title: The two overlapping Azospirillum brasilense upstream activator sequences have differential effects on nifH promoter activity.
abstract: The Azospirillum brasilense nifH promoter is positively controlled by the NifA protein bound to the upstream activator sequences (UASs). Two overlapping UASs located at -191 and -182 were identified with the consensus TGT-N10-ACA motif. The role of the two UASs of Azospirillum brasilense nifH promoter was examined by introducing base substitutions in the NifA binding sites. Both the promoter down phenotype of a mutation in UAS2 and increased activation when UAS1 was mutated reveal that the integrity of the UAS2 is required for the efficient activation of nifH promoter. This atypical NifA-binding site may represent a region interacting with two NifA dimers.
authors.affiliation: Departamento de Genética, Universidade Federal do Rio Grande do Sul, Brazil.
authors.forename: L M
authors.initials: LM
authors.lastname: Passaglia
authors.forename: A
authors.initials: A
authors.lastname: Schrank
authors.forename: I S
authors.initials: IS
authors.lastname: Schrank
mesh_terms: D015806:Azospirillum brasilense / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009586:Nitrogen Fixation / Q000235:genetics; D009591:Nitrogenase / Q000235:genetics* / Q000378:metabolism; D009876:Operon / Q000235:genetics; D010088:Oxidoreductases; D017354:Point Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C061338:NifA protein, Bacteria; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase