RECONSTITUTED SERVICING AGREEMENT

THIS RECONSTITUTED SERVICING AGREEMENT (this “Agreement”), entered into as of the 1^st day of July, 2006, by and among THORNBURG MORTGAGE HOME LOANS, INC., a Delaware corporation (“Thornburg” or the “Seller”), WELLS FARGO BANK, N.A., as servicer (the “Servicer”) and THORNBURG MORTGAGE SECURITIES TRUST 2006-4 (the “Trust”), and acknowledged by WELLS FARGO BANK, N.A., as master servicer (the “Master Servicer”), recites and provides as follows:

RECITALS

WHEREAS, the Seller has conveyed certain mortgage loans identified on Schedule I hereto (the “Mortgage Loans”) to Structured Asset Securities Corporation, a Delaware special purpose corporation (“SASCO”), which in turn has conveyed the Mortgage Loans to the Thornburg Mortgage Securities Trust 2006-4 (the “Trust”), under a trust agreement dated as of July 1, 2006 (the “Trust Agreement”), among LaSalle Bank National Association, as Trustee (the “Trustee”), the Master Servicer, SASCO, as seller (referred to herein as the “Depositor”), Wilmington Trust Company, as Delaware trustee, Wells Fargo Bank, N.A., as securities administrator and the Seller.

WHEREAS, the Mortgage Loans are currently being serviced by the Servicer pursuant to a Second Amended and Restated Master Seller’s Warranties and Servicing Agreement between Bank of America, National Association (“Bank of America”) and the Servicer dated as of May 1, 2006 (the “Master Servicing Agreement”), a copy of which is attached hereto as Exhibit B;

WHEREAS, the Seller, Bank of America, and the Servicer entered into an Assignment, Assumption and Recognition Agreement dated July 25, 2006 (the “AAR”), pursuant to which, among otqher things, the Seller purchased the Mortgage Loans from Bank of America and the Servicer agreed to service and administer the Mortgage Loans in accordance with the terms of the Master Servicing Agreement, as modified by the AAR (collectively the “Servicing Agreement”), a copy of which is attached hereto as Exhibit C;

WHEREAS, the Seller desires that the Servicer continue to service the Mortgage Loans, and the Servicer has agreed to do so in accordance with the Servicing Agreement as modified in the attached Exhibit A;

WHEREAS, the Master Servicer and any successor master servicer shall be obligated, among other things, to supervise the servicing of the Mortgage Loans on behalf of the Trustee, and shall have the right, under certain circumstances, to terminate the rights and obligations of the Servicer upon the occurrence and continuance of an Event of Default by the Servicer under this Agreement;

WHEREAS, the Seller and the Servicer desire that the provisions of the Servicing Agreement shall apply to the Mortgage Loans, but only to the extent provided herein and that this Agreement shall constitute a “Reconstitution Agreement” as defined under the Servicing Agreement which shall govern the Mortgage Loans for so long as such Mortgage Loans remain subject to the provisions of the Trust Agreement;

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NOW, THEREFORE, in consideration of the mutual agreements hereinafter set forth and for other good and valuable consideration, the receipt and adequacy of which are hereby acknowledged, the Seller and the Servicer hereby agree as follows:

AGREEMENT

1.Definitions. Capitalized terms used and not defined in this Agreement, including Exhibit A hereto, shall have the meanings ascribed to such terms in the Servicing Agreement.

2.Servicing. The Servicer agrees, with respect to the Mortgage Loans, to perform and observe the duties, responsibilities and obligations that are to be performed and observed under the provisions of the Servicing Agreement, except as otherwise provided herein and on Exhibit A hereto, and that the provisions of the Servicing Agreement, as so modified, are and shall be a part of this Agreement to the same extent as if set forth herein in full.

3.Servicer. From and after the date hereof (the “Closing Date”), the Servicer shall and does hereby recognize that the Seller will transfer the Mortgage Loans and assign its rights under the Servicing Agreement to SASCO and that SASCO will thereafter transfer the Mortgage Loans and assign its rights under the Servicing Agreement and this Agreement to the Trust. The Servicer acknowledges and agrees that from and after the date hereof (i) the Trust will be the owner of the Mortgage Loans, (ii) the Servicer shall look solely to the Trust for performance of any obligations of the Seller insofar as they relate to the enforcement of the representations, warranties and covenants with respect to the Mortgage Loans, (iii) the Trust (including the Trustee and, with respect to the servicing of the Mortgage Loans, the Master Servicer acting on the Trust’s behalf) shall have all the rights and remedies available to the Seller insofar as they relate to the Mortgage Loans, under the Servicing Agreement, including, without limitation, the enforcement of the document delivery requirements set forth in Section 2.03 of the Master Servicing Agreement, and shall be entitled to enforce all of the obligations of the Servicer thereunder insofar as they relate to the Mortgage Loans, and (iv) all references to the Purchaser (insofar as they relate to the rights, title and interest and, with respect to obligations of the Purchaser, only insofar as they relate to the enforcement of the representations, warranties and covenants of the Servicer) under the Servicing Agreement insofar as they relate to the Mortgage Loans, shall be deemed to refer to the Trust. Neither the Servicer nor the Seller shall amend or agree to amend, modify, waive, or otherwise alter any of the terms or provisions of the Servicing Agreement which amendment, modification, waiver or other alteration would in any way affect the Mortgage Loans or the Servicer’s performance under the Servicing Agreement with respect to the Mortgage Loans without the prior written consent of the Trustee and the Master Servicer.

4.Notwithstanding any statement to the contrary in Section 3 above, the Seller shall and does hereby acknowledge that the indemnification provisions set forth in Sections 3.03, 8.01 and 9.01(f) of the Master Servicing Agreement shall be available to and for the benefit of the Seller, SASCO and the Trust (including the Trustee and the Master Servicer acting on the Trust’s behalf).

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5.The Servicer hereby acknowledges that Wells Fargo Bank, N.A. has been appointed as the master servicer of the Mortgage Loans pursuant to the Trust Agreement and, therefore, has the right to enforce all obligations of the Servicer under the Servicing Agreement. Such rights will include, without limitation, the right to terminate the Servicer under the Servicing Agreement upon the occurrence of an Event of Default thereunder, the right to receive all remittances required to be made by the Servicer under the Servicing Agreement, the right to receive all monthly reports and other data required to be delivered by the Servicer under the Servicing Agreement, the right to examine the books and records of the Servicer, indemnification rights and the right to exercise certain rights of consent and approval relating to actions taken by the Servicer. All assessments, reports and certifications required to be delivered by the Servicer under this Agreement and the Servicing Agreement shall include the Master Servicer as an addressee, and the Master Servicer shall be entitled to rely on all such assessments, reports and certifications.

6.Representations. The Servicer shall not be obligated or required to make any further representations and warranties regarding the characteristics of the Mortgage Loans in connection with the transactions contemplated by the Trust Agreement and issuance of the Certificates pursuant thereto. The Servicer does hereby make the representations made in Section 3.01 of the Master Servicing Agreement as of the Closing Date.

7.Notices. All notices, consents, certificates and other communications required to be delivered between or among the parties hereto (including any third party beneficiary thereof) or required to be provided to the Trustee shall be in writing, may be in the form of facsimile or electronic transmission, and shall be deemed received or given when mailed first-class mail, postage prepaid, addressed to each other party at its address specified below or, if sent by facsimile or electronic mail, when facsimile or electronic confirmation of receipt by the recipient is received by the sender of such notice. Each party may designate to the other parties in writing, from time to time, other addresses to which notices and communications hereunder shall be sent. All notices and other written information required to be delivered to the Master Servicer under this Agreement shall be delivered to the Master Servicer at the following address:

Wells Fargo Bank, N.A.

9062 Old Annapolis Road

Columbia, Maryland 21045-1951

Attention: Master Servicing Department, Thornburg 2006-4

Telephone: (410) 884-2000

Telecopier: (410) 715-2380

All remittances required to be made to the Master Servicer under this Agreement shall be made to the following wire account:

Wells Fargo Bank, N.A.

ABA# 121-000-248

Account Name: SAS Clearing

Account No. 3970771416

FFC: 50934700, Thornburg 2006-4

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All notices and other written information required to be delivered to the Trustee hereunder shall be delivered to the Trustee at the following address:

LaSalle Bank National Association

135 South LaSalle Street, Suite 1625

Chicago, IL 60603

Attention: Thornburg 2006-4

Telephone: (312) 992-1743

Facsimile: (312) 904-1368

All notices and other written information required to be delivered to the Seller hereunder shall be delivered to it at the following address:

Thornburg Mortgage Home Loans, Inc.

150 Washington Avenue, Suite 302

Santa Fe, New Mexico 87501

Attention: Deborah Burns (Thornburg 2006-4)

Telephone: (505) 954-5315

Facsimile: (505) 989-8156

All notices and written information required to be delivered to the Servicer hereunder shall be delivered to the Servicer at the following address:

Wells Fargo Bank, N.A.

1 Home Campus

Des Moines, Iowa 50328-0001

Attention: John B. Brown, MAC X2401-042

Fax: 515-213-7121

with a copy to:

Wells Fargo Bank, N.A.

