scholarly journals Complex Regulation of Arsenite Oxidation in Agrobacterium tumefaciens

2006 ◽  
Vol 188 (3) ◽  
pp. 1081-1088 ◽  
Author(s):  
Des R. Kashyap ◽  
Lina M. Botero ◽  
William L. Franck ◽  
Daniel J. Hassett ◽  
Timothy R. McDermott
Keyword(s):  
Signal Transduction ◽  
Agrobacterium Tumefaciens ◽  
Quorum Sensing ◽  
Response Regulator ◽  
Structural Features ◽  
Rt Pcr ◽  
Two Component ◽  
In The Wild ◽  
Two Component Signal Transduction ◽  
Operon Expression

ABSTRACT Seminal regulatory controls of microbial arsenite [As(III)] oxidation are described in this study. Transposon mutagenesis of Agrobacterium tumefaciens identified genes essential for As(III) oxidation, including those coding for a two-component signal transduction pair. The transposon interrupted a response regulator gene (referred to as aoxR), which encodes an ntrC-like protein and is immediately downstream of a gene (aoxS) encoding a protein with primary structural features found in sensor histidine kinases. The structural genes for As(III) oxidase (aoxAB), a c-type cytochrome (cytc 2), and molybdopterin biosynthesis (chlE) were downstream of aoxR. The mutant could not be complemented by aoxSR in trans but was complemented by a clone containing aoxS-aoxR-aoxA-aoxB-cytc 2 and consistent with reverse transcriptase (RT) PCR experiments, which demonstrated these genes are cotranscribed as an operon. Expression of aoxAB was monitored by RT-PCR and found to be up-regulated by the addition of As(III) to cell cultures. Expression of aoxAB was also controlled in a fashion consistent with quorum sensing in that (i) expression of aoxAB was absent in As(III)-unexposed early-log-phase cells but was observed in As(III)-unexposed, late-log-phase cells and (ii) treating As(III)-unexposed, early-log-phase cells with ethyl acetate extracts of As(III)-unexposed, late-log-phase culture supernatants also resulted in aoxAB induction. Under inducing conditions, aoxS expression was readily observed in the wild-type strain but significantly reduced in the mutant, indicating that AoxR is autoregulatory and at least partially controls the expression of the aox operon. In summary, regulation of A. tumefaciens As(III) oxidation is complex, apparently being controlled by As(III) exposure, a two-component signal transduction system, and quorum sensing.

scholarly journals Constitutive Activation of Two-Component Response Regulators: Characterization of VirG Activation in Agrobacterium tumefaciens

2006 ◽  
Vol 188 (14) ◽  
pp. 5204-5211 ◽  
Author(s):  
Rong Gao ◽  
Aindrila Mukhopadhyay ◽  
Fang Fang ◽  
David G. Lynn
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Conformational Changes ◽  
Response Regulator ◽  
Structural Features ◽  
Response Regulators ◽  
Two Component System ◽  
Plant Host ◽  
Two Component ◽  
Two Component Signal Transduction

ABSTRACT Response regulators are the ultimate modulators in two-component signal transduction pathways. The N-terminal receiver domains generally accept phosphates from cognate histidine kinases to control output. VirG for example, the response regulator of the VirA/VirG two-component system in Agrobacterium tumefaciens, mediates the expression of virulence genes in response to plant host signals. Response regulators have a highly conserved structure and share a similar conformational activation upon phosphorylation, yet the sequence and structural features that determine or perturb the cooperative activation events are ill defined. Here we use VirG and the unique features of the Agrobacterium system to extend our understanding of the response regulator activation. Two previously isolated constitutive VirG mutants, VirGN54D and VirGI77V/D52E, provide the foundation for our studies. In vivo phosphorylation patterns establish that VirGN54D is able to accumulate phosphates from small-molecule phosphate donors, such as acetyl phosphate, while the VirGI77V/D52E allele carries conformational changes mimicking the active conformation. Further structural alterations on these two alleles begin to reveal the changes necessary for response regulator activation.

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.

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.

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.

scholarly journals Signal Detection and Target Gene Induction by the CpxRA Two-Component System

2003 ◽  
Vol 185 (8) ◽  
pp. 2432-2440 ◽  
Author(s):  
Patricia A. DiGiuseppe ◽  
Thomas J. Silhavy
Keyword(s):  
Signal Transduction ◽  
Feedback Inhibition ◽  
Response Regulator ◽  
Negative Regulator ◽  
Outer Membrane Lipoprotein ◽  
Envelope Stress ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Cpx Pathway ◽  
Target Gene Induction

ABSTRACT The Cpx pathway is a two-component signal transduction system that senses a variety of envelope stresses, including misfolded proteins, and responds by upregulating periplasmic folding and trafficking factors. CpxA resides in the inner membrane and has both kinase and phosphatase activities. CpxR, the response regulator, mediates a response by activating transcription of stress-combative genes. Signal transduction is subject to feedback inhibition via regulon member CpxP and autoamplification. Recently, it was shown that the Cpx pathway is also upregulated when cells adhere to hydrophobic surfaces and that this response is dependent on the outer membrane lipoprotein NlpE. Here we show that while NlpE is required for induction of the Cpx pathway by adhesion, induction by envelope stress and during growth is NlpE independent. We show that while all of the envelope stresses tested induce the Cpx pathway in a manner that is dependent on the periplasmic domain of CpxA, induction during growth is independent of CpxA. Therefore, we propose that the Cpx pathway can sense inducing cues that enter the signaling pathway at three distinct points. Although CpxP is not required for induction of the Cpx pathway, we show that its activity as a negative regulator of CpxA is inactivated by envelope stress. Moreover, the cpxP promoter is more inducible than any other regulon member tested. Consistent with these results, we suggest that CpxP performs a second function, most likely that of a chaperone. Finally, we show that two Cpx-regulated genes are differentially upregulated in response to different envelope stresses, suggesting the existence of three stress-responsive systems.

