Transcriptional regulation of nitric oxide reduction in Ralstonia eutropha H16.
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 sigma(54)-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-(N(7))-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.
Büsch
A
A
Institut für Biologie/Mikrobiologie, Humboldt-Universität zu Berlin, Chausseestrasse 117, 10115 Berlin, Germany.
Strube
K
K
Friedrich
B
B
Cramm
R
R
D002384:Catalysis; D020118:Cupriavidus necator / Q000201:enzymology / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic
D009569:Nitric Oxide; D010088:Oxidoreductases; C034747:nitric-oxide reductase