An Abnormal Fibrinogen Fukuoka II (Gly-Bβ 15 → Cys) Characterized by Defective Fibrin Lateral Association and Mixed Disulfide Formation

Abstract A dysfibrinogenemia was attributable to a single amino acid substitution from glycine to cysteine at residue 15 of the Bβ chain in a fibrinogen molecule designated as fibrinogen Fukuoka II. The fibrinogen Fukuoka II showed prolonged thrombin and reptilase times and impaired fibrinopeptide B release by thrombin, resulting in abolition of fibrin monomer repolymerization under physiological conditions. Repolymerization of the des-(Bβ 1-42)-fibrin monomers, however, was not distinguished from the normal pattern of des-(Bβ 1-42)-fibrin monomers, suggesting that no other abnormality existed in fibrinogen Fukuoka II. Although an additional cysteine was substituted at residue 15 of the Bβ chain, fibrinogen Fukuoka II had no free sulfhydryl group within the molecule. Instead, fibrinogen Fukuoka II formed a disulfide bond with cysteine, albumin, another mutated Bβ chain within the same molecule, or intermolecular dimeric fibrinogen Fukuoka II. The mutation in fibrinogen Fukuoka II was the same as that in fibrinogen Ise published previously (Yoshida, N., Wada, H., Morita, K., Hirata, H., Matsuda, M., Yamazumi, K., Asakura, S., and Shirakawa, S.(1991) Blood 77, 1958-1963). Fibrinogen Ise, however, has been described as having prolonged thrombin time but normal reptilase time. Reasons for the discrepancy were not clear. Analysis of the Bβ 1-42 fragment showed that fibrinogen was heterogeneous at position 31 of the Bβ chain with respect to proline or hydroxyproline.