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Hybrid Histidine Kinase BinK Represses Vibrio fischeri Biofilm Signaling at Multiple Developmental Stages. J Bacteriol 2021; 203:e0015521. [PMID: 34031036 DOI: 10.1128/jb.00155-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The symbiosis between the Hawaiian bobtail squid, Euprymna scolopes, and its exclusive light organ symbiont, Vibrio fischeri, provides a natural system in which to study host-microbe specificity and gene regulation during the establishment of a mutually beneficial symbiosis. Colonization of the host relies on bacterial biofilm-like aggregation in the squid mucus field. Symbiotic biofilm formation is controlled by a two-component signaling (TCS) system consisting of regulators RscS-SypF-SypG, which together direct transcription of the symbiosis polysaccharide Syp. TCS systems are broadly important for bacteria to sense environmental cues and then direct changes in behavior. Previously, we identified the hybrid histidine kinase BinK as a strong negative regulator of V. fischeri biofilm regulation, and here we further explore the function of BinK. To inhibit biofilm formation, BinK requires the predicted phosphorylation sites in both the histidine kinase (H362) and receiver (D794) domains. Furthermore, we show that RscS is not essential for host colonization when binK is deleted from strain ES114, and imaging of aggregate size revealed no benefit to the presence of RscS in a background lacking BinK. Strains lacking RscS still suffered in competition. Finally, we show that BinK functions to inhibit biofilm gene expression in the light organ crypts, providing evidence for biofilm gene regulation at later stages of host colonization. Overall, this study provides direct evidence for opposing activities of RscS and BinK and yields novel insights into biofilm regulation during the maturation of a beneficial symbiosis. IMPORTANCE Bacteria are often in a biofilm state, and transitions between planktonic and biofilm lifestyles are important for pathogenic, beneficial, and environmental microbes. The critical nature of biofilm formation during Vibrio fischeri colonization of the Hawaiian bobtail squid light organ provides an opportunity to study development of this process in vivo using a combination of genetic and imaging approaches. The current work refines the signaling circuitry of the biofilm pathway in V. fischeri, provides evidence that biofilm regulatory changes occur in the host, and identifies BinK as one of the regulators of that process. This study provides information about how bacteria regulate biofilm gene expression in an intact animal host.
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Binns AN, Zhao J. The MexE/MexF/AmeC Efflux Pump of Agrobacterium tumefaciens and Its Role in Ti Plasmid Virulence Gene Expression. J Bacteriol 2020; 202:e00609-19. [PMID: 32015146 PMCID: PMC7099130 DOI: 10.1128/jb.00609-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 01/25/2020] [Indexed: 12/21/2022] Open
Abstract
Expression of the tumor-inducing (Ti) plasmid virulence genes of Agrobacterium tumefaciens is required for the transfer of DNA from the bacterium into plant cells, ultimately resulting in the initiation of plant tumors. The vir genes are induced as a result of exposure to certain phenol derivatives, monosaccharides, and low pH in the extracellular milieu. The soil, as well as wound sites on a plant-the usual site of the virulence activity of this bacterium-can contain these signals, but vir gene expression in the soil would be a wasteful utilization of energy. This suggests that mechanisms may exist to ensure that vir gene expression occurs only at the higher concentrations of inducers typically found at a plant wound site. In a search for transposon-mediated mutations that affect sensitivity for the virulence gene-inducing activity of the phenol, 3,5-dimethoxy-4-hydroxyacetophenone (acetosyringone [AS]), an RND-type efflux pump homologous to the MexE/MexF/OprN pump of Pseudomonas aeruginosa was identified. Phenotypes of mutants carrying an insertion or deletion of pump components included hypersensitivity to the vir-inducing effects of AS, hypervirulence in the tobacco leaf explant virulence assay, and hypersensitivity to the toxic effects of chloramphenicol. Furthermore, the methoxy substituents on the phenol ring of AS appear to be critical for recognition as a pump substrate. These results support the hypothesis that the regulation of virulence gene expression is integrated with cellular activities that elevate the level of plant-derived inducers required for induction so that this occurs preferentially, if not exclusively, in a plant environment.IMPORTANCE Expression of genes controlling the virulence activities of a bacterial pathogen is expected to occur preferentially at host sites vulnerable to that pathogen. Host-derived molecules that induce such activities in the plant pathogen Agrobacterium tumefaciens are found in the soil, as well as in the plant. Here, we tested the hypothesis that mechanisms exist to suppress the sensitivity of Agrobacterium species to a virulence gene-inducing molecule by selecting for mutant bacteria that are hypersensitive to its inducing activity. The mutant genes identified encode an efflux pump whose proposed activity increases the concentration of the inducer necessary for vir gene expression; this pump is also involved in antibiotic resistance, demonstrating a relationship between cellular defense activities and the control of virulence in Agrobacterium.
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Affiliation(s)
- Andrew N Binns
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jinlei Zhao
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Borland S, Prigent-Combaret C, Wisniewski-Dyé F. Bacterial hybrid histidine kinases in plant-bacteria interactions. MICROBIOLOGY-SGM 2016; 162:1715-1734. [PMID: 27609064 DOI: 10.1099/mic.0.000370] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Two-component signal transduction systems are essential for many bacteria to maintain homeostasis and adapt to environmental changes. Two-component signal transduction systems typically involve a membrane-bound histidine kinase that senses stimuli, autophosphorylates in the transmitter region and then transfers the phosphoryl group to the receiver domain of a cytoplasmic response regulator that mediates appropriate changes in bacterial physiology. Although usually found on distinct proteins, the transmitter and receiver modules are sometimes fused into a so-called hybrid histidine kinase (HyHK). Such structure results in multiple phosphate transfers that are believed to provide extra-fine-tuning mechanisms and more regulatory checkpoints than classical phosphotransfers. HyHK-based regulation may be crucial for finely tuning gene expression in a heterogeneous environment such as the rhizosphere, where intricate plant-bacteria interactions occur. In this review, we focus on roles fulfilled by bacterial HyHKs in plant-associated bacteria, providing recent findings on the mechanistic of their signalling properties. Recent insights into understanding additive regulatory properties fulfilled by the tethered receiver domain of HyHKs are also addressed.
