scholarly journals Feedback Control of a Two-Component Signaling System by an Fe-S-Binding Receiver Domain

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Benjamin J. Stein ◽  
Aretha Fiebig ◽  
Sean Crosson
Keyword(s):  
Histidine Kinase ◽  
Oxygen Sensor ◽  
Cell Physiology ◽  
Phosphoryl Transfer ◽  
Environmental Cues ◽  
Sensor Kinase ◽  
Signaling System ◽  
Receiver Domain ◽  
Two Component ◽  
Feedback Inhibitor

ABSTRACT Two-component signaling systems (TCSs) function to detect environmental cues and transduce this information into a change in transcription. In its simplest form, TCS-dependent regulation of transcription entails phosphoryl-transfer from a sensory histidine kinase to its cognate DNA-binding receiver protein. However, in certain cases, auxiliary proteins may modulate TCSs in response to secondary environmental cues. Caulobacter crescentus FixT is one such auxiliary regulator. FixT is composed of a single receiver domain and functions as a feedback inhibitor of the FixL-FixJ (FixLJ) TCS, which regulates the transcription of genes involved in adaptation to microaerobiosis. We sought to define the impact of fixT on Caulobacter cell physiology and to understand the molecular mechanism by which FixT represses FixLJ signaling. fixT deletion results in excess production of porphyrins and premature entry into stationary phase, demonstrating the importance of feedback inhibition of the FixLJ signaling system. Although FixT is a receiver domain, it does not affect dephosphorylation of the oxygen sensor kinase FixL or phosphoryl-transfer from FixL to its cognate receiver FixJ. Rather, FixT represses FixLJ signaling by inhibiting the FixL autophosphorylation reaction. We have further identified a 4-cysteine motif in Caulobacter FixT that binds an Fe-S cluster and protects the protein from degradation by the Lon protease. Our data support a model in which the oxidation of this Fe-S cluster promotes the degradation of FixT in vivo. This proteolytic mechanism facilitates clearance of the FixT feedback inhibitor from the cell under normoxia and resets the FixLJ system for a future microaerobic signaling event. IMPORTANCE Two-component signal transduction systems (TCSs) are broadly conserved in the bacterial kingdom and generally contain two molecular components, a sensor histidine kinase and a receiver protein. Sensor histidine kinases alter their phosphorylation state in direct response to a physical or chemical cue, whereas receiver proteins “receive” the phosphoryl group from the kinase to regulate a change in cell physiology. We have discovered that a single-domain receiver protein, FixT, binds an Fe-S cluster and controls Caulobacter heme homeostasis though its function as a negative-feedback regulator of the oxygen sensor kinase FixL. We provide evidence that the Fe-S cluster protects FixT from Lon-dependent proteolysis in the cell and endows FixT with the ability to function as a second, autonomous oxygen/redox sensor in the FixL-FixJ signaling pathway. This study introduces a novel mechanism of regulated TCS feedback control by an Fe-S-binding receiver domain.

scholarly journals Feedback control of a two-component signaling system by an Fe-S-binding receiver domain

2019 ◽  
Author(s):  
Benjamin J. Stein ◽  
Aretha Fiebig ◽  
Sean Crosson
Keyword(s):  
Feedback Control ◽  
Histidine Kinase ◽  
Oxygen Sensor ◽  
Cell Physiology ◽  
Environmental Cues ◽  
Sensor Kinase ◽  
Signaling System ◽  
Receiver Domain ◽  
Two Component ◽  
Feedback Inhibitor

