Crystallization and crystallographic analysis of a bradyrhizobium elkanii usda94 haloalkane dehalogenase variant with an eliminated halide-binding site

Haloalkane dehalogenases are a very important class of microbial enzymes for environmental detoxification of halogenated pollutants, for biocatalysis, biosensing and molecular tagging. The double mutant (Ile44Leu + Gln102His) of the haloalkane dehalogenase DbeA from Bradyrhizobium elkanii USDA94 (DbeA∆Cl) was constructed to study the role of the second halide-binding site previously discovered in the wild-type structure. The variant is less active, less stable in the presence of chloride ions and exhibits significantly altered substrate specificity when compared with the DbeAwt. DbeA∆Cl was crystallized using the sitting-drop vapour-diffusion procedure with further optimization by the random microseeding technique. The crystal structure of the DbeA∆Cl has been determined and refined to the 1.4 Å resolution. The DbeA∆Cl crystals belong to monoclinic space group C121. The DbeA∆Cl molecular structure was characterized and compared with five known haloalkane dehalogenases selected from the Protein Data Bank.