ON 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 tripeptide, 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‐Glu‐Arg‐His‐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 fibrinopeptide 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. Copyright © 1969, Wiley Blackwell. All rights reserved