Converting Escherichia coli RNA polymerase into an enhancer-responsive enzyme: role of an NH2-terminal leucine patch in sigma 54.
The protein sigma 54 associates with Escherichia coli core RNA polymerase to form a holoenzyme that binds promoters but is inactive in the absence of enhancer activation. Here, mutants of sigma 54 enabled polymerases to transcribe without enhancer protein and adenosine triphosphate. The mutations are in leucines within the NH2-terminal glutamine-rich domain of sigma 54. Multiple leucine substitutions mimicked the effect of enhancer protein, which suggests that the enhancer protein functions to disrupt a leucine patch. The results indicate that sigma 54 acts both as an inhibitor of polymerase activity and as a receptor that interacts with enhancer protein to overcome this inhibition, and that these two activities jointly confer enhancer responsiveness.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology*; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029968:Escherichia coli Proteins; D007930:Leucine / Q000737:chemistry; D008969:Molecular Sequence Data; D009154:Mutation; D051922:PII Nitrogen Regulatory Proteins; D011401:Promoter Regions, Genetic; D051877:RNA Polymerase Sigma 54; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D051922:PII Nitrogen Regulatory Proteins; D012808:Sigma Factor; D015534:Trans-Activators; D014157:Transcription Factors; C497751:rpoN protein, E coli; D000255:Adenosine Triphosphate; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54; D007930:Leucine