Data collection, phasing and refinement of the histidine kinase domain from LOV-HK from the pathogenic bacterium Brucella abortus.

S. KLINKE, J.J. RINALDI, G. SYCZ, G. PARIS, F. A. GOLDBAUM.

Córdoba

Congreso; IX Reunión de la Asociación Argentina de Cristalografía; 2013

Asociación Argentina de Cristalografía

Two-component signal transduction systems are modules that allow bacteria to rapidly adapt to changing environmental conditions. In the most common case, they are formed by a sensor histidine kinase (HK) which, upon sensing of an external signal, is able to phosphorylate a cognate response regulator (RR). The latter protein undergoes structural changes that are able to modify gene expression by directly binding to DNA, catalyze metabolic reactions or alter protein-protein interactions. The pathogenic bacterium Brucella abortus, the causative agent of brucellosis, bears a particular two-component system formed by a blue light sensor HK called LOV-HK and two RRs called PhyR and CheY. The activation of LOV-HK has been shown to increase the virulence of this pathogen [1]. Additionally, a mutant in the LOV-HK gene presents reduced infectivity, suggesting that this system is a virulence factor and an important regulatory system during the infection process. As part of our project, we solved the three-dimensional structure of the histidine kinase domain from LOV-HK by X-ray crystallography at 2.51 Å resolution, using sulfur-SAD as phasing method with over 30 heavy atom sites and highly redundant diffraction data collected at the SOLEIL synchrotron, France. Interestingly, the asymmetric unit of the crystal (about 100 kDa) contains two dimers with different arrangements. As judged by their interface area and contact nature, both dimers may exist in solution, yet a monomer is found in static light scattering experiments, probably because of dissociation during the previous gel filtration step. The structure shown here corresponds to the first histidine kinase from the HWE family with known three-dimensional structure [2]. [1] Swartz, T. et al., Science, 317, 1090-1093 (2007). [2] Karniol, B. et al., J. Bact., 186, 445-453 (2004).