Dataset Information

Chlorinated phenols control the expression of the multidrug resistance efflux pump MexAB-OprM in Pseudomonas aeruginosa by interacting with NalC.

ABSTRACT: NalC is a TetR type regulator that represses the multidrug efflux pump MexAB-OprM in Pseudomonas aeruginosa. Here we explain the mechanism of NalC-mediated regulation of MexAB-OprM. We show that NalC non-covalently binds chlorinated phenols and chemicals containing chlorophenol side-chains such as triclosan. NalC-chlorinated phenol binding results in its dissociation from promoter DNA and upregulation of NalC's downstream targets, including the MexR antirepressor ArmR. ArmR upregulation and MexR-ArmR complex formation have previously been shown to upregulate MexAB-OprM. In vivo mexB and armR expression analyses were used to corroborate in vitro NalC-chlorinated phenol binding. We also show that the interaction between chlorinated phenols and NalC is reversible, such that removal of these chemicals restored NalC promoter DNA binding. Thus, the NalC-chlorinated phenol interaction is likely a pertinent physiological mechanism that P. aeruginosa uses to control expression of the MexAB-OprM efflux pump.

SUBMITTER: Ghosh S

PROVIDER: S-EPMC3135978 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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Chlorinated phenols control the expression of the multidrug resistance efflux pump MexAB-OprM in Pseudomonas aeruginosa by interacting with NalC.

Ghosh Sudeshna S Cremers Claudia M CM Jakob Ursula U Love Nancy G NG

Molecular microbiology 20110215 6

NalC is a TetR type regulator that represses the multidrug efflux pump MexAB-OprM in Pseudomonas aeruginosa. Here we explain the mechanism of NalC-mediated regulation of MexAB-OprM. We show that NalC non-covalently binds chlorinated phenols and chemicals containing chlorophenol side-chains such as triclosan. NalC-chlorinated phenol binding results in its dissociation from promoter DNA and upregulation of NalC's downstream targets, including the MexR antirepressor ArmR. ArmR upregulation and MexR ...[more]

PMID: 21231970

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Project description:The integral inner membrane resistance-nodulation-division (RND) components of three-component RND-membrane fusion protein-outer membrane factor multidrug efflux systems define the substrate selectivity of these efflux systems. To gain a better understanding of what regions of these proteins are important for substrate recognition, a plasmid-borne mexB gene encoding the RND component of the MexAB-OprM multidrug efflux system of Pseudomonas aeruginosa was mutagenized in vitro by using hydroxylamine and mutations compromising the MexB contribution to antibiotic resistance identified in a DeltamexB strain. Of 100 mutants that expressed wild-type levels of MexB and showed increased susceptibility to one or more of carbenicillin, chloramphenicol, nalidixic acid, and novobiocin, the mexB genes of a representative 46 were sequenced, and 19 unique single mutations were identified. While the majority of mutations occurred within the large periplasmic loops between transmembrane segment 1 (TMS-1) and TMS-2 and between TMS-7 and TMS-8 of MexB, mutations were seen in the TMSs and in other periplasmic as well as cytoplasmic loops. By threading the MexB amino acid sequence through the crystal structure of the homologous RND transporter from Escherichia coli, AcrB, a three-dimensional model of a MexB trimer was obtained and the mutations were mapped to it. Unexpectedly, most mutations mapped to regions of MexB predicted to be involved in trimerization or interaction with MexA rather than to regions expected to contribute to substrate recognition. Intragenic second-site suppressor mutations that restored the activity of the G220S mutant version of MexB, which was compromised for resistance to all tested MexAB-OprM antimicrobial substrates, were recovered and mapped to the apparently distal portion of MexB that is implicated in OprM interaction. As the G220S mutation likely impacted trimerization, it appears that either proper assembly of the MexB trimer is necessary for OprM interaction or OprM association with an unstable MexB trimer might stabilize it, thereby restoring activity.

Dataset Information

Chlorinated phenols control the expression of the multidrug resistance efflux pump MexAB-OprM in Pseudomonas aeruginosa by interacting with NalC.

Publications

Chlorinated phenols control the expression of the multidrug resistance efflux pump MexAB-OprM in Pseudomonas aeruginosa by interacting with NalC.

Similar Datasets

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