Comparison of molecular structure and fibrin polymerization between two Bß-chain N-terminal region fibrinogen variants, Bßp.G45C and Bßp.R74C.

ABSTRACT

We identified two heterozygous dysfibrinogenemias, Bßp.Gly45Cys (Kyoto VII; K-VII) and Bßp.Arg74Cys (Iida II; I-II). The impairment of polymerization of Bßp.G45C has been well analyzed; however, that of Bßp.R74C has not. Thus, we compared fibrin polymerization between these variants. To determine the structural and functional characterization of purified fibrinogens, we performed immunoblotting analysis, kinetic analyses of fibrinopeptide A and B release, and thrombin- or batroxobin-catalyzed fibrin or fibrin monomer polymerization. Immunoblotting analysis showed that both variant fibrinogens had variant fibrinogen-albumin complexes and variant fibrinogen multimers, and the amounts of fibrinogen-albumin complexes with fibrinogen K-VII was more than with fibrinogen I-II. Moreover, fibrinopeptide B release from fibrinogen K-VII was about 50% of the control, whereas the others were normal. The maximum slopes of polymerization for variant fibrinogens were reduced, but fibrinogen K-VII was reduced more than fibrinogen I-II. The present study demonstrated that both Bßp.G45C and Bßp.R74C variants showed the presence of variant fibrinogen-albumin complexes and variant fibrinogen multimers, and polymerization of Bßp.G45C was impaired more than Bßp.R74C. Our study and several previous reports concerning the clinical phenotype of both variants suggested the risks of bleeding for patients with Bßp.G45C and thrombosis for patients with Bßp.R74C.