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Affiliation(s)
- Stéphanie Borland
- Université de Lyon, Université Lyon 1, Ecologie Microbienne, CNRS UMR5557, INRA UMR1418, Villeurbanne, France
| | - Claire Prigent-Combaret
- Université de Lyon, Université Lyon 1, Ecologie Microbienne, CNRS UMR5557, INRA UMR1418, Villeurbanne, France
| | - Florence Wisniewski-Dyé
- Université de Lyon, Université Lyon 1, Ecologie Microbienne, CNRS UMR5557, INRA UMR1418, Villeurbanne, France
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Wise AA, Binns AN. The Receiver of the Agrobacterium tumefaciens VirA Histidine Kinase Forms a Stable Interaction with VirG to Activate Virulence Gene Expression. Front Microbiol 2016; 6:1546. [PMID: 26779177 PMCID: PMC4705274 DOI: 10.3389/fmicb.2015.01546] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 12/21/2015] [Indexed: 01/20/2023] Open
Abstract
The plant pathogen Agrobacterium tumefaciens carries a virulence gene system that is required for the initiation of crown gall tumors on susceptible plants. Expression of the vir genes is activated by the VirA/VirG two component regulatory system. VirA is a histidine kinase which signals the presence of certain chemicals found at the site of a plant wound. The receiver domain located at its carboxyl terminus defines VirA as a hybrid histidine kinase. Here, we show that the VirA receiver interacts with the DNA-binding domain of VirG. This finding supports the hypothesis that the receiver acts as a recruiting factor for VirG. In addition, we show that removal of the VirA receiver allowed vir gene expression in response to glucose in a dose dependent manner, indicating that the receiver controls VirG activation and suggesting that the supplementary ChvE-sugar signal increases this activity.
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Affiliation(s)
- Arlene A Wise
- Binns Lab, Department of Biology, University of Pennsylvania, Philadelphia PA, USA
| | - Andrew N Binns
- Binns Lab, Department of Biology, University of Pennsylvania, Philadelphia PA, USA
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Fang F, Lin YH, Pierce BD, Lynn DG. A Rhizobium radiobacter Histidine Kinase Can Employ Both Boolean AND and OR Logic Gates to Initiate Pathogenesis. Chembiochem 2015; 16:2183-90. [PMID: 26310519 DOI: 10.1002/cbic.201500334] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Indexed: 11/12/2022]
Abstract
The molecular logic gates that regulate gene circuits are necessarily intricate and highly regulated, particularly in the critical commitments necessary for pathogenesis. We now report simple AND and OR logic gates to be accessible within a single protein receptor. Pathogenesis by the bacterium Rhizobium radiobacter is mediated by a single histidine kinase, VirA, which processes multiple small molecule host signals (phenol and sugar). Mutagenesis analyses converged on a single signal integration node, and finer functional analyses revealed that a single residue could switch VirA from a functional AND logic gate to an OR gate where each of two signals activate independently. Host range preferences among natural strains of R. radiobacter correlate with these gate logic strategies. Although the precise mechanism for the signal integration node requires further analyses, long-range signal transmission through this histidine kinase can now be exploited for synthetic signaling circuits.
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Affiliation(s)
- Fang Fang
- Departments of Chemistry and Biology, Emory University, Atlanta, GA, 30322, USA
| | - Yi-Han Lin
- Departments of Chemistry and Biology, Emory University, Atlanta, GA, 30322, USA
| | - B Daniel Pierce
- Departments of Chemistry and Biology, Emory University, Atlanta, GA, 30322, USA
| | - David G Lynn
- Departments of Chemistry and Biology, Emory University, Atlanta, GA, 30322, USA.
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Lin YH, Pierce BD, Fang F, Wise A, Binns AN, Lynn DG. Role of the VirA histidine autokinase of Agrobacterium tumefaciens in the initial steps of pathogenesis. FRONTIERS IN PLANT SCIENCE 2014; 5:195. [PMID: 24860585 PMCID: PMC4030172 DOI: 10.3389/fpls.2014.00195] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 04/23/2014] [Indexed: 05/27/2023]
Abstract
Histidine kinases serve as critical environmental sensing modules, and despite their designation as simple two-component modules, their functional roles are remarkably diverse. In Agrobacterium tumefaciens pathogenesis, VirA serves with VirG as the initiating sensor/transcriptional activator for inter-kingdom gene transfer and transformation of higher plants. Through responses to three separate signal inputs, low pH, sugars, and phenols, A. tumefaciens commits to pathogenesis in virtually all flowering plants. However, how these three signals are integrated to regulate the response and why these signals might be diagnostic for susceptible cells across such a broad host-range remains poorly understood. Using a homology model of the VirA linker region, we provide evidence for coordinated long-range transmission of inputs perceived both outside and inside the cell through the creation of targeted VirA truncations. Further, our evidence is consistent with signal inputs weakening associations between VirA domains to position the active site histidine for phosphate transfer. This mechanism requires long-range regulation of inter-domain stability and the transmission of input signals through a common integrating domain for VirA signal transduction.
