title: Governor of the glnAp2 promoter of Escherichia coli.
abstract: Low-affinity sites for the activator NRI-P (NtrC-P) that map between the enhancer and the glnAp2 promoter were responsible for limiting promoter activity at high concentrations of NRI approximately P in intact cells and in an in vitro transcription system consisting of purified bacterial components. That is, the low-affinity sites constitute a 'governor', limiting the maximum promoter activity. As the governor sites are themselves far from the promoter, they apparently act either by preventing the formation of the activation DNA loop that brings the enhancer-bound activator and the promoter-bound polymerase into proximity or by preventing a productive interaction between the enhancer-bound activator and polymerase. The combination of potent enhancer and governor sites at the glnAp2 promoter provides for efficient activation of the promoter when the activator concentration is low, while limiting the maximum level of promoter activity when the activator concentration is high.
authors.affiliation: Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109-0606, USA.
authors.forename: Mariette R
authors.initials: MR
authors.lastname: Atkinson
authors.forename: Narinporn
authors.initials: N
authors.lastname: Pattaramanon
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Ninfa
mesh_terms: D001426:Bacterial Proteins; D001483:Base Sequence; D001665:Binding Sites; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005974:Glutamate-Ammonia Ligase / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D051922:PII Nitrogen Regulatory Proteins; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D015534:Trans-Activators; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D051922:PII Nitrogen Regulatory Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C497876:glnG protein, E coli; C081173:glutamine synthetase I; D005974:Glutamate-Ammonia Ligase