Collagen structural microheterogeneity and a possible role for glycosylated hydroxylysine in type I collagen

Publisher Website
Google Scholar
Abstract
A 3-chained peptide from type I collagen, crosslinked by hydroxyaldolhistidine, was isolated from a tryptic digest of 5 M guanidine.cntdot.HCl-insoluble bovine skin collagen (a small but as yet unknown percentage of the total collagen in whole skin). OsO4/NaIO4 specifically cleaved the crosslink at its double bond into a 2-chained crosslink peptide and a single peptide. The sequence of the 2-chained peptide containing the bifunctional crosslink was determined after amino acid analysis of the separated peptides. The crosslink consists of an aldehyde derived from hydroxylysine-87 in the aldehyde-containing cyanogen bromide fragment .alpha.1CB5ald and an aldehyde derived from the lysine in the COOH-terminal nonhelical region of the .alpha.1CB6ald fragment. The .alpha.1CB6ald portion of the peptide exhibited structural microheterogeneity containing the inverted sequence Ala-Lys-His instead of the normal sequence Lys-Ala-His. Another structural gene evidently exists for .alpha.1(I) chain. The original 3-chained peptide did not contain any glycosylated hydroxylysine or glycosylated hydroxyaldolhistidine. The lack of glycosylation of hydroxylysine-87 in .alpha.1CB5, which is usually glycosylated, allowed formation of the aldehyde, and this, coupled with the sequence inversion, may have allowed formation of the nonreducible crosslink hydroxyaldolhistidine. The role of glycosylation, a posttranslational modification of specific hydroxylysine residues apparently is to prevent their oxidative deamination to aldehydes, thereby precluding formation of complex stable crosslinks. Complex crosslinks would decrease the rate of collagen turnover. The decrease, with time, would increase the population of stable crosslinked collagen molecules, which would eventually accumulate with age.

This publication has 30 references indexed in Scilit: