Isolation and properties of a soluble chondroitin sulfate proteoglycan from brain

A proteoglycan in which the glycosaminoglycans are predominantly chondroitin sulfate has been isolated from the soluble fraction of rat brain by ion exchange chromatography and gel filtration. Glycoprotein oligosaccharides are also present, and result in adsorption of the proteoglycan by Concanavalin A-Sepharose. The proteoglycan-glycoprotein complex eluted from the affinity column by alpha-methylglucoside floats near the top of a cesium chloride density gradient run under dissociative conditions (4 M guanidine), but after beta-elimination of the chondroitin sulfate polysaccharide chains from their low buoyant density glycoprotein complex they sediment to the bottom of the gradient. These results suggest that relatively few polysaccharide chains are covalently linked to a large protein core in the dissociated chondroitin sulfate proteoglycan "subunit" from brain, and that the proteoglycans are closely associated with soluble glycoproteins.