A lower molecular weight gamma-chain variant in a congenital abnormal fibrinogen (Kyoto)

A gamma-chain variant with a lower molecular weight than the normal gamma chain was detected in a new congenital abnormal fibrinogen with impaired polymerization of the fibrin monomer and with normal release of fibrinopeptides A and B in a 45-year-old male. Purified fibrinogen analyzed on SDS-polyacrylamide gel electrophoresis under the reduced condition contained an abnormal protein band with an apparent molecular weight of 48,000 compared with the gamma chain with a molecular weight of 50,000. This abnormal protein band was found to be a gamma-chain variant from the molar ratio of A alpha chain:B beta chain:gamma chain:abnormal protein (about 2:2:1:1), with positive staining for carbohydrate and crosslinking ability. Crosslinked fibrin contained three types of gamma-gamma dimers with apparent molecular weights of 94,000 (the same as normal major gamma-gamma dimer), 92,000 and 90,000, and the plasmic digests of crosslinked fibrin in the presence of calcium retained three types of gamma-gamma dimer remnants. This suggests that the abnormal gamma-chain variant has a shorter polypeptide chain not in the NH2-terminal but in the COOH-terminal portion, probably at or near the polymerization site. This patient's two daughters had the same abnormal fibrinogen. This unique inherited abnormal fibrinogen was designated as fibrinogen Kyoto, and the gamma- chain variant as gamma Kyoto.