High molecular weight mucin-like glycoproteins of the bovine interphotoreceptor matrix

摘要: Abstract A very high molecular weight mucin-like glycoprotein was isolated by gel filtration of interphotoreceptor matrix (IPM) from fresh bovine eyes and purified to apparent homogeneity cesium chloride/guanidine hydrochloride (GuHCl) equilibrium density gradient centrifugation. Although a in excess 107 Da is suggested filtration, the presence SDS or GuHCl did not alter its elution position, indicating that large size simply due aggregation. Treatment this material with disulfide reagents, however, led decrease size. On relative basis, substantially more present IPM prepared retina than retinal pigment epithelium. While carbohydrate amino acid composition are those true ‘mucin’, many other properties quite ‘mucin-like’. The suggests both N- O-glycosidically linked sugar chains. mucin-type O-glycosidic linkage indicated susceptibility alkaline cleavage, concomitant loss serine threonine increase 240 nm absorbance; production fluorescent product upon reaction cyanoacetamide; lectin binding properties; N-acetylgalactosaminitol borohydride elimination. This digested pronase trypsin, confirming protein nature, but resistant digestion chondroitin ABC lyase, hyaluronidase heparinase, as well RNAase, these components were any appreciable extent. ELISA for cartilage keratan sulfate also negative. Centrifugation CsCl gradients much lower proteoglycan nucleic well. In vitro biosynthetic studies suggest epithelium may be major sources IPM. patterns radioactivity strikingly similar UV medium incubations contained which enzymes hydrolyse glycosaminoglycans, suggesting source weight, glycoprotein.