A peptide fraction isolated from a cyanogen bromide digest of bovine dentin collagen had a molecular weight of 46 000. Its size and amino acid composition indicated that it could not consist of peptides derived from the cleavage of a single a chain. On reduction with tritiated sodium borohydride, radioactivity was incorporated primarily into 5,5′-dihydroxylysinonorleucine without degradation at the peptide backbone. Periodate cleavage of the reduced or nonreduced peptide fraction generated one fragment of molecular weight 28 000 and one of 18 000 completely accounting for the size of the parent peptide. On amino acid analysis the constituent single-chain peptides were determined to be α2CB4 and α1CB6. Both peptides isolated after periodate oxidation of the tritiated borohydride reduced cross-link peptide were found to contain [3H]hydroxynorvaline. These data show that some hydroxylysine of α2CB4, a helical region peptide, was present in aldehyde form and could act as the aldehyde donor in cross-link, Schiff s base formation. The only cross-linkage of this α2CB4 acting as an aldehyde donor peptide to α1CB6 would be a helical region to helical region bond, perhaps accounting for the unusual stability and low solubility of dentin collagen.
ASJC Scopus subject areas