AbstractTwo-component signaling systems (TCSs) function to detect environmental cues and transduce this information into a change in transcription. In its simplest form, TCS-dependent regulation of transcription entails phosphoryl-transfer from a sensory histidine kinase to its cognate DNA-binding receiver protein. However, in certain cases, auxiliary proteins may modulate TCSs in response to secondary environmental cues. Caulobacter crescentus FixT is one such auxiliary regulator. FixT is composed of a single receiver domain and functions as a feedback inhibitor of the FixL-FixJ (FixLJ) TCS, which regulates the transcription of genes involved in adaptation to microaerobiosis. We sought to define the impact of fixT on Caulobacter cell physiology and to understand the molecular mechanism by which FixT represses FixLJ signaling. fixT deletion results in excess production of porphyrins and premature entry into stationary phase, demonstrating the importance of feedback inhibition of the FixLJ signaling system. Although FixT is a receiver domain, it does not affect dephosphorylation of the oxygen-sensor kinase FixL or phosphoryltransfer from FixL to its cognate receiver FixJ. Rather, FixT represses FixLJ signaling by inhibiting the FixL autophosphorylation reaction. We have further identified a 4-cysteine motif in Caulobacter FixT that binds an Fe-S cluster and protects the protein from degradation by the Lon protease. Our data support a model in which oxidation of this Fe-S cluster promotes degradation of FixT in vivo. This proteolytic mechanism facilitates clearance the of the FixT feedback inhibitor from the cell under normoxia and resets the FixLJ system for a future microaerobic signaling event.ImportanceTwo-component signal transduction systems (TCSs) are broadly conserved in the bacterial kingdom and generally contain two molecular components: a sensor histidine kinase and a receiver protein. Sensor histidine kinases alter their phosphorylation state in direct response to a physical or chemical cue, whereas receiver proteins “receive” the phosphoryl group from the kinase to regulate a change in cell physiology. We have discovered that a single-domain receiver protein, FixT, binds an Fe-S cluster and controls Caulobacter heme homeostasis though its function as a negative feedback regulator of the oxygen-sensor kinase, FixL. We provide evidence that the Fe-S cluster protects FixT from Lon-dependent proteolysis in the cell and endows FixT with the ability to function as a second, autonomous oxygen/redox sensor in the FixL-FixJ signaling pathway. This study introduces a novel mechanism of regulated TCS feedback control by an Fe-S-binding receiver domain.

scholarly journals Novel Role for an HPt Domain in Stabilizing the Phosphorylated State of a Response Regulator Domain

2000 ◽  
Vol 182 (23) ◽  
pp. 6673-6678 ◽  
Author(s):  
Fabiola Janiak-Spens ◽  
David P. Sparling ◽  
Ann H. West
Keyword(s):  
Response Regulator ◽  
Phosphoryl Transfer ◽  
Sensor Kinase ◽  
Signaling System ◽  
Phosphorylated Protein ◽  
Physiological Conditions ◽  
Regulatory Domains ◽  
Regulatory Systems ◽  
Two Component ◽  
Stabilization Effect

ABSTRACT Two-component regulatory systems that utilize a multistep phosphorelay mechanism often involve a histidine-containing phosphotransfer (HPt) domain. These HPt domains serve an essential role as histidine-phosphorylated protein intermediates during phosphoryl transfer from one response regulator domain to another. InSaccharomyces cerevisiae, the YPD1 protein facilitates phosphoryl transfer from a hybrid sensor kinase, SLN1, to two distinct response regulator proteins, SSK1 and SKN7. Because the phosphorylation state largely determines the functional state of response regulator proteins, we have carried out a comparative study of the phosphorylated lifetimes of the three response regulator domains associated with SLN1, SSK1, and SKN7 (R1, R2, and R3, respectively). The isolated regulatory domains exhibited phosphorylated lifetimes within the range previously observed for other response regulator domains (i.e., several minutes to several hours). However, in the presence of YPD1, we found that the half-life of phosphorylated SSK1-R2 was dramatically extended (almost 200-fold longer than in the absence of YPD1). This stabilization effect was specific for SSK1-R2 and was not observed for SLN1-R1 or SKN7-R3. Our findings suggest a mechanism by which SSK1 is maintained in its phosphorylated state under normal physiological conditions and demonstrate an unprecedented regulatory role for an HPt domain in a phosphorelay signaling system.

scholarly journals A Novel Redox-Sensing Histidine Kinase That Controls Carbon Catabolite Repression inAzoarcussp. CIB

