A flavorubredoxin and its associated oxidoreductase (encoded by norV and norW respectively) detoxify NO (nitric oxide) to form N2O (nitrous oxide) under anaerobic conditions in Escherichia coli. Transcription of the norVW genes is activated in response to NO by the σ54-dependent regulator and dedicated NO sensor, NorR, a member of the bacterial enhancer-binding protein family. In the absence of NO, the catalytic activity of the central ATPase domain of NorR is repressed by the N-terminal regulatory domain that contains a non-haem iron centre. Binding of NO to this centre results in the formation of a mononitrosyl iron species, enabling the activation of ATPase activity. Our studies suggest that the highly conserved GAFTGA loop in the ATPase domain, which engages with the alternative σ factor σ54 to activate transcription, is a target for intramolecular repression by the regulatory domain. Binding of NorR to three conserved enhancer sites upstream of the norVW promoter is essential for transcriptional activation and promotes the formation of a stable higher-order NorR nucleoprotein complex. We propose that enhancer-driven assembly of this oligomeric complex, in which NorR apparently forms a DNA-bound hexamer in the absence of NO, provides a ‘poised’ system for transcriptional activation that can respond rapidly to nitrosative stress.
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Conference Article|
January 19 2011
Transcriptional regulation by the dedicated nitric oxide sensor, NorR: a route towards NO detoxification
Matthew Bush;
Matthew Bush
1
*Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Colney NR4 7UH, U.K.
1To whom correspondence should be addressed: (email matt.bush@bbsrc.ac.uk).
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Tamaswati Ghosh;
Tamaswati Ghosh
†Division of Molecular Bioscience, Imperial College London, London SW7 2AZ, U.K.
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Nicholas Tucker;
Nicholas Tucker
*Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Colney NR4 7UH, U.K.
‡Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, U.K.
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Xiaodong Zhang;
Xiaodong Zhang
†Division of Molecular Bioscience, Imperial College London, London SW7 2AZ, U.K.
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Ray Dixon
Ray Dixon
*Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Colney NR4 7UH, U.K.
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Publisher: Portland Press Ltd
Received:
September 03 2010
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2011 Biochemical Society
2011
Biochem Soc Trans (2011) 39 (1): 289–293.
Article history
Received:
September 03 2010
Citation
Matthew Bush, Tamaswati Ghosh, Nicholas Tucker, Xiaodong Zhang, Ray Dixon; Transcriptional regulation by the dedicated nitric oxide sensor, NorR: a route towards NO detoxification. Biochem Soc Trans 1 February 2011; 39 (1): 289–293. doi: https://doi.org/10.1042/BST0390289
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