Characterization of an apparently lower molecular weight gamma-chain variant in fibrinogen Kyoto I. The replacement of gamma-asparagine 308 by lysine which causes accelerated cleavage of fragment D1 by plasmin and the generation of a new plasmin cleavage site.

Congenitally abnormal fibrinogen Kyoto I with impaired fibrin monomer polymerization contains a normal gamma-chain and a gamma-chain variant (gamma Kyoto I) that has an apparently lower Mr on sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the Laemmli system (Laemmli, U. K. (1970) Nature 227, 680-685) but migrates with apparently normal Mr in the Weber and Osborn system (Weber, K., and Osborn, M. (1969) J. Biol. Chem. 244, 4406-4412). Reverse-phase high performance liquid chromatographic analyses of the cyanogen bromide or lysyl endopeptidase cleavage fragments of the purified gamma-chains of fibrinogen Kyoto I showed the presence of peptides not seen from normal fibrinogen. Amino acid sequence analysis of these peptides indicated that gamma Asn308 of the gamma-chain variant is replaced by lysine. Purified fragment D1 of fibrinogen Kyoto I also contains two types of D1 gamma-remnants: normal and apparently lower Mr types. Abnormal fragment D1 is cleaved faster to fragments D2 and D3 by plasmin in the presence of [ethylenebis(oxyethylenenitrilo)]tetraacetic acid (EGTA) than normal fragment D1, as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by immunoblotting using anti-gamma-chain monoclonal antibody. Analysis of peptides released from fragment D1 by plasmin in the presence of EGTA demonstrated the cleavage of the gamma Lys308-Gly309 bond. Fragment D1 of fibrinogen Kyoto I has normal calcium binding properties. The data suggest that a region or conformation containing gamma Asn308 affects the polymerization of fibrin monomers and that the gamma Asn308----Lys replacement causes a conformational change in the gamma-chain which results in the accelerated cleavage of gamma Lys356-Ala357 and gamma Lys302-Phe303 bonds by plasmin and also results in the generation of a new plasmin cleavage site between Lys308 and Gly309 in the presence of EGTA. During these studies, we found that part of the gamma Lys212-Glu213 bond in fragment D1 is cleaved by plasmin in the presence of EGTA.