Regulation of RpoS proteolysis in Escherichia coli: the response regulator RssB is a recognition factor that interacts with the turnover element in RpoS.
The degradation of the RpoS (sigmaS) subunit of RNA polymerase in Escherichia coli is a prime example of regulated proteolysis in prokaryotes. RpoS turnover depends on ClpXP protease, the response regulator RssB, and a hitherto uncharacterized "turnover element" within RpoS itself. Here we localize the turnover element to a small element (around the crucial amino acid lysine-173) directly downstream of the promoter-recognizing region 2.4 in RpoS. Its sequence as well as its location identify the turnover element as a unique proteolysis-promoting motif. This element is shown to be a site of interaction with RssB. Thus, RssB is functionally unique among response regulators as a direct recognition factor in ClpXP-dependent RpoS proteolysis. Binding of RssB to RpoS is stimulated by phosphorylation of the RssB receiver domain, suggesting that environmental stress affects RpoS proteolysis by modulating RssB affinity for RpoS. Initial evidence indicates that lysine-173 in RpoS, besides being essential of RpoS proteolysis, may play a role in promoter recognition. Thus the same region in RpoS is crucial for proteolysis as well as for activity as a transcription factor.
Becker
G
G
Institute of Plant Physiology and Microbiology, Free University of Berlin, 14195 Berlin, Germany.
Klauck
E
E
Hengge-Aronis
R
R
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014157:Transcription Factors
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C098923:rssB protein, E coli; C069567:sigma factor KatF protein, Bacteria; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases