The antigenicity of cartilage proteoglycans: The relationship of the antigenic determinants present in Smith degraded and intact proteoglycans

Abstract

In cartilage proteoglycans, chains of chondroitin sulphate are attached through a linkage region of neutral sugars to the protein core. Smith degradation, in which periodate oxidation is employed, cleaves the linkage at the terminal xylose residue, removing the entire chain without modifying the amino acids involved in the linkage. Rabbits were immunised with Smith degraded proteoglycan from bovine nasal cartilage, as well as with the intact proteoglycan and with proteoglycan from pig laryngeal cartilage. Cross reaction between all of the antigens and antisera showed that there was an antigenic determinant common to all three proteoglycans. Results obtained with the Smith degraded proteoglycan and its antiserum showed that the sugars of the linkage region and the chondroitin sulphate chains did not contribute to the expression of the species-common determinant, which must be due solely to amino acid sequence. Immunodiffusion and tanned-cell haemagglutination experiments showed that this species-common determinant was localised in that region of the core protein which in intact proteoglycans is resistant to trypsin and chymotrypsin.