Bradyrhizobium japonicum NnrR, a denitrification regulator, expands the FixLJ-FixK2 regulatory cascade.
In Bradyrhizobium japonicum, a gene named nnrR was identified which encodes a protein with high similarity to FNR/CRP-type transcriptional regulators. Mutant strains carrying an nnrR null mutation were unable to grow anaerobically in the presence of nitrate or nitrite, and they lacked both nitrate and nitrite reductase activities. Anaerobic activation of an nnrR'-'lacZ fusion required FixLJ and FixK(2). In turn, N oxide-mediated induction of nir and nor genes encoding nitrite and nitric oxide reductase, respectively, depended on NnrR. Thus, NnrR expands the FixLJ-FixK(2) regulatory cascade by an additional control level which integrates the N oxide signal required for maximal induction of the denitrification genes.
Mesa
Socorro
S
Institute of Microbiology, Eidgenössische Technische Hochschule, CH-8092 Zürich, Switzerland. mesam@micro.biol.ethz.ch
Bedmar
Eulogio J
EJ
Chanfon
Astrid
A
Hennecke
Hauke
H
Fischer
Hans-Martin
HM
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020369:Bradyrhizobium / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006420:Hemeproteins / Q000235:genetics / Q000378:metabolism; D000071677:Histidine Kinase; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009569:Nitric Oxide / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D006420:Hemeproteins; D007506:Iron-Sulfur Proteins; D009573:Nitrites; C066628:FixK protein, Bacteria; C069289:FixJ protein, Bacteria; D009569:Nitric Oxide; C067929:FixL protein, Bacteria; D000071677:Histidine Kinase