Amino acid sequence of the carboxy-terminal cyanogen bromide peptide of the human fibrinogen beta-chain: homology with the corresponding gamma-chain peptide and presence in fragment D.

The carboxy-terminal cyanogen bromide fragment of the human fibrinogen beta-chain has been isolated and its structure determined. It is a nonapeptide with the sequence Lys-Ile-Arg-Pro-Phe-Phe-Pro-Gln-Gln and is homologous with a portion of the carboxy-terminal cyanogen bromide fragment of the gamma-chain. The peptide has also been isolated in full yield from cyanogen bromide digests of the plasmin-derived fragment D, indicating that the carboxy-terminal region of the beta-chain is resistant to plasmin digestion. In contrast, a small portion of the corresponding gamma-chain carboxy-terminal region was missing in the same fragment D.