Isolation and characterization of a proteodermatan sulfate from calf skin

A proteodermatan sulfate was extracted from calf skin with 3 M MgCl2 at 4 degrees C in the presence of protease inhibitors and purified by DEAE-cellulose chromatography followed by CsCl density gradient centrifugation. The molecular weight of the proteoglycan was estimated to be approximately 115,000, based on the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The proteoglycan contains neutral sugars such as galactose, xylose, mannose, fucose, and glucose, but its amino acid composition is similar to that of proteodermatan sulfates from bovine heart valve, tendon, sclera, and pig and rat skin. The core protein is a glycoprotein with a molecular weight of 56,000 and seems to be monodisperse. However, the dermatan sulfate component, which is the only glycosaminoglycan constituent composed of 95% 4-sulfated disaccharide unit and 5% 6-sulfated disaccharide unit, seems to be polydisperse with a number average molecular weight of 17,000, as judged from both gel chromatography and chemical analysis. Analysis by beta-elimination and reduction of the dermatan sulfate-peptide(s) indicated that the glycan components are linked to the core protein through an O-glycosidic linkage between xylose and serine residues. From these results, we propose a model for the structure of calf skin proteodermatan sulfate that is composed of 3--4 chains of dermatan sulfate components which are covalently linked to a core (glyco-) protein via O-glycosidic linkages.