Fine-tuned regulation by oxygen and nitric oxide of the activity of a semi-synthetic FNR-dependent promoter and expression of denitrification enzymes in Paracoccus denitrificans.
In Paracoccus denitrificans at least three fumarate and nitrate reductase regulator (FNR)-like proteins [FnrP, nitrite and nitric oxide reductases regulator (NNR) and NarR] control the expression of several genes necessary for denitrifying growth. To gain more insight into this regulation, beta-galactosidase activity from a plasmid carrying the lacZ gene fused to the Escherichia coli melR promoter with the consensus FNR-binding (FF) site was examined. Strains defective in the fnrP gene produced only very low levels of beta-galactosidase, indicating that FnrP is the principal activator of the FF promoter. Anoxic beta-galactosidase levels were much higher relative to those under oxic growth and were strongly dependent on the nitrogen electron acceptor used, maximal activity being promoted by N(2)O. Additions of nitrate or nitroprusside lowered beta-galactosidase expression resulting from an oxic to micro-oxic switch. These results suggest that the activity of FnrP is influenced not only by oxygen, but also by other factors, most notably by NO concentration. Observations of nitric oxide reductase (NOR) activity in a nitrite-reductase-deficient strain and in cells treated with haemoglobin provided evidence for dual regulation of the synthesis of this enzyme, partly independent of NO. Both regulatory modes were operative in the FnrP-deficient strain, but not in the NNR-deficient strain, suggesting involvement of the NNR protein. This conclusion was further substantiated by comparing the respective NOR promoter activities.
Mazoch
Jiří
J
Department of Biochemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic.
Kuňák
Michal
M
Department of Biochemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic.
Kučera
Igor
I
Department of Biochemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic.
van Spanning
Rob J M
RJM
Department of Molecular Cell Physiology, Faculty of Biology, BioCentrum Amsterdam, Vrije Universiteit, NL-1081 HV Amsterdam, The Netherlands.
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005798:Genes, Bacterial; D017930:Genes, Reporter; D007763:Lac Operon; D009154:Mutation; D009569:Nitric Oxide / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D010088:Oxidoreductases / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C445305:FnrP protein, Paracoccus denitrificans; C120062:NNR protein, Paracoccus denitrificans; D015534:Trans-Activators; D014157:Transcription Factors; D009599:Nitroprusside; D009569:Nitric Oxide; D010088:Oxidoreductases; C034747:nitric-oxide reductase; D001616:beta-Galactosidase; D010100:Oxygen