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Affiliation(s)
- Yi-Han Lin
- Lynn Lab, Department of Chemistry and Biology, Emory UniversityAtlanta, GA, USA
| | - B. Daniel Pierce
- Lynn Lab, Department of Chemistry and Biology, Emory UniversityAtlanta, GA, USA
| | - Fang Fang
- Lynn Lab, Department of Chemistry and Biology, Emory UniversityAtlanta, GA, USA
| | - Arlene Wise
- Binns Lab, Department of Biology, Plant Sciences Institute, University of PennsylvaniaPhiladelphia, PA, USA
| | - Andrew N. Binns
- Binns Lab, Department of Biology, Plant Sciences Institute, University of PennsylvaniaPhiladelphia, PA, USA
| | - David G. Lynn
- Lynn Lab, Department of Chemistry and Biology, Emory UniversityAtlanta, GA, USA
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Khodai-Kalaki M, Aubert DF, Valvano MA. Characterization of the AtsR hybrid sensor kinase phosphorelay pathway and identification of its response regulator in Burkholderia cenocepacia. J Biol Chem 2013; 288:30473-30484. [PMID: 24014026 DOI: 10.1074/jbc.m113.489914] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
AtsR is a membrane-bound hybrid sensor kinase of Burkholderia cenocepacia that negatively regulates quorum sensing and virulence factors such as biofilm production, type 6-secretion, and protease secretion. Here we elucidate the mechanism of AtsR phosphorelay by site-directed mutagenesis of predicted histidine and aspartic acid phosphoacceptor residues. We demonstrate by in vitro phosphorylation that histidine 245 and aspartic acid 536 are conserved sites of phosphorylation in AtsR, and we also identify the cytosolic response regulator AtsT (BCAM0381) as a key component of the AtsR phosphorelay pathway. Monitoring the function of AtsR and its derivatives in vivo by measuring extracellular protease activity and swarming motility confirmed the in vitro phosphorylation results. Together we find that the AtsR receiver domain plays a fine-tuning role in determining the levels of phosphotransfer from its sensor kinase domain to the AtsT response regulator.
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Affiliation(s)
- Maryam Khodai-Kalaki
- From the Centre for Human Immunology, Department of Microbiology and Immunology, Schulich School of Medicine, University of Western Ontario, London, Ontario N6A 5C1, Canada and
| | - Daniel F Aubert
- From the Centre for Human Immunology, Department of Microbiology and Immunology, Schulich School of Medicine, University of Western Ontario, London, Ontario N6A 5C1, Canada and
| | - Miguel A Valvano
- From the Centre for Human Immunology, Department of Microbiology and Immunology, Schulich School of Medicine, University of Western Ontario, London, Ontario N6A 5C1, Canada and; the Centre for Infection and Immunity, Queen's University Belfast, BT9 5GZ Belfast, United Kingdom.
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Lacroix B, Citovsky V. The roles of bacterial and host plant factors in Agrobacterium-mediated genetic transformation. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2013. [PMID: 24166430 DOI: 10.1387/ijdb.130199b1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The genetic transformation of plants mediated by Agrobacterium tumefaciens represents an essential tool for both fundamental and applied research in plant biology. For a successful infection, culminating in the integration of its transferred DNA (T-DNA) into the host genome, Agrobacterium relies on multiple interactions with host-plant factors. Extensive studies have unraveled many of such interactions at all major steps of the infection process: activation of the bacterial virulence genes, cell-cell contact and macromolecular translocation from Agrobacterium to host cell cytoplasm, intracellular transit of T-DNA and associated proteins (T-complex) to the host cell nucleus, disassembly of the T-complex, T-DNA integration, and expression of the transferred genes. During all these processes, Agrobacterium has evolved to control and even utilize several pathways of host-plant defense response. Studies of these Agrobacterium-host interactions substantially enhance our understanding of many fundamental cellular biological processes and allow improvements in the use of Agrobacterium as a gene transfer tool for biotechnology.
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Affiliation(s)
- Benoît Lacroix
- Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, NY, USA.
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Wise AA, Fang F, Lin YH, He F, Lynn DG, Binns AN. The receiver domain of hybrid histidine kinase VirA: an enhancing factor for vir gene expression in Agrobacterium tumefaciens. J Bacteriol 2010; 192:1534-42. [PMID: 20081031 PMCID: PMC2832513 DOI: 10.1128/jb.01007-09] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Accepted: 12/22/2009] [Indexed: 11/20/2022] Open
Abstract
The plant pathogen Agrobacterium tumefaciens expresses virulence (vir) genes in response to chemical signals found at the site of a plant wound. VirA, a hybrid histidine kinase, and its cognate response regulator, VirG, regulate vir gene expression. The receiver domain at the carboxyl end of VirA has been described as an inhibitory element because its removal increased vir gene expression relative to that of full-length VirA. However, experiments that characterized the receiver region as an inhibitory element were performed in the presence of constitutively expressed virG. We show here that VirA's receiver domain is an activating factor if virG is expressed from its native promoter on the Ti plasmid. When virADeltaR was expressed from a multicopy plasmid, both sugar and the phenolic inducer were essential for vir gene expression. Replacement of wild-type virA on pTi with virADeltaR precluded vir gene induction, and the cells did not accumulate VirG or induce transcription of a virG-lacZ fusion in response to acetosyringone. These phenotypes were corrected if the virG copy number was increased. In addition, we show that the VirA receiver domain can interact with the VirG DNA-binding domain.
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Affiliation(s)
- Arlene A Wise
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.
