Transcriptional regulation by the dedicated nitric oxide sensor, NorR: a route towards NO detoxification. (19th January 2011)

• Record Type: Journal Article
• Authors: Bush, Matthew; Ghosh, Tamaswati; Tucker, Nicholas; Zhang, Xiaodong; Dixon, Ray
• Is Part Of: Biochemical Society transactions. Volume 39:Number 1(2011)
• Page Start: 289
• Page End: 293
• Publication Date: 2011-01-19
• Subjects: GAFTGA motif -- interdomain repression -- nitric oxide -- NorR -- oligomerization -- σ54-dependent transcription; Biochemistry -- Congresses; 572
• DOI: 10.1042/BST0390289
• Languages: English
• ISSNs: 0300-5127

Abstract

Abstract : A flavorubredoxin and its associated oxidoreductase (encoded by norV and norW respectively) detoxify NO (nitric oxide) to form N2 O (nitrous oxide) under anaerobic conditions in Escherichia coli . Transcription of the norVW genes is activated in response to NO by the σ 54 -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 σ 54 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.