1
|
Flores-Ibarra A, Maia RNA, Olasz B, Church JR, Gotthard G, Schapiro I, Heberle J, Nogly P. Light-Oxygen-Voltage (LOV)-sensing Domains: Activation Mechanism and Optogenetic Stimulation. J Mol Biol 2024; 436:168356. [PMID: 37944792 DOI: 10.1016/j.jmb.2023.168356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 10/11/2023] [Accepted: 11/02/2023] [Indexed: 11/12/2023]
Abstract
The light-oxygen-voltage (LOV) domains of phototropins emerged as essential constituents of light-sensitive proteins, helping initiate blue light-triggered responses. Moreover, these domains have been identified across all kingdoms of life. LOV domains utilize flavin nucleotides as co-factors and undergo structural rearrangements upon exposure to blue light, which activates an effector domain that executes the final output of the photoreaction. LOV domains are versatile photoreceptors that play critical roles in cellular signaling and environmental adaptation; additionally, they can noninvasively sense and control intracellular processes with high spatiotemporal precision, making them ideal candidates for use in optogenetics, where a light signal is linked to a cellular process through a photoreceptor. The ongoing development of LOV-based optogenetic tools, driven by advances in structural biology, spectroscopy, computational methods, and synthetic biology, has the potential to revolutionize the study of biological systems and enable the development of novel therapeutic strategies.
Collapse
Affiliation(s)
- Andrea Flores-Ibarra
- Dioscuri Center for Structural Dynamics of Receptors, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Raiza N A Maia
- Department of Chemistry, The University of Texas at Austin, 78712-1224 Austin, TX, USA
| | - Bence Olasz
- Dioscuri Center for Structural Dynamics of Receptors, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Jonathan R Church
- Institute of Chemistry, The Hebrew University of Jerusalem, 91905 Jerusalem, Israel
| | | | - Igor Schapiro
- Institute of Chemistry, The Hebrew University of Jerusalem, 91905 Jerusalem, Israel
| | - Joachim Heberle
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Przemyslaw Nogly
- Dioscuri Center for Structural Dynamics of Receptors, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland.
| |
Collapse
|
2
|
Pucelik S, Becker M, Heyber S, Wöhlbrand L, Rabus R, Jahn D, Härtig E. The blue light-dependent LOV-protein LdaP of Dinoroseobacter shibae acts as antirepressor of the PpsR repressor, regulating photosynthetic gene cluster expression. Front Microbiol 2024; 15:1351297. [PMID: 38404597 PMCID: PMC10890935 DOI: 10.3389/fmicb.2024.1351297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 01/17/2024] [Indexed: 02/27/2024] Open
Abstract
In the marine α-proteobacterium Dinoroseobacter shibae more than 40 genes of the aerobic anoxygenic photosynthesis are regulated in a light-dependent manner. A genome-wide screen of 5,605 clones from a D. shibae transposon library for loss of pigmentation and changes in bacteriochlorophyll absorbance identified 179 mutant clones. The gene encoding the LOV-domain containing protein Dshi_1135 was identified by its colorless phenotype. The mutant phenotype was complemented by the expression of a Dshi_1135-strep fusion protein in trans. The recombinantly produced and chromatographically purified Dshi_1135 protein was able to undergo a blue light-induced photocycle mediated by bound FMN. Transcriptome analyses revealed an essential role for Dshi_1135 in the light-dependent expression of the photosynthetic gene cluster. Interactomic studies identified the repressor protein PpsR as an interaction partner of Dshi_1135. The physical contact between PpsR and the Dshi_1135 protein was verified in vivo using the bacterial adenylate cyclase-based two-hybrid system. In addition, the antirepressor function of the Dshi_1135 protein was demonstrated in vivo testing of a bchF-lacZ reporter gene fusion in a heterologous Escherichia coli-based host system. We therefore propose to rename the Dshi_1135 protein to LdaP (light-dependent antirepressor of PpsR). Using the bacterial two-hybrid system, it was also shown that cobalamin (B12) is essential for the interaction of the antirepressor PpaA with PpsR. A regulatory model for the photosynthetic gene cluster in D. shibae was derived, including the repressor PpsR, the light-dependent antirepressor LdaP and the B12-dependent antirepressor PpaA.
