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Gene Review

narG  -  nitrate reductase 1, alpha subunit

Escherichia coli str. K-12 substr. MG1655

Synonyms: ECK1218, JW1215, chlC, narC
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Disease relevance of narG


High impact information on narG

  • Expression of narL does not require the fnr gene product, a pleiotropic activator that is required for full expression of narC, frd, and tor [2].
  • DNase I footprinting studies revealed that IHF protects a 37-base pair region centered 125 base pairs 5' of the narG transcription site [3].
  • Previous studies established that the first two genes in the operon narG and narH encode the alpha and beta subunits, respectively, while formation of the gamma subunit, cytochrome bNR, depends on expression of the promoter distal genes [4].
  • Previous work has shown that nucleotide substitutions in two of these heptamers, centred at positions -195 and -89, severely reduce nitrate induction of narG operon expression in vivo and significantly interfere with NarL-DNA interactions in vitro [5].
  • Substitutions in heptamers -185 and -101 affected narG operon induction only when the concentration of phospho-NarL was low (during growth in the presence of nitrite) [5].

Chemical compound and disease context of narG

  • This places the tdk gene at approximately minute 27.35 on the E. coli W3110 chromosome, about 15 kb downstream from the narG locus and approximately 25 kb upstream of the trp operon [6].

Biological context of narG


Anatomical context of narG

  • The nitrate reductase in the wild type was completely stable in vivo under inducing or noninducing conditions, whereas in the chlC and chlE mutants nitrate reductase was degraded extensively in both the cytoplasm and membranes, even under inducing conditions [11].

Associations of narG with chemical compounds

  • In the present study we found that a molybdenum coeffector acted synergistically with nitrate in the regulation of frd and narC [12].
  • In chlB mutants, which are known to accumulate the Mo cofactor because of its failure to be inserted as a prosthetic group into proteins such as nitrate reductase, nitrate repression of frd and induction of narC were also intensified by molybdate supplementation [12].

Physical interactions of narG


Other interactions of narG

  • Protein fusions of lacZ with the N-terminal sequence of the narG gene were constructed so that beta-galactosidase formation was under the control of the nar promoter and one or both regulatory domains [13].
  • From the nucleotide sequence of the narI region of the operon we conclude that, in addition to the narG and narH genes, the nar operon contains two other open reading frames (ORFs), ORF1 and ORF2, that encode proteins of 26.5 and 25.5 kilodaltons, respectively [14].
  • The narGHJI operon, encoding nitrate reductaseA, is located in the chlC locus at 27 minutes, along with several functionally related genes: narK, encoding a nitrate/nitrite antiporter, and the narXL operon, encoding a nitrate-activated, two component regulatory system [15].
  • The chlC locus is suggested to be the structural gene for nitrate reductase subunit A and chlE is suggested to be involved in the synthesis of the cytochrome b1 apoprotein [16].
  • In light of these findings, prior models for the roles of nitrate and nitrite in control of narG and napF expression must be reconsidered [17].


  1. Presence in the 'silent' terminus region of the Escherichia coli K12 chromosome of cryptic gene(s) encoding a new nitrate reductase. Bonnefoy, V., Burini, J.F., Giordano, G., Pascal, M.C., Chippaux, M. Mol. Microbiol. (1987) [Pubmed]
  2. The narL gene product activates the nitrate reductase operon and represses the fumarate reductase and trimethylamine N-oxide reductase operons in Escherichia coli. Iuchi, S., Lin, E.C. Proc. Natl. Acad. Sci. U.S.A. (1987) [Pubmed]
  3. Activation of the Escherichia coli nitrate reductase (narGHJI) operon by NarL and Fnr requires integration host factor. Schröder, I., Darie, S., Gunsalus, R.P. J. Biol. Chem. (1993) [Pubmed]
  4. Roles of the narJ and narI gene products in the expression of nitrate reductase in Escherichia coli. Sodergren, E.J., Hsu, P.Y., DeMoss, J.A. J. Biol. Chem. (1988) [Pubmed]
  5. Analysis of nitrate regulatory protein NarL-binding sites in the fdnG and narG operon control regions of Escherichia coli K-12. Darwin, A.J., Li, J., Stewart, V. Mol. Microbiol. (1996) [Pubmed]
  6. Nucleotide sequence of the Escherichia coli thymidine kinase gene provides evidence for conservation of functional domains and quaternary structure. Black, M.E., Hruby, D.E. Mol. Microbiol. (1991) [Pubmed]
  7. Delineation of two distinct regulatory domains in the 5' region of the nar operon of Escherichia coli. Li, S., Rabi, T., DeMoss, J.A. J. Bacteriol. (1985) [Pubmed]
  8. Bacterial catalysis of nitrosation: involvement of the nar operon of Escherichia coli. Ralt, D., Wishnok, J.S., Fitts, R., Tannenbaum, S.R. J. Bacteriol. (1988) [Pubmed]
  9. Endonuclease V of Escherichia coli prevents mutations from nitrosative deamination during nitrate/nitrite respiration. Weiss, B. Mutat. Res. (2001) [Pubmed]
  10. Organization of the nar genes at the chlZ locus. Bonnefoy, V., Ratouchniak, J., Blasco, F., Chippaux, M. FEMS Microbiol. Lett. (1997) [Pubmed]
  11. Synthesis and degradation of nitrate reductase in Escherichia coli. Hackett, C.S., MacGregor, C.H. J. Bacteriol. (1981) [Pubmed]
  12. Molybdenum effector of fumarate reductase repression and nitrate reductase induction in Escherichia coli. Iuchi, S., Lin, E.C. J. Bacteriol. (1987) [Pubmed]
  13. Promoter region of the nar operon of Escherichia coli: nucleotide sequence and transcription initiation signals. Li, S.F., DeMoss, J.A. J. Bacteriol. (1987) [Pubmed]
  14. narI region of the Escherichia coli nitrate reductase (nar) operon contains two genes. Sodergren, E.J., DeMoss, J.A. J. Bacteriol. (1988) [Pubmed]
  15. Nitrate reductases in Escherichia coli. Bonnefoy, V., Demoss, J.A. Antonie Van Leeuwenhoek (1994) [Pubmed]
  16. Synthesis of nitrate reductase components in chlorate-resistant mutants of Escherichia coli. MacGregor, C.H. J. Bacteriol. (1975) [Pubmed]
  17. The napF and narG nitrate reductase operons in Escherichia coli are differentially expressed in response to submicromolar concentrations of nitrate but not nitrite. Wang, H., Tseng, C.P., Gunsalus, R.P. J. Bacteriol. (1999) [Pubmed]
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