title: Regulation of Organic Hydroperoxide Stress Response by Two OhrR Homologs in Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa ohrR and ospR are gene homologs encoding oxidant sensing transcription regulators. OspR is known to regulate gpx, encoding a glutathione peroxidase, while OhrR regulates the expression of ohr that encodes an organic peroxide specific peroxiredoxin. Here, we show that ospR mediated gpx expression, like ohrR and ohr, specifically responds to organic hydroperoxides as compared to hydrogen peroxide and superoxide anion. Furthermore, the regulation of these two systems is interconnected. OspR is able to functionally complement an ohrR mutant, i.e. it regulates ohr in an oxidant dependent manner. In an ohrR mutant, in which ohr is derepressed, the induction of gpx expression by organic hydroperoxide is reduced. Likewise, in an ospR mutant, where gpx expression is constitutively high, oxidant dependent induction of ohr expression is reduced. Moreover, in vitro binding assays show that OspR binds the ohr promoter, while OhrR binds the gpx promoter, albeit with lower affinity. The binding of OhrR to the gpx promoter may not be physiologically relevant; however, OspR is shown to mediate oxidant-inducible expression at both promoters. Interestingly, the mechanism of OspR-mediated, oxidant-dependent induction at the two promoters appears to be distinct. OspR required two conserved cysteines (C24 and C134) for oxidant-dependent induction of the gpx promoter, while only C24 is essential at the ohr promoter. Overall, this study illustrates possible connection between two regulatory switches in response to oxidative stress.
authors: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok, Thailand.
authors: Sopapan
authors: S
authors: Atichartpongkul
authors: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok, Thailand.|Applied Biological Sciences Program, Chulabhorn Graduate Institute, Lak Si, Bangkok, Thailand.|Center of Excellence on Environmental Health and Toxicology (EHT), Bangkok, Thailand.
authors: Paiboon
authors: P
authors: Vattanaviboon
authors: Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok, Thailand.
authors: Ratiphorn
authors: R
authors: Wisitkamol
authors: Applied Biological Sciences Program, Chulabhorn Graduate Institute, Lak Si, Bangkok, Thailand.
authors: Juthamas
authors: J
authors: Jaroensuk
authors: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok, Thailand.|Center of Excellence on Environmental Health and Toxicology (EHT), Bangkok, Thailand.|Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok, Thailand.|Center of Excellence on Emerging Bacterial Diseases, Faculty of Science, Mahidol University, Bangkok, Thailand.
authors: Skorn
authors: S
authors: Mongkolsuk
authors: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok, Thailand.|Applied Biological Sciences Program, Chulabhorn Graduate Institute, Lak Si, Bangkok, Thailand.|Center of Excellence on Environmental Health and Toxicology (EHT), Bangkok, Thailand.
authors: Mayuree
authors: M
authors: Fuangthong
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005816:Genetic Complementation Test; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009154:Mutation; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological; D020122:tert-Butylhydroperoxide / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D016877:Oxidants; C112257:organic hydroperoxide resistance protein, Xanthomonas campestris; D020122:tert-Butylhydroperoxide; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase