On the Primary Structure of Human Fibrinogen: Isolation and Characterization of N-Terminal Fragments from Plasmic Digests.

Two N-terminal fragments of α(A)-chain and β(B)-chain in human fibrinogen have been isolated from a plasmic hydrolyzate. The fragment from the α(A)-chain consisted of 43 amino acid residues including two half-cystine residues. On treatment with thrombin, this fragment produced two other peptides in addition to fibrinopeptide A and its analogues. One was a tri-peptide, Gly-Pro-Arg, and the other a peptide containing 24 amino acid residues having N-terminal valine. The partial amino acid sequence of the α(A)-chain has been found to be: Ala-Asp- Ser-Gly-Glu-Gly-Asp-Phe-Leu-Ala-Glu-Gly-Gly-Gly-Val-Arg-Gly-Pro-Arg-Val-Val-GIu-Arg-I{is- Gln-Ser-Ala-Cys-Lys.Asp-Ser-Asp-Trp-Pro-Phe-(Cys-Ser-Asp-Glu-Trp-Asn-Tyr)-Lys. The fragment from the β(B)-chain consisted of 21 amino acid residues. This fragment released fibninopeptide B on treatment with thrombin. The amino acid sequence of the β(B)-chain fragment is: Pyr-Gly-Val-Asn-Asp-Asn-Glu-Glu-Gly-Phe-Phe-Ser-Ala-Arg-Gly-His-Arg-Pro-Leu-Asp-Lys. The linkages between fibrinopeptides and fibrin, which are rapidly hydrolyzed by thrombin, are very resistant towards plasmin. [ABSTRACT FROM AUTHOR]