Purification and characterization of a peptide from the carboxy-terminal region of chick tendon procollagen type I.

A disulfide-bonded peptide with a molecular weight of about 100 000 was isolated from the medium of cultured chick embryo tendons. It was shown to be a trimer with two types of subunits in a 2:1 ratio, and tryptic fingerprinting and immunological evidence indicated that it was derived from the carboxy-terminal-precursor-specific region of procollagen. Amino acid analysis after reduction and alkylation indicated that the trimer contains about 30 residues of half-cystine involved in intrachain as well as interchain disulfide bonding. The interchain bonds could be reduced and alkylated under nondenaturing conditions. Carbohydrate analysis showed that each of the three peptide chains in the trimer contains about two residues of N-acetylglucosamine and about ten residues of mannose. This suggests the presence of one or two oligosaccharide units per chain.