Studies on the primary structure of bovine high-molecular-weight kininogen. Amino acid sequence of a fragment ("histidine-rich peptide") released by plasma kallikrein

An unknown peptide fragment, which was released from bovine high-molecular-weight kininogen by bovine plasma kallikrein [EC 3.4.21.8], was isolated and its chemical structure was established. The fragment consisted of 41 amino acids with serine and arginine at the NH2- and COOH-termini, respectively. The molecular weight was calculated to be 4,584. It was very basic and contained eleven residues each of histidine and glycine and seven residues of lysine. Thus, the total number of these three amino acids accounted for about 70 percent of the total residues constituting the fragment. The amino acid sequence of the fragment, designated tentatively as "His-rich peptide," was studied by Edman degradation and standard enzymatic and chemical techniques. These data made it possible to deduce the following sequence: H-Ser-His-Gly-Leu-Gly-His-Gly-His-Gln-Lys-Gln-His-Gly-Leu-Gly-His-Gly-His-Lys-His-Gly-His-Gly-His-Gly-Lys-His-Lys-Asn-Lys-Gly-Lys-Asn-Asn-Gly-Lys-His-Tyr-Asp-Trp-Arg-OH. The fragment had an extremely interesting feature in that repeating sequences occur along the peptide chain. The repeats were of the type His-Gly-X or Gly-His-X and this sequence appeared six or seven times up to 26 residues from the N-terminal end. Moreover, three tetrapeptide sequences of Gly-His-Gly-His and two heptapeptide sequence consisting of His-Gly-Leu-Gly-His-Gly-His were found in the N-terminal portion. It should be noted that plasma kallikrein liberates such a histidine-rich peptide from the kininogen in addition to a physiologically active peptide, bradykinin. The location of the "His-rich peptide" fragment in the percursor protein is also discussed.

Carboxyl-terminal residues of mammalian fibrinogen and fibrin

The carboxyl-terminal residues of mammalian fibrinogens of six different species and the chain peptides, alpha(A), beta(B) and gamma, isolated from these fibrinogens were determined by hydrazinolysis, digestion with carboxypeptidases and selective tritium labelling. The C-terminal ends of bovine fibrinogen and fibrin were identified as proline and valine, in the molar ratio of approximately 1:2. Proline was identified as the C-terminus of the alpha(A)-chain, and C-terminal valine was found on both the beta(B)- and gamma-chains. On hydrazinolysis after selective tritium labelling of fibrinogen, radioactive C-terminal valine was also identified. The same C-terminal ends as those of bovine fibrinogen were found on the corresponding chain peptides isolated from sheep fibrinogen. The C-terminal residues of all the chain peptides of human and horse fibrinogens, however, were valine. In hog and dog fibrinogens, proline was identified at the C-termini of the alpha(A)-chains, and C-terminal valine and isoleucine were found on the beta(B)- and gamma-chains, respectively. Thus, the C-terminal amino acid residues of the fibrinogens of all mammalian species tested were very similar. It should be noted that hydrophobic amino acids, like isoleucine, valine and proline, are mainly located in the C-terminal ends of all three chain peptides in the fibrinogen molecule.