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Gene Review

ECs1726  -  transcriptional regulator NarL

Escherichia coli O157:H7 str. Sakai

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Disease relevance of ECs1726


High impact information on ECs1726

  • Dimerization allows DNA target site recognition by the NarL response regulator [4].
  • However, previous work discovered that NarL-mediated nitrate regulation is essentially normal in delta narX deletion mutants [1].
  • Previous work has identified two cis-acting sites in the nar operon control region: a proximal site required for anaerobic induction mediated by the activator Fnr and a remote upstream site required for nitrate induction mediated by the activator NarL [Li, S. & DeMoss, J. A. (1988) J. Biol. Chem. 263, 13700-13705] [5].
  • The C-terminal domain is composed of four alpha-helices where two central helices form a helix-turn-helix motif similar to the structures of the regulatory proteins GerE, NarL, and TraR [6].
  • Both the phosphorylation and dephosphorylation of NarL required Mg2+, and neither reaction was affected by the presence of nitrate [7].

Chemical compound and disease context of ECs1726

  • Expression from the Escherichia coli nir promoter is co-dependent on Fnr (a transcription factor triggered by oxygen starvation) and on NarL or NarP (transcription factors triggered by nitrite and nitrate ions) [8].
  • Hierarchical control of anaerobic gene expression in Escherichia coli K-12: the nitrate-responsive NarX-NarL regulatory system represses synthesis of the fumarate-responsive DcuS-DcuR regulatory system [9].
  • The Escherichia coli K-12 NarL and NarP Proteins Insulate the nrf Promoter from the Effects of Integration Host Factor [10].

Biological context of ECs1726

  • A base sequence no longer than 27 bp, located at about -200 bp, was essential for the stimulation by nitrate coupled with NarL [11].
  • Integration host factor protein (IHF) was shown to be required for Fnr- and NarL-dependent activation of the nitrate reductase (narGHJI) operon of Escherichia coli in response to nitrate availability and anaerobiosis [12].
  • Further stimulation of transcription occurs in the presence of nitrate and is dependent on activation of the transacting factor NarL and a cis-acting sequence (NarL box) located approximately 200 base pairs upstream from the transcription start site [13].
  • To define the structure of the NarL box, alterations in the NarL box region, generated by saturation mutagenesis of the sequence from positions -184 to -202 in the narGHJI promoter of a narG::lacZ fusion-bearing plasmid, were analyzed for their effects on NarL-mediated stimulation of transcription [13].
  • Furthermore, shifting of most of the intervening sequence or defined segments of the sequence by 4 bases while maintaining the position of the NarL box relative to sequences required for Fnr-dependent, anaerobic transcription also eliminated the NarL-mediated stimulation [13].

Associations of ECs1726 with chemical compounds

  • The relative stabilities of the phosphorylated forms of the two proteins at different pH values were consistent with the proposal that, in analogy to other related two-component regulatory systems, NarX and NarL were phosphorylated on specific histidine and aspartate residues, respectively [7].
  • NarL-phosphate, stabilized by the addition of EDTA, ran as a monomer on gel filtration [7].
  • These mutations also suppress induction by nitrite: single mutations at symmetry-related positions have similar effects, whilst double mutations have more severe effects, probably because two NarL subunits bind to the inverted repeat [14].
  • By gel retardation and DNase I protection studies, we have demonstrated that NarL-phosphate, produced by the reaction of purified NarL with acetyl phosphate, specifically binds to a fragment derived from the upstream region of the narG promoter [15].
  • Therefore, expression of nuo is regulated by O2 and nitrate via ArcA, NarL, FNR and IHF at sites within the -277 region, and by other factors including C4 dicarboxylates at a site between -277 and -899 [16].

Analytical, diagnostic and therapeutic context of ECs1726


  1. Either of two functionally redundant sensor proteins, NarX and NarQ, is sufficient for nitrate regulation in Escherichia coli K-12. Rabin, R.S., Stewart, V. Proc. Natl. Acad. Sci. U.S.A. (1992) [Pubmed]
  2. Genetic evidence that NarL function is not required for nitrate regulation of nitrate assimilation in Klebsiella pneumoniae M5al. Stewart, V., Cali, B.M. J. Bacteriol. (1990) [Pubmed]
  3. The Pseudomonas aeruginosa hemA promoter is regulated by Anr, Dnr, NarL and Integration Host Factor. Krieger, R., Rompf, A., Schobert, M., Jahn, D. Mol. Genet. Genomics (2002) [Pubmed]
  4. Dimerization allows DNA target site recognition by the NarL response regulator. Maris, A.E., Sawaya, M.R., Kaczor-Grzeskowiak, M., Jarvis, M.R., Bearson, S.M., Kopka, M.L., Schröder, I., Gunsalus, R.P., Dickerson, R.E. Nat. Struct. Biol. (2002) [Pubmed]
  5. In vivo requirement of integration host factor for nar (nitrate reductase) operon expression in Escherichia coli K-12. Rabin, R.S., Collins, L.A., Stewart, V. Proc. Natl. Acad. Sci. U.S.A. (1992) [Pubmed]
  6. Structural analysis of the DNA-binding domain of the Erwinia amylovora RcsB protein and its interaction with the RcsAB box. Pristovsek, P., Sengupta, K., Löhr, F., Schäfer, B., von Trebra, M.W., Rüterjans, H., Bernhard, F. J. Biol. Chem. (2003) [Pubmed]
  7. Phosphorylation and dephosphorylation catalyzed in vitro by purified components of the nitrate sensing system, NarX and NarL. Walker, M.S., DeMoss, J.A. J. Biol. Chem. (1993) [Pubmed]
  8. Regulation of transcription initiation at the Escherichia coli nir operon promoter: a new mechanism to account for co-dependence on two transcription factors. Wu, H., Tyson, K.L., Cole, J.A., Busby, S.J. Mol. Microbiol. (1998) [Pubmed]
  9. Hierarchical control of anaerobic gene expression in Escherichia coli K-12: the nitrate-responsive NarX-NarL regulatory system represses synthesis of the fumarate-responsive DcuS-DcuR regulatory system. Goh, E.B., Bledsoe, P.J., Chen, L.L., Gyaneshwar, P., Stewart, V., Igo, M.M. J. Bacteriol. (2005) [Pubmed]
  10. The Escherichia coli K-12 NarL and NarP Proteins Insulate the nrf Promoter from the Effects of Integration Host Factor. Browning, D.F., Lee, D.J., Wolfe, A.J., Cole, J.A., Busby, S.J. J. Bacteriol. (2006) [Pubmed]
  11. Location of sequences in the nar promoter of Escherichia coli required for regulation by Fnr and NarL. Li, S.F., DeMoss, J.A. J. Biol. Chem. (1988) [Pubmed]
  12. 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]
  13. Upstream sequence elements required for NarL-mediated activation of transcription from the narGHJI promoter of Escherichia coli. Dong, X.R., Li, S.F., DeMoss, J.A. J. Biol. Chem. (1992) [Pubmed]
  14. Definition of nitrite and nitrate response elements at the anaerobically inducible Escherichia coli nirB promoter: interactions between FNR and NarL. Tyson, K.L., Bell, A.I., Cole, J.A., Busby, S.J. Mol. Microbiol. (1993) [Pubmed]
  15. NarL-phosphate must bind to multiple upstream sites to activate transcription from the narG promoter of Escherichia coli. Walker, M.S., DeMoss, J.A. Mol. Microbiol. (1994) [Pubmed]
  16. Transcriptional regulation of the proton translocating NADH dehydrogenase genes (nuoA-N) of Escherichia coli by electron acceptors, electron donors and gene regulators. Bongaerts, J., Zoske, S., Weidner, U., Unden, G. Mol. Microbiol. (1995) [Pubmed]
  17. Site-specific DNA cleavage of synthetic NarL sites by an engineered Escherichia coli NarL protein-1,10-phenanthroline cleaving agent. Xiao, G., Cole, D.L., Gunsalus, R.P., Sigman, D.S., Chen, C.H. Protein Sci. (2002) [Pubmed]
  18. Transcriptional regulation of a hybrid cluster (prismane) protein. Filenko, N.A., Browning, D.F., Cole, J.A. Biochem. Soc. Trans. (2005) [Pubmed]
  19. Microarray analysis of gene regulation by oxygen, nitrate, nitrite, FNR, NarL and NarP during anaerobic growth of Escherichia coli: new insights into microbial physiology. Overton, T.W., Griffiths, L., Patel, M.D., Hobman, J.L., Penn, C.W., Cole, J.A., Constantinidou, C. Biochem. Soc. Trans. (2006) [Pubmed]
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