Transcriptional regulation of the mexEF-oprN multidrug efflux pump operon by MexT and an unidentified repressor in nfxC-type mutant of Pseudomonas aeruginosa.
Expression of the MexEF-OprN efflux pump in Pseudomonas aeruginosa seems to be upregulated by MexT. The region upstream of the mexEF-oprN operon contains mexT arranged in tandem with mexEF-oprN and separated by 230 bp of mexT-mexE intergenic DNA. Therefore, it is likely that this intergenic DNA contains the promoter-operator element of mexEF-oprN. To characterize how the expression of the mexEF-oprN operon was controlled, we analyzed the mexT-mexE intergenic DNA by constructing a series of intergenic DNA deletions connected with the mexE∷lacZ reporter and made two important discoveries. The first was that the central region of the DNA contained two nod boxes. The mexT-proximal nod box was identified as the MexT-binding site by gel-shift assays using purified MexT. The mexT-distal nod box was required for the transcription of the mexEF-oprN operon, but not for the binding of MexT, suggesting that this region accommodates the binding of the RNA polymerase. The second observation is that there is a 13 bp inverted repeat sequence separated by 10 bp immediately upstream of the mexE gene. Deletion of this region caused a sudden rise in MexEF-OprN production, suggesting that this region accommodates the binding of a putative repressor protein.
Maseda
Hideaki
H
Department of Biological Science & Technology, Institute of Technology and Science, The University of Tokushima Graduate School, Tokushima, Japan. maseda@bio.tokushima-u.ac.jp
Uwate
Maki
M
Nakae
Taiji
T
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D009876:Operon; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D001425:Bacterial Outer Membrane Proteins; C105708:OprN protein, Pseudomonas aeruginosa; D012097:Repressor Proteins