Purification of a noncollagenous high molecular weight protein from bovine articular cartilage

A noncollagenous high molecular weight protein (HMW) was isolated from bovine articular cartilage by CsCl density gradient centrifugation followed by DEAE-cellulose chromatography and gel filtration chromatography. The molecular weight was estimated to be 320 kDa and the reduced HMW had a molecular weight of 105 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The amino acid composition of HMW showed a high content of aspartic acid, but no hydroxylysine and hydroxyproline were detected, indicating that the protein was not a collagen. Affinity purified rabbit antibody against HMW reacted specifically with HMW, but there was no immunoreaction with cartilage-specific proteoglycan, type II collagen and type I collagen. HMW showed dose-dependent attachment to types I, II, III and V collagens. However, HMW did not bind to fibronectin, decorin and heparin. Furthermore, the binding of HMW to heat-denatured collagens was lower than native collagens. In these observation, HMW may be recognized the triple helix structure of collagen for the interaction.