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The stress sigma factor of RNA polymerase RpoS/σ S is a solvent-exposed open molecule in solution

Abstract : In bacteria, one primary and multiple alternative sigma (σ) factors associate with the RNA polymerase core enzyme (E) to form holoenzymes (Eσ) with different promoter recognition specificities. The alternative σ factor RpoS/σ S is produced in stationary phase and under stress conditions and reprograms global gene expression to promote bacterial survival. To date, the three-dimensional structure of a full-length free σ factor remains elusive. The current model suggests that extensive interdomain contacts in a free σ factor result in a compact conformation that masks the DNA-binding determinants of σ, explaining why a free σ factor does not bind double-stranded promoter DNA efficiently. Here, we explored the solution conformation of σ S using amide hydrogen/deuterium exchange coupled with mass spectrometry, NMR, analytical ultracentrifugation and molecular dynamics. Our data strongly argue against a compact conformation of free σ S. Instead, we show that σ S adopts an open conformation in solution in which the folded σ 2 and σ 4 domains are interspersed by domains with a high degree of disorder. These findings suggest that E binding induces major changes in both the folding and domain arrangement of σ S and provide insights into the possible mechanisms of regulation of σ S activity by its chaperone Crl.
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Submitted on : Tuesday, January 16, 2018 - 10:12:14 AM
Last modification on : Tuesday, July 5, 2022 - 10:23:57 AM
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Paola Cavaliere, Sebastien Brier, Petr Filipenko, Christina Sizun, Bertrand Raynal, et al.. The stress sigma factor of RNA polymerase RpoS/σ S is a solvent-exposed open molecule in solution. Biochemical Journal, Portland Press, 2018, 475 (1), pp.341 - 354. ⟨10.1042/BCJ20170768⟩. ⟨pasteur-01685123⟩



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