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
J. Andrés Valderrama ◽  
Helena Gómez-Álvarez ◽  
Zaira Martín-Moldes ◽  
M. Álvaro Berbís ◽  
F. Javier Cañada ◽  
...  
Keyword(s):  
Aromatic Compounds ◽  
Histidine Kinase ◽  
Catabolite Repression ◽  
Carbon Catabolite Repression ◽  
Response Regulator ◽  
Sensor Kinase ◽  
General Role ◽  
Two Component ◽  
Redox Switch ◽  
Redox Sensing

ABSTRACTWe have identified and characterized the AccS multidomain sensor kinase that mediates the activation of the AccR master regulator involved in carbon catabolite repression (CCR) of the anaerobic catabolism of aromatic compounds inAzoarcussp. CIB. A truncated AccS protein that contains only the soluble C-terminal autokinase module (AccS′) accounts for the succinate-dependent CCR control. In vitroassays with purified AccS′ revealed its autophosphorylation, phosphotransfer from AccS′∼P to the Asp60 residue of AccR, and the phosphatase activity toward its phosphorylated response regulator, indicating that the equilibrium between the kinase and phosphatase activities of AccS′ may control the phosphorylation state of the AccR transcriptional regulator. Oxidized quinones, e.g., ubiquinone 0 and menadione, switched the AccS′ autokinase activity off, and three conserved Cys residues, which are not essential for catalysis, are involved in such inhibition. Thiol oxidation by quinones caused a change in the oligomeric state of the AccS′ dimer resulting in the formation of an inactive monomer. This thiol-based redox switch is tuned by the cellular energy state, which can change depending on the carbon source that the cells are using. This work expands the functional diversity of redox-sensitive sensor kinases, showing that they can control new bacterial processes such as CCR of the anaerobic catabolism of aromatic compounds. The AccSR two-component system is conserved in the genomes of some betaproteobacteria, where it might play a more general role in controlling the global metabolic state according to carbon availability.IMPORTANCETwo-component signal transduction systems comprise a sensor histidine kinase and its cognate response regulator, and some have evolved to sense and convert redox signals into regulatory outputs that allow bacteria to adapt to the altered redox environment. The work presented here expands knowledge of the functional diversity of redox-sensing kinases to control carbon catabolite repression (CCR), a phenomenon that allows the selective assimilation of a preferred compound among a mixture of several carbon sources. The newly characterized AccS sensor kinase is responsible for the phosphorylation and activation of the AccR master regulator involved in CCR of the anaerobic degradation of aromatic compounds in the betaproteobacteriumAzoarcussp. CIB. AccS seems to have a thiol-based redox switch that is modulated by the redox state of the quinone pool. The AccSR system is conserved in several betaproteobacteria, where it might play a more general role controlling their global metabolic state.

scholarly journals The Eukaryotic Two-Component Histidine Kinase Sln1p RegulatesOCH1via the Transcription Factor, Skn7p

2002 ◽  
Vol 13 (2) ◽  
pp. 412-424 ◽  
Author(s):  
Sheng Li ◽  
Susan Dean ◽  
Zhijian Li ◽  
Joe Horecka ◽  
Robert J. Deschenes ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
Osmotic Stress ◽  
Binding Site ◽  
Histidine Kinase ◽  
Response Regulators ◽  
Hog Pathway ◽  
Receiver Domain ◽  
Osmotic Response ◽  
Two Component

The yeast “two-component” osmotic stress phosphorelay consists of the histidine kinase, Sln1p, the phosphorelay intermediate, Ypd1p and two response regulators, Ssk1p and Skn7p, whose activities are regulated by phosphorylation of a conserved aspartyl residue in the receiver domain. Dephospho-Ssk1p leads to activation of the hyper-osmotic response (HOG) pathway, whereas phospho-Skn7p presumably leads to activation of hypo-osmotic response genes. The multifunctional Skn7 protein is important in oxidative as well as osmotic stress; however, the Skn7p receiver domain aspartate that is the phosphoacceptor in the SLN1 pathway is dispensable for oxidative stress. Like many well-characterized bacterial response regulators, Skn7p is a transcription factor. In this report we investigate the role of Skn7p in osmotic response gene activation. Our studies reveal that the Skn7p HSF-like DNA binding domain interacts with acis-acting element identified upstream ofOCH1 that is distinct from the previously defined HSE-like Skn7p binding site. Our data support a model in which Skn7p receiver domain phosphorylation affects transcriptional activation rather than DNA binding to this class of DNA binding site.

