Interaction of the conserved region 4.2 of sigma(E) with the RseA anti-sigma factor.
ABSTRACT Esigma(E) RNA polymerase transcribes a regulon of folding factors for the bacterial envelope and is induced by physical and chemical stresses. The RseA anti-sigma factor inhibits the activity of Esigma(E) RNA polymerase. It is shown here that the N-terminal portion of sigma(E), residues 1-153, binds core RNA polymerase. RseA interacts with residues 154-191 of sigma(E), a site that is homologous to region 4, the sigma factor binding site for promoter DNA. Mutations that reduce transcription of Esigma(E) RNA polymerase map to sigma(E) residues 178, 181, and 183. Variant sigma(E) proteins with amino acid substitutions at residues 178, 181, or 183 do not associate with RseA. A regulatory mechanism is proposed whereby RseA binds to a C-terminal peptide of sigma(E) and inhibits the transcription of Esigma(E) RNA polymerase by blocking promoter recognition.
Article: Structural basis of a protein partner switch that regulates the general stress response of α-proteobacteria.[show abstract] [hide abstract]
ABSTRACT: α-Proteobacteria uniquely integrate features of two-component signal transduction (TCS) and alternative sigma factor (σ) regulation to control transcription in response to general stress. The core of this regulatory system is the PhyR protein, which contains a σ-like (SL) domain and a TCS receiver domain. Aspartyl phosphorylation of the PhyR receiver in response to stress signals promotes binding of the anti-σ factor, NepR, to PhyR-SL. This mechanism, whereby NepR switches binding between its cognate σ factor and phospho-PhyR (PhyR∼P), controls transcription of the general stress regulon. We have defined the structural basis of the PhyR∼P/NepR interaction in Caulobacter crescentus and characterized the effect of aspartyl phosphorylation on PhyR structure by molecular dynamics simulations. Our data support a model in which phosphorylation of the PhyR receiver domain promotes its dissociation from the PhyR-SL domain, which exposes the NepR binding site. A highly dynamic loop-helix region (α3-α4) of the PhyR-SL domain plays an important role in PhyR∼P binding to NepR in vitro, and in stress-dependent activation of transcription in vivo. This study provides a foundation for understanding the protein-protein interactions and protein structural dynamics that underpin general stress adaptation in a large and metabolically diverse clade of the bacterial kingdom.Proceedings of the National Academy of Sciences 05/2012; 109(21):E1415-23. · 9.68 Impact Factor