8-K 1 mab03op1.txt JULY 8K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington D. C. 20549 Form 8-K Current Report Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 25, 2003 MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2003-OP1 Trust (Exact name of registrant as specified in its charter) New York (governing law of 333-75724-15 54-2102389 Pooling and Servicing Agreement) (Commission 54-2102390 (State or other File Number) IRS EIN jurisdiction of Incorporation) c/o Wells Fargo Bank Minnesota, N.A. 9062 Old Annapolis Road Columbia, MD 21045 (Address of principal executive offices) (Zip Code) Registrant's telephone number, including area code: (410) 884-2000 (Former name or former address, if changed since last report) ITEM 5. Other Events On July 25, 2003 a distribution was made to holders of MASTR ASSET BACKED SECURITIES TRUST, Mortgage Pass-Through Certificates, Series 2003-OP1 Trust. ITEM 7. Financial Statements and Exhibits (c) Exhibits furnished in accordance with Item 601(a) of Regulation S-K Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2003-OP1 Trust, relating to the July 25, 2003 distribution. Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2003-OP1 Trust By: Wells Fargo Bank Minnesota, N.A., as Trustee By: /s/ Beth Belfield, Assistant Vice President By: Beth Belfield, Assistant Vice President Date: 8/6/03 INDEX TO EXHIBITS Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2003-OP1 Trust, relating to the July 25, 2003 distribution. EX-99.1

Class A-1 524,901,347.20 35.85388172% 498,785,739.35 36.70498290% 63.295010% 0.000000% Class A-2 175,794,347.20 12.00779873% 175,793,010.85 12.93637518% 23.768608% 0.000000% Class M-1 117,194,347.20 8.00507045% 117,193,010.85 8.62407868% 4.312297% 0.000000% Class M-2 65,919,347.20 4.50268320% 65,918,010.85 4.85081924% 3.773259% 0.000000% Class M-3 43,944,347.20 3.00166009% 43,943,010.85 3.23370805% 1.617111% 0.000000% Class M-4 25,631,347.20 1.75077335% 25,630,010.85 1.88607860% 1.347629% 0.000000% Class CE 0.00 0.00000000% 0.00 0.00000000% 0.808004% 0.000000% Class R-I 0.00 0.00000000% 0.00 0.00000000% 0.000000% 0.000000% Class R-II 0.00 0.00000000% 0.00 0.00000000% 0.000000% 0.000000% Please Refer to the Prospectus Supplement for a Full Description of Loss Exposure

MORTGAGE ASSET SECURITIZATION TRANSACTIONS INC SER 2003-OPT1 8-K