scholarly journals The Ssk1p Response Regulator and Chk1p Histidine Kinase Mutants of Candida albicans Are Hypersensitive to Fluconazole and Voriconazole

2007 ◽  
Vol 51 (10) ◽  
pp. 3747-3751 ◽  
Author(s):  
Neeraj Chauhan ◽  
Michael Kruppa ◽  
Richard Calderone
Keyword(s):  
Signal Transduction ◽  
Candida Albicans ◽  
Histidine Kinase ◽  
Response Regulator ◽  
Wild Type ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Signal Transduction Proteins

ABSTRACT Hypersensitivity to the triazoles fluconazole and voriconazole associated with two-component signal transduction proteins has not been reported in Candida albicans. Herein, we show that strains of C. albicans lacking the response regulator Ssk1p or the Chk1p histidine kinase signal transduction proteins are hypersensitive to fluconazole and voriconazole compared to wild-type (wt) as well as gene-reconstituted strains, reflecting an increased hypersensitivity to these drugs of about 16- to 500-fold. In comparison to wt cells, both mutants had elevated levels of fluconazole accumulation and reduced viability upon incubation with either drug, suggesting that in the absence of Ssk1p or Chk1p, fluconazole and voriconazole have significantly increased fungicidal effects on C. albicans.

scholarly journals The Two-Component Signal Transduction System VxrAB Positively Regulates Vibrio cholerae Biofilm Formation

2017 ◽  
Vol 199 (18) ◽  
Author(s):  
Jennifer K. Teschler ◽  
Andrew T. Cheng ◽  
Fitnat H. Yildiz
Keyword(s):  
Signal Transduction ◽  
Vibrio Cholerae ◽  
Histidine Kinase ◽  
Biofilm Formation ◽  
Pathogenic Bacteria ◽  
Response Regulator ◽  
Systematic Analysis ◽  
Content Type ◽  
Two Component ◽  
Two Component Signal Transduction

ABSTRACT Two-component signal transduction systems (TCSs), typically composed of a sensor histidine kinase (HK) and a response regulator (RR), are the primary mechanism by which pathogenic bacteria sense and respond to extracellular signals. The pathogenic bacterium Vibrio cholerae is no exception and harbors 52 RR genes. Using in-frame deletion mutants of each RR gene, we performed a systematic analysis of their role in V. cholerae biofilm formation. We determined that 7 RRs impacted the expression of an essential biofilm gene and found that the recently characterized RR, VxrB, regulates the expression of key structural and regulatory biofilm genes in V. cholerae. vxrB is part of a 5-gene operon, which contains the cognate HK vxrA and three genes of unknown function. Strains carrying ΔvxrA and ΔvxrB mutations are deficient in biofilm formation, while the ΔvxrC mutation enhances biofilm formation. The overexpression of VxrB led to a decrease in motility. We also observed a small but reproducible effect of the absence of VxrB on the levels of cyclic di-GMP (c-di-GMP). Our work reveals a new function for the Vxr TCS as a regulator of biofilm formation and suggests that this regulation may act through key biofilm regulators and the modulation of cellular c-di-GMP levels. IMPORTANCE Biofilms play an important role in the Vibrio cholerae life cycle, providing protection from environmental stresses and contributing to the transmission of V. cholerae to the human host. V. cholerae can utilize two-component systems (TCS), composed of a histidine kinase (HK) and a response regulator (RR), to regulate biofilm formation in response to external cues. We performed a systematic analysis of V. cholerae RRs and identified a new regulator of biofilm formation, VxrB. We demonstrated that the VxrAB TCS is essential for robust biofilm formation and that this system may regulate biofilm formation via its regulation of key biofilm regulators and cyclic di-GMP levels. This research furthers our understanding of the role that TCSs play in the regulation of V. cholerae biofilm formation.

scholarly journals Regulation of Iron Transport in Streptococcus pneumoniae by RitR, an Orphan Response Regulator

2004 ◽  
Vol 186 (23) ◽  
pp. 8123-8136 ◽  
Author(s):  
Andrew T. Ulijasz ◽  
David R. Andes ◽  
Jeremy D. Glasner ◽  
Bernard Weisblum
Keyword(s):  
Signal Transduction ◽  
Streptococcus Pneumoniae ◽  
Iron Transport ◽  
Response Regulator ◽  
Lung Model ◽  
Mrna Levels ◽  
Regulator Gene ◽  
Wild Type ◽  
Two Component ◽  
Two Component Signal Transduction

