Interaction of link protein with collagen.

Link protein (Mr = 42,000) is an integral component of cartilage as well as of some noncartilagenous tissues. In cartilage, it forms a macromolecular complex with cartilage proteoglycan and hyaluronic acid, but its function in other tissues is unknown. We provide evidence here that the link protein of cartilage binds well to native collagen types I and III. The binding occurs only if both link protein and collagen are native. The binding of link protein to collagen type fibrils is higher than to monomeric collagen. Link protein binding to collagen fibrils is saturable and occurs at molar ratio of collagen to link protein of 7-13:1. These data suggest that the link protein binds to collagen and that the binding requires the collagen to be in its native triple helical structure. This interaction may play a role in collagen fibril formation.