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de Been M, Tempelaars MH, van Schaik W, Moezelaar R, Siezen RJ, Abee T. A novel hybrid kinase is essential for regulating the sigma(B)-mediated stress response of Bacillus cereus. Environ Microbiol 2009; 12:730-45. [PMID: 19958380 DOI: 10.1111/j.1462-2920.2009.02116.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A common bacterial strategy for monitoring environmental challenges is to use two-component systems, which consist of a sensor histidine kinase (HK) and a response regulator (RR). In the food-borne pathogen Bacillus cereus, the alternative sigma factor sigma(B) is activated by the RR RsbY. Here we present strong indications that the PP2C-type phosphatase RsbY receives its input from the multi-sensor hybrid kinase BC1008 (renamed RsbK). Genome analyses revealed that, across bacilli, rsbY and rsbK are located in a conserved gene cluster. A B. cereus rsbK deletion strain was shown to be incapable of inducing sigma(B) upon stress conditions and was impaired in its heat adaptive response. Comparison of the wild-type and rsbK mutant transcriptomes upon heat shock revealed that RsbK was primarily involved in the activation of the sigma(B)-mediated stress response. Truncation of the RsbK RR receiver domain demonstrated the importance of this domain for sigma(B) induction upon stress. The domain architecture of RsbK suggests that in the B. cereus group and in other bacilli, environmental and intracellular stress signalling routes are combined into one single protein. This strategy is markedly different from the sigma(B) activation pathway in other low-GC Gram-positives.
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Affiliation(s)
- Mark de Been
- TI Food and Nutrition (TIFN), Wageningen, the Netherlands.
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Lin YH, Gao R, Binns AN, Lynn DG. Capturing the VirA/VirG TCS of Agrobacterium tumefaciens. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 631:161-77. [PMID: 18792688 DOI: 10.1007/978-0-387-78885-2_11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Two-component systems (TCS) regulate pathogenic commitment in many interactions and provide an opportunity for unique therapeutic intervention. The VirA/VirG TCS of Agrobacterium tumefaciens mediates inter-kingdom gene transfer in the development of host tumors and sets in motion the events that underlie the great success of this multi-host plant pathogen. Significant proof for the feasibility of interventions has now emerged with the discovery of a natural product that effectively "blinds" the pathogen to the host via inhibition of VirA/VirG signal transduction. Moreover, the emerging studies on the mechanism of signal perception have revealed general sites suitable for intervention of TCS signaling. Given the extensive functional homology, it should now be possible to transfer the models discovered for VirA/VirG broadly to other pathogenic interactions.
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Affiliation(s)
- Yi-Han Lin
- Center for Fundamental and Applied Molecular Evolution, Department of Chemistry, Emory University, Atlanta, GA 30322, USA
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Inclán YF, Laurent S, Zusman DR. The receiver domain of FrzE, a CheA-CheY fusion protein, regulates the CheA histidine kinase activity and downstream signalling to the A- and S-motility systems of Myxococcus xanthus. Mol Microbiol 2008; 68:1328-39. [PMID: 18430134 DOI: 10.1111/j.1365-2958.2008.06238.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Frz chemosensory system is a two-component signal transduction pathway that controls cell reversals and directional movements for the two motility systems in Myxococcus xanthus. To trigger cell reversals, FrzE, a hybrid CheA-CheY fusion protein, autophosphorylates the kinase domain at His-49, and phosphoryl groups are transferred to aspartate residues (Asp-52 and Asp-220) in the two receiver domains of FrzZ, a dual CheY-like protein that serves as the pathway output. The role of the receiver domain of FrzE was unknown. In this paper, we characterize the FrzE protein in vitro and show that the receiver domain of FrzE negatively regulates the autophosphorylation activity of the kinase domain of FrzE. Unexpectedly, it does not appear to play a direct role in phospho-relay as in most other histidine kinase receiver domain hybrid systems. The regulatory role of the FrzE receiver domain suggests that it may interact with or be phosphorylated by an unknown protein. We also show the dynamics of motility system-specific marker proteins in FrzE mutants as cells move forward and reverse. Our studies indicate that the two motility systems are functionally co-ordinated and that any system-specific branching of the pathway most likely occurs downstream of FrzE.
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Affiliation(s)
- Yuki F Inclán
- University of California, Graduate Group in Biophysics, Berkeley, CA 94720-3204, USA
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Hsu JL, Chen HC, Peng HL, Chang HY. Characterization of the histidine-containing phosphotransfer protein B-mediated multistep phosphorelay system in Pseudomonas aeruginosa PAO1. J Biol Chem 2008; 283:9933-44. [PMID: 18256026 DOI: 10.1074/jbc.m708836200] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Certain bacterial two-component sensor kinases possess a histidine-containing phosphotransfer (Hpt) domain to carry out a multistep phosphotransferring reaction to a cognate response regulator. Pseudomonas aeruginosa PAO1 contains three genes that encode proteins with an Hpt domain but lack a kinase domain. To identify the sensor kinase coupled to these Hpt proteins, a phosphorelay profiling assay was performed. Among the 12 recombinant orphan sensor kinases tested, 4 of these sensors (PA1611, PA1976, PA2824, and RetS) transferred the phosphoryl group to HptB (PA3345). The in vivo interaction between HptB and each of the sensors was also confirmed using the bacterial two-hybrid assay. Interestingly, the phosphoryl groups from these sensors all appeared to be transferred via HptB to PA3346, a novel phosphatase consisting of an N-terminal receiver domain and a eukaryotic type Ser/Thr phosphatase domain, and resulted in a significant increase of its phosphatase activity. The subsequent reverse transcription-PCR analysis revealed an operon structure of hptB-PA3346-PA3347, suggesting a coordinate expression of the three genes to carry out a signal transduction. The possibility was supported by the analysis showing PA3347 is able to be phosphorylated on Ser-56, and this phosphoryl group could be removed by PA3346 protein. Finally, analysis of PA3346 and PA3347 gene knock-out mutants revealed that these genes are associated with bacterial swarming activity and biofilm formation. Together, these results disclose a novel multistep phosphorelay system that is essential for P. aeruginosa to respond to a wide spectrum of environmental signals.