ABSTRACT RitR (formerly RR489) is an orphan two-component signal transduction response regulator in Streptococcus pneumoniae that has been shown to be required for lung pathogenicity. In the present study, by using the rough strain R800, inactivation of the orphan response regulator gene ritR by allele replacement reduced pathogenicity in a cyclophosphamide-treated mouse lung model but not in a thigh model, suggesting a role for RitR in regulation of tissue-specific virulence factors. Analysis of changes in genome-wide transcript mRNA levels associated with the inactivation of ritR compared to wild-type cells was performed by the use of high-density DNA microarrays. Genes with a change in transcript abundance associated with inactivation of ritR included piuB, encoding an Fe permease subunit, and piuA, encoding an Fe carrier-binding protein. In addition, a dpr ortholog, encoding an H2O2 resistance protein that has been shown to reduce synthesis of reactive oxygen intermediates, was activated in the wild-type (ritR +) strain. Microarray experiments suggested that RitR represses Fe uptake in vitro by negatively regulating the Piu hemin-iron transport system. Footprinting experiments confirmed site-specific DNA-binding activity for RitR and identified three binding sites that partly overlap the +1 site for transcription initiation upstream of piuB. Transcripts belonging to other gene categories found to be differentially expressed in our array studies include those associated with (i) H2O2 resistance, (ii) repair of DNA damage, (iii) sugar transport and capsule biosynthesis, and (iv) two-component signal transduction elements. These observations suggest that RitR is an important response regulator whose primary role is to maintain iron homeostasis in S. pneumoniae. The name ritR (repressor of iron transport) for the orphan response regulator gene, rr489, is proposed.

scholarly journals rgf Encodes a Novel Two-Component Signal Transduction System of Streptococcus agalactiae

2002 ◽  
Vol 70 (5) ◽  
pp. 2434-2440 ◽  
Author(s):  
Barbara Spellerberg ◽  
Eva Rozdzinski ◽  
Simone Martin ◽  
Josefine Weber-Heynemann ◽  
Rudolf Lütticken
Keyword(s):  
Signal Transduction ◽  
Amino Acids ◽  
Histidine Kinase ◽  
Wild Type ◽  
Signal Transduction System ◽  
Transcription Analysis ◽  
Ecm Proteins ◽  
Fibrinogen Binding ◽  
Two Component ◽  
Two Component Signal Transduction

ABSTRACT The adhesion of gram-positive bacteria to extracellular matrix (ECM) proteins is regarded as an important determinant of pathogenicity. A comparison of the adhesion of Streptococcus agalactiae strain O90R to different ECM proteins showed that the most pronounced binding could be observed for immobilized fibrinogen. To investigate the genetic determinants of S. agalactiae fibrinogen binding, a pGhost9:ISS1 mutant library was screened for mutants displaying reduced agglutination of fibrinogen-coated latex beads. A putative two-component signal transduction system was identified and designated rgfBDAC. It comprises genes encoding a putative response regulator of 218 amino acids and a putative histidine kinase of 426 amino acids. Comparison of the deduced proteins with the GenBank database revealed a significant similarity to quorum-sensing systems of gram-positive pathogens. Transcription analysis of the rgf locus showed that the encoding genes are located on one transcript. To further characterize the influence of the putative histidine kinase encoded in the rgf locus on the adhesion of S. agalactiae to immobilized fibrinogen, a targeted mutant of rgfC was generated. In comparison to the wild-type strain this mutant demonstrated altered fibrinogen binding capacities depending on bacterial cell density. Transcription analysis of secreted and surface-localized S. agalactiae proteins in the wild type and the rgfC mutant strain revealed that mRNA levels of the C5a peptidase gene scpB were increased in the mutant strain while the transcription of the secreted CAMP factor gene cfb was unaffected by this mutation. Based on these results, we hypothesize that rgf regulates the expression of bacterial cell surface components.

scholarly journals FixJ family regulator AcfR of Azorhizobium caulinodans is involved in symbiosis with the host plant

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Wei Liu ◽  
Xue Bai ◽  
Yan Li ◽  
Haikun Zhang ◽  
Xiaoke Hu
Keyword(s):  
Signal Transduction ◽  
Host Plant ◽  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Azorhizobium Caulinodans ◽  
Wild Type ◽  
Response Regulators ◽  
Free Living ◽  
Two Component

