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Chapter 16 : The General Stress Response in Alphaproteobacteria

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Abstract:

Extensive studies with the model organisms and have led to the identification of two regulatory networks controlling general stress response. Genes encoding histidine kinases are found in the vicinity of in several Alphaproteobacteria. However, the involvement of one of these histidine kinases in the PhyR cascade has not been demonstrated so far. Francez-Charlot et al. proposed that σ or several members of the σ family are responsible for transcription of stress-related genes. In several Alphaproteobacteria, a gene encoding a histidine kinase is found at the locus. Signal perception in the σ and σ regulatory cascades has been described as highly complex, as a result of the necessity to integrate multiple signals; such complexity can be expected in Alphaproteobacteria too and may reflect an adaptation to the various environments in which the organisms live. In , the RpoE2/ σ homolog, RpoE4, was shown to be involved in oxidative and osmotic stresses. Genes encoding catalase, the DNA protection protein Dps or DNA repair enzymes, known to be crucial for σ-dependent resistance to oxidative stress, are controlled by the cascade in several species. All regulons contain several regulators whose functions are mainly unknown, such as kinases and response regulators of His-Asp phosphorelays, onecomponent systems, and sigma factors, such as RpoH.

Citation: Francez-Charlot A, Frunzke J, Vorholt J. 2011. The General Stress Response in Alphaproteobacteria, p 291-300. In Storz G, Hengge R (ed), Bacterial Stress Responses, Second Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816841.ch16

Key Concept Ranking

General Stress Response
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Glycogen Debranching Enzyme
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DNA Repair Enzyme
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Reactive Oxygen Species
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Figures

Image of Figure 1A.
Figure 1A.

(A) Conservation of the - - locus in selected members of the Alphaproteobacteria. Adapted from Gourion et al. ( ).

Citation: Francez-Charlot A, Frunzke J, Vorholt J. 2011. The General Stress Response in Alphaproteobacteria, p 291-300. In Storz G, Hengge R (ed), Bacterial Stress Responses, Second Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816841.ch16
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Image of Figure 1B.
Figure 1B.

(B) Multiple sequence alignment of PhyR (top) and σ (bottom) homologs. Conserved residues are highlighted in black (identical residues) and gray (similar residues). The regions important for σ factor function are indicated above. (B) Francez-Charlot et al. ( ).

Citation: Francez-Charlot A, Frunzke J, Vorholt J. 2011. The General Stress Response in Alphaproteobacteria, p 291-300. In Storz G, Hengge R (ed), Bacterial Stress Responses, Second Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816841.ch16
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Image of Figure 2.
Figure 2.

Model of the core cascade controlling general stress response in Alphaproteobacteria. Under nonstressed conditions (left box) σ is inhibited by the anti-sigma factor NepR. Upon sensing of a stress stimulus (right box) the corresponding histidine kinase activates PhyR by phosphorylation of the conserved aspartate residue in the C-terminal receiver domain (a kinase activating PhyR has not yet been identified experimentally; however, genes encoding histidine kinases are often genetically linked to in Alphaproteobacteria). In its phosphorylated state, PhyR is able to sequester the anti-sigma factor NepR. This partner-switching mechanism allows the release of the ECF sigma factor σ, leading to the activation of stress genes.

Citation: Francez-Charlot A, Frunzke J, Vorholt J. 2011. The General Stress Response in Alphaproteobacteria, p 291-300. In Storz G, Hengge R (ed), Bacterial Stress Responses, Second Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816841.ch16
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References

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Tables

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Table 1.

and homologs present in the genomes of selected Alphaproteobacteria

Citation: Francez-Charlot A, Frunzke J, Vorholt J. 2011. The General Stress Response in Alphaproteobacteria, p 291-300. In Storz G, Hengge R (ed), Bacterial Stress Responses, Second Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816841.ch16
Generic image for table
Table 2.

Overview of stress-related target genes of the PhyR/NepR/σ cascade

Citation: Francez-Charlot A, Frunzke J, Vorholt J. 2011. The General Stress Response in Alphaproteobacteria, p 291-300. In Storz G, Hengge R (ed), Bacterial Stress Responses, Second Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816841.ch16

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