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Title: Regulation of organic hydroperoxide stress response by two OhrR homologs in Pseudomonas aeruginosa
Authors: Sopapan Atichartpongkul
Paiboon Vattanaviboon
Ratiphorn Wisitkamol
Juthamas Jaroensuk
Skorn Mongkolsuk
Mayuree Fuangthong
Chulabhorn Research Institute
Chulabhorn Graduate Institute
Center of Excellence on Environmental Health and Toxicology (EHT)
Mahidol University
Keywords: Agricultural and Biological Sciences;Biochemistry, Genetics and Molecular Biology
Issue Date: 1-Aug-2016
Citation: PLoS ONE. Vol.11, No.8 (2016)
Abstract: © 2016 Atichartpongkul et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 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.
ISSN: 19326203
Appears in Collections:Scopus 2016-2017

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