In vivo localization of the Salmonella enterica PhoP/PhoQ two-component system

SCIARA, M; SONCINI, F. C.; GARCÍA VÉSCOVI, E.

Rosario, Argentina

Congreso; 42th Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2006

Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular

The PhoP/PhoQ two-component system controls the expression of essential virulence traits in the pathogenic bacteria Salmonella enterica serovar Typhimurium. Environmental deprivation of Mg2+ activates the PhoP/PhoQ signal transduction cascade, which results in an increased expression of genes necessary for survival inside the host. Recent work showed that constituents of prokaryotic two-component systems such as P. aeruginosa PilS/PilR and E.coli OmpR/EnvZ show preferential localization. In order to investigate the localization of S. enterica PhoP and PhoQ and the effect of the input signal on their spatial distribution, we designed translational fusions to GFP and we also set up the recently developed FlAsH labelling technique, which just adds a hexa-aminoacid motif to the target protein. We demonstrate that, using both approaches, PhoP and PhoQ are recruited to the cell poles when extracelular Mg2+ is limiting. This polar localization is abrogated by high extracellular Mg2+ and when the fusion proteins are expressed in the DphoPQ background. This indicates that Mg2+ exerts a modulatory effect on PhoP and PhoQ localization provided both components are present in the cell. Besides, we show that the biarsenical-tetracysteine label is a convenient method for the in vivo fluorescent protein localization in prokaryotic cells, avoiding bulky tagging techniques and fixation procedures.