The Crystal Structure of Dihydrodipicolinate Synthase from Escherichia coliat 2.5 Å Resolution

Abstract

The crystal structure of dihydrodipicolinate synthase from E. coliwas determined by multiple isomorphous replacement methods. The structure was refined at a resolution of 2.5 Å and the final R-factor is 19.6% for 32,190 reflections between 10.0 Å and 2.5 Å and F2σ( F). The crystallographic asymmetric unit contains two monomers related by approximat 2-fold symmetry. A tetramer with approximate 222 symmetry is built up by crystallographic symmetry. The tetramer is almost planar with no contacts between the subunits related by the non-crystallographic dyad. The active sites are accssible from a wide water-filled channel in the center of th tetramer. The dihydrodipicolinate synthase monomer is composd of two domains. Each polypeptide chain is folded into an 8-fold α/β barrel and a C-terminal α-helical domain comprising residues 224 to 292. The fold is similar to that of N-acetylneuraminate lyase. The active site lysine 161 is located in the α/β barrel and has access viatwo entrances from the C-terminal side of the barrel.