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 Å. 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°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 α4 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.

Faculty of Science University of South Bohemia in Ceske Budejovice Branisovska 1760 370 05 Ceske Budejovice Czech Republic

Institute of Organic Chemistry and Biochemistry Academy of Sciences of the Czech Republic v v i Flemingovo nam 2 166 10 Prague Czech Republic

Loschmidt Laboratories Department of Experimental Biology and RECETOX Faculty of Science Masaryk University Kamenice 5 A13 625 00 Brno Czech Republic

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