Binding of nidogen and the laminin‐nidogen complex to basement membrane collagen type IV

Abstract

The laminin‐nidogen complex and purified nidogen both bind collagen IV but not other collagens, as shown by solid‐state ligand‐binding and inhibition assays. Laminin purified from the dissociated complex and a variety of laminin proteolytic fragments failed to bind collagen IV. Complexes formed in solution between nidogen or laminin‐nidogen and collagen IV were visualized by rotary shadowing which identified one major binding site about 80 nm away from the C‐terminus of the collagen triple helix. A second, weaker binding site may exist closer to its N‐terminus. Binding sites of nidogen were assigned to its C‐terminal globular domain which also possesses laminin‐binding structures. A more diverse collagen‐IV‐binding pattern was observed for the laminin‐nidogen complex, whereby interactions may involve both nidogen and short‐arm structures of laminin.