title: Structural basis of a protein partner switch that regulates the general stress response of α-proteobacteria.
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.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Julien
authors.initials: J
authors.lastname: Herrou
authors.forename: Grant
authors.initials: G
authors.lastname: Rotskoff
authors.forename: Yun
authors.initials: Y
authors.lastname: Luo
authors.forename: Benoît
authors.initials: B
authors.lastname: Roux
authors.forename: Sean
authors.initials: S
authors.lastname: Crosson
mesh_terms: D020561:Alphaproteobacteria / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016935:Caulobacter crescentus / Q000235:genetics* / Q000378:metabolism; D003461:Crystallography; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating) / Q000502:physiology; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012808:Sigma Factor / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013312:Stress, Physiological / Q000235:genetics*; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating)