title: Antibiotic inducibility of the mexXY multidrug efflux operon of Pseudomonas aeruginosa: involvement of the MexZ anti-repressor ArmZ.
abstract: Expression of the mexXY multidrug efflux operon in wild type Pseudomonas aeruginosa is substantially enhanced by the ribosome-targeting antimicrobial spectinomycin (18-fold) and this is wholly dependent upon the product of the PA5471 gene. In a mutant strain lacking the mexZ gene encoding a repressor of mexXY gene expression, expression of the efflux operon increases modestly (5-fold) and is still responsive (18-fold) to spectinomycin. Spectinomycin induction of mexXY expression in the mexZ mutant is, however, independent of PA5471 suggesting that PA5471 functions as an anti-repressor (dubbed ArmZ for anti-repressor MexZ) that serves only to modulate MexZ's repressor activity, with additional gene(s)/gene product(s) providing for the bulk of the antimicrobial-inducible mexXY expression. Consistent with PA5471/ArmZ functioning as a MexZ anti-repressor, an interaction between MexZ and ArmZ was confirmed using a bacterial 2-hybrid assay. Mutations compromising this interaction (P68S, G76S, R216C, R221W, R221Q, G231D and G252S) were identified and localized to one region of an ArmZ structural model that may represent a MexZ-interacting domain. Introduction of representative mutations into the chromosome of P. aeruginosa reduced (P68S, G76S) or obviated (R216C, R2211W) antimicrobial induction of mexXY gene expression, rendering the mutants pan-aminoglycoside-susceptible. These data confirm the importance of an ArmZ-MexZ interaction for antimicrobial-inducible mexXY expression and intrinsic aminoglycoside resistance in P. aeruginosa.
authors: Department of Biomedical and Molecular Sciences, Botterell Hall, Queen's University, Kingston, Ontario, Canada.
authors: Thomas
authors: T
authors: Hay
authors: Sebastien
authors: S
authors: Fraud
authors: Calvin Ho-Fung
authors: CH
authors: Lau
authors: Christie
authors: C
authors: Gilmour
authors: Keith
authors: K
authors: Poole
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D009154:Mutation; D009876:Operon; D011485:Protein Binding; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C402791:MexXY protein, Pseudomonas aeruginosa; C402792:MexZ protein, Pseudomonas aeruginosa