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.

Three disulfide-linked peptides with molecular weights of about 6000, 7000 and 45000, respectively, were isolated from bovine fibrinogen cleaved with cyanogen bromide. The chain constituents of these peptides were separated after reduction and alkylation and identified by partial amino acid sequence analysis. Of the five polypeptide chains of the largest fragment F-CB2, three are derived from the central region of Bbeta chain, one from the Aalpha chain and one from the gamma chain. The smaller peptides F-CB4 and F-CB5 consist of one and two polypeptide chains and originate from central regions of the Bbeta and gamma chains, respectively, indicating that they represent intrachain disulfide loops. These and previous data show that the disulfide-bonded regions of bovine fibrinogen are similar to those in human fibrinogen.