scholarly journals Systematic Inactivation and Phenotypic Characterization of Two-Component Signal Transduction Systems of Enterococcus faecalis V583

2004 ◽  
Vol 186 (23) ◽  
pp. 7951-7958 ◽  
Author(s):  
Lynn E. Hancock ◽  
Marta Perego
Keyword(s):  
Signal Transduction ◽  
Antibiotic Resistance ◽  
Environmental Stress ◽  
Enterococcus Faecalis ◽  
Response Regulator ◽  
Phenotypic Characterization ◽  
Response Regulators ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Biofilm Development

ABSTRACT The ability of enterococci to adapt and respond to different environmental stimuli, including the host environment, led us to investigate the role of two-component signal transduction in the regulation of Enterococcus faecalis physiology. Using a bioinformatic approach, we previously identified 17 two-component systems (TCS), consisting of a sensory histidine kinase and the cognate response regulator, as well as an additional orphan response regulator (L. E. Hancock and M. Perego, J. Bacteriol. 184:5819-5825, 2002). In an effort to identify the potential function of each TCS in the biology of E. faecalis clinical isolate strain V583, we constructed insertion mutations in each of the response regulators. We were able to inactivate 17 of 18 response regulators, the exception being an ortholog of YycF, previously shown to be essential for viability in a variety of gram-positive microorganisms. The biological effects of the remaining mutations were assessed by using a number of assays, including antibiotic resistance, biofilm formation, and environmental stress. We identified TCS related to antibiotic resistance and environmental stress and found one system which controls the initiation of biofilm development by E. faecalis.

scholarly journals Cpx Two-Component Signal Transduction inEscherichia coli: Excessive CpxR-P Levels Underlie CpxA* Phenotypes

2000 ◽  
Vol 182 (5) ◽  
pp. 1423-1426 ◽  
Author(s):  
Peter De Wulf ◽  
E. C. C. Lin
Keyword(s):  
Signal Transduction ◽  
Response Regulator ◽  
Response Regulators ◽  
Signal Transduction System ◽  
Regulate Gene Expression ◽  
Adverse Conditions ◽  
Two Component ◽  
Sensor Protein ◽  
Two Component Signal Transduction ◽  
Cognate Response Regulator

ABSTRACT In Escherichia coli, the CpxA-CpxR two-component signal transduction system and the ςE and ς32response pathways jointly regulate gene expression in adaptation to adverse conditions. These include envelope protein distress, heat shock, oxidative stress, high pH, and entry into stationary phase. Certain mutant versions of the CpxA sensor protein (CpxA* proteins) exhibit an elevated ratio of kinase to phosphatase activity on CpxR, the cognate response regulator. As a result, CpxA* strains display numerous phenotypes, many of which cannot be easily related to currently known functions of the CpxA-CpxR pathway. It is unclear whether CpxA* phenotypes are caused solely by hyperphosphorylation of CpxR. We here report that all of the tested CpxA* phenotypes depend on elevated levels of CpxR-P and not on cross-signalling of CpxA* to noncognate response regulators.

scholarly journals Development and Validation of a High-Throughput Cell-Based Screen To Identify Activators of a Bacterial Two-Component Signal Transduction System

2015 ◽  
Vol 59 (7) ◽  
pp. 3789-3799 ◽  
Author(s):  
Julia J. van Rensburg ◽  
Kate R. Fortney ◽  
Lan Chen ◽  
Andrew J. Krieger ◽  
Bruno P. Lima ◽  
...  
Keyword(s):  
Signal Transduction ◽  
High Throughput ◽  
Response Regulator ◽  
Phosphoryl Group ◽  
Signal Transduction System ◽  
Membrane Repair ◽  
Content Type ◽  
Two Component ◽  
Serovar Typhimurium ◽  
Two Component Signal Transduction

ABSTRACTCpxRA is a two-component signal transduction system (2CSTS) found in many drug-resistant Gram-negative bacteria. In response to periplasmic stress, CpxA autophosphorylates and donates a phosphoryl group to its cognate response regulator, CpxR. Phosphorylated CpxR (CpxR-P) upregulates genes involved in membrane repair and downregulates multiple genes that encode virulence factors, which are trafficked across the cell membrane. Mutants that constitutively activate CpxRA inSalmonella entericaserovar Typhimurium andHaemophilus ducreyiare avirulent in mice and humans, respectively. Thus, the activation of CpxRA has high potential as a novel antimicrobial/antivirulence strategy. Using a series ofEscherichia colistrains containing a CpxR-P-responsivelacZreporter and deletions in genes encoding CpxRA system components, we developed and validated a novel cell-based high-throughput screen (HTS) for CpxRA activators. A screen of 36,000 compounds yielded one hit compound that increased reporter activity in wild-type cells. This is the first report of a compound that activates, rather than inhibits, a 2CSTS. The activity profile of the compound against CpxRA pathway mutants in the presence of glucose suggested that the compound inhibits CpxA phosphatase activity. We confirmed that the compound induced the accumulation of CpxR-P in treated cells. Although the hit compound contained a nitro group, a derivative lacking this group retained activity in serum and had lower cytotoxicity than that of the initial hit. This HTS is amenable for the screening of larger libraries to find compounds that activate CpxRA by other mechanisms, and it could be adapted to find activators of other two-component systems.

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