Rapid Dephosphorylation of the TorR Response Regulator by the TorS Unorthodox Sensor in
            <i>Escherichia coli</i>

Ansaldi, Mireille; Jourlin-Castelli, Cécile; Lepelletier, Michèle; Théraulaz, Laurence; Méjean, Vincent

doi:10.1128/jb.183.8.2691-2695.2001

Cited by 38 publications

(23 citation statements)

References 34 publications

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“…Phosphorelays are a common variation of the two-component system (3) that contains sequential His (H1) 3 Asp (D1) 7 His (H2) 7 Asp (D2) phosphotransfer. The second two steps are reversible, and often phosphoryl groups are lost from the system via D1 autodephosphorylation (Scheme 1) (44,45). In PilChp, the ATP-reactive ChpA Xpts (Hpt4 -6) have a similar role as the phosphorelay DHp domain (H1), whereas the ATP-unreactive Xpts (Hpt2 and 3) play the role of H2.…”

Section: Discussionmentioning

confidence: 99%

Phosphoryl Group Flow within the Pseudomonas aeruginosa Pil-Chp Chemosensory System

Silversmith¹,

Wang

Fulcher

et al. 2016

Journal of Biological Chemistry

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Bacterial chemosensory signal transduction systems that regulate motility by type IV pili (T4P) can be markedly more complex than related flagellum-based chemotaxis systems. In T4P-based systems, the CheA kinase often contains numerous potential sites of phosphorylation, but the signaling mechanisms of these systems are unknown. In Pseudomonas aeruginosa, the Pil-Chp system regulates T4P-mediated twitching motility and cAMP levels, both of which play roles in pathogenesis. The Pil-Chp histidine kinase (ChpA) has eight "Xpt" domains; six are canonical histidine-containing phosphotransfer (Hpt) domains and two have a threonine (Tpt) or serine (Spt) in place of the histidine. Additionally, there are two stand-alone receiver domains (PilG and PilH) and a ChpA C-terminal receiver domain (ChpArec). Here, we demonstrate that the ChpA Xpts are functionally divided into three categories as follows: (i) those phosphorylated with ATP (Hpt4 -6); (ii) those reversibly phosphorylated by ChpArec (Hpt2-6), and (iii) those with no detectable phosphorylation (Hpt1, Spt, and Tpt). There was rapid phosphotransfer from Hpt2-6 to ChpArec and from Hpt3 to PilH, whereas transfer to PilG was slower. ChpArec also had a rapid rate of autodephosphorylation. The biochemical results together with in vivo cAMP and twitching phenotypes of key ChpA phosphorylation site point mutants supported a scheme whereby ChpArec functions both as a phosphate sink and a phosphotransfer element linking Hpt4 -6 to Hpt2-3. Hpt2 and Hpt3 are likely the dominant sources of phosphoryl groups for PilG and PilH, respectively. The data are synthesized in a signaling circuit that contains fundamental features of twocomponent phosphorelays.

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Section: Discussionmentioning

confidence: 99%

Phosphoryl Group Flow within the Pseudomonas aeruginosa Pil-Chp Chemosensory System

Silversmith¹,

Wang

Fulcher

et al. 2016

Journal of Biological Chemistry

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“…The bacterial response to the environmental signal is itself tightly regulated. In many cases, HKs have kinase activity and function as phosphatases, where they remove the phosphate group from its cognate RR (23)(24)(25)(26)(27)(28)(29) (18). Another well-described mechanism of TCS regulation involves the self-catalyzed dephosphorylation of the RR (18,(30)(31)(32).…”

mentioning

confidence: 99%

The ChrSA and HrrSA Two-Component Systems Are Required for Transcriptional Regulation of the hemA Promoter in Corynebacterium diphtheriae

Burgos

Schmitt

2016

J Bacteriol

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Corynebacterium diphtheriae utilizes heme and hemoglobin (Hb) as iron sources for growth in low-iron environments. In C. diphtheriae, the two-component signal transduction systems (TCSs) ChrSA and HrrSA are responsive to Hb levels and regulate the transcription of promoters for hmuO, hrtAB, and hemA. ChrSA and HrrSA activate transcription at the hmuO promoter and repress transcription at hemA in an Hb-dependent manner. In this study, we show that HrrSA is the predominant repressor at hemA and that its activity results in transcriptional repression in the presence and absence of Hb, whereas repression of hemA by ChrSA is primarily responsive to Hb. DNA binding studies showed that both ChrA and HrrA bind to the hemA promoter region at virtually identical sequences. ChrA binding was enhanced by phosphorylation, while binding to DNA by HrrA was independent of its phosphorylation state. ChrA and HrrA are phosphorylated in vitro by the sensor kinase ChrS, whereas no kinase activity was observed with HrrS in vitro. Phosphorylated ChrA was not observed in vivo, even in the presence of Hb, which is likely due to the instability of the phosphate moiety on ChrA. However, phosphorylation of HrrA was observed in vivo regardless of the presence of the Hb inducer, and genetic analysis indicates that ChrS is responsible for most of the phosphorylation of HrrA in vivo. Phosphorylation studies strongly suggest that HrrS functions primarily as a phosphatase and has only minimal kinase activity. These findings collectively show a complex mechanism of regulation at the hemA promoter, where both two-component systems act in concert to optimize expression of heme biosynthetic enzymes. IMPORTANCEUnderstanding the mechanism by which two-component signal transduction systems function to respond to environmental stimuli is critical to the study of bacterial pathogenesis. The current study expands on the previous analyses of the ChrSA and HrrSA TCSs in the human pathogen C. diphtheriae. The findings here underscore the complex interactions between the ChrSA and HrrSA systems in the regulation of the hemA promoter and demonstrate how the two systems complement one another to refine and control transcription in the presence and absence of Hb.C orynebacterium diphtheriae, a strict human pathogen, is the etiologic agent of diphtheria (1-3). After colonizing the upper respiratory tract, actively dividing cells secrete the potent diphtheria toxin (DT), which disseminates throughout the host and elicits the major clinical symptoms of the disease (1-3). Expression of DT is negatively regulated at the transcriptional level by iron and the diphtheria toxin repressor protein DtxR (3, 4). Although essential for bacterial physiology, iron is not readily available for invading pathogens since much of it is sequestered by host proteins such as transferrin, lactoferrin, and hemoglobin (Hb) (5-7).To thrive in such a stringent environment, bacteria utilize a variety of tightly regulated iron-and heme-scavenging systems (7,8). C. diphtheriae, in part...

