The subunit structure of fibrinogen Baltimore and fibrin formed from this inherited dysfibrinogenemia was analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The molecular weights of the alpha-, b- and gamma-chains of fibrinogen Baltimore were found to be identical to those of normal fibrinogen. Noncross-linked fibrin formed from both purified fibrinogen Baltimore as well as normal fibrinogen contained two alpha-monomers (alpha1 and alpha2). alpha2 was presumed to be alpha-monomer from which fibrinopeptide A had been released. The evolution of alpha2 during clotting of fibrinogen Baltimore was delayed and appeared to be quantitatively reduced when compared to normal. Crosslinked fibrin formed from fibrinogen Baltimore possessed an abnormal subunit structure. alpha-polymers were not generated in thrombin-induced, factor XIII-rich clots of fibrinogen Baltimore under conditions of pH and calcium concentration suitable for complete alpha-polymerization in normal fibrin. If clotting was carried out with calcium concentrations twice that required for normal clots or at pH 6.4, fibrin from fibrinogen Baltimore was completely cross-linked. These structural analyses of fibrin formed from fibrinogen Baltimore substantiate earlier findings that indicate a defect in the alpha-chain of this dysfibrinogenemia.
C H Brown, M F Crowe