TEN (
      = joint tenants with right of survivorship and not as tenants in common), CUST
      (
      = Custodian) and U/G/M/A ( = Uniform Gifts to Minors Act).

     

    The
      Company will
      furnish to any Note holder of record, upon written request, without charge,
      a
      copy of the Indenture. Requests may be made to: Colorado Interstate Gas Company,
      El Paso Building, 1001 Louisiana Street, Houston, Texas 77002, Attention:
      Corporate Secretary.

     

    [If
      a Transfer
      Restricted Security, insert—The Holder of this Note is entitled to the benefits
      of the Registration Rights Agreement dated as of November 1, 2005 (the
“Registration
      Rights Agreement”)
      by and among the
      Company and the Initial Purchasers named therein, and such Holders shall also
      have certain obligations to indemnify the Company under certain circumstances,
      all as more fully set forth in the Registration Rights Agreement. In certain
      events, the Company shall be required to pay to the Holder of this Note
      liquidated damages on this Note, on the terms and subject to the conditions
      of
      the Registration Rights Agreement.]

     

    This
      Note shall be
      governed by and construed in accordance with the laws of the State of New York
      without regard to principles of conflicts of law.

     

    


     


    
      
        
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            Supplemental Indenture

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

      

    


    ASSIGNMENT
      FORM

     

    FOR
      VALUE RECEIVED,
      the undersigned hereby sell(s), assign(s) and transfer(s) unto
      _____________________________________ (Please Print or Typewrite Name and
      Address of Assignee) the within instrument of COLORADO INTERSTATE GAS COMPANY
      and does hereby irrevocably constitute and appoint ________________________
      Attorney to transfer said instrument on the books of the within-named Company,
      with full power of substitution in the premises.

     

    Please
      Insert
      Social Security or 

     

    Other
      Identifying
      Number of Assignee: 

     

     

    Dated:
             

     

    (Signature)
      

     

    


     

    Signature
      Guarantee:
      ____________________________________________________________________________

    (Participant
      in a Recognized
      Signature

    Guaranty
      Medallion
      Program)

     

    NOTICE:
      The
      signature to this assignment must correspond with the name as written upon
      the
      face of the within instrument in every particular, without alteration or
      enlargement or any change whatever.

     

    


     


    
      
        
          HOU:2509545.3
            

           

          A-Third
            Supplemental Indenture

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

      

    


    EXCHANGE/TRANSFER
      CERTIFICATE

     

    Re: 6.80%
      Senior Notes
      due 2015 of Colorado Interstate Gas Company (the “Notes”).

     

    This
      Exchange/Transfer Certificate relates to $____ principal amount of Notes held
      by
      _____________________ (the “Transferor”).

     

    The
      Transferor has
      requested the Trustee by written order to exchange or register the transfer
      of a
      Note or Notes.

     

    In
      connection with
      such request and in respect of each such Note, the Transferor does hereby
      certify that the Transferor is familiar with the Indenture relating to the
      above-captioned Notes and that the transfer of this Note does not require
      registration under the Securities Act (as defined below) because:**

     

    ‪ Such
      Note is being
      acquired for the Transferor’s own account without transfer.

     

    ‪ Such
      Note is being
      transferred (i) to a “qualified institutional buyer” (as defined in Rule 144A
      under the Securities Act of 1933, as amended (the “Securities
      Act”)),
      in accordance
      with Rule 144A under the Securities Act or (ii) pursuant to an exemption from
      registration in accordance with Rule 904 of Regulation S under the Securities
      Act (and in the case of clause (ii), based upon an opinion of counsel if the
      Company or the Trustee so requests, together with a certification in
      substantially the form of the Regulation S Certificate included in such
      Note).

     

    ‪ Such
      Note is being
      transferred (i) pursuant to an exemption from registration in accordance with
      Rule 144 under the Securities Act (and based upon an opinion of counsel if
      the
      Company or the Trustee so requests) or (ii) pursuant to an effective
      registration statement under the Securities Act.

     

    ‪ Such
      Note is being
      transferred in reliance on and in compliance with another exemption from the
      registration requirements of the Securities Act (and based upon an opinion
      of
      counsel if the Company or the Trustee so requests).

     

    [INSERT
      NAME OF
      TRANSFEROR]

    


    By:


    Name:

    Title:

    Address:

    


    Date:
 

    


    **Check
      appropriate
      box.

     


    
      
        
          HOU:2509545.3
            

           

          A-Third
            Supplemental Indenture

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

      

    


    REGULATION
      S CERTIFICATE

    


    _________________,
      _____

    


    The
      Bank of New
      York Trust Company, N.A., as Registrar

    600
      North Pearl
      Street, Suite 420

    Dallas,
      TX
      75201

     

    Attention:
      Corporate Trust Administration

     

    Ladies
      and
      Gentlemen:

     

    In
      connection with
      our proposed sale of $_______________ principal amount of 6.80% Senior Notes
      due
      2015 (the “Notes”)
      of Colorado
      Interstate Gas Company (the “Company”),
      we confirm that
      such sale has been effected pursuant to and in accordance with Regulation S
      under the United States Securities Act of 1933, as amended (the “Securities
      Act”),
      and,
      accordingly, we represent that:

     

    (i) the
      offer of the
      Notes was not made to a person in the United States of America;

     

    
      	 	
              (ii)

            	
              at
                the time
                the buy order was originated, the transferee was outside the United
                States
                of America or we and any person acting on our behalf reasonably believed
                that the transferee was outside the United States of
                America;

            


    

     

    
      	 	
              (iii)

            	
              no
                directed
                selling efforts have been made by us in contravention of Rule 903
                or Rule
                904 of Regulation S under the Securities Act, as
                applicable;

            


    

     

    
      	 	
              (iv)

            	
              the
                transaction is not part of a plan or scheme to evade the registration
                requirements of the Securities Act;
                and

            


    

     

    
      	 	
              (v)

            	
              if
                the
                proposed transfer is being made prior to the expiration of the 40-day
                distribution compliance period as set forth in Regulation S, the
                transfer
                is not being made to, or for the benefit or account of, a U.S. Person
                (other than a distributor).

            


    

     

    You
      and the Company
      are entitled to rely upon this Regulation S Certificate and you are irrevocably
      authorized to produce this Regulation S Certificate or a copy hereof to any
      interested party in any administrative or legal proceedings or official inquiry
      with respect to the matters covered hereby. Terms used but not defined in this
      Regulation S Certificate have the meanings set forth in Regulation S under
      the
      Securities Act.

     

    Very
      truly
      yours,

    


    


    [Name]

    


    By:


    Name:

    Title:

    Address:

    


     


    
      
        
          HOU:2509545.3
            

           

          A-Third
            Supplemental Indenture

           

        

        
        

      

      
        
        

        
          

        

      

      
        
        

      

    


    [If
      a Global
      Security, insert as a separate page—

     

    SCHEDULE
      OF
      INCREASES OR DECREASES

     

    IN
      GLOBAL
      SECURITY

     

    The
      following
      increases or decreases in this Global Security have been made:

     

    
      	
               

               

               

               

               

               

               

               

              Date
                of Exchange

               

            	
              Amount
                of Decrease in Principal Amount of this Global
                Security

               

            	
              Amount
                of Increase in Principal Amount of this 

               

              Global
                Security

               

            	
              Principal
                Amount of this Global Security following such decrease
                

               

              (or
                increase)

               

            	
               

               

              Signature
                of authorized signatory of Trustee or Depository]