Collapse
Affiliation(s)
- Saskia Pucelik
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Miriam Becker
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Steffi Heyber
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Lars Wöhlbrand
- Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Ralf Rabus
- Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Dieter Jahn
- Braunschweig Integrated Centre of Systems Biology (BRICS), Technische Universität Braunschweig, Braunschweig, Germany
| | - Elisabeth Härtig
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
| |
Collapse
|
3
|
Dikiy I, Swingle D, Toy K, Edupuganti UR, Rivera-Cancel G, Gardner KH. Diversity of function and higher-order structure within HWE sensor histidine kinases. J Biol Chem 2023; 299:104934. [PMID: 37331599 PMCID: PMC10359499 DOI: 10.1016/j.jbc.2023.104934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 06/09/2023] [Accepted: 06/12/2023] [Indexed: 06/20/2023] Open
Abstract
Integral to the protein structure/function paradigm, oligomeric state is typically conserved along with function across evolution. However, notable exceptions such as the hemoglobins show how evolution can alter oligomerization to enable new regulatory mechanisms. Here, we examine this linkage in histidine kinases (HKs), a large class of widely distributed prokaryotic environmental sensors. While the majority of HKs are transmembrane homodimers, members of the HWE/HisKA2 family can deviate from this architecture as exemplified by our finding of a monomeric soluble HWE/HisKA2 HK (EL346, a photosensing light-oxygen-voltage [LOV]-HK). To further explore the diversity of oligomerization states and regulation within this family, we biophysically and biochemically characterized multiple EL346 homologs and found a range of HK oligomeric states and functions. Three LOV-HK homologs are primarily dimeric with differing structural and functional responses to light, while two Per-ARNT-Sim-HKs interconvert between differentially active monomers and dimers, suggesting dimerization might control enzymatic activity for these proteins. Finally, we examined putative interfaces in a dimeric LOV-HK, finding that multiple regions contribute to dimerization. Our findings suggest the potential for novel regulatory modes and oligomeric states beyond those traditionally defined for this important family of environmental sensors.
Collapse
Affiliation(s)
- Igor Dikiy
- Structural Biology Initiative, CUNY Advanced Science Research Center, New York, New York, USA
| | - Danielle Swingle
- Structural Biology Initiative, CUNY Advanced Science Research Center, New York, New York, USA; PhD. Program in Biochemistry, The Graduate Center - City University of New York, New York, New York, USA
| | - Kaitlyn Toy
- Structural Biology Initiative, CUNY Advanced Science Research Center, New York, New York, USA; Department of Chemistry and Biochemistry, City College of New York, New York, New York, USA
| | - Uthama R Edupuganti
- Structural Biology Initiative, CUNY Advanced Science Research Center, New York, New York, USA; PhD. Program in Biochemistry, The Graduate Center - City University of New York, New York, New York, USA
| | - Giomar Rivera-Cancel
- Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Kevin H Gardner
- Structural Biology Initiative, CUNY Advanced Science Research Center, New York, New York, USA; Department of Chemistry and Biochemistry, City College of New York, New York, New York, USA; PhD. Programs in Biochemistry, Biology, and Chemistry, The Graduate Center - City University of New York, New York, New York, USA.
| |
Collapse
|
4
|
Wülser J, Ernst C, Vetsch D, Emmenegger B, Michel A, Lutz S, Ahrens CH, Vorholt JA, Ledermann R, Fischer HM. Salt- and Osmo-Responsive Sensor Histidine Kinases Activate the Bradyrhizobium diazoefficiens General Stress Response to Initiate Functional Symbiosis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2022; 35:604-615. [PMID: 35322688 DOI: 10.1094/mpmi-02-22-0051-fi] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The general stress response (GSR) enables bacteria to sense and overcome a variety of environmental stresses. In alphaproteobacteria, stress-perceiving histidine kinases of the HWE and HisKA_2 families trigger a signaling cascade that leads to phosphorylation of the response regulator PhyR and, consequently, to activation of the GSR σ factor σEcfG. In the nitrogen-fixing bacterium Bradyrhizobium diazoefficiens, PhyR and σEcfG are crucial for tolerance against a variety of stresses under free-living conditions and also for efficient infection of its symbiotic host soybean. However, the molecular players involved in stress perception and activation of the GSR remained largely unknown. In this work, we first showed that a mutant variant of PhyR where the conserved phosphorylatable aspartate residue D194 was replaced by alanine (PhyRD194A) failed to complement the ΔphyR mutant in symbiosis, confirming that PhyR acts as a response regulator. To identify the PhyR-activating kinases in the nitrogen-fixing symbiont, we constructed in-frame deletion mutants lacking single, distinct combinations, or all of the 11 predicted HWE and HisKA_2 kinases, which we named HRXXN histidine kinases HhkA through HhkK. Phenotypic analysis of the mutants and complemented derivatives identified two functionally redundant kinases, HhkA and HhkE, that are required for nodulation competitiveness and during initiation of symbiosis. Using σEcfG-activity reporter strains, we further showed that both HhkA and HhkE activate the GSR in free-living cells exposed to salt and hyperosmotic stress. In conclusion, our data suggest that HhkA and HhkE trigger GSR activation in response to osmotically stressful conditions which B. diazoefficiens encounters during soybean host infection.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Collapse
Affiliation(s)
- Janine Wülser
- Institute of Microbiology, ETH Zurich, CH-8093 Zürich, Switzerland
| | - Chantal Ernst
- Institute of Microbiology, ETH Zurich, CH-8093 Zürich, Switzerland
| | - Dominik Vetsch
- Institute of Microbiology, ETH Zurich, CH-8093 Zürich, Switzerland
| | | | - Anja Michel
- Institute of Microbiology, ETH Zurich, CH-8093 Zürich, Switzerland
| | - Stefanie Lutz
- Agroscope, Research Group Molecular Diagnostics, Genomics and Bioinformatics and Swiss Institute of Bioinformatics, CH-8820 Wädenswil, Switzerland
| | - Christian H Ahrens
- Agroscope, Research Group Molecular Diagnostics, Genomics and Bioinformatics and Swiss Institute of Bioinformatics, CH-8820 Wädenswil, Switzerland
| | - Julia A Vorholt
- Institute of Microbiology, ETH Zurich, CH-8093 Zürich, Switzerland
| | | | | |
Collapse
|
5
|
Abstract
Bacteria employ two-component systems (TCSs) to sense and respond to changes in their surroundings. At the core of the TCS signaling pathway is the multidomain sensor histidine kinase, where the enzymatic activity of its output domain is allosterically controlled by the input signal perceived by the sensor domain. The ability to sense and respond to environmental cues is essential for adaptation and survival in living organisms. In bacteria, this process is accomplished by multidomain sensor histidine kinases that undergo autophosphorylation in response to specific stimuli, thereby triggering downstream signaling cascades. However, the molecular mechanism of allosteric activation is not fully understood in these important sensor proteins. Here, we report the full-length crystal structure of a blue light photoreceptor LOV histidine kinase (LOV-HK) involved in light-dependent virulence modulation in the pathogenic bacterium Brucella abortus. Joint analyses of dark and light structures determined in different signaling states have shown that LOV-HK transitions from a symmetric dark structure to a highly asymmetric light state. The initial local and subtle structural signal originated in the chromophore-binding LOV domain alters the dimer asymmetry via a coiled-coil rotary switch and helical bending in the helical spine. These amplified structural changes result in enhanced conformational flexibility and large-scale rearrangements that facilitate the phosphoryl transfer reaction in the HK domain.
Collapse
|
6
|
Rajeev L, Garber ME, Mukhopadhyay A. Tools to map target genes of bacterial two-component system response regulators. ENVIRONMENTAL MICROBIOLOGY REPORTS 2020; 12:267-276. [PMID: 32212247 PMCID: PMC7318608 DOI: 10.1111/1758-2229.12838] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/17/2020] [Accepted: 03/18/2020] [Indexed: 05/05/2023]
Abstract
Studies on bacterial physiology are incomplete without knowledge of the signalling and regulatory systems that a bacterium uses to sense and respond to its environment. Two-component systems (TCSs) are among the most prevalent bacterial signalling systems, and they control essential and secondary physiological processes; however, even in model organisms, we lack a complete understanding of the signals sensed, the phosphotransfer partners and the functions regulated by these systems. In this review, we discuss several tools to map the genes targeted by transcriptionally acting TCSs. Many of these tools have been used for studying individual TCSs across diverse species, but systematic approaches to delineate entire signalling networks have been very few. Since genome sequences and high-throughput technologies are now readily available, the methods presented here can be applied to characterize the entire DNA-binding TCS signalling network in any bacterial species and are especially useful for non-model environmental bacteria.
Collapse
Affiliation(s)
- Lara Rajeev
- Biological Systems and Engineering DivisionLawrence Berkeley National LaboratoryBerkeleyCA94720USA
| | - Megan E. Garber
- Biological Systems and Engineering DivisionLawrence Berkeley National LaboratoryBerkeleyCA94720USA
- Department of Comparative BiochemistryUniversity of CaliforniaBerkeleyCA94720USA
| | - