In vivo activity of the nitrogen control transcription factor NtcA is subjected to metabolic regulation in Synechococcus sp. strain PCC 7942.
The cyanobacterial protein NtcA is a global transcriptional regulator of genes involved in nitrogen assimilation that are subjected to ammonium-promoted repression and is itself controlled by positive autoregulation. Strain CSI70 derived from Synechococcus sp. strain PCC 7942 was constructed to overexpress an additional ntcA gene copy from a constitutive promoter. This strain exhibited high levels of the NtcA protein both in the presence and in the absence of ammonium. However, expression of the NtcA-dependent nir operon and glnA gene (tested by RNA/DNA hybridization and enzyme activity) was still subjected to nitrogen regulation. These results indicate in vivo regulation of the activity of NtcA at activation of transcription of nitrogen-regulated genes as a function of the nitrogen status of the cell.
Luque
Ignacio
I
Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avda. Americo Vespucio s/n, E-41092 Seville, Spain.
Vázquez-Bermúdez
María Félix
MF
Paz-Yepes
Javier
J
Flores
Enrique
E
Herrero
Antonia
A
D001426:Bacterial Proteins; D000458:Cyanobacteria / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000378:metabolism; D009572:Nitrite Reductases / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics*
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D000644:Quaternary Ammonium Compounds; D014157:Transcription Factors; C075617:ntcA protein, Synechococcus; D009565:Nitrate Reductases; D009572:Nitrite Reductases; D050901:Nitrate Reductase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen