Isolation and Molecular Characterization of the Locked-on Mutant of Mg2+ Sensor PhoQ in Escherichia coli

A Mg2+ sensor mutant (PhoQD179L(A)) in which D179 of PhoQ was changed into L or A was isolated and characterized in Escherichia coli. PhoQ–PhoP regulon genes, phoPQ, mgtA and mgrB transcriptions were repressed at a high Mg2+ concentration in WQ3007 (phoQ-defective strain)/pHO119, but not in WQ3007/pHO179L(A). The in vitro autophosphorylation activity of membrane-bound PhoQ was repressed by Mg2+ (10 mM), but that of membrane-bound PhoQD179L(A) was not. Furthermore, the phosphotransfer from membrane-bound PhoQ to PhoP was also repressed by Mg2+, but was not observed in membrane-bound PhoQD179L(A). These results suggest that PhoQD179L(A) is a locked-on mutant that is defective in extracellular Mg2+-sensing and that the D179 amino acid residue of PhoQ plays an essential role in signal transfer between the Mg2+-sensory and histidine kinase domain of PhoQ.

[1]  Hirotada Mori,et al.  Identification and Molecular Characterization of the Mg2+ Stimulon of Escherichia coli , 2003, Journal of bacteriology.

[2]  Sangpen Chamnongpol,et al.  Mg2+ sensing by the Mg2+ sensor PhoQ of Salmonella enterica. , 2003, Journal of molecular biology.

[3]  C. Waldburger,et al.  Mutational Analysis of the Escherichia coli PhoQ Sensor Kinase: Differences with the Salmonella enterica Serovar Typhimurium PhoQ Protein and in the Mechanism of Mg2+ and Ca2+ Sensing , 2002, Journal of bacteriology.

[4]  Akira Ishihama,et al.  Novel mode of transcription regulation of divergently overlapping promoters by PhoP, the regulator of two‐component system sensing external magnesium availability , 2002, Molecular microbiology.

[5]  Eduardo A. Groisman,et al.  The Pleiotropic Two-Component Regulatory System PhoP-PhoQ , 2001, Journal of bacteriology.

[6]  H. Le Moual,et al.  Characterization of the Catalytic Activities of the PhoQ Histidine Protein Kinase of Salmonella entericaSerovar Typhimurium , 2001, Journal of bacteriology.

[7]  R. Utsumi,et al.  Molecular Characterization of the PhoP-PhoQ Two-Component System in Escherichia coli K-12: Identification of Extracellular Mg2+-Responsive Promoters , 1999, Journal of bacteriology.

[8]  D. Koshland,et al.  Conformational changes in the cytoplasmic domain of the Escherichia coli aspartate receptor upon adaptive methylation. , 1998, Biochemistry.

[9]  E. Groisman,et al.  Characterization of the Bacterial Sensor Protein PhoQ , 1997, The Journal of Biological Chemistry.

[10]  S. Miller,et al.  Transcriptional regulation of Salmonella virulence: a PhoQ periplasmic domain mutation results in increased net phosphotransfer to PhoP , 1996, Journal of bacteriology.

[11]  R. Sauer,et al.  Signal Detection by the PhoQ Sensor-Transmitter , 1996, The Journal of Biological Chemistry.

[12]  E. Groisman,et al.  Mg2+ as an Extracellular Signal: Environmental Regulation of Salmonella Virulence , 1996, Cell.

[13]  S. Miller,et al.  Constitutive expression of the phoP regulon attenuates Salmonella virulence and survival within macrophages , 1990, Journal of bacteriology.