scholarly journals Oligomeric states in sodium ion–dependent regulation of cyanobacterial histidine kinase-2

2017 ◽  
Author(s):  
Iskander M. Ibrahim ◽  
Liang Wang ◽  
Sujith Puthiyaveetil ◽  
Norbert Krauß ◽  
Jon Nield ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Histidine Kinase ◽  
Phosphate Group ◽  
Sodium Ion ◽  
Ion Concentration ◽  
Phosphoryl Transfer ◽  
Chemical Crosslinking ◽  
Response Regulators ◽  
Oligomeric State ◽  
Two Component

ABSTRACTTwo-component signal transduction systems (TCSs) consist of sensor histidine kinases and response regulators. TCSs mediate adaptation to environmental changes in bacteria, plants, fungi, and protists. Histidine kinase 2 (Hik2) is a sensor histidine kinase found in all known cyanobacteria and as chloroplast sensor kinase in eukaryotic algae and plants. Sodium ions have been shown to inhibit the autophosphorylation activity of Hik2 that precedes phosphoryl transfer to response regulators, but the mechanism of inhibition has not been determined. We report on the mechanism of Hik2 activation and inactivation probed by chemical crosslinking and size exclusion chromatography together with direct visualisation of the kinase using negative-stain transmission electron microscopy of single particles. We show that the functional form of Hik2 is a higher order oligomer such as a hexamer or octamer. Increased NaCl concentration converts the active hexamer into an inactive tetramer. Furthermore, the action of NaCl appears to be confined to the Hik2 kinase domain.IMPORTANCEBacteria sense change and respond to it by means of two-component regulatory systems. The sensor component is a protein that becomes covalently modified by a phosphate group on a histidine side chain. The response regulator accepts the phosphate group onto an aspartate, with structural and functional consequences, often for gene transcription. Histidine kinase 2 is a sensor of sodium ion concentration and redox potential, regulating transcription of genes for light-harvesting and reaction center proteins of photosynthesis in cyanobacteria and chloroplasts of algae and plants. Using radiolabeling, chemical crosslinking, chromatography and electron microscopy, we find that sodium ion concentration governs the oligomeric state of Histidine Kinase 2 and its phosphorylation by ATP.

scholarly journals Pneumococcal HtrA Protease Mediates Inhibition of Competence by the CiaRH Two-Component Signaling System

2005 ◽  
Vol 187 (12) ◽  
pp. 3969-3979 ◽  
Author(s):  
M. E. Sebert ◽  
K. P. Patel ◽  
M. Plotnick ◽  
J. N. Weiser
Keyword(s):  
Histidine Kinase ◽  
Transformation Efficiency ◽  
Signaling System ◽  
Inhibitory Effects ◽  
Genetic Competence ◽  
Constitutive Activation ◽  
Protein Target ◽  
Protein Levels ◽  
Unknown Protein ◽  
Two Component

ABSTRACT Activation of the CiaRH two-component signaling system prevents the development of competence for genetic transformation in Streptococcus pneumoniae through a previously unknown mechanism. Earlier studies have shown that CiaRH controls the expression of htrA, which we show encodes a surface-expressed serine protease. We found that mutagenesis of the putative catalytic serine of HtrA, while not impacting the competence of a ciaRH + strain, restored a normal competence profile to a strain having a mutation that constitutively activates the CiaH histidine kinase. This result implies that activity of HtrA is necessary for the CiaRH system to inhibit competence. Consistent with this finding, recombinant HtrA (rHtrA) decreased the competence of pneumococcal cultures. The rHtrA-mediated decline in transformation efficiency could not be corrected with excess competence-stimulating peptide (CSP), suggesting that HtrA does not act through degradation of this signaling molecule. The inhibitory effects of rHtrA and activated CiaH, however, were largely overcome in a strain having constitutive activation of the competence pathway through a mutation in the cytoplasmic domain of the ComD histidine kinase. Although these results suggested that HtrA might act through degradation of the extracellular portion of the ComD receptor, Western immunoblots for ComD did not reveal changes in protein levels attributable to HtrA. We therefore postulate that HtrA may act on an unknown protein target that potentiates the activation of the ComDE system by CSP. These findings suggest a novel regulatory role for pneumococcal HtrA in modulating the activity of a two-component signaling system that controls the development of genetic competence.

