Collagen structure and cartilage matrix integrity.

We continue to explore the molecular interactions that characterize the underlying heteropolymeric assembly of types II, IX, and XI collagen in articular cartilage. Structural studies on bovine articular cartilage reveal a high degree of specificity in the interactions of the individual alpha-chains of types IX and XI collagens. The results predict that type IX collagen molecules are not only heavily crosslinked to type II collagen, in an antiparallel orientation, but also to other type IX collagen molecules through specific sites. Type XI collagen molecules are primarily crosslinked to each other in the tissue, but the results are also consistent with type XI-II covalent interactions. We propose that selective proteolysis of types IX and XI collagens is a potential modulator of collagen network architecture.