Antibiotic inducibility of the mexXY multidrug efflux operon of Pseudomonas aeruginosa: involvement of the MexZ anti-repressor ArmZ

• Published in: PloS one Vol. 8; no. 2; p. e56858
• Main Authors: Hay, Thomas, Fraud, Sebastien, Lau, Calvin Ho-Fung, Gilmour, Christie, Poole, Keith
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 18.02.2013; Public Library of Science (PLoS)
• Subjects: Aminoglycoside antibiotics; Anti-Bacterial Agents - pharmacology; Antibiotics; Antiinfectives and antibacterials; Antimicrobial agents; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biology; Chromosomes; Cloning; Cystic fibrosis; Deoxyribonucleic acid; DNA; DNA polymerase; Drug Resistance, Multiple, Bacterial - genetics; E coli; Efflux; Escherichia coli; Gene expression; Gene Expression Regulation, Bacterial; Genetic engineering; Gram-negative bacteria; Laboratories; Microbial Sensitivity Tests; Models, Molecular; Mutagenesis; Mutants; Mutation; Operon; Plasmids; Protein Binding; Protein Conformation; Proteins; Pseudomonas aeruginosa; Pseudomonas aeruginosa - drug effects; Pseudomonas aeruginosa - genetics; Spectinomycin
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0056858

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.