Abstract Background A wide variety of bacterial adaptative responses to environmental conditions are mediated by signal transduction pathways. Two-component signal transduction systems are one of the predominant means used by bacteria to sense the signals of the host plant and adjust their interaction behaviour. A total of seven open reading frames have been identified as putative two-component response regulators in the gram-negative nitrogen-fixing bacteria Azorhizobium caulinodans ORS571. However, the biological functions of these response regulators in the symbiotic interactions between A. caulinodans ORS571 and the host plant Sesbania rostrata have not been elucidated to date. Results In this study, we identified and investigated a two-component response regulator, AcfR, with a phosphorylatable N-terminal REC (receiver) domain and a C-terminal HTH (helix-turn-helix) LuxR DNA-binding domain in A. caulinodans ORS571. Phylogenetic analysis showed that AcfR possessed close evolutionary relationships with NarL/FixJ family regulators. In addition, six histidine kinases containing HATPase_c and HisKA domains were predicted to interact with AcfR. Furthermore, the biological function of AcfR in free-living and symbiotic conditions was elucidated by comparing the wild-type strain and the ΔacfR mutant strain. In the free-living state, the cell motility behaviour and exopolysaccharide production of the ΔacfR mutant were significantly reduced compared to those of the wild-type strain. In the symbiotic state, the ΔacfR mutant showed a competitive nodule defect on the stems and roots of the host plant, suggesting that AcfR can provide A. caulinodans with an effective competitive ability for symbiotic nodulation. Conclusions Our results showed that AcfR, as a response regulator, regulates numerous phenotypes of A. caulinodans under the free-living conditions and in symbiosis with the host plant. The results of this study help to elucidate the involvement of a REC + HTH_LuxR two-component response regulator in the Rhizobium-host plant interaction.

Histidine kinases in signal transduction pathways of eukaryotes

1997 ◽  
Vol 110 (10) ◽  
pp. 1141-1145 ◽  
Author(s):  
W.F. Loomis ◽  
G. Shaulsky ◽  
N. Wang
Keyword(s):  
Signal Transduction ◽  
Response Regulator ◽  
Signal Transduction Pathways ◽  
Response Regulators ◽  
Histidine Kinases ◽  
Camp Phosphodiesterase ◽  
Wide Range ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Dependent Protein

Autophosphorylating histidine kinases are an ancient conserved family of enzymes that are found in eubacteria, archaebacteria and eukaryotes. They are activated by a wide range of extracellular signals and transfer phosphate moieties to aspartates found in response regulators. Recent studies have shown that such two-component signal transduction pathways mediate osmoregulation in Saccharomyces cerevisiae, Dictyostelium discoideum and Neurospora crassa. Moreover, they play pivotal roles in responses of Arabidopsis thaliana to ethylene and cytokinin. A transmembrane histidine kinase encoded by dhkA accumulates when Dictyostelium cells aggregate during development. Activation of DhkA results in the inhibition of its response regulator, RegA, which is a cAMP phosphodiesterase that regulates the cAMP dependent protein kinase PKA. When PKA is activated late in the differentiation of prespore cells, they encapsulate into spores. There is evidence that this two-component system participates in a feedback loop linked to PKA in prestalk cells such that the signal to initiate encapsulation is rapidly amplified. Such signal transduction pathways can be expected to be found in a variety of eukaryotic differentiations since they are rapidly reversible and can integrate disparate signals.

Kinetic and mechanistic analyses of new classes of inhibitors of two-component signal transduction systems using a coupled assay containing HpkA–DrrA from Thermotoga maritima

Microbiology ◽  
2004 ◽  
Vol 150 (4) ◽  
pp. 885-896 ◽  
Author(s):  
J. Estelle Foster ◽  
Qin Sheng ◽  
Jonathan R. McClain ◽  
Mark Bures ◽  
Thalia I. Nicas ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Histidine Kinase ◽  
Competitive Inhibition ◽  
Thermotoga Maritima ◽  
Phosphorylation Site ◽  
Phosphoryl Group ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Coupled Assay ◽  
Signal Transduction Systems

Two-component signal transduction systems (TCSs) play fundamental roles in bacterial survival and pathogenesis and have been proposed as targets for the development of novel classes of antibiotics. A new coupled assay was developed and applied to analyse the kinetic mechanisms of three new kinds of inhibitors of TCS function. The assay exploits the biochemical properties of the cognate HpkA–DrrA histidine kinase–response regulator pair from Thermotoga maritima and allows multiple turnovers of HpkA, linear formation of phosphorylated DrrA, and Michaelis–Menten analysis of inhibitors. The assay was validated in several ways, including confirmation of competitive inhibition by adenosine 5′-β,γ-imidotriphosphate (AMP-PNP). The coupled assay, autophosphorylation and chemical cross-linking were used to determine the mechanisms by which several compounds inhibit TCS function. A cyanoacetoacetamide showed non-competitive inhibition with respect to ATP concentration in the coupled assay. The cyanoacetoacetamide also inhibited autophosphorylation of histidine kinases from other bacteria, indicating that the coupled assay could detect general inhibitors of histidine kinase function. Inhibition of HpkA autophosphorylation by this compound was probably caused by aggregation of HpkA, consistent with a previous model for other hydrophobic compounds. In contrast, ethodin was a potent inhibitor of the combined assay, did not inhibit HpkA autophosphorylation, but still led to aggregation of HpkA. These data suggest that ethodin bound to the HpkA kinase and inhibited transfer of the phosphoryl group to DrrA. A peptide corresponding to the phosphorylation site of DrrA appeared to inhibit TCS function by a mechanism similar to that of ethodin, except that autophosphorylation was inhibited at high peptide concentrations. The latter mechanism of inhibition of TCS function is unusual and its analysis demonstrates the utility of these approaches to the kinetic analyses of additional new classes of inhibitors of TCS function.

scholarly journals Functional reconstitution of the Salmonella typhimurium PhoQ histidine kinase sensor in proteoliposomes

2005 ◽  
Vol 390 (3) ◽  
pp. 769-776 ◽  
Author(s):  
Sarah Sanowar ◽  
Hervé Le Moual
Keyword(s):  
Salmonella Typhimurium ◽  
Histidine Kinase ◽  
Catalytic Domain ◽  
Response Regulator ◽  
Phosphoryl Group ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
High Concentrations

Two-component signal-transduction systems are widespread in bacteria. They are usually composed of a transmembrane histidine kinase sensor and a cytoplasmic response regulator. The PhoP/PhoQ two-component system of Salmonella typhimurium contributes to virulence by co-ordinating the adaptation to low concentrations of environmental Mg2+. Limiting concentrations of extracellular Mg2+ activate the PhoP/PhoQ phosphorylation cascade modulating the transcription of PhoP-regulated genes. In contrast, high concentrations of extracellular Mg2+ stimulate the dephosphorylation of the response regulator PhoP by the PhoQ kinase sensor. In the present study, we report the purification and functional reconstitution of PhoQHis, a PhoQ variant with a C-terminal His tag, into Escherichia coli liposomes. The functionality of PhoQHis was essentially similar to that of PhoQ as shown in vivo and in vitro. Purified PhoQHis was inserted into liposomes in a unidirectional orientation, with the sensory domain facing the lumen and the catalytic domain facing the extraluminal environment. Reconstituted PhoQHis exhibited all the catalytic activities that have been described for histidine kinase sensors. Reconstituted PhoQHis was capable of autokinase activity when incubated in the presence of Mg2+-ATP. The phosphoryl group could be transferred from reconstituted PhoQHis to PhoP. Reconstituted PhoQHis catalysed the dephosphorylation of phospho-PhoP and this activity was stimulated by the addition of extraluminal ADP.

Phosphorylation activity of the response regulator of the two-component signal transduction system AtoS–AtoC in E. coli

2005 ◽  
Vol 1725 (3) ◽  
pp. 257-268 ◽  
Author(s):  
Efthimia E. Lioliou ◽  
Eleni P. Mimitou ◽  
Asterios I. Grigoroudis ◽  
Cynthia H. Panagiotidis ◽  
Christos A. Panagiotidis ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Response Regulator ◽  
Signal Transduction System ◽  
E Coli ◽  
Two Component ◽  
Two Component Signal Transduction

scholarly journals CheX in the Three-Phosphatase System of Bacterial Chemotaxis

2007 ◽  
Vol 189 (19) ◽  
pp. 7007-7013 ◽  
Author(s):  
Travis J. Muff ◽  
Richard M. Foster ◽  
Peter J. Y. Liu ◽  
George W. Ordal
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
Bacillus Subtilis ◽  
Mutant Strain ◽  
Response Regulator ◽  
Bacterial Chemotaxis ◽  
Signal Transduction System ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Phosphatase System

ABSTRACT Bacterial chemotaxis involves the regulation of motility by a modified two-component signal transduction system. In Escherichia coli, CheZ is the phosphatase of the response regulator CheY but many other bacteria, including Bacillus subtilis, use members of the CheC-FliY-CheX family for this purpose. While Bacillus subtilis has only CheC and FliY, many systems also have CheX. The effect of this three-phosphatase system on chemotaxis has not been studied previously. CheX was shown to be a stronger CheY-P phosphatase than either CheC or FliY. In Bacillus subtilis, a cheC mutant strain was nearly complemented by heterologous cheX expression. CheX was shown to overcome the ΔcheC adaptational defect but also generally lowered the counterclockwise flagellar rotational bias. The effect on rotational bias suggests that CheX reduced the overall levels of CheY-P in the cell and did not truly replicate the adaptational effects of CheC. Thus, CheX is not functionally redundant to CheC and, as outlined in the discussion, may be more analogous to CheZ.

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