Crystallographic analysis of 1,2,3-trichloropropane biodegradation by the haloalkane dehalogenase DhaA31

Vapour soaking of crystals of the R. rhodochrous haloalkane dehalogenase variant DhaA31 with 1,2,3-trichloropropane at room temperature and pH 6.5 facilitated the production of a protein-substrate complex. Comparison of the substrate-free DhaA31 structure with that of the DhaA31-substrate complex revealed two alternative conformations of the nucleophilic residue Asp106 and a possible pathway for halide release, while comparison of DhaA31 with wild-type DhaA revealed reduced size and solvent-accessibility of the active site.

Structural and functional analysis of a novel haloalkane dehalogenase with two halide-binding sites

Two halide-binding sites were identified in the crystal structure of the newly isolated haloalkane dehalogenase DbeA from Bradyrhizobium elkanii USDA94. Elimination of the second halide-binding site significantly modified the enzyme substrate specificity, catalytic activity and stability in the presence of chloride salts. A shift in the substrate-specificity class after mutagenesis was demonstrated for the first time for haloalkane dehalogenases.