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Affiliation(s)
- Jye-Lin Hsu
- Institute of Molecular Medicine, National Tsing Hua University, 101 Guang Fu Road 2nd Section, Hsin Chu 300, Taiwan, Republic of China
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Gao R, Lynn DG. Integration of rotation and piston motions in coiled-coil signal transduction. J Bacteriol 2007; 189:6048-56. [PMID: 17573470 PMCID: PMC1952043 DOI: 10.1128/jb.00459-07] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
A coordinated response to a complex and dynamic environment requires an organism to simultaneously monitor and interpret multiple signaling cues. In bacteria and some eukaryotes, environmental responses depend on the histidine autokinases (HKs). For example, VirA, a large integral membrane HK from Agrobacterium tumefaciens, regulates the expression of virulence genes in response to signals from multiple molecular classes (phenol, pH, and sugar). The ability of this pathogen to perceive inputs from different known host signals within a single protein receptor provides an opportunity to understand the mechanisms of signal integration. Here we exploited the conserved domain organization of the HKs and engineered chimeric kinases to explore the signaling mechanisms of phenol sensing and pH/sugar integration. Our data implicate a piston-assisted rotation of coiled coils for integration of multiple inputs and regulation of critical responses during pathogenesis.
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Affiliation(s)
- Rong Gao
- Center for Fundamental and Applied Molecular Evolution, Departments of Chemistry and Biology, Emory University, Atlanta, GA 30322, USA
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Rasmussen AA, Wegener-Feldbrügge S, Porter SL, Armitage JP, Søgaard-Andersen L. Four signalling domains in the hybrid histidine protein kinase RodK of Myxococcus xanthus are required for activity. Mol Microbiol 2006; 60:525-34. [PMID: 16573700 DOI: 10.1111/j.1365-2958.2006.05118.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In prokaryotes, the principal signal transduction systems operating at the level of protein phosphorylation are the two-component systems. A number of hybrid histidine protein kinases in these systems contain several receiver domains, however, the function of these receiver domains is unknown. The RodK kinase in Myxococcus xanthus has an unconventional domain composition with a putative N-terminal sensor domain followed by a histidine kinase domain and three receiver domains. RodK is essential for the spatial coupling of the two morphogenetic events underlying fruiting body formation in M. xanthus, aggregation of cells into nascent fruiting bodies and the subsequent sporulation of these cells. RodK kinase activity is indispensable for RodK activity. By systematically substituting the conserved, phosphorylatable aspartate residues in the three receiver domains, genetic evidence is provided that each receiver domain is important for RodK function and that each receiver domain has a distinct function, which depends on phosphorylation. Biochemical analyses provided indirect evidence for phosphotransfer from the RodK kinase domain to the third receiver domain. This is the first example of a hybrid histidine protein kinase in which four signalling domains have been shown to be required for full activity.
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Affiliation(s)
- Anders Aa Rasmussen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
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Biondi EG, Skerker JM, Arif M, Prasol MS, Perchuk BS, Laub MT. A phosphorelay system controls stalk biogenesis during cell cycle progression in Caulobacter crescentus. Mol Microbiol 2006; 59:386-401. [PMID: 16390437 DOI: 10.1111/j.1365-2958.2005.04970.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A fundamental question in developmental biology is how morphogenesis is coordinated with cell cycle progression. In Caulobacter crescentus, each cell cycle produces morphologically distinct daughter cells, a stalked cell and a flagellated swarmer cell. Construction of both the flagellum and stalk requires the alternative sigma factor RpoN (sigma(54)). Here we report that a sigma(54)-dependent activator, TacA, is required for cell cycle regulated stalk biogenesis by collaborating with RpoN to activate gene expression. We have also identified the first histidine phosphotransferase in C. crescentus, ShpA, and show that it too is required for stalk biogenesis. Using a systematic biochemical technique called phosphotransfer profiling we have identified a multicomponent phosphorelay which leads from the hybrid histidine kinase ShkA to ShpA and finally to TacA. This pathway functions in vivo to phosphorylate and hence, activate TacA. Finally, whole genome microarrays were used to identify candidate members of the TacA regulon, and we show that at least one target gene, staR, regulates stalk length. This is the first example of a general method for identifying the connectivity of a phosphorelay and can be applied to any organism with two-component signal transduction systems.
