Glycosylation and cross-linking in bone type I collagen [Genomics and Proteomics]

June 23rd, 2014 by Terajima, M., Perdivara, I., Sricholpech, M., Deguchi, Y., Pleshko, N., Tomer, K. B., Yamauchi, M.

Fibrillar type I collagen is the major organic component in bone providing a stable template for mineralization. During collagen biosynthesis, specific hydroxylysine residues become glycosylated in the form of galactosyl- and glucosylgalactosyl-hydroxylysine. Furthermore, key glycosylated hydroxylysine residues, α1/2-87, are involved in covalent intermolecular cross-linking. While cross-linking is crucial for the stability and mineralization of collagen, the biological function of glycosylation in cross-linking is not well understood. In this study, we quantitatively characterized glycosylation of non-cross-linked and cross-linked peptides by biochemical and nanoscale liquid chromatography - high resolution tandem mass spectrometric analyses. The results showed that glycosylation of non-cross-linked hydroxylysine is different from that involved in cross-linking. Among the cross-linked species involving α1/2-87, divalent cross-links were glycosylated with both mono- and di saccharides while the mature, trivalent cross-links were primarily mono-glycosylated. Markedly diminished diglycosylation in trivalent cross-links at this locus was also confirmed in type II collagen. The data, together with our recent report (Sricholpech et al J Biol Chem 287:22998-23009, 2012), indicates that the extent and pattern of glycosylation may regulate cross-link maturation in fibrillar collagen.