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

• The mtr gene of Escherichia coli K-12 encodes an L-tryptophan-specific permease [7].
• The tryptophan-specific permease gene, mtr, is differentially regulated by the tryptophan and tyrosine repressors in Escherichia coli K-12 [8].

Biological context of mtr

• The precise location of the mtr gene at 69 min on the E. coli chromosome was determined [9].
• Sequences homologous to sigma 70- and sigma 54-dependent promoters were identified upstream of the transcription start point of mtr [9].
• Cells with lesions in mtr display a phenotype of 5-methyltryptophan resistance [7].
• Cloning, nucleotide sequence, and characterization of mtr, the structural gene for a tryptophan-specific permease of Escherichia coli K-12 [7].
• Site-directed mutagenesis confirmed that sequences in the mtr regulatory region homologous to TyrR protein and to Trp repressor-binding sites were involved in the activation and repression of mtr expression, respectively [9].

Associations of mtr with chemical compounds

• Possible operator sites for the tyrosine and tryptophan repressors are situated within the region of DNA that is likely to be the mtr promoter [7].
• Small internal deletions of residues 10 to 19, 20 to 29, or 30 to 39 also destroy phenylalanine- or tyrosine-mediated activation of mtr and tyrP [10].
• However, when 1-methyltryptophan replaces tryptophan as the inducer in this medium, mutations in both mtr and tnaB are required to prevent maximum induction [11].
• This region of the chromosome has been cloned by inserting the kanamycin-resistant transposon Tn5 near the argG and mtr loci at 68.5 min [12].

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].

References