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Affiliation(s)
- Emanuele G Biondi
- Bauer Center for Genomics Research, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA
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17
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Brencic A, Angert ER, Winans SC. Unwounded plants elicit Agrobacterium vir gene induction and T-DNA transfer: transformed plant cells produce opines yet are tumour free. Mol Microbiol 2005; 57:1522-31. [PMID: 16135221 DOI: 10.1111/j.1365-2958.2005.04763.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Agrobacterium tumefaciens is well known to cause crown gall tumours at plant wound sites and to benefit from this plant association by obtaining nutrients called opines that are produced by these tumours. Tumourigenesis requires expression of the vir regulon in response to chemical signals that are thought to be released from wound sites. Here, we examine chemical interactions between A. tumefaciens and unwounded plants. To determine whether unwounded plants can release significant amounts of vir gene inducers, we constructed an A. tumefaciens strain carrying a PvirB-gfp fusion. This fusion was strongly induced by co-culture with tobacco seedlings that have been germinated without any intentional wounding. The release of phenolic vir gene inducers was confirmed by GC/MS analysis. We also constructed a strain containing the gfp reporter located on an artificial T-DNA and expressed from a plant promoter. A. tumefaciens efficiently transferred this T-DNA into cells of unwounded plants in the absence of exogenous vir gene inducers. Many cells of seedlings colonized by the bacteria also produced octopine, which was detected using a Pocc-gfp reporter strain. This indicates transfer of the native T-DNA. However, these transformed plant cells did not form tumours. These results suggest that successful colonization of plants by A. tumefaciens, including T-DNA transfer and opine production, does not require wounding and does not necessarily cause cell proliferation. Transformation of plant cells without inciting tumours may represent a colonization strategy for this pathogen that has largely been overlooked.
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Affiliation(s)
- Anja Brencic
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
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18
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Zhang W, Shi L. Distribution and evolution of multiple-step phosphorelay in prokaryotes: lateral domain recruitment involved in the formation of hybrid-type histidine kinases. Microbiology (Reading) 2005; 151:2159-2173. [PMID: 16000707 DOI: 10.1099/mic.0.27987-0] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although most two-component signal transduction systems use a simple phosphotransfer pathway from one histidine kinase (HK) to one response regulator (RR), a multiple-step phosphorelay involving a phosphotransfer scheme of His–Asp–His–Asp was also discovered. Central to this multiple-step-type signal transduction pathway are a hybrid-type HK, containing both an HK domain and an RR receiver domain in a single protein, and a histidine-containing phosphotransfer (HPT) that can exist either as a domain in hybrid-type HKs or as a separate protein. Although multiple-step phosphorelay systems are predominant in eukaryotes, it has been previously suggested that they are less common in prokaryotes. In this study, it was found that putative hybrid-type HKs were present in 56 of 156 complete prokaryotic genomes, indicating that multiple-step phosphorelay systems are more common in prokaryotes than previously appreciated. Large expansions of hybrid-type HKs were observed in 26 prokaryotic species, including photosynthetic cyanobacteria such asNostocsp. PCC 7120, and several pathogenic bacteria such asCoxiella burnetii. Phylogenetic analysis indicated that there was no common ancestor for hybrid-type HKs, and their origin and expansion was achieved by lateral recruitment of a receiver domain into an HK molecule and then duplication as one unit. Lateral recruitment of additional sensory domains such as PAS was also evident. HPT domains or proteins were identified in 32 of the genomes with hybrid-type HKs; however, no significant gene expansion was observed for HPTs even in a genome with a large number of hybrid-type HKs. In addition, fewer HPTs than hybrid-type HKs were identified in all prokaryotic genomes.
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Affiliation(s)
- Weiwen Zhang
- Microbiology Department, Pacific Northwest National Laboratory, 902 Battelle Blvd, PO Box 999, Mail Stop P7-50, Richland, WA 99352, USA
| | - Liang Shi
- Microbiology Department, Pacific Northwest National Laboratory, 902 Battelle Blvd, PO Box 999, Mail Stop P7-50, Richland, WA 99352, USA
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19
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Gao R, Lynn DG. Environmental pH sensing: resolving the VirA/VirG two-component system inputs for Agrobacterium pathogenesis. J Bacteriol 2005; 187:2182-9. [PMID: 15743967 PMCID: PMC1064044 DOI: 10.1128/jb.187.6.2182-2189.2005] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Agrobacterium tumefaciens stands as one of biotechnology's greatest successes, with all plant genetic engineering building on the strategies of this pathogen. By integrating responses to external pHs, phenols, and monosaccharides, this organism mobilizes oncogenic elements to efficiently transform most dicotyledonous plants. We now show that the complex signaling network used to regulate lateral gene transfer can be resolved as individual signaling modules. While pH and sugar perception are coupled through a common pathway, requiring both low pH and sugar for maximal virulence gene expression, various VirA and ChvE alleles can decouple pH and monosaccharide perception. This VirA and ChvE system may represent a common mechanism that underpins external pH perception in prokaryotes, and the use of these simple genetic elements may now be extended to research on specific responses to changes in environmental pH.
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Affiliation(s)
- Rong Gao
- Center for Fundamental and Applied Molecular Evolution, Department of Chemistry, Emory University, Atlanta, GA 30322, USA
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20
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Mukhopadhyay A, Gao R, Lynn DG. Integrating Input from Multiple Signals: The VirA/VirG Two-Component System of Agrobacterium tumefaciens. Chembiochem 2004; 5:1535-42. [PMID: 15515087 DOI: 10.1002/cbic.200300828] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Bacteria, fungi, and plants exploit histidine sensor kinase/response regulators to mobilize complex responses to inputs as diverse as environmental stimuli and hormonal regulation. More than 50 such two-component systems are found in many organisms, yet the mechanisms of signal perception, phosphotransfer regulation, and even the nature of the activating signals remain poorly defined. Here we resolve each phosphate transfer event in vivo for the Agrobacterium tumefaciens virulence two-component system VirA/VirG. The input signals for this system are known, and the complex autocatalytic regulation of the signaling components has been removed. Two separate and independent phosphotransfer events are resolved, an initial ATP-->sensorHis approximately PO(4)-->receiver approximately PO(4), that may be activated by xenognostic sugar/low pH, and a subsequent ATP-->His approximately PO(4)-->VirG approximately PO(4) that requires xenognostic phenol activation. The identification of these separate pathways places biochemical limits on the regulated steps in this two-component signal transduction module and further extends the model of how a single sensor is able to integrate multiple input stimuli.
