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Gene Review

narX  -  sensory histidine kinase in two-component...

Escherichia coli str. K-12 substr. MG1655

Synonyms: ECK1216, JW1213, frdR, narR
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Disease relevance of narX


High impact information on narX

  • The narX, narQ and narL genes of Escherichia coli encode a nitrate-responsive two-component regulatory system that controls the expression of many anaerobic electron-transport- and fermentation-related genes [2].
  • In this study we report the isolation and characterization of narX* (star) mutants that constitutively activate nitrate reductase (narGHJI) gene expression and repress fumarate reductase (frdABCD) gene expression when no nitrate is provided for the cell [2].
  • The narQ gene was cloned, sequenced, and compared with the narX gene [3].
  • The narL and narX gene products are required for this nitrate-dependent control, and apparently function as members of a two-component regulatory system [3].
  • These findings suggest that the narX and narQ products have complementary sensor-transmitter functions for nitrate detection, and can work independently to activate NarL, for eliciting nitrate-dependent regulation of anaerobic electron transport and fermentation functions [3].

Biological context of narX


Associations of narX with chemical compounds

  • These data establish a clear role for the narX gene product in gene regulation and strongly suggest its role in sensing nitrate and molybdenum [9].
  • This regulation requires molybdate and is mediated by the narX and narL gene products, which together form a two-component regulatory system [9].
  • We have previously identified a locus called frdR which pleiotropically affects nitrate repression of fumarate reductase, trimethylamine N-oxide reductase, and alcohol dehydrogenase gene expression and nitrate induction of nitrate reductase expression (L. V. Kalman and R. P. Gunsalus, J. Bacteriol. 170:623-629, 1988) [8].
  • The frdR mutant was also derepressed for nitrate control of the trimethylamine-N-oxide reductase and alcohol dehydrogenase enzymes [10].

Other interactions of narX

  • narL and narX mediate nitrate induction of nitrate reductase synthesis and nitrate repression of fumarate reductase synthesis [5].
  • Analysis of these operon fusions indicated that narL and narX are transcribed counterclockwise with respect to the E. coli genetic map and that narK is transcribed clockwise [11].
  • Expression of phi (narX-lacZ) operon fusions was induced by nitrate and was decreased by narL and fnr mutations [11].
  • DNA truncation experiments for fnr and narX genes indicated that multiple anaero-boxes in each promoter region are essential for repression by the FNR protein, but they also suggest that factor-independent upstream activation signals are operating with these promoters [12].
  • These narX* alleles also caused the induction of nitrate reductase gene expression and the repression of a dmsA-lacZ fusion in the absence of nitrate [9].


  1. The narX and narL genes encoding the nitrate-sensing regulators of Escherichia coli are homologous to a family of prokaryotic two-component regulatory genes. Nohno, T., Noji, S., Taniguchi, S., Saito, T. Nucleic Acids Res. (1989) [Pubmed]
  2. Role of the periplasmic domain of the Escherichia coli NarX sensor-transmitter protein in nitrate-dependent signal transduction and gene regulation. Cavicchioli, R., Chiang, R.C., Kalman, L.V., Gunsalus, R.P. Mol. Microbiol. (1996) [Pubmed]
  3. Identification and characterization of narQ, a second nitrate sensor for nitrate-dependent gene regulation in Escherichia coli. Chiang, R.C., Cavicchioli, R., Gunsalus, R.P. Mol. Microbiol. (1992) [Pubmed]
  4. Dual response regulators (NarL and NarP) interact with dual sensors (NarX and NarQ) to control nitrate- and nitrite-regulated gene expression in Escherichia coli K-12. Rabin, R.S., Stewart, V. J. Bacteriol. (1993) [Pubmed]
  5. Structure of genes narL and narX of the nar (nitrate reductase) locus in Escherichia coli K-12. Stewart, V., Parales, J., Merkel, S.M. J. Bacteriol. (1989) [Pubmed]
  6. Instability of sensory histidine kinase mRNAs in Escherichia coli. Aiso, T., Ohki, R. Genes Cells (2003) [Pubmed]
  7. Influence of nar (nitrate reductase) genes on nitrate inhibition of formate-hydrogen lyase and fumarate reductase gene expression in Escherichia coli K-12. Stewart, V., Berg, B.L. J. Bacteriol. (1988) [Pubmed]
  8. Identification of a second gene involved in global regulation of fumarate reductase and other nitrate-controlled genes for anaerobic respiration in Escherichia coli. Kalman, L.V., Gunsalus, R.P. J. Bacteriol. (1989) [Pubmed]
  9. Nitrate- and molybdenum-independent signal transduction mutations in narX that alter regulation of anaerobic respiratory genes in Escherichia coli. Kalman, L.V., Gunsalus, R.P. J. Bacteriol. (1990) [Pubmed]
  10. The frdR gene of Escherichia coli globally regulates several operons involved in anaerobic growth in response to nitrate. Kalman, L.V., Gunsalus, R.P. J. Bacteriol. (1988) [Pubmed]
  11. Identification and expression of genes narL and narX of the nar (nitrate reductase) locus in Escherichia coli K-12. Stewart, V., Parales, J. J. Bacteriol. (1988) [Pubmed]
  12. Repression of in vitro transcription of the Escherichia coli fnr and nar X genes by FNR protein. Takahashi, K., Hattori, T., Nakanishi, T., Nohno, T., Fujita, N., Ishihama, A., Taniguchi, S. FEBS Lett. (1994) [Pubmed]
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