A negative feedback loop is critical for recovery of RpoS after stress in Escherichia coli.

RpoS is an alternative sigma factor needed for the induction of the general stress response in many gammaproteobacteria. Tight regulation of RpoS levels and activity is required for bacterial growth and survival under stress. In Escherichia coli, various stresses lead to higher levels of RpoS due to increased translation and decreased degradation.

RpoS and the bacterial general stress response.

SUMMARYThe general stress response (GSR) is a widespread strategy developed by bacteria to adapt and respond to their changing environments. The GSR is induced by one or multiple simultaneous stresses, as well as during entry into stationary phase and leads to a global response that protects cells against multiple stresses. The alternative sigma factor RpoS is the central GSR regulator in and conserved in most γ-proteobacteria.

A negative feedback loop is critical for recovery of RpoS after stress in .

RpoS is an alternative sigma factor needed for the induction of the general stress response in many gammaproteobacteria. Tight regulation of RpoS levels and activity is required for bacterial growth and survival under stress. In , various stresses lead to higher levels of RpoS due to increased translation and decreased degradation.

Defining Two Chemosensory Arrays in .

has 2 functional chemosensory systems named Che1 and Che3, and 27 chemoreceptors. Che3 is dedicated to chemotaxis while Che1 could be involved in RpoS post-translational regulation. In this study, we have shown that two chemoreceptors Aer2so and McpAso, genetically related to the Che1 system, form distinct core-signaling units and signal to Che1 and Che3, respectively.

Structural asymmetry does not indicate hemiphosphorylation in the bacterial histidine kinase CpxA.

Histidine protein kinases (HKs) are prevalent prokaryotic sensor kinases that are central to phosphotransfer in two-component signal transduction systems, regulating phosphorylation of response regulator proteins that determine the output responses. HKs typically exist as dimers and can potentially autophosphorylate at each conserved histidine residue in the individual protomers, leading to diphosphorylation. However, analyses of HK phosphorylation in biochemical assays suggest negative cooperativity, whereby phosphorylation in one protomer of the dimer inhibits phosphorylation in the second protomer, leading to ∼50% phosphorylation of the available sites in dimers.

Structural Basis of Response Regulator Function.

Response regulators function as the output components of two-component systems, which couple the sensing of environmental stimuli to adaptive responses. Response regulators typically contain conserved receiver (REC) domains that function as phosphorylation-regulated switches to control the activities of effector domains that elicit output responses. This modular design is extremely versatile, enabling different regulatory strategies tuned to the needs of individual signaling systems.

Connected partner-switches control the life style of Pseudomonas aeruginosa through RpoS regulation.

Biofilm formation is a complex process resulting from the action of imbricated pathways in response to environmental cues. In this study, we showed that biofilm biogenesis in the opportunistic pathogen Pseudomonas aeruginosa depends on the availability of RpoS, the sigma factor regulating the general stress response in bacteria. Moreover, it was demonstrated that RpoS is post-translationally regulated by the HsbR-HsbA partner switching system as has been demonstrated for its CrsR-CrsA homolog in Shewanella oneidensis.

Regulation of σ factors by conserved partner switches controlled by divergent signalling systems.

Partner-Switching Systems (PSS) are widespread regulatory systems, each comprising a kinase-anti-σ, a phosphorylatable anti-σ antagonist and a phosphatase module. The anti-σ domain quickly sequesters or delivers the target σ factor according to the phosphorylation state of the anti-σ antagonist induced by environmental signals. The PSS components are proteins alone or merged to other domains probably to adapt to the input signals.

Protection of the general stress response σ factor by the CrsR regulator allows a rapid and efficient adaptation of .

To cope with environmental stresses, bacteria have evolved various strategies, including the general stress response (GSR). GSR is governed by an alternative transcriptional σ factor named σ (RpoS) that associates with RNA polymerase and controls the expression of numerous genes. Previously, we have reported that posttranslational regulation of σ in the aquatic bacterium involves the CrsR-CrsA partner-switching regulatory system, but the exact mechanism by which CrsR and CrsA control σ activity is not completely unveiled.

The General Stress Response σS Is Regulated by a Partner Switch in the Gram-negative Bacterium Shewanella oneidensis.

Here, we show that a partner-switching system of the aquatic Proteobacterium Shewanella oneidensis regulates post-translationally σ (also called RpoS), the general stress response sigma factor. Genes SO2118 and SO2119 encode CrsA and CrsR, respectively. CrsR is a three-domain protein comprising a receiver, a phosphatase, and a kinase/anti-sigma domains, and CrsA is an anti-sigma antagonist.

Chaperones in maturation of molybdoenzymes: Why specific is better than general?

Molybdoenzymes play essential functions in living organisms and, as a result, in various geochemical cycles. It is thus crucial to understand how these complex proteins become highly efficient enzymes able to perform a wide range of catalytic activities. It has been established that specific chaperones are involved during their maturation process.