title: A mutant Escherichia coli sigma 70 subunit of RNA polymerase with altered promoter specificity.
abstract: A mutation is described that alters the promoter specificity of sigma 70, the primary sigma factor of Escherichia coli RNA polymerase. In strains carrying both the mutant and wild-type sigma gene (rpoD), the mutant sigma causes a large increase in the activity of mutant P22 ant promoters with A.T or C.G instead of the wild-type, consensus G.C base-pair at position -33, the third position of the consensus -35 hexamer 5'-TTGACA-3'. There is little or no effect on the activities of the wild-type and 23 other mutant ant promoters, including one with T.A at -33. The mutant sigma also activates E. coli lac promoters with A.T or C.G, but not T.A, at the corresponding position. The rpoD mutation (rpoD-RH588) changes a CGT codon to CAT. The corresponding change in sigma 70 is Arg588----His. This residue is in a region that is conserved among most sigma factors, a region that is also homologous with the helix-turn-helix motif of DNA-binding proteins. These results suggest that this region of sigma 70 is directly involved in recognition of the -35 hexamer.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01605.
authors.forename: T
authors.initials: T
authors.lastname: Gardella
authors.forename: H
authors.initials: H
authors.lastname: Moyle
authors.forename: M M
authors.initials: MM
authors.lastname: Susskind
mesh_terms: D001483:Base Sequence; D002872:Chromosome Deletion; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D007763:Lac Operon; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D012808:Sigma Factor; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases