Crystal structure and mutational analysis of a perlecan-binding fragment of nidogen-1

Nidogen, an invariant component of basement membranes, is a multifunctional protein that interacts with most other major basement membrane proteins. H ere, we report the crystal structure of the mouse nidogen-l GZ fragment, wh ich contains binding sites for collagen IV and perlecan. The structure is c omposed of an EGF-like domain and an Ii-stranded beta -barrel with a centra l helix. The beta -barrel domain has unexpected similarity to green fluores cent protein. A large surface patch on the beta -barrel is strikingly conse rved in all metazoan nitrogens. Site-directed mutagenesis demonstrates that the conserved residues are involved in perlecan binding.