Structural analysis of Helicobacter pylori glutamate racemase in a monoclinic crystal form

Glutamate racemase (MurI) catalyzes the stereochemical interconversion of L-glutamate and D-glutamate, a key element of bacterial peptidoglycan biosynthesis. In this study, we present the crystal structure of Helicobacter pylori glutamate racemase at 1.43 Å resolution and with monoclinic symmetry, as in previously reported models, but with different unit-cell parameters. The present model contains a single dimer in the asymmetric unit and retains the previously described head-to-head dimer arrangement. Comparative analysis of crystal packing reveals that the conserved dimeric assembly frequently adopts similar packing motifs, while differences in the relative arrangement of these dimeric arrays result in altered crystal packing and variations in unit-cell parameters. The monomeric fold and active-site architecture remain conserved and are consistent with the catalytic features described for bacterial glutamate racemases. This structure provides an updated, high-resolution structural model for H. pylori glutamate racemase and highlights the variability of crystal-packing arrangements within related monoclinic crystal forms.