scholarly journals Phosphotransfer Reactions of the CbbRRS Three-Protein Two- Component System from Rhodopseudomonas palustris CGA010 Appear To Be Controlled by an Internal Molecular Switch on the Sensor Kinase

2006 ◽  
Vol 189 (2) ◽  
pp. 325-335 ◽  
Author(s):  
Simona Romagnoli ◽  
F. Robert Tabita
Keyword(s):  
Response Regulator ◽  
Rhodopseudomonas Palustris ◽  
Molecular Switch ◽  
Sensor Kinase ◽  
Two Component System ◽  
Conserved Residues ◽  
Component System ◽  
Receiver Domain ◽  
Two Component

ABSTRACT The CbbRRS system is an atypical three-protein two-component system that modulates the expression of the cbb I CO2 fixation operon of Rhodopseudomonas palustris, possibly in response to a redox signal. It consists of a membrane-bound hybrid sensor kinase, CbbSR, with a transmitter and receiver domain, and two response regulator proteins, CbbRR1 and CbbRR2. No detectable helix-turn-helix DNA binding domain is associated with either response regulator, but an HPt domain and a second receiver domain are predicted at the C-terminal region of CbbRR1 and CbbRR2, respectively. The abundance of conserved residues predicted to participate in a His-Asp phosphorelay raised the question of their de facto involvement. In this study, the role of the multiple receiver domains was elucidated in vitro by generating site-directed mutants of the putative conserved residues. Distinct phosphorylation patterns were obtained with two truncated versions of the hybrid sensor kinase, CbbSRT189 and CbbSRR96 (CbbSR beginning at residues T189 and R96, respectively). These constructs also exhibited substantially different affinities for ATP and phosphorylation stability, which was found to be dependent on a conserved Asp residue (Asp-696) within the kinase receiver domain. Asp-696 also played an important role in defining the specificity of phosphorylation for response regulators CbbRR1 or CbbRR2, and this residue appeared to act in conjunction with residues within the region from Arg-96 to Thr-189 at the N terminus of the sensor kinase. The net effect of concerted interactions at these distinct regions of CbbSR created an internal molecular switch that appears to coordinate a unique branched phosphorelay system.

scholarly journals Molecular basis of unidirectional information transmission in two-component systems: lessons from the DesK-DesR thermosensor

2021 ◽  
Author(s):  
Sofia Lima ◽  
Juan Blanco ◽  
Federico Olivieri ◽  
Juan Andres Imelio ◽  
Federico Carrion ◽  
...  
Keyword(s):  
Histidine Kinase ◽  
Regulatory Networks ◽  
Response Regulator ◽  
Signal Transmission ◽  
Phosphoryl Transfer ◽  
Signaling Systems ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems ◽  
Histidine Phosphorylation

Cellular signaling systems transmit information over long distances using allosteric transitions and/or post-translational modifications. In two-component systems the sensor histidine kinase and response regulator are wired through phosphoryl-transfer reactions, using either a uni- or bi-directional transmission mode, allowing to build rich regulatory networks. Using the thermosensor DesK-DesR two-component system from Bacillus subtilis and combining crystal structures, QM/MM calculations and integrative kinetic modeling, we uncover that: i) longer or shorter distances between the phosphoryl-acceptor and -donor residues can shift the phosphoryl-transfer equilibrium; ii) the phosphorylation-dependent dimerization of the regulator acts as a sequestering mechanism by preventing the interaction with the histidine kinase; and iii) the kinase's intrinsic conformational equilibrium makes the phosphotransferase state unlikely in the absence of histidine phosphorylation, minimizing backwards transmission. These mechanisms allow the system to control the direction of signal transmission in a very efficient way, showcasing the key role that structure-encoded allostery plays in signaling proteins to store and transmit information.

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