Carboxyl-terminal residues of mammalian fibrinogen and fibrin

Abstract

The carboxyl-terminal residues of mammalian fibrinogens of six different species and the chain peptides, α(A), β(B) and γ, 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 α(A)-chain, and C-terminal valine was found on both the β(B)-and γ-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 α(A)-chains, and C-terminal valine and isoleucine were found on the β(B)- and γ-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.