Sulfation of a gamma-chain variant of human fibrinogen

Biosynthetic sulfation of human fibrinogen was investigated using a hepatoma-derived cell line in culture. Very little 35]sulfate was incorporated into the major forms of the A alpha, B beta, or gamma-chains of fibrinogen, but there was a labeled peptide chain with electrophoretic mobility intermediate between the B beta and gamma-chains. Base hydrolysis of the sulfate-labeled product released tyrosine sulfate. The labeled peptide is identified as a form of gamma-chain by its resistance to proteolysis during extended periods of incubation, in contrast with A alpha and B beta-chains which are converted to smaller forms. The results indicate that human fibrinogen contains tyrosine sulfate primarily within a variant form of the gamma-chain.