ABNORMAL POLYMERIZATION AND NORMAL BINDING OF PLASMINOGEN AND T-PA IN3 NEW DYSFIBRINOGENAEMIAS - BARCELONA-III AND BARCELONA-IV (GAMMA-ARG275-]HIS) AND VILLAJOYOSA (GAMMA-ARG 275-]CYS)

Congenital dysfibrinogenaemia was found in three non-related patients. None of them had a haemorrhagic tendency, but one gave a thrombotic h istory. When their fibrinogens were treated with thrombin, they releas ed fibrinopeptides A and B at normal rates, but the resultant fibrin m onomers produced exhibited abnormal polymerization curves. This abnorm ality was more marked in fibrinogen Villajoyosa than in Barcelonas III and IV. Plasminogen and t-PA binding to fibrin monomers from the thre e dysfibrinogenaemias was similar to that of normal fibrin monomers. T he gamma chain was purified from the three fibrinogens, treated with C NBr and the peptides produced were separated by reversed-phase HPLC. C hromatograms of digested fibrinogens showed an abnormal peak that was not present in the normal gamma chain. Amino acid sequence analysis of abnormal peptides and genomic DNA sequencing revealed that the gamma arginine 275 had been changed in the three fibrinogens; in two cases i t was substituted by histidine, and in the third by cysteine. The alte red properties observed in fibrin monomers produced from fibrinogen wi th the gamma Arg 275-->His or gamma Arg 275-->Cys substitution, sugges ts that this amino acid is important in maintaining the protein struct ure necessary for normal polymerization, but is not essential for the binding of t-PA or plasminogen to fibrin. It also suggests that the ch ange Arg-->Cys produces more severe alterations in the functions of fi brinogen than the substitution Arg-->His.