2-Oxoglutarate increases the binding affinity of the NtcA (nitrogen control) transcription factor for the Synechococcus glnA promoter.
The cyanobacterial NtcA global nitrogen regulator belongs to the catabolite activator protein (CAP) family and activates transcription of nitrogen assimilation genes in response to nitrogen step-down. The binding affinity of NtcA towards a DNA fragment carrying the promoter of the glnA gene from Synechococcus sp. PCC 7942, analyzed in vitro by band-shift assay, was increased five-fold by 2-oxoglutarate in the presence of Mg(2+) ions. The 2-oxoglutarate effect peaked at about 0.6 mM, a rather physiological concentration for this compound under nitrogen-limiting conditions, and could be partially reproduced by 3-oxoglutarate but not by oxaloacetate or glutamate. These results suggest 2-oxoglutarate as a signal of the C to N balance of the cells to regulate NtcA activity and provide a new example of regulation in the versatile CAP family of proteins.
Vázquez-Bermúdez
María Félix
MF
Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Universidad de Sevilla, Avda. Américo Vespucio s/n, E-41092, Sevilla, Spain. flores@cica.es
Herrero
Antonia
A
Flores
Enrique
E
D001426:Bacterial Proteins; D002413:Cations, Divalent / Q000494:pharmacology; D000458:Cyanobacteria / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005974:Glutamate-Ammonia Ligase / Q000235:genetics*; D007656:Ketoglutaric Acids / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism*
D001426:Bacterial Proteins; D002413:Cations, Divalent; D004268:DNA-Binding Proteins; D007656:Ketoglutaric Acids; D014157:Transcription Factors; C075617:ntcA protein, Synechococcus; C081173:glutamine synthetase I; D005974:Glutamate-Ammonia Ligase; D008274:Magnesium