Characterization and regulation of the gene encoding nitrite reductase in Rhodobacter sphaeroides 2.4.3.
Nitrite reductase catalyzes the reduction of nitrite to nitric oxide, the first step in denitrification to produce a gaseous product. We have cloned the gene nirK, which encodes the copper-type nitrite reductase from a denitrifying variant of Rhodobacter sphaeroides, strain 2.4.3. The deduced open reading frame has significant identity with other copper-type nitrite reductases. Analysis of the promoter region shows that transcription initiates 31 bases upstream of the translation start codon. The transcription initiation site is 43.5 bases downstream of a putative binding site for a transcriptional activator. Maximal expression of a nirK-lacZ construct in 2.4.3 requires both a low level of oxygen and the presence of a nitrogen oxide. nirK-lacZ expression was severely impaired in a nitrite reductase-deficient strain of 2.4.3. This suggests that nirK expression is dependent on nitrite reduction. The inability of microaerobically grown nitrite reductase-deficient cells to induce nirK-lacZ expression above basal levels in medium unamended with nitrate demonstrates that changes in oxygen concentrations are not sufficient to modulate nirK expression.
Tosques
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IE
Section of Microbiology, Cornell University, Ithaca, New York 14853, USA.
Kwiatkowski
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AV
Shi
J
J
Shapleigh
J P
JP
D000332:Aerobiosis; D000595:Amino Acid Sequence; D000693:Anaerobiosis; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism; D009572:Nitrite Reductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000201:enzymology / Q000235:genetics*
D004251:DNA Transposable Elements; D009566:Nitrates; D009573:Nitrites; D011993:Recombinant Fusion Proteins; D010088:Oxidoreductases; D009572:Nitrite Reductases; C034747:nitric-oxide reductase