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 α, β, and γ 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 β 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 γ 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 NH ₂ terminal sequence analyses of fibrinogen Fragment E and fibrin Fragment E were identical, indicating that plasmin had cleaved the NH ₂ terminal regions of the Aα or α and Bβ or β chains of both Fragment E Species.