The H box-harboring domain is key to the function of the Salmonella enterica PhoQ Mg2+-sensor in the recognition of its partner PhoP.

MARÍA EUGENIA CASTELLI; ANA CAUERHFF; MARCELA AMONGERO; FERNANDO C. SONCINI; ELEONORA GARCÍA VÉSCOVI

JOURNAL OF BIOLOGICAL CHEMISTRY

American Society for Biochemistry and Molecular Biology

Año: 2003 vol. 278 p. 23579 - 23585

0021-9258

In two-component signaling systems the transduction strategy relies on a conserved His-Asp phosphoryl exchange between the sensor-histidine kinase and its cognate response-regulator, and structural and functional consensus motifs are found when comparing either the diverse histidine kinases or response regulators present in a single cell.  Therefore, the mechanism that guarantees the specific recognition between partners of an individual pair is essential to unequivocally generate the appropriate adaptive response.  Based on sequence alignments with other histidine kinases, we dissected the S. enterica Mg2+-sensor PhoQ in different sub-domains and examined by in vivo and in vitro assays its interaction with the associated response regulator PhoP.  This signal transduction system allows Salmonella to withstand environmental Mg2+-limitation by triggering gene expression that is vital throughout the infective cycle in the host.  Using resonant mirror biosensor technology we calculated the kinetic and equilibrium binding constants and determined that the His-phosphotransfer domain is essential for the PhoQ specific recognition and interaction with PhoP.  Besides, we show the role of this domain in the bimolecular transphosphorylation and provide evidence that this region undergoes dimerization