A new type of NtrC transcriptional activator.
AUTOR(ES)
Foster-Hartnett, D
RESUMO
The enteric NtrC (NRI) protein has been the paradigm for a class of bacterial enhancer-binding proteins (EBPs) that activate transcription of RNA polymerase containing the sigma 54 factor. Activators in the NtrC class are characterized by essentially three properties: (i) they bind to sites distant from the promoters that they activate (> 100 bp upstream of the transcriptional start site), (ii) they contain a conserved nucleotide-binding fold and exhibit ATPase activity that is required for activation, and (iii) they activate the sigma 54 RNA polymerase. We have characterized the NtrC protein from a photosynthetic bacterium, Rhodobacter capsulatus, which represents a metabolically versatile group of bacteria found in aquatic environments. We have shown that the R. capsulatus NtrC protein (RcNtrC) binds to two tandem sites that are distant from promoters that it activates, nifA1 and nifA2. These tandem binding sites are shown to be important for RcNtrC-dependent nitrogen regulation in vivo. Moreover, the conserved nucleotide-binding fold of RcNtrC is required to activate nifA1 and nifA2 but is not required for DNA binding of RcNtrC to upstream activation sequences. However, nifA1 and nifA2 genes do not require the sigma 54 for activation and do not contain the highly conserved nucleotides that are present in all sigma 54-type, EBP-activated promoters. Thus, the NtrC from this photosynthetic bacterium represents a novel member of the class of bacterial EBPs. It is probable that this class of EBPs is more versatile in prokaryotes than previously envisioned.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=196956Documentos Relacionados
- Urea Utilization in the Phototrophic Bacterium Rhodobacter capsulatus Is Regulated by the Transcriptional Activator NtrC
- Motility of Helicobacter pylori Is Coordinately Regulated by the Transcriptional Activator FlgR, an NtrC Homolog
- The effect on the function of the transcriptional activator NtrC from Klebsiella pneumoniae of mutations in the DNA-recognition helix.
- Regulation of the transcriptional activator NtrC1: structural studies of the regulatory and AAA+ ATPase domains
- Repressor Mutant Forms of the Azospirillum brasilense NtrC Protein