Polydispersity and heterogeneity of squid cranial cartilage proteoglycans as assessed by immunochemical methods and electron microscopy

The three populations of squid cranial cartilage proteoglycans, D1D1A, D1D1 B and D1D2 appeared to have a high degree of polydispersity. Gel electropho resis and immunoblotting analysis showed that polydispersity was mainly due to the variable size of chondroitin sulphate E chains. This was further as certained after rotary shadowing electron microscopy of proteoglycan core p roteins and glycosaminoglycan side chains and statistical, analysis of the sizes measured for both components. Enzymic treatment of the proteoglycan c ore proteins produced different peptides from each population, suggesting t hat the observed heterogeneity of the proteoglycans is due to their core pr oteins. Antibodies were raised in rabbits against all proteoglycans and enz yme-linked immunosorbent analysis of proteoglycan core proteins revealed th at the proteoglycans, even heterogeneous, shared many common epitopes. Part of the common proteoglycan epitopes were found to be located in chondroiti n sulphate E chains. Heterogeneity of squid proteoglycans was also investig ated by studying their interactions with collagen and it was found that onl y the two populations of high molecular mass, D1D1A and D1D2, were able to interact with only collagen type I, the latter stronger than the former. (C ) 2000 Societe francaise de biochimie et biologie moleculaire / Editions sc ientifiques et medicales Elsevier SAS.