STRUCTURE AND COMPOSITION OF TYPE-IV COLLAGEN OF BOVINE AORTA

To determine the chain composition of type IV collagen of bovine thora cic aorta, we analyzed collagenase-solubilized carboxyl-terminal nonco llagenous (NC1)-domains by high-pressure liquid chromatography, two-di mensional electrophoresis, immunoblotting and enzyme-linked immunoassa y. In addition to the classical alpha1- and alpha2-chains, we found sm all amounts of the recently discovered alpha3-, alpha4- and alpha5-cha ins. The alpha3-and alpha4-chains were, collectively, 7-13% of the tot al, and the alpha5-chain was present in a low amount. Seventy-nine per cent of the NC1-domains were dimerized. Immunolocalization studies on sections of aorta showed that the alpha3- and alpha5-chains were prese nt, along with alpha1 and alpha2-chains, in the subendothelium and med ia. In capillaries of the media, the alpha3-chain was found at relativ ely high levels and was co-localized with alpha1- and alpha2-chains. D igestion of aorta with Pseudomonas aeruginosa elastase yielded soluble multimolecular assemblies of type IV collagen. Electron microscopy re sults provided a direct demonstration of the supramolecular structure, in which the collagen molecules were tetramerized at the amino-termin al end and dimerized at the carboxyl-terminal end.