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Gene Review

phoQ  -  virulence sensor histidine kinase PhoQ

Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

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Disease relevance of phoQ

  • Regulation of lipid A modifications by Salmonella typhimurium virulence genes phoP-phoQ [1].
  • A previous clinical study of phoP/phoQ-deleted S. enterica serovar Typhi expressing Helicobacter pylori urease from a multicopy plasmid showed that none of eight subjects had detectable immune responses to the vectored antigen [2].

High impact information on phoQ

  • The deduced amino acid sequence of the phoP and phoQ gene products are highly similar to other members of bacterial two-component transcriptional regulators that respond to environmental stimuli [3].
  • Genetic crosses established the gene order to be cobB pepT phoQ, and the direction of cobB transcription was shown to be clockwise [4].
  • Our data show extrachromosomal phoQ24 to be dominant over the chromosomal copy of the phoQ gene, conferring the PhoPc phenotype on the recipient strains [5].
  • The PhoPc phenotype results from a point mutation in phoQ, the gene encoding the sensor component of a two-component regulatory system (PhoP-PhoQ) that controls the expression of a number of virulence factors in Salmonellae [5].
  • The phoP-phoQ virulence locus of serovar Typhimurium also influenced the ability of DC to process Crl-OVA-expressing serovar Typhimurium for OVA(265-277)/I-A(b) presentation but not for OVA(257-264)/K(b) presentation [6].

Biological context of phoQ


Anatomical context of phoQ

  • The virulence defect conferred by mutations in the phoP-phoQ two-component regulatory system is not completely explained by alterations in resistance to cationic proteins and involves the control of other proteins necessary for S. typhimurium survival within macrophages [9].

Regulatory relationships of phoQ

  • This response to the macrophage intracellular environment is simulated by phoP/phoQ constitutive mutations (phenotype PhoPc) that increase the expression of pag genes and repress the synthesis of approximately 20 proteins encoded by phoP-repressed genes (prg genes) (S. I. Miller and J. J. Mekalanos, J. Bacteriol. 172:2485-2490, 1990) [10].

Other interactions of phoQ

  • Whereas mgtCB was completely dependent on regulation via phoPQ, the secondary late Mg(2+)-dependent phase of mgtA transcription was still evident in strains carrying a mutation in either phoP or phoQ, albeit substantially diminished [11].

Analytical, diagnostic and therapeutic context of phoQ


  1. Regulation of lipid A modifications by Salmonella typhimurium virulence genes phoP-phoQ. Guo, L., Lim, K.B., Gunn, J.S., Bainbridge, B., Darveau, R.P., Hackett, M., Miller, S.I. Science (1997) [Pubmed]
  2. Pilot study of phoP/phoQ-deleted Salmonella enterica serovar typhimurium expressing Helicobacter pylori urease in adult volunteers. Angelakopoulos, H., Hohmann, E.L. Infect. Immun. (2000) [Pubmed]
  3. A two-component regulatory system (phoP phoQ) controls Salmonella typhimurium virulence. Miller, S.I., Kukral, A.M., Mekalanos, J.J. Proc. Natl. Acad. Sci. U.S.A. (1989) [Pubmed]
  4. CobB, a new member of the SIR2 family of eucaryotic regulatory proteins, is required to compensate for the lack of nicotinate mononucleotide:5,6-dimethylbenzimidazole phosphoribosyltransferase activity in cobT mutants during cobalamin biosynthesis in Salmonella typhimurium LT2. Tsang, A.W., Escalante-Semerena, J.C. J. Biol. Chem. (1998) [Pubmed]
  5. Immunogenicity against human papillomavirus type 16 virus-like particles is strongly enhanced by the PhoPc phenotype in Salmonella enterica serovar Typhimurium. Baud, D., Benyacoub, J., Revaz, V., Kok, M., Ponci, F., Bobst, M., Curtiss, R., De Grandi, P., Nardelli-Haefliger, D. Infect. Immun. (2004) [Pubmed]
  6. Salmonella enterica serovar typhimurium-induced maturation of bone marrow-derived dendritic cells. Svensson, M., Johansson, C., Wick, M.J. Infect. Immun. (2000) [Pubmed]
  7. PhoP-PhoQ homologues in Pseudomonas aeruginosa regulate expression of the outer-membrane protein OprH and polymyxin B resistance. Macfarlane, E.L., Kwasnicka, A., Ochs, M.M., Hancock, R.E. Mol. Microbiol. (1999) [Pubmed]
  8. Mutational analysis of the residue at position 48 in the Salmonella enterica Serovar Typhimurium PhoQ sensor kinase. Sanowar, S., Martel, A., Moual, H.L. J. Bacteriol. (2003) [Pubmed]
  9. Characterization of defensin resistance phenotypes associated with mutations in the phoP virulence regulon of Salmonella typhimurium. Miller, S.I., Pulkkinen, W.S., Selsted, M.E., Mekalanos, J.J. Infect. Immun. (1990) [Pubmed]
  10. A PhoP-repressed gene promotes Salmonella typhimurium invasion of epithelial cells. Behlau, I., Miller, S.I. J. Bacteriol. (1993) [Pubmed]
  11. Magnesium transport in Salmonella typhimurium: biphasic magnesium and time dependence of the transcription of the mgtA and mgtCB loci. Tao, T., Grulich, P.F., Kucharski, L.M., Smith, R.L., Maguire, M.E. Microbiology (Reading, Engl.) (1998) [Pubmed]
  12. Evaluation of a phoP/phoQ-deleted, aroA-deleted live oral Salmonella typhi vaccine strain in human volunteers. Hohmann, E.L., Oletta, C.A., Miller, S.I. Vaccine (1996) [Pubmed]
  13. Specific detection of Salmonella spp. by multiplex polymerase chain reaction. Way, J.S., Josephson, K.L., Pillai, S.D., Abbaszadegan, M., Gerba, C.P., Pepper, I.L. Appl. Environ. Microbiol. (1993) [Pubmed]
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