Characterization of fragment E from fibrinogen and cross-linked fibrin

Fragment E, a terminal plasmin digestion product of fibrinogen or fibrin, contains portions of the alpha, beta, and gamma chains linked by disulfide bonds. In this study, Fragment E from fibrinogen and fully cross-linked fibrin were purified by gel filtration of the soluble fraction from heated plasmin digests of either fibrinogen or fibrin or by step-wise chromatography of terminal plasmin digests of fibrinogen or cross-linked fibrin on DEAE-cellulose. Fibrinogen Fragment E and fibrin Fragment E migrated as single bands with identical mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis or on polyacrylamide gel electrophoresis at pH 3.2 or pH 8.6. After reduction by beta-mercaptoethanol, the two Fragment E species had very similar patterns on sodium dodecyl sulfate gel electrophoresis; each contained three subunits which had molecular weights ranging from 5,000 to 12,000. Only the subunit polypeptide derived from the gamma chain in either Fragment E contained carbohydrate. The two Fragment E species had identical sedimentation coefficients and identical molecular weights by equilibrium ultracentrifugation. The amino acid compositions were indistinguishable. Partial NH2-terminal sequence analyses of fibrinogen Fragment E and fibrin E were identical, indicating that plasmin had cleaved the NH2-terminal regions of the Aalpha or alpha and Bbeta or beta chains of both Fragment E Species.