Structural studies on Functional Abnormality of Factor XII and Fibrinogen.

点击翻译按钮获取中文摘要

(1) Fibrinogen Nagoya, a Replacement of Glutamine-329 by Arginine in the -chain. That Impairs the Polymerization of Fibrin Monomer: Structural studies on a hereditary abnormal fibrinogen, fibrinogen Nagoya were performed to identify the abnormality responsible for the impaired polymerization of fibrin nomomer. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. fibrinogen Nagoya showed the presence of an extra protein band with an apparent molecular weight of 49,500 in addition to the normal three subunit chains. Amino acid sequence analysis of a peptide isolated from a lysyl endopeptidase digest of one of the cnbr fragments derived from fibrinogen nagoya indicated that Gln-329 in the -chain had been replaced by Arg. This substitution can be explained by a single uncleotide chainge in the dodon for Gln-329 (CAG - CGG). We conclude that GLN-329 in the -chain is indispensable for the normal polymerization of fibrin monomer.(2) Blood Clontting Factor IX Niigata: Substitution of Alanine-390 by Valine in the Catalytic Domain: Factor IX Niigata is s mutant factor IX responsible for the moderately severe hemophilia B in a patient who has a normal level of factor IX antigen with reduced clotting activity (1-4% of normal). We reported previously that the purified mutant protein could be converted to the factor IXa form by factor XIa/Ca^<2+> at a rate similar to that in the case of normal factor IX, but the resulting mutant factor IXa could not activate factor X in the presence of factor XIII, Ca^<2+>, and phospholipids. In the present study, we analyzed factor IX Niigata at the structural level to elucidate the molecular abnormality responsible for the loss of clotting activity. Amino acid sequence analysis of a peptide obtained on lysyl endopeptidase digestion, coupled with subsequent SP-V8 digestion, demonstrated that the alanine at position 390 was substituted by valine in the catalytic domain of the factor IX Niigata molecule.