RsrA, an anti-sigma factor regulated by redox change

We described a novel extracytoplasmic function sigma factor, σR, that is required for induction of the thioredoxin reductase/thioredoxin operon

J.-G. Kang

2002

Scholarcy highlights

  • The reducing environment of the cytoplasm seldom permits the formation of stable protein disulfide bonds, living cells have evolved several highly conserved pathways to deal with the potentially lethal consequences of thiol oxidation
  • We described a novel extracytoplasmic function sigma factor, σR, that is required for induction of the thioredoxin reductase/thioredoxin operon
  • Oxidized RsrA is a direct substrate for thioredoxin In S.coelicolor, transcription from the p1 promoter of the trxBA operon is induced at least 50-fold within 10 min of exposure to diamide in a σR-dependent manner
  • We have shown that RsrA is a σR-specific anti-sigma factor, that loss of anti-sigma factor activity correlates with the formation of one or more intramolecular disulfide bonds and that oxidized RsrA is a substrate for the thioredoxin system in vitro
  • Exposure to oxidative stress induces the formation of one or more intramolecular disulfide bonds in RsrA, which cause it to lose its affinity for σR, thereby allowing σR to bind core RNA polymerase and induce transcription of the trxBA operon
  • Expression of the thioredoxin system in turn leads to reduction of RsrA to its active state in which it re-binds σR, thereby shutting off σR-dependent transcription and completing the feedback regulatory loop
  • Reduced RsrA was incubated with σR in the binding buffer without DTT, or with added diamide

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