Interactions between different corneal proteoglycans

Abstract

Proteoglycans were extracted from bovine cornea with 4M-guanidinium chloride and purified by CsCl-density-gradient centrifugation. Under associative conditions 2 fractions were found, one capable of forming assemblies of high MW and another lacking this property. The heavier fraction (density 1.59 g/ml) was eluted as a single retarded peak from Sepharose 2B, but on DEAE-Sephadex chromatography, gave 2 peaks: the 1st (eluted with 0.75 M-NaCl) contained mainly proteochondroitin sulfate and the 2nd (eluted with 1.25 M-NaCl) mainly proteokeratan sulfate. Each of these proteoglycans was more retarded on Sepharose 2B than was the original sample from density-gradient centrifugation. Re-aggregation was obtained by recombination of the 2 fractions. The lighter fraction (density 1.44 g/ml), containing predominantly keratan sulfate chains, was eluted from DEAE-Sephadex as a single peak with 1.25 M-NaCl and was retarded on Sepharose 2B: this fraction was not able to form aggregates with proteochondroitin sulfate. Chemical analyses of the carbohydrate and protein moieties of the proteoglycans from DEAE-Sephadex confirmed that, in the cornea, different subunits are present with characteristic aggregation properties and hydrodynamic volumes.