Different levels of glycosylation contribute to the heterogeneity of α1(II) collagen chains derived from a transplantable rat chondrosarcoma

Abstract

Three collagen fractions, each of which contain molecules composed of α1(II) chains, have been isolated from pepsin-solubilized rat chondrosarcoma collagen. One fraction could be selectively precipitated from the pepsin digest at 0.7 m NaCl. Two additional fractions were obtained on chromatography of the collagen precipitating at 1.2 m NaCl on carboxymethyl cellulose under nondenaturing conditions. When chromatographed on carboxymethyl cellulose under denaturing conditions, each fraction contained components eluting in the position expected for α1(II) chains. One of the fractions precipitating at 1.2 m NaCl contained the recently described 1α and 2α chains in addition to material eluting as α1(II) chains. Comparison of the chains eluting as α1(II) chains in the various fractions with respect to amino acid composition, carbohydrate content, and cyanogen bromide-cleavage products showed that they differed only in the number of glycosylated hydroxylysyl residues. In this regard, α1(II) chains obtained from collagens precipitated at 1.2 m NaCl exhibited significantly higher levels of glucosylgalactosylhydroxylysyl residues than α1(II) chains precipitated at 0.7 m NaCl. These results indicate that molecules composed of α1(II) chains are heterogeneous with respect to levels of hydroxylysine-linked carbohydrate moieties and that the more highly glycosylated molecules require higher salt concentrations for precipitation from acidic solutions. The data also indicate that a proportion of the more highly glycosylated α1(II) chains are involved in the formation of one or more molecular species with 1α and 2α chains.