Distinct interaction of versican/PG-M with hyaluronan and link protein

The proteoglycan aggregate is the major structural component of the cartilage matrix, comprising hyaluronan (HA), link protein (LP), and a large chondroitin sulfate (CS) proteoglycan, aggrecan. Here, we found that another member of aggrecan family, versican, biochemically binds to both HA and LP. Functional analyses of recombinant looped domains (subdomains) A, B, and B' of the N-terminal G(1) domain revealed that the B-B' segment of versican is adequate for binding to HA and LP, whereas A and B-B' of aggrecan bound to LP and HA, respectively. BIAcore(TM) analyses showed that the A subdomain of versican G(1) enhances HA binding but has a negligible effect on LP binding. Overlay sensorgrams demonstrated that versican G(1) or its B-B' segment forms a complex with both HA and LP. We generated a molecular model of the B-B' segment, in which a deletion and an insertion of B' and B are critical for stable structure and HA binding. These results provide important insights into the mechanisms of formation of the proteoglycan aggregate and HA binding of molecules containing the link module.