STRUCTURE OF THE NIDOGEN BINDING LE MODULE OF THE LAMININ GAMMA-1 CHAIN IN SOLUTION

The structure of the single LE module between residues 791 and 848 of the laminin gamma 1 chain, which contains the high affinity binding si te for nidogen, has been probed using NMR methods. The module folds in to an autonomous domain which has a stable and unique three-dimensiona l (3D) structure in solution. The 3D structure was determined on the b asis of 362 interproton distance constraints derived from nuclear Over hauser enhancement measurements and 39 phi angles, supplemented by 5 p si and 22 chi(1) angles. The main features of the NMR structures are t wo-stranded antiparallel beta-sheets which are separated by loops and cross-connected by four disulfide bridges. The N-terminal segment whic h contains the first three disulfide bridges is similar to epidermal g rowth factor. The C-terminal segment has an S-like backbone profile wi th a crossover at the last disulfide bridge and comprises two three-re sidue long beta-strands that form an antiparallel beta-sheet. The LE m odule possesses an exposed nidogen binding loop that projects away fro m the main body of the protein. The side-chains of three amino acids w hich are crucial for binding (Asp, Asn, Val) are all exposed at the do main surface. An inactivating Asn-Ser mutation in this region showed t he same 3D structure indicating that these three residues, and possibl y an additional Tyr in an adjacent loop, provide direct contacts In th e interaction with nidogen. (C) 1996 Academic Press Limited