Amino acid sequence studies on the α chain of human fibrinogen. Isolation and characterization of two linked α-chain cyanogen bromide fragments from fully cross-linked fibrin

Abstract

Fully cross-linked human fibrin was digested with cyanogen bromide and the resulting fragments were characterized and compared with the fragments produced upon cyanogen bromide treatment of fibrinogen .alpha. chains. The largest MW fraction isolated by gel filtration on Sephadex G-150 was reduced and alkylated, and upon rechromatography on Sephadex G-150, it eluted at the same place as the original material. This large MW fraction was subjected to amino acid analysis and the amino-terminal sequences of its constituent chains were determined by both dimethylaminonaphthyl sulfonation (Dns) and thioacetylation procedures. The identified sequences corresponded to 2 cyanogen bromide fragments previously found in .alpha. chains isolated from fibrinogen, one of which has a MW of about 30,000 and the other, 6000. The latter is thought to be the carboxy-terminal penultimate cyanogen bromide fragment of the .alpha. chain.