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General Stress Signaling in the Alphaproteobacteria.

ABSTRACT: The Alphaproteobacteria uniquely integrate features of two-component signal transduction and alternative ? factor regulation to control transcription of genes that ensure growth and survival across a range of stress conditions. Research over the past decade has led to the discovery of the key molecular players of this general stress response (GSR) system, including the sigma factor ?(EcfG), its anti-? factor NepR, and the anti-anti-? factor PhyR. The central molecular event of GSR activation entails aspartyl phosphorylation of PhyR, which promotes its binding to NepR and thereby releases ?(EcfG) to associate with RNAP and direct transcription. Recent studies are providing a new understanding of complex, multilayered sensory networks that activate and repress this central protein partner switch. This review synthesizes our structural and functional understanding of the core GSR regulatory proteins and highlights emerging data that are defining the systems that regulate GSR transcription in a variety of species.

SUBMITTER: Fiebig A

PROVIDER: S-EPMC4710059 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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General Stress Signaling in the Alphaproteobacteria.

Fiebig Aretha A Herrou Julien J Willett Jonathan J Crosson Sean S

Annual review of genetics 20151005

The Alphaproteobacteria uniquely integrate features of two-component signal transduction and alternative σ factor regulation to control transcription of genes that ensure growth and survival across a range of stress conditions. Research over the past decade has led to the discovery of the key molecular players of this general stress response (GSR) system, including the sigma factor σ(EcfG), its anti-σ factor NepR, and the anti-anti-σ factor PhyR. The central molecular event of GSR activation ent ...[more]

PMID: 26442844

Similar Datasets

Complex two-component signaling regulates the general stress response in Alphaproteobacteria.

Project description:The general stress response (GSR) in Alphaproteobacteria was recently shown to be controlled by a partner-switching mechanism that is triggered by phosphorylation of the response regulator PhyR. Activation of PhyR ultimately results in release of the alternative extracytoplasmic function sigma factor σ(EcfG), which redirects transcription toward the GSR. Little is known about the signal transduction pathway(s) controlling PhyR phosphorylation. Here, we identified the single-domain response regulator (SDRR) SdrG and seven histidine kinases, PakA to PakG, belonging to the HWE/HisKA2 family as positive modulators of the GSR in Sphingomonas melonis Fr1. Phenotypic analyses, epistasis experiments, and in vitro phosphorylation assays indicate that Paks directly phosphorylate PhyR and SdrG, and that SdrG acts upstream of or in concert with PhyR, modulating its activity in a nonlinear pathway. Furthermore, we found that additional SDRRs negatively affect the GSR in a way that strictly requires PhyR and SdrG. Finally, analysis of GSR activation by thermal, osmotic, and oxidative stress indicates that Paks display different degrees of redundancy and that a specific kinase can sense multiple stresses, suggesting that the GSR senses a particular condition as a combination of, rather than individual, molecular cues. This study thus establishes the alphaproteobacterial GSR as a complex and interlinked network of two-component systems, in which multiple histidine kinases converge to PhyR, the phosphorylation of which is, in addition, subject to regulation by several SDRRs. Our finding that most HWE/HisKA2 kinases contribute to the GSR in S. melonis Fr1 opens the possibility that this notion might also be true for other Alphaproteobacteria.

| S-EPMC4260549 | biostudies-literature

Structural basis for sigma factor mimicry in the general stress response of Alphaproteobacteria.

Project description:Reprogramming gene expression is an essential component of adaptation to changing environmental conditions. In bacteria, a widespread mechanism involves alternative sigma factors that redirect transcription toward specific regulons. The activity of sigma factors is often regulated through sequestration by cognate anti-sigma factors; however, for most systems, it is not known how the activity of the anti-sigma factor is controlled to release the sigma factor. Recently, the general stress response sigma factor in Alphaproteobacteria, σ(EcfG), was identified. σ(EcfG) is inactivated by the anti-sigma factor NepR, which is itself regulated by the response regulator PhyR. This key regulator sequesters NepR upon phosphorylation of its PhyR receiver domain via its σ(EcfG) sigma factor-like output domain (PhyR(SL)). To understand the molecular basis of the PhyR-mediated partner-switching mechanism, we solved the structure of the PhyR(SL)-NepR complex using NMR. The complex reveals an unprecedented anti-sigma factor binding mode: upon PhyR(SL) binding, NepR forms two helices that extend over the surface of the PhyR(SL) subdomains. Homology modeling and comparative analysis of NepR, PhyR(SL), and σ(EcfG) mutants indicate that NepR contacts both proteins with the same determinants, showing sigma factor mimicry at the atomic level. A lower density of hydrophobic interactions, together with the absence of specific polar contacts in the σ(EcfG)-NepR complex model, is consistent with the higher affinity of NepR for PhyR compared with σ(EcfG). Finally, by reconstituting the partner switch in vitro, we demonstrate that the difference in affinity of NepR for its partners is sufficient for the switch to occur.

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The Brucella abortus virulence regulator, LovhK, is a sensor kinase in the general stress response signaling pathway

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The Brucella abortus virulence regulator, LovhK, is a sensor kinase in the general stress response signaling pathway

2014-09-25 | GSE59513 | GEO

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Project description:Root growth and rhizosphere bacterial community of soybean intercropped with sugarcane mediated with the Ea-DREB2B gene

| PRJNA596989 | ENA

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Project description:Alphaproteobacteria Raw sequence reads

| PRJNA480949 | ENA

A General Mechanism for the General Stress Response in Bacteria.

Project description:Bacteria have a widely conserved General Stress Response (GSR) that allows them to survive adverse environmental conditions. However, because the signaling proteins that initiate the GSR have evolved to respond to a vast range of species-specific signals, we lack a general understanding of how they are controlled. Here, we determined the molecular mechanism by which a member of the PPM family of protein serine/threonine phosphatases, RsbU, activates the GSR in B. subtilis. It was known that the phosphatase activity of RsbU is activated through interaction with a partner protein, RsbT, when it is released from a megadalton stress-sensing complex upon environmental stress, but how RsbT activates RsbU was not understood. Here we report that RsbT binds an otherwise flexible linker of RsbU to dimerize and activate its phosphatase domains through a conserved allosteric switch element. Conformational flexibility of the homologous linker was known to control activity of the E. coli GSR-activating protein (RssB), which lacks phosphatase activity and functions as a protease adapter protein, suggesting a unifying model for GSR activation across bacterial phyla. Furthermore, and as we now show, the crossing α-helical conformation of RsbU linkers in the active dimeric state is similar to that predicted for paralogous bacterial phosphatases with diverse N-terminal sensory domains, and to linkers known to control the activity of GGDEF diguanylate cyclases and histidine kinases. We propose that this shared regulatory mechanism provides a modularly exchangeable toolkit for bacteria to recognize diverse environmental signals.

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