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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Analysis of the Organic Hydroperoxide Response of Chromobacterium violaceum Reveals That OhrR Is a Cys-Based Redox Sensor Regulated by Thioredoxin

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da Silva Neto, Jose F. [1] ; Negretto, Caroline C. [1] ; Netto, Luis E. S. [1]
Total Authors: 3
[1] Univ Sao Paulo, Inst Biociencias, Dept Genet & Biol Evolut, Sao Paulo - Brazil
Total Affiliations: 1
Document type: Journal article
Source: PLoS One; v. 7, n. 10 OCT 11 2012.
Web of Science Citations: 17

Organic hydroperoxides are oxidants generated during bacterial-host interactions. Here, we demonstrate that the peroxidase OhrA and its negative regulator OhrR comprise a major pathway for sensing and detoxifying organic hydroperoxides in the opportunistic pathogen Chromobacterium violaceum. Initially, we found that an ohrA mutant was hypersensitive to organic hydroperoxides and that it displayed a low efficiency for decomposing these molecules. Expression of ohrA and ohrR was specifically induced by organic hydroperoxides. These genes were expressed as monocistronic transcripts and also as a bicistronic ohrR-ohrA mRNA, generating the abundantly detected ohrA mRNA and the barely detected ohrR transcript. The bicistronic transcript appears to be processed. OhrR repressed both the ohrA and ohrR genes by binding directly to inverted repeat sequences within their promoters in a redox-dependent manner. Site-directed mutagenesis of each of the four OhrR cysteine residues indicated that the conserved Cys21 is critical to organic hydroperoxide sensing, whereas Cys126 is required for disulfide bond formation. Taken together, these phenotypic, genetic and biochemical data indicate that the response of C. violaceum to organic hydroperoxides is mediated by OhrA and OhrR. Finally, we demonstrated that oxidized OhrR, inactivated by intermolecular disulfide bond formation, is specifically regenerated via thiol-disulfide exchange by thioredoxin (but not other thiol reducing agents such as glutaredoxin, glutathione and lipoamide), providing a physiological reducing system for this thiol-based redox switch. (AU)

FAPESP's process: 07/58147-6 - Biological aspects of thiols: protein structure, antioxidant defense, cell signaling and redox states
Grantee:Luis Eduardo Soares Netto
Support Opportunities: Research Projects - Thematic Grants
FAPESP's process: 08/57721-3 - Redoxome
Grantee:Ohara Augusto
Support Opportunities: Research Projects - Thematic Grants