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Gene Review

mtr  -  tryptophan transporter of high affinity

Escherichia coli str. K-12 substr. MG1655

Synonyms: ECK3149, JW3130
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Disease relevance of mtr

  • The mtr gene of Escherichia coli K-12 encodes an inner membrane protein which is responsible for the active transport of trypotophan into the cell [1].
  • The mtr operon, which is involved in iron reduction, was poorly conserved among other known metal-reducing Shewanella species [2].
  • The mtr (multiple transferable resistance) system of Neisseria gonorrhoeae determines levels of gonococcal resistance to hydrophobic agents (HAs), including detergent-like fatty acids and bile salts that bathe certain mucosal surfaces [3].

High impact information on mtr

  • The pattern of loss of activation function was exactly parallel to the effects of the same tyrR mutations on the mtr promoter, which is known to be activated by the TyrR protein [4].
  • However, the putative UP element is not needed for activator-dependent activation of the mtr promoter by TyrR and phenylalanine [5].
  • The results from in vitro studies indicated that the alpha-subunit residues leucine-262, arginine-265, and lysine-297 are critical for interaction with the putative UP element of the mtr promoter and play major roles in TyrR-dependent transcription activation [5].
  • In vivo and in vitro analyses using a mutant mtr promoter carrying a disrupted putative UP element showed that this AT-rich sequence is responsible for interactions with the alpha-subunit which influence transcription in the absence of TyrR protein [5].
  • The functional behavior of the mutant TyrR proteins was evaluated in vivo by using single-copy lacZ reporter systems based on the mtr promoter (10-fold activation by wild-type TyrR protein, mediated by phenylalanine or tyrosine) or the aroF promoter (over 20-fold repression by wild-type TyrR protein, mediated by tyrosine) [6].

Chemical compound and disease context of mtr


Biological context of mtr


Associations of mtr with chemical compounds


Other interactions of mtr

  • The regulation of transcription of the gene for the tryptophan-specific permease, mtr, was evaluated in several genetically marked Escherichia coli strains through the use of a single-copy lacZ reporter system [8].
  • In activation-defective tyrR mutants, expression of mtr is repressed in the presence of tyrosine [10].
  • The mtr and aroL operators have not been studied previously in vitro [13].
  • Residues Arg-2 and Leu-3 were shown to be critical for the activation of the mtr promoter [14].


  1. Membrane topology analysis of Escherichia coli K-12 Mtr permease by alkaline phosphatase and beta-galactosidase fusions. Sarsero, J.P., Pittard, A.J. J. Bacteriol. (1995) [Pubmed]
  2. DNA/DNA hybridization to microarrays reveals gene-specific differences between closely related microbial genomes. Murray, A.E., Lies, D., Li, G., Nealson, K., Zhou, J., Tiedje, J.M. Proc. Natl. Acad. Sci. U.S.A. (2001) [Pubmed]
  3. Resistance of Neisseria gonorrhoeae to antimicrobial hydrophobic agents is modulated by the mtrRCDE efflux system. Hagman, K.E., Pan, W., Spratt, B.G., Balthazar, J.T., Judd, R.C., Shafer, W.M. Microbiology (Reading, Engl.) (1995) [Pubmed]
  4. The tpl promoter of Citrobacter freundii is activated by the TyrR protein. Smith, H.Q., Somerville, R.L. J. Bacteriol. (1997) [Pubmed]
  5. Amino acid residues in the alpha-subunit C-terminal domain of Escherichia coli RNA polymerase involved in activation of transcription from the mtr promoter. Yang, J., Murakami, K., Camakaris, H., Fujita, N., Ishihama, A., Pittard, A.J. J. Bacteriol. (1997) [Pubmed]
  6. Mutational uncoupling of the transcriptional activation function of the TyrR protein of Escherichia coli K-12 from the repression function. Cui, J., Somerville, R.L. J. Bacteriol. (1993) [Pubmed]
  7. Cloning, nucleotide sequence, and characterization of mtr, the structural gene for a tryptophan-specific permease of Escherichia coli K-12. Heatwole, V.M., Somerville, R.L. J. Bacteriol. (1991) [Pubmed]
  8. The tryptophan-specific permease gene, mtr, is differentially regulated by the tryptophan and tyrosine repressors in Escherichia coli K-12. Heatwole, V.M., Somerville, R.L. J. Bacteriol. (1991) [Pubmed]
  9. Regulation of expression of the Escherichia coli K-12 mtr gene by TyrR protein and Trp repressor. Sarsero, J.P., Wookey, P.J., Pittard, A.J. J. Bacteriol. (1991) [Pubmed]
  10. Mutations in the tyrR gene of Escherichia coli which affect TyrR-mediated activation but not TyrR-mediated repression. Yang, J., Camakaris, H., Pittard, A.J. J. Bacteriol. (1993) [Pubmed]
  11. Physiological studies of tryptophan transport and tryptophanase operon induction in Escherichia coli. Yanofsky, C., Horn, V., Gollnick, P. J. Bacteriol. (1991) [Pubmed]
  12. Cloning and orientation of the gene encoding polynucleotide phosphorylase in Escherichia coli. Crofton, S., Dennis, P.P. J. Bacteriol. (1983) [Pubmed]
  13. Studies of the Escherichia coli Trp repressor binding to its five operators and to variant operator sequences. Jeeves, M., Evans, P.D., Parslow, R.A., Jaseja, M., Hyde, E.I. Eur. J. Biochem. (1999) [Pubmed]
  14. A mutational analysis of the structural basis for transcriptional activation and monomer-monomer interaction in the TyrR system of Escherichia coli K-12. Cui, J., Somerville, R.L. J. Bacteriol. (1993) [Pubmed]
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