title: Molecular mechanism of MexR-mediated regulation of MexAB-OprM efflux pump expression in Pseudomonas aeruginosa.
abstract: To elucidate the molecular mechanism by which the MexR repressor regulates expression of the MexAB-OprM efflux pump, we investigated MexR and the mexR-mexA intergenic DNA (mexOP) interaction, and transcription of the mexA-lacZ reporter gene containing different lengths of mexOP. Homogeneously purified MexR bound specifically to mexOP proximal to mexR. The mexOP-lacZ fusion gene lacking the region immediately proximal to mexR showed minimum enzyme activity, thereby suggesting that a promoter element is located between mexR and the MexR-binding sites. These observations explain the mechanism of self-regulation of mexR expression as well as low and elevated expression of MexAB-OprM in the wild-type strain and nalB-type mutant, respectively, of Pseudomonas aeruginosa.
authors.affiliation: Department of Molecular Life Science, Tokai University School of Medicine, Isehara, 259-1193, Kanagawa, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Saito
authors.forename: S
authors.initials: S
authors.lastname: Eda
authors.forename: H
authors.initials: H
authors.lastname: Maseda
authors.forename: T
authors.initials: T
authors.lastname: Nakae
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D004352:Drug Resistance, Microbial; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D026901:Membrane Transport Proteins; C118598:MexA protein, Pseudomonas aeruginosa; C118597:MexB protein, Pseudomonas aeruginosa; C423620:MexR protein, Pseudomonas aeruginosa; C402263:OprM protein, Pseudomonas aeruginosa; D012097:Repressor Proteins; D001616:beta-Galactosidase