Primary structure of the amino terminal regions of chicken fibrin chains

Abstract

Fibrinogen and fibrin, isolated from chicken plasma, was studied in terms of a) its subunit polypeptide chain amino acid composition, b) their respective molecular size, and c) their partial NH 2-terminal amino acid sequence. Based on the observation that intact fibrinogen yielded only tyrosine as an N-terminal residue, it was concluded that the N-terminal residues of both Aα and Bβ chains are probably blocked. Consistent with this observation was the finding that neither the isolated Aα and Bβ chain S-carboxymethyl derivatives could be sequenced. The γ-chain was sequenced 34 steps with 31 definite identifications. NH 2-terminal amino acii sequence analysis was successfully carried out for 12 steps on all three (α, β, γ) S-carboxymethyl chains derived from fibrin. When compared to mammalian species (man and dog) the amino acid composition and partial NH 2-terminal primary structure of the three fibrin chains did not differ dramatically. One major difference observed was the slightly reduced molecular size of the α-chain.