Control of the PhoP/PhoQ signal transduction by magnesium

SONCINI, FERNANDO CARLOS; GARCÍA VÉSCOVI, ELEONORA

San Francisco. EE.UU.

Congreso; XI International Congress of Bacteriology and Applied Microbiology; 2005

International Union of Microbiologial Societies

In the pathogenic bacterium Salmonella enterica, magnesium plays a fundamental role during the infection process. Salmonella utilizes the level of environmental Mg2+ as a signal to control the expression of several essential virulence determinants. This sensing process is mediated by a specific signal-transduction system known as PhoP/PhoQ. We have identified that phosphorylation of the response regulator promotes its self-association, allowing the protein to recognize and interact with a direct-repeat sequence located in the promoter region of a set of orthodox PhoP-activated genes (pags), and that extracellular Mg2+ controls a specific response-regulator (PhoP) phosphatase activity in the membrane-associated sensor protein PhoQ, inactivating the transcriptional regulator. The N-terminal domain of the sensor protein is responsible for the extracellular Mg2+ recognition, and mutants in this region that affect the proper signal-transduction process were identified. The analysis of the PhoP/PhoQ regulatory system is relevant to understand how intracellular Mg2+ is kept within a precise range to guarantee the proper function of vital intracellular mechanisms.