Isolation and Characterization

Previous studies show that the collagen fibrils of the mammalian vitreous humor are assembled largely from type I1 collagen with smaller amounts of type IX collagen and either type V or type XI collagen. In this paper, we report the separation of two chains of type V/type XI collagen from type I1 collagen by heparinSepharose chromatography. These chains were characterized by sequencing of selected cyanogen bromide or tryptic peptides with subsequent comparison of these sequences with cDNA-derived amino acid sequences of the a l ( V ) , al(XI), a2(V), and a2(XI) chains. The results show that vitreous fibrils are assembled from molecules containing the al(X1) and a2(V) chains. These results, together with recent results from other laboratories, indicate that type V and type XI collagens are not separate collagen types but are part of a larger collagen family in which chains of both type V and type XI collagens participate in the formation of a variety of native molecules.