title: Alterations in the β flap and β' dock domains of the RNA polymerase abolish NusA-mediated feedback regulation of the metY-nusA-infB operon.
abstract: The RimM protein in Escherichia coli is important for the in vivo maturation of 30S ribosomal subunits and a ΔrimM mutant grows poorly due to assembly and translational defects. These deficiencies are suppressed partially by mutations that increase the synthesis of another assembly protein, RbfA, encoded by the metY-nusA-infB operon. Among these suppressors are mutations in nusA that impair the NusA-mediated negative-feedback regulation at internal intrinsic transcriptional terminators of the metY-nusA-infB operon. We describe here the isolation of two new mutations, one in rpoB and one in rpoC (encoding the β and β' subunits of the RNA polymerase, respectively), that increase the synthesis of RbfA by preventing NusA from stimulating termination at the internal intrinsic transcriptional terminators of the metY-nusA-infB operon. The rpoB2063 mutation changed the isoleucine in position 905 of the β flap-tip helix to a serine, while the rpoC2064 mutation duplicated positions 415 to 416 (valine-isoleucine) at the base of the β' dock domain. These findings support previously published in vitro results, which have suggested that the β flap-tip helix and β' dock domain at either side of the RNA exit tunnel mediate the binding to NusA during transcriptional pausing and termination.
authors.affiliation: Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Göran O
authors.initials: GO
authors.lastname: Bylund
authors.forename: Stefan
authors.initials: S
authors.lastname: Nord
authors.forename: J Mattias
authors.initials: JM
authors.lastname: Lövgren
authors.forename: P Mikael
authors.initials: PM
authors.lastname: Wikström
mesh_terms: D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D009154:Mutation; D009876:Operon / Q000235:genetics / Q000502:physiology*; D010445:Peptide Elongation Factors / Q000235:genetics / Q000378:metabolism*; D039881:Prokaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology; D035602:Transcriptional Elongation Factors
chemical_list: D029968:Escherichia coli Proteins; D010445:Peptide Elongation Factors; D039881:Prokaryotic Initiation Factor-2; D012269:Ribosomal Proteins; C436973:RimM protein, E coli; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; C068727:nusA protein, E coli; D012321:DNA-Directed RNA Polymerases