Covalent Structure of Collagen: Isolation of Chymotryptic Peptides and Amino Acid Sequence of the Amino-Terminal Region of alpha2-CB3 from Chick Skin

Five chymotryptic peptides were isolated from alpha2-CB3 of chick skin collagen by a combination of ion-exchange and molecular sieve chromatography. Together, they account for the entire amino acid content of the parent peptide. Their alignment was deduced by isolation and sequence analyses of overlapping tryptic peptides. In addition, the amino acid sequence of the three consecutive chymotryptic peptides, containing 132 amino acid residues, from the NH2-terminus of alpha2-CB3 was determined by automated Edman degradation of the peptides and tryptic peptides derived from them. The resulting sequence shows an identity of approximately 80% when compared with those of the homologous portions of rat and calf skin collagen. In contrast, extensive substitutions are present when the sequence was compared with that of the corresponding segment of the alpha1 chain from the same species.