Haloalkane dehalogenases (HLDs) convert halogenated aliphatic pollutants to less toxic compounds by a hydrolytic mechanism. Owing to their broad substrate specificity and high enantioselectivity, haloalkane dehalogenases can function as biosensors to detect toxic compounds in the environment or can be used for the production of optically pure compounds. Here, the structural analysis of the haloalkane dehalogenase DpcA isolated from the psychrophilic bacterium Psychrobacter cryohalolentis K5 is presented at the atomic resolution of 1.05 A. This enzyme exhibits a low temperature optimum, making it attractive for environmental applications such as biosensing at the subsurface environment, where the temperature typically does not exceed 25 degrees C. The structure revealed that DpcA possesses the shortest access tunnel and one of the most widely open main tunnels among structural homologs of the HLD-I subfamily. Comparative analysis revealed major differences in the region of the alpha4 helix of the cap domain, which is one of the key determinants of the anatomy of the tunnels. The crystal structure of DpcA will contribute to better understanding of the structure-function relationships of cold-adapted enzymes.
Haloalkane dehalogenases are hydrolytic enzymes with a broad range of potential practical applications such as biodegradation, biosensing, biocatalysis and cellular imaging. Two newly isolated psychrophilic haloalkane dehalogenases exhibiting interesting catalytic properties, DpcA from Psychrobacter cryohalolentis K5 and DmxA from Marinobacter sp. ELB17, were purified and used for crystallization experiments. After the optimization of crystallization conditions, crystals of diffraction quality were obtained. Diffraction data sets were collected for native enzymes and complexes with selected ligands such as 1-bromohexane and 1,2-dichloroethane to resolutions ranging from 1.05 to 2.49 A.
Representative scheme of Haloalkane_dehalogenase-HLD1 structure and an image from PDBsum server
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6F9O Previously Class, Architecture, Topology and Homologous superfamily - PDB-Sum server
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6F9OFold classification based on Structure-Structure alignment of Proteins - FSSP server
