Disulfide-Linked Cyanogen Bromide Peptides of Bovine Fibrinogen. III. Isolation and Identification by Sequence Analysis of the Chain Constituents in Peptides F-CB2, F-CB4 and F-CB5

Abstract

Three disulfide-linked peptides with MW of about 6000, 7000 and 45,000, respectively, were isolated from bovine fibrinogen cleaved with cyanogen bromide. The chain constitutents of these peptides were separated after reduction and alkylation and identified by partial amino acid sequence analysis. Of the 5 polypeptide chains of the largest fragment F-CB2, 3 were derived from the central region of B.beta. chain, 1 from the A.alpha. chain and 1 from the .gamma. chain. The smaller peptides F-CB4 and F-CB5 consisted of 1 and 2 polypeptide chains and originated from central regions of the B.beta. and .gamma. chains, respectively, indicating that they represented intrachain disulfide loops. The disulfide-bonded regions of bovine fibrinogen are similar to those in human fibrinogen.