BINDING-PROPERTIES AND PROTEASE STABILITY OF RECOMBINANT HUMAN NIDOGEN

Recombinant human nidogen was obtained from transfected kidney cell cl ones as a 150-kDa protein with a three-globule structure. It was modif ied by sulfation and O-glycosylation and a lower level of N-glycosylat ion than mouse nidogen. Recombinant nidogens of both species were, how ever, indistinguishable in their affinities for laminin-1 and a recomb inant laminin gamma 1 chain fragment and showed a similar binding to c ollagen IV and the heparan sulfate proteoglycan perlecan. The two nido gens were also equivalent in the promotion of ternary complex formatio n between these ligands, indicating that this function has been conser ved during mammalian evolution. Fewer zinc-binding sites could be iden tified in human nidogen and correlated with a lower capacity of zinc t o prevent binding to laminin and collagen IV. Most remarkable was the greater sensitivity of human nidogen to endogenous proteolysis in cell culture, yielding fragments of 90-145 kDa. Studies with several exoge nous proteases, including thrombin and leucocyte elastase, showed lack of stability of the N-terminal globular domain G1 in contrast to what was found for mouse nidogen. Since such degradation could be importan t for basement membrane remodelling, this difference between human and mouse may be biologically significant.