A small proteoglycan isolated from human cartilage containing a nonfunctional hyaluronic acid binding region.

A low buoyant density fraction (A4) was isolated from human cartilage by CsCl density gradient ultracentrifugation. This fraction contained a hydrodynamically small proteoglycan (Kav, 0.74 on Sepharose CL-2B) that reacted with monoclonal antibody 12/20/1C6 specific for the hyaluronic acid binding region (G1 globe) of the large aggregating high-density proteoglycan isolated from many animal cartilages. Despite the presence of the hyaluronic acid binding region, this small proteoglycan did not form proteoglycan aggregates with hyaluronan, not even in the presence of link protein.