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“…TorS can also dephosphorylate phospho-TorR when TMAO is exhausted. Dephosphorylation is a rapid process occurring by reverse phosphorelay (12).…”

mentioning

confidence: 99%

TorT, a Member of a New Periplasmic Binding Protein Family, Triggers Induction of the Tor Respiratory System upon Trimethylamine N-Oxide Electron-acceptor Binding in Escherichia coli

Baraquet

Théraulaz

Guiral

et al. 2006

Journal of Biological Chemistry

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In anaerobiosis, Escherichia coli can use trimethylamine N-oxide (TMAO) as a terminal electron acceptor. Reduction of TMAO in trimethylamine (TMA) is mainly performed by the respiratory TMAO reductase. This system is encoded by the torCAD operon, which is induced in the presence of TMAO. This regulation involves a two-component system comprising TorS, an unorthodox histidine kinase, and TorR, a response regulator. A third protein, TorT, sharing homologies with periplasmic binding proteins, plays a key role in this regulation because disruption of the torT gene abolishes tor expression. In this study we showed that TMAO protects TorT against degradation by the GluC endoproteinase and modifies its temperature-induced CD spectrum. We also isolated a TorT negative mutant that is no longer protected by TMAO from degradation by GluC. Isothermal titration calorimetry confirmed that TorT binds TMAO with a binding constant of 150 M. Therefore, we conclude that TorT binds TMAO and that this binding promotes a conformational change of TorT. We also showed that TorT interacts with the periplasmic domain of TorS in both the presence and absence of TMAO but the TorT-TMAO complex induces a higher GluC protection of TorS than TorT alone. These results support the idea that TMAO binding to TorT induces a cascade of conformational changes from TorT to TorS, leading to TorS activation. We identified several homologues of the TorT protein that define a new family of periplasmic binding proteins. We thus propose that the members of this family bind TMAO or related compounds and that they are involved in signal transduction or even substrate transport.In anaerobiosis, Escherichia coli can use alternative terminal electron acceptors such as nitrate, nitrite, fumarate, dimethyl sulfoxide (Me 2 SO), or trimethylamine N-oxide (TMAO) 3 for respiration (1). Reduction of TMAO in trimethylamine (TMA) mainly involves the TMAO reductase system. This respiratory system comprises three proteins: TorC, TorA, and TorD. The TorC protein is a pentahemic c-type cytochrome anchored to the membrane and oriented toward the periplasmic compartment. The TorA protein, located in the periplasm, is the terminal reductase and receives the electrons from TorC (2). TorD is a cytoplasmic protein that acts as both a specific chaperone and an escort protein for TorA, allowing TorA maturation and protection before its translocation into the periplasm by the Tat system (3-6).The Tor respiratory system is encoded by the torCAD operon that is induced in the presence of TMAO (7). The TMAO control is strict because there is almost no expression of the tor operon in the absence of TMAO. The three genes torS, torT, and torR, located upstream of the tor operon, are involved in this regulation. Disruption of either one of these genes abolishes tor operon induction. The torS and torR genes encode a two-component regulatory system in which TorS is an unorthodox sensor containing three phosphorylation sites and TorR a response regulator of the OmpR family (8, 9). At its N-term...

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Rapid Dephosphorylation of the TorR Response Regulator by the TorS Unorthodox Sensor in Escherichia coli

Cited by 38 publications

References 34 publications

Phosphoryl Group Flow within the Pseudomonas aeruginosa Pil-Chp Chemosensory System

Phosphoryl Group Flow within the Pseudomonas aeruginosa Pil-Chp Chemosensory System

The ChrSA and HrrSA Two-Component Systems Are Required for Transcriptional Regulation of the hemA Promoter in Corynebacterium diphtheriae

TorT, a Member of a New Periplasmic Binding Protein Family, Triggers Induction of the Tor Respiratory System upon Trimethylamine N-Oxide Electron-acceptor Binding in Escherichia coli

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