Cytolocalization of the Salmonella enterica PhoP response regulador

MARIELA I. SCIARA; FERNANDO C. SONCINI; ELEONORA GARCÍA VÉSCOVI

Mar del Plata

Congreso; XLIII Reunión anual; 2007

Sociedad de Investigación en Bioquímica y Biología Molecular

The Salmonella enterica two-component regulatory system controls the expression of several genes necessary for virulence, in response to extracellular (extracel) concentration (cc) of Mg . PhoQ interacts with extracel Mg and controls the phosphorylation state of PhoP. PhoP overexpression can substitute for PhoQ- and phosphorylation-dependent activation. Many bacterial processes involve asymmetric localization of protein activity (i.e., proteins involved in chemotaxis, development or signal transduction). In order to investigate the localization of PhoP and the effect of the input signal and the phosphorylation state on its spatial distribution, we set up the FlAsH labelling technique, which adds a hexaaminoacid motif to the target protein. We show in that PhoP was recruited to the cell poles when extracel Mg was limiting. This localization disappeared when the cognate component was absent. The non-phosphorylatable PhoP was uniformly localized in the cytoplasm, irrespective of the extracel. Mg cc or the presence of PhoQ. In over-expression conditions, both proteins showed a massive polar localization, not altered by the Mg cc used or by the absence of endogenous PhoQ. These results indicate that the migration of PhoP to the poles occurs when it is in its activated dimeric state, either due to PhoQ-dependent phosphorylation or to protein-protein interaction forced by over-expression.