Nitric oxide reduction in Ralstonia eutropha H16 is catalysed by the quinol-dependent NO reductase NorB. norB and the adjacent norA form an operon that is controlled by the σ54-dependent transcriptional activator NorR in response to NO. A NorR derivative containing MalE in place of the N-terminal domain binds to a 73 bp region upstream of norA that includes three copies of the putative upstream activator sequence GGT-(N7)-ACC. Mutations altering individual bases of this sequence resulted in an 80–90% decrease in transcriptional activation by wild-type NorR. Similar motifs are present in several proteobacteria upstream of genes encoding proteins of NO metabolism. The N-terminal domain of NorR contains a GAF module and is hypothesized to interact with a signal molecule. A NorR derivative lacking this domain activates the norAB promoter constitutively. Amino acid exchanges within the GAF module identified a cysteine residue that is essential for promoter activation by NorR. Signal sensing by NorR is negatively modulated by the iron-containing protein NorA.
Conference Article| February 01 2005
Transcriptional regulation of nitric oxide reduction in Ralstonia eutropha H16
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A. Büsch, K. Strube, B. Friedrich, R. Cramm; Transcriptional regulation of nitric oxide reduction in Ralstonia eutropha H16. Biochem Soc Trans 1 February 2005; 33 (1): 193–194. doi: https://doi.org/10.1042/BST0330193
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