Structure of a halophilic nucleoside diphosphate kinase from Halobacterium salinarum

Nucleoside diphosphate kinase from the halophilic archaeon Halobacterium salinarum was crystallized in a free state and a substrate-bound form with CDP. The structures were solved to a resolution of 2.35 and 2.2 angstrom, respectively. Crystals with the apo-form were obtained with His(6)-tagged enzyme, whereas the untagged form was used for co-crystallization with the nucleotide. Crosslinking under different salt and pH conditions revealed a stronger oligomerization tendency for the tagged protein at low and high salt concentrations. The influence of the His(6)-tag on the halophilic nature of the enzyme is discussed on the basis of the observed structural properties. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.