title: The helix-turn-helix motif of sigma 54 is involved in recognition of the -13 promoter region.
abstract: Residue Arg-383 in the proposed helix-turn-helix motif of the novel RNA polymerase sigma factor sigma 54 has been changed by site-directed mutagenesis to all possible alternative amino acids. Only two mutants, RK383 and RH383, are active in promoting transcription from either the glnAp2 promoter or the nifL promoter. We constructed a set of mutant derivatives of glnAp2 such that each base in the conserved GG and GC doublets at -24 and -12 was changed to all possible alternatives. All 12 mutant glnAp2 promoters showed a marked promoter-down phenotype with wild-type sigma 54, but RK383 suppressed changes of both G to C and G to T at -13. This result suggests that the sigma 54 helix-turn-helix is involved in recognition of the -13 region of sigma 54-dependent promoters.
authors.affiliation: AFRC Nitrogen Fixation Laboratory, University of Sussex, Brighton, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Merrick
authors.forename: S
authors.initials: S
authors.lastname: Chambers
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D017433:Protein Structure, Secondary; D051877:RNA Polymerase Sigma 54; D012808:Sigma Factor / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D012808:Sigma Factor; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54