The altered fibrous form of vitreous collagen following solubilization with pepsin

Collagen occurs in the extracellular matrix of the bovine vitreous as fibers which have a fairly uniform diameter of approximately 195 A and exhibit an indistinct axial periodicity. Following treatment with pepsin approximately three quarters of the collagen was rendered soluble and by gel electrophoresis and comparison with calf skin collagen was shown to be composed of alpha1 chains, a high molecular weight alpha chain component, beta, as well as other high order components. No alpha2 chains were detected. The amino acid composition of the pepsin soluble collagen was different from that of other collagens composed only of alpha1 chains which suggests that it is composed of either a distinct type or mixture of alpha chains. When fibers were reconstituted from the pepsin solubilized collagen they differed markedly from the native fibers and exhibited a pronounced axial periodicity (approximately 640 A) and had diameters up to 1500 A. The difference between the reconstituted and native fibers suggests that the presence of the peptides cleaved by pepsin may be one of the factors which determines the particular fibrous form of collagen in the bovine vitreous.