• dysfibrinogen;
  • fibrinopeptide B;
  • lateral aggregation;
  • reptilase;
  • thrombin

Summary. Background and objectives: Analysis of dysfibrinogens has improved our understanding of molecular defects and their effects on the function of intact fibrinogen. To eliminate the influence of plasma heterozygous molecules, we synthesized and analyzed recombinant-variant fibrinogens. Methods: We synthesized two recombinant-variant fibrinogens with a single amino acid substitution at the 15Gly residue in the Bβ-chain: namely, Bβ15Cys and Bβ15Ala. Results: Western blotting analysis of purified fibrinogen revealed the existence of a small amount of a dimeric form only for Bβ15Cys fibrinogen. For Bβ15Cys fibrinogen, functional analysis indicated (a) no thrombin-catalyzed fibrinopeptide B (FPB) release and (b) markedly impaired lateral aggregation in thrombin- and reptilase-catalyzed fibrin polymerizations. For Bβ15Ala fibrinogen, such analysis indicated slight impairments of both thrombin-catalyzed FPB release and lateral aggregation in thrombin-catalyzed fibrin polymerization, but nearly normal lateral aggregation in reptilase-catalyzed fibrin polymerization. These impaired lateral aggregations were accompanied by thinner fibrin fiber diameters (determined by scanning electron microscopy of the corresponding fibrin clots). Conclusion: We conclude that a region adjacent to Bβ15Gly plays important roles in lateral aggregation not only in desA fibrin polymerization, but also in desAB fibrin polymerization, and we speculate that the marked functional differences between Bβ15A and Bβ15C fibrinogens in FPB release and fibrin polymerization might not only be due to the presence of a substituted cysteine residue in Bβ15C fibrinogen, but also to the existence of disulfide-bonded forms. Finally, our data indicate that the Bβ15Gly residue plays important roles in FPB release and lateral aggregation of protofibrils.