title: Deletion loop mutagenesis of the nifL promoter from Klebsiella pneumoniae: role of the -26 to -12 region in promoter function.
abstract: Nine single C-to-T transitions were introduced into the -26 to -12 region of the Klebsiella pneumoniae nifL promoter by bisulphite mutagenesis of M13 heteroduplexes containing a 15 nucleotide single-stranded loop. Mutant promoter fragments were inserted into translational lac fusion vectors to utilise beta-galactosidase activity as a measure of promoter efficiency. Mutations in invariant nucleotides found in the consensus sequence for nif promoters gave a strong 'down' promoter phenotype with respect to transcriptional activation. Mutations in semi-conserved residues had a much weaker down phenotype, whereas a mutation which increased homology to the consensus sequence enhanced promoter strength. One mutant showed increased activation by ntrC and decreased activation by nifA.
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002872:Chromosome Deletion; D004926:Escherichia coli / Q000235:genetics; D005796:Genes; D005798:Genes, Bacterial; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000235:genetics*; D009153:Mutagens; D009154:Mutation; D011401:Promoter Regions, Genetic; D013447:Sulfites / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D009153:Mutagens; D013447:Sulfites; C009279:sodium bisulfite