Expression of the nifA gene of Herbaspirillum seropedicae: role of the NtrC and NifA binding sites and of the -24/-12 promoter element.
The nifA promoter of Herbaspirillum seropedicae contains potential NtrC, NifA and IHF binding sites together with a -12/-24 sigma(N)-dependent promoter. This region has now been investigated by deletion mutagenesis for the effect of NtrC and NifA on the expression of a nifA::lacZ fusion. A 5' end to the RNA was identified at position 641, 12 bp downstream from the -12/-24 promoter. Footprinting experiments showed that the G residues at positions -26 and -9 are hypermethylated, and that the region from -10 to +10 is partially melted under nitrogen-fixing conditions, confirming that this is the active nifA promoter. In H. seropedicae nifA expression from the sigma(N)-dependent promoter is repressed by fixed nitrogen but not by oxygen and is probably activated by the NtrC protein. NifA protein is apparently not essential for nifA expression but it can still bind the NifA upstream activating sequence.
Souza
E M
EM
BBSRC, IPSR - Nitrogen Fixation Laboratory, University of Norwich, Norwich, UK1.
Pedrosa
F O
FO
Departamento de Bioquı́mica - UFPR, C. Postal 19046, 81531-970, Curitiba, PR, Brazil2.
Rigo
L U
LU
Departamento de Bioquı́mica - UFPR, C. Postal 19046, 81531-970, Curitiba, PR, Brazil2.
Machado
H B
HB
Departamento de Farmacologia, UFPR, 81531-990, Curitiba, PR, Brazil3.
Yates
M G
MG
BBSRC, IPSR - Nitrogen Fixation Laboratory, University of Norwich, Norwich, UK1.
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D020562:Betaproteobacteria / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D015870:Gene Expression; D005798:Genes, Bacterial; D007763:Lac Operon; D008969:Molecular Sequence Data; D009154:Mutation; D051922:PII Nitrogen Regulatory Proteins; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000235:genetics; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C061338:NifA protein, Bacteria; D051922:PII Nitrogen Regulatory Proteins; D012329:RNA, Bacterial; D015534:Trans-Activators; D014157:Transcription Factors; C497876:glnG protein, E coli