The cyanogen bromide peptides of bovine soluble and insoluble collagens: II. Tissue specific Cross-linked peptides of insoluble skin and dentin collagen

Cyanogen bromide peptides were prepared from insoluble bovine skin and dentin collagens and compared by electrophoresis in polyacrylamide gels containing sodium dodecylsulphate, with those of the α1 and α2 chains of soluble type I and type III collagen. Both insoluble collagens yielded predominantly the peptides of type I collagen. Insoluble skin collagen was approximately 13% type III. Type III collagen, if present in dentin, is present in smaller quantity not detected by the technique used here. Several new fragments, different in each tissue, were obtained which could not be accounted for as uncleaved peptides. Three of those from dentin were isolated by gel chromatography and characterized by amino acid analysis. Two were found to contain 3-hydroxyproline, suggesting the presence of α1CB6. The recovery of only 25-30% of α1CB6 in the expected position on SDS gel electrophoresis indicated that it was involved in interactions with other peptides in these two tissues to the extent of one and a half cross-links per tropocollagen molecule. The nature and distribution of cross-link peptides of bovine skin and dentin collagens was distinctly different.