Rare Nature of Crystals of the Novel Multimeric Haloalkane Dehalogenase DpaA from Paraglaciecola agarilytica NO2.

Manuscript reports on novel haloalkane dehalogenase DpaA isolated from a psychrophilic and halophilic bacterium Paraglaciecola agarilytica NO2 that was crystallized and two independent crystallization and data collection experiments resulted in several data sets with a resolution ranging from 2.2 to 3.7 Å. X-ray diffraction data analysis hinted at oligomeric nature of DpaA leading to certain issues with the solution of structure. Our results unveil a rare example of an oligomeric dehalogenase belonging the subfamily I as well as highlight new findings in the solution of crystallographic data with unusual crystal packing. The crystal structures of HLD-I subfamily already deposited into the PDB database are monomeric. There are only a few examples of oligomeric haloalkane dehalogenases from the other subfamilies HLD-II and HLD-III that can form dimers and tetramers. The crystal structures of enzymes from the HLD-III subfamily showing oligomeric properties in gel-filtration experiments have not been solved to date. DpaA’s propensity to oligomerization likely causes the problems with solution of the structure, such as pseudo-translation, in a wide range of crystallization conditions and across various crystal lattices. Our results contribute to explaining new findings in solving the structures of oligomeric proteins that exhibit unusual crystal packing and mark the DpaA enzyme as an uncommon oligomeric example of the HLD-I subfamily.