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Affiliation(s)
- Aindrila Mukhopadhyay
- Center for Fundamental and Applied Molecular Evolution, Department of Chemistry and Biology, Emory University, Atlanta, GA 30322, USA
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21
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Brencic A, Xia Q, Winans SC. VirA of Agrobacterium tumefaciens is an intradimer transphosphorylase and can actively block vir gene expression in the absence of phenolic signals. Mol Microbiol 2004; 52:1349-62. [PMID: 15165238 DOI: 10.1111/j.1365-2958.2004.04057.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The VirA-VirG two-component system regulates the 30-gene vir regulon in response to host-released chemical signals. VirA is a homodimeric membrane-spanning histidine protein kinase. Here, we show that mutations in two essential VirA residues, His-474 and Gly-657, can be complemented by the formation of mixed heterodimers, indicating that each subunit of a VirA dimer transphosphorylates the opposite subunit. VirA contains a receiver domain that inhibits kinase activity. We use the forced heterodimer system to show that the two receiver domains of a VirA dimer act independently and that each inhibits the phosphoacceptor subdomain of the opposite subunit. We also demonstrate that merodiploid strains co-expressing constitutive VirA mutants and wild-type VirA show levels of vir gene expression far lower than haploid strains expressing just the constitutive alleles. The fact that wild-type VirA can actively block vir gene expression in the absence of phenolic signals suggests that it might have a phospho-VirG phosphatase activity. The receiver domain of VirA is essential for this activity, whereas residues H474 and G657 of the kinase domain are not required. Merodiploid strains co-expressing a constitutive VirA allele and an allele that is kinase inactive but proficient in the inhibitory activity show strongly inducible vir gene expression, indicating that the inhibitory activity is modulated by environmental signals.
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Affiliation(s)
- Anja Brencic
- Department of Microbiology, 360A Wing Hall, Cornell University, Ithaca, NY 14853, USA
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22
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Bijlsma JJE, Groisman EA. Making informed decisions: regulatory interactions between two-component systems. Trends Microbiol 2003; 11:359-66. [PMID: 12915093 DOI: 10.1016/s0966-842x(03)00176-8] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Jetta J E Bijlsma
- Department of Molecular Microbiology, Howard Hughes Medical Institute, Washington University School of Medicine, Campus Box 8230, 660 S. Euclid Avenue, St Louis, MO 63110, USA
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23
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Clarke DJ, Joyce SA, Toutain CM, Jacq A, Holland IB. Genetic analysis of the RcsC sensor kinase from Escherichia coli K-12. J Bacteriol 2002; 184:1204-8. [PMID: 11807084 PMCID: PMC134787 DOI: 10.1128/jb.184.4.1204-1208.2002] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Rcs two-component pathway is involved in the regulation of capsule production in Escherichia coli. RcsC is predicted to be the sensor component of this two-component pathway, and in this study we present the first genetic data that support the role of RcsC as a hybrid sensor kinase.
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Affiliation(s)
- D J Clarke
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom.
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24
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Abstract
Most prokaryotic signal-transduction systems and a few eukaryotic pathways use phosphotransfer schemes involving two conserved components, a histidine protein kinase and a response regulator protein. The histidine protein kinase, which is regulated by environmental stimuli, autophosphorylates at a histidine residue, creating a high-energy phosphoryl group that is subsequently transferred to an aspartate residue in the response regulator protein. Phosphorylation induces a conformational change in the regulatory domain that results in activation of an associated domain that effects the response. The basic scheme is highly adaptable, and numerous variations have provided optimization within specific signaling systems. The domains of two-component proteins are modular and can be integrated into proteins and pathways in a variety of ways, but the core structures and activities are maintained. Thus detailed analyses of a relatively small number of representative proteins provide a foundation for understanding this large family of signaling proteins.
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Affiliation(s)
- A M Stock
- Center for Advanced Biotechnology and Medicine and Howard Hughes Medical Institute, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
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25
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Campbell AM, Tok JB, Zhang J, Wang Y, Stein M, Lynn DG, Binns AN. Xenognosin sensing in virulence: is there a phenol receptor in Agrobacterium tumefaciens? CHEMISTRY & BIOLOGY 2000; 7:65-76. [PMID: 10662683 DOI: 10.1016/s1074-5521(00)00065-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND The mechanisms of signal perception and transmission in the 'two-component' autokinase transmitters/response regulators are poorly understood, especially considering the vast number of such systems now known. Virulence induction from the tumor-inducing (Ti) plasmid of Agrobacterium tumefaciens represents one of the best understood systems with regard to the chemistry of the activating signal, and yet the existing data does not support a receptor-mediated perception event for the xenognostic phenols. RESULTS Here we provide the first conclusive evidence that a specific receptor must be involved in xenognostic phenol perception, detail structural requirements of the xenognosins necessary for perception by this receptor, and develop a genetic strategy that demonstrates critical components of the phenol recognition system are not encoded on the Ti plasmid. CONCLUSIONS Although the basic elements of the two-component system required for phenol-mediated induction of virulence gene expression are encoded on the Ti plasmid, they are dependent on the chromosomal background for even the very first stage of signal perception. This discovery suggests a curious evolutionary history, and also provides functional insight into the mechanisms of two-component signal detection and transmission in general.
