The crystal structure of dihydrodipicolinate reductase from the human-pathogenic bacteriumBartonella henselaestrain Houston-1 at 2.3 Å resolution

Abstract

In bacteria, the second committed step in the diaminopimelate/lysine anabolic pathways is catalyzed by the enzyme dihydrodipicolinate reductase (DapB). DapB catalyzes the reduction of dihydrodipicolinate to yield tetrahydrodipicolinate. Here, the cloning, expression, purification, crystallization and X-ray diffraction analysis of DapB from the human-pathogenic bacteriumBartonella henselae, the causative bacterium of cat-scratch disease, are reported. Protein crystals were grown in conditions consisting of 5%(w/v) PEG 4000, 200 mMsodium acetate, 100 mMsodium citrate tribasic pH 5.5 and were shown to diffract to ∼2.3 Å resolution. They belonged to space groupP4322, with unit-cell parametersa= 109.38,b= 109.38,c= 176.95 Å.Rr.i.m.was 0.11,Rworkwas 0.177 andRfreewas 0.208. The three-dimensional structural features of the enzymes show that DapB fromB. henselaeis a tetramer consisting of four identical polypeptides. In addition, the substrate NADP+was found to be bound to one monomer, which resulted in a closed conformational change in the N-terminal domain.