Immunological studies of the fragments of bovine cartilage proteoglycan produced by chondroitinase-trypsin digestion

Abstract

Bovine nasal cartilage proteoglycan has at least three antigenic determinants: one associated with the “link proteins,” a second, “KS,” associated with keratan sulfate-con-taining peptide fragments of the proteoglycan subunit and a third, “CS,” associated with chondroitin sulfate-containing peptides. In this study, the distribution of these antigenic determinants in the products of chondroitinase-trypsin digestion of bovine nasal cartilage proteoglycan complex was determined. As shown by Heinegård and Hascall, Sepharose 2B chromatography of the chondroitinase-trypsin digest yielded early and late eluting peaks. By Sephadex G200 gel chromatography in 4 m guanidine, the initial Sepharose 2B peak was separated into three components: a link protein, a proteoglycan subunit fragment with the “KS” antigenic determinant and an immunologically unreactive polysaccharide, presumably hyaluronic acid, with which the other components bind under nondissociative conditions. The second Sepharose 2B peak of the chrondroitinase-trypsin digest was found to consist of “CS” antigen-containing fragments from the proteoglycan subunit, as well as a link protein and a “KS” antigen-containing proteoglycan subunit fragment similar to those found in the first Sepharose 2B peak. The presence of the latter proteoglycan components in the second Sepharose 2B peak most likely resulted from partial degradation of the hyaluronic acid in proteoglycan complex.