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Affiliation(s)
- A M Campbell
- Plant Sciences Institute, University of Pennsylvania, Philadelphia, PA 19104-1018, USA
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26
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Chang CH, Schindler JF, Unkefer CJ, Vanderberg LA, Brainard JR, Terwilliger TC. In vivo screening of haloalkane dehalogenase mutants. Bioorg Med Chem 1999; 7:2175-81. [PMID: 10579523 DOI: 10.1016/s0968-0896(99)00148-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Haloalkane dehalogenase (Dh1A) from Xanthobacter autotrophicus GJ10 catalyzes the dehalogenation of short chain primary alkyl halides. Due to the high Km and low turnover, wild type Dh1A is not optimal for applications in bioremediation. We have developed an in vivo screen, based on a colorimetric pH indicator, to identify Dh1A mutant with improved catalytic activity. After screening 50,000 colonies, we identified a Dh1A mutant with a lower pH optimum. Sequence analysis of the mutant revealed a single substitution, alanine 149 to threonine, which is located close to the active site of Dh1A. Replacement of alanine 149 via site-directed mutagenesis with threonine, serine or cysteine retained the mutant phenotype. Other substitutions at position 149 show little or no activity.
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Affiliation(s)
- C H Chang
- Structural Biology Group, Los Alamos National Laboratory, NM 87545, USA
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27
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Peng WT, Lee YW, Nester EW. The phenolic recognition profiles of the Agrobacterium tumefaciens VirA protein are broadened by a high level of the sugar binding protein ChvE. J Bacteriol 1998; 180:5632-8. [PMID: 9791112 PMCID: PMC107621 DOI: 10.1128/jb.180.21.5632-5638.1998] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The formation of crown gall tumors by Agrobacterium tumefaciens requires that the virulence (vir) genes be induced by chemical signals which consist of specific phenolic compounds and monosaccharides, synthesized at plant wound sites. Signal transduction in the activation of these genes is mediated by the VirA-VirG two-component regulatory system, together with ChvE, a glucose-galactose binding protein which interacts with VirA. We have previously presented genetic evidence that virA senses phenolic compounds directly (Y.-W. Lee, S. Jin, W.-S. Sim, and E. W. Nester, Proc. Natl. Acad. Sci. USA 92:12245-12249, 1995). The vir genes of strain KU12 can be induced by 4-hydroxyacetophenone, p-coumaric acid, and phenol, whereas these same phenolic compounds are weak inducers of the vir genes of strain A6. In this report, we show that a specific inducing sugar can broaden the specificity of the phenolic compound which VirA senses. 4-Hydroxyacetophenone and other related phenolic compounds function as inducing phenolic compounds with the virA gene of A6 if arabinose replaces glucose as the inducing sugar. We further demonstrate that this broadened specificity for phenolic inducers results from the increased level of ChvE through induction by arabinose via the regulatory protein GbpR. If high levels of ChvE are present, then poorly inducing phenolic compounds can induce the vir genes to high levels in combination with glucose. Comparing the induction response of the wild type and that of a VirA mutant with a mutation in its receiver domain revealed that the activity of the receiver domain is controlled by the periplasmic domain. We discuss these observations in terms of how VirA senses and transduces signals elicited by the two classes of plant signal molecules.
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Affiliation(s)
- W T Peng
- Department of Microbiology, University of Washington, Seattle, Washington 98195, USA
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28
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Jourlin C, Ansaldi M, Méjean V. Transphosphorylation of the TorR response regulator requires the three phosphorylation sites of the TorS unorthodox sensor in Escherichia coli. J Mol Biol 1997; 267:770-7. [PMID: 9135110 DOI: 10.1006/jmbi.1997.0919] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Two-component regulatory systems allow cells to adapt to environmental changes. In Escherichia coli, the TorS/TorR two-component system induces the expression of the tor structural operon encoding the trimethylamine N-oxide reductase respiratory system in response to substrate availability. TorS belongs to a sensor subfamily that includes a classical transmitter domain, a receiver, and a C-terminal alternative transmitter domain. The histidine phosphorylation sites of each TorS transmitter domain and the aspartate phosphorylation site of the TorS receiver were individually changed by site-directed mutagenesis. All three phosphorylation sites proved essential for in vivo induction of the tor structural operon and for in vitro transphosphorylation of the cognate TorR response regulator. The His to Gln change in the classical transmitter domain abolished TorS autophosphorylation, whereas TorS underwent significant autophosphorylation when the phosphorylation site of its receiver or alternative transmitter was changed. Complementation between pairs of defective TorS proteins was achieved in vitro, allowing TorR transphosphorylation. This strongly suggests that TorS is a multimer in which intermolecular phosphorylation occurs. The wild-type alternative transmitter domain alone was shown to complement a TorS protein mutated in its C-terminal alternative transmitter. Interestingly, overproduction of the alternative transmitter domain led to in vivo TorR-dependent constitutive expression of the tor operon in a torS+ or torS context. Hence, the TorS alternative transmitter contains the phosphodonor site for TorR. Taken together, our results support a TorS phosphorylation cascade from the classical transmitter to the sensor receiver and the alternative transmitter phosphorylation sites.
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Affiliation(s)
- C Jourlin
- Laboratoire de Chimie Bactérienne, Institut de Biologie Structurale etMicrobiologie, Centre National de la Recherche Scientifique, Marseille, France
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29
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Appleby JL, Parkinson JS, Bourret RB. Signal transduction via the multi-step phosphorelay: not necessarily a road less traveled. Cell 1996; 86:845-8. [PMID: 8808618 DOI: 10.1016/s0092-8674(00)80158-0] [Citation(s) in RCA: 332] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- J L Appleby
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill 27599-7290, USA
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