1 Home Campus

Des Moines, Iowa 50328-0001

Attention: General Counsel MAC X2401-06T

8.Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO ITS CHOICE OF LAW RULES EXCEPT FOR SECTION 5-1401 OF THE GENERAL OBLIGATION LAW, WHICH SHALL APPLY HERETO.

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

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10.Reconstitution. The Seller and the Servicer agree that this Agreement is a “Reconstitution Agreement” and that the date hereof is the “Reconstitution Date,” each as defined in the Servicing Agreement.

11.REMIC Status. The Servicer is hereby notified, and the Servicer hereby acknowledges such notice, that the Mortgage Loans will be held in a securitization pursuant to which a REMIC election will be made.

12.Limitation of Liability. It is expressly understood and agreed by the parties hereto that (a) this Agreement is executed and delivered by LaSalle Bank National Association (“LaSalle Bank”), not individually or personally but solely as the Trustee of the Trust, in the exercise of the powers and authority conferred and vested in it, (b) the representations, warranties, covenants, undertakings and agreements herein made on the part of the Trustee are made and intended not as personal representations, undertakings and agreements by LaSalle Bank but are made and intended for the purpose of binding on the Trust, (c) nothing herein contained shall be construed as creating any liability on LaSalle Bank, individually or personally, to perform any covenant either expressly or implied contained herein, all such liability, if any, being expressly waived by the parties who are signatories to this Agreement and by any person claiming by, through or under such parties and (d) under no circumstances shall LaSalle Bank be personally liable for payment of any indemnity, indebtedness, fees or expenses of the Trust or be liable for the breach or failure of any obligation, representation, warranty or covenant made or undertaken by the Trust under this Agreement.

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Executed as of the day and year first above written.

THORNBURG MORTGAGE HOME LOANS, INC., as Seller

By: /s/ Deborah J. Burns

Deborah J. Burns

Senior Vice President

WELLS FARGO BANK, N.A., as Servicer

By: /s/ Patrick Greene

Name: Patrick Greene

Title: Senior Vice President

THORNBURG MORTGAGE SECURITIES TRUST 2006-4

BY:LASALLE BANK NATIONAL

 ASSOCIATION, not in its individual

 capacity, but solely as Trustee on behalf of

 the Trust

By: /s/ Rita Lopez

Name: Rita Lopez

Title: Vice President

Acknowledged By:

WELLS FARGO BANK, N.A.

as Master Servicer

By: /s/ Peter J. Masterman

Name: Peter Masterman

Title: Vice President

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EXHIBIT A

Modifications to the Servicing Agreement

1.The definition of “Business Day” in Article I is hereby amended to read as follows:

Business Day: Any day other than (a) a Saturday or Sunday or (b) a day on which banking and savings and loan institutions in the States of California, Delaware, New York, Maryland, Minnesota, or Iowa are authorized or obligated by law or executive order to be closed.

2.The definition of “Qualified Substitute Mortgage Loan” in Article I is hereby amended by the addition of the following language at the end of the first sentence thereof:

and (xii) qualify as a Qualified Substitute Mortgage Loan under the Trust Agreement.

3.The definition of “Repurchase Price” in Article I is hereby amended to read as follows:

Repurchase Price. Unless agreed otherwise by the Purchaser and the Company, a price equal to (i) the Stated Principal Balance of the Mortgage Loan plus (ii) interest on such Stated Principal Balance at the Mortgage Loan Remittance Rate from the date on which interest has last been paid and distributed to the Purchaser through the last day of the month in which such repurchase takes place, less amounts received or advanced in respect of such repurchased Mortgage Loan which are being held in the Custodial Account for distribution in the month of repurchase.

4.A new definition of “Document Transfer Event” is hereby added to Article I to read as follow:

Document Transfer Event. The day on which (i) Wells Fargo Bank, N.A. or any successor thereto is no longer the servicer of any of the Mortgage Loans, (ii) the senior, unsecured long-term debt rating of Wells Fargo Home Mortgage, a division of Wells Fargo Bank, N.A., is less than “BBB-” by Fitch Ratings or (iii) any Rating Agency requires the Company to deliver the Retained Mortgage Files (as defined in the Sale Agreement) to the Custodian.

5.Section 4.01 (Company to Act as Servicer) is modified to add the following at the end of the second paragraph:

“Further, with respect to any permitted modification, the Company shall determine, in consultation with counsel, that such a change would not be treated as a “significant modification” that would cause a deemed exchange under Section 1001(a) of the Code or applicable temporary or final regulations thereunder at any time when the Mortgage Loan is held by a REMIC or grantor trust.”

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6.Section 4.04 (Establishment of and Deposits to Custodial Account) is hereby amended by deleting the language “Bank of America, National Association, its successors or assigns, and/or subsequent purchasers of Mortgage Loans - P&I” at the end of the first sentence in the first paragraph and replacing it with the phrase “Thornburg Mortgage Securities Trust 2006-4.”

7.Section 4.05 (Permitted Withdrawals From Custodial Account) is hereby amended by deleting clause (vii) and replacing it with the following:

“(vii)to reimburse itself for any Monthly Advances, Servicing Advances and REO expenses after liquidation of the Mortgaged Property not otherwise reimbursed above;”

8.Section 4.06 (Establishment of Deposits to Escrow Accounts) is hereby amended by deleting the phrase “Bank of America, National Association, its successors and assigns, and/or subsequent purchasers of Residential Mortgage Loans and various Mortgagers - T&I” at the end of the first sentence of the first paragraph, and replacing it with the phrase “Thornburg Mortgage Securities Trust 2006-4.”

9.Section 4.16 (Title, Management and Disposition of REO Property) is hereby amended by:

(i)deleting the first paragraph and replacing it with the following:

“In the event that title to the Mortgaged Property is acquired in foreclosure or by deed in lieu of foreclosure, the deed or certificate of sale shall be taken in the name of the Trust.”

(ii)deleting the second paragraph in its entirety;

(iii)deleting the phrase “In the event the Purchaser does not elect to manage an REO Property, “ from the third paragraph (before the amendment made by (ii) above).

10.Section 4.30 (Delivery of Retained File) is added to the Master Servicing Agreement to read as follows:

Within 60 days of the occurrence of a Document Transfer Event, the Company shall deliver to the Trustee or any other party per written instructions from the Trustee, the additional documents from its Retained Mortgage File (as defined in the Sale Agreement).

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11.Section 5.01 (Remittances) is hereby amended by deleting the first and second use of the phrase “Business Day” in the second paragraph and replacing it with the phrase “Remittance Date.”

12.Section 12.01 (Successor to Company) is hereby amended by:

(i)replacing the words “Prior to” with the word “Upon” in the first line of the first paragraph thereto;

(ii)adding the phrase “, in accordance with the Trust Agreement,” after the word “shall” in the second line of the first paragraph thereto; and

(iii)adding the following sentence immediately after the first sentence of the first paragraph:

Any successor to the Company shall be subject to the approval of the Master Servicer and each Rating Agency, as evidenced by a letter from such Rating Agency delivered to the Trustee that the transfer of servicing will not result in a qualification, withdrawal or downgrade of the then-current rating of any of the Certificates.

(iv)adding the following paragraph after the fourth paragraph thereof:

Except as otherwise provided in this Agreement, all reasonable costs and expenses incurred in connection with any transfer of servicing due to an Event of Default under Section 10.01, including, without limitation, the costs and expenses of the Master Servicer or any other Person in appointing a successor servicer, or of the Master Servicer in assuming the responsibilities of the Company hereunder, or of transferring the Mortgage Files and the other necessary data, including the completion, correction or manipulation of such servicing data as may be required to correct any errors or insufficiencies in the servicing data, to the successor servicer shall be paid by the terminated or resigning Company from its own funds without reimbursement.

13.New Section 12.21 (Intended Third Party Beneficiaries) is added to the Servicing Agreement to read as follows:

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Section 12.21. Intended Third Party Beneficiaries. Notwithstanding any provision herein to the contrary, the parties to this Agreement agree that it is appropriate, in furtherance of the intent of such parties as set forth herein, that the Trustee, on behalf of the Trust, receive the benefit of the provisions of this Agreement as intended third party beneficiary of this Agreement to the extent of such provisions. The Company shall have the same obligations to the Trustee as if it were a party to this Agreement, and the Trustee, on behalf of the Trust, shall have the same rights and remedies to enforce the provisions of this Agreement as if it were a party to this Agreement. The Company shall only take direction from the Master Servicer (if direction by the Master Servicer is required under this Agreement) unless otherwise directed by this Agreement. Notwithstanding the foregoing, all rights and obligations of the Master Servicer and the Trustee hereunder (other than the right to indemnification and the indemnification obligations) shall terminate upon termination of the Trust pursuant to the Trust Agreement.

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EXHIBIT B

Master Servicing Agreement

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EXHIBIT C

Assignment, Assumption and Recognition

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SCHEDULE I

Mortgage Loan Schedule

(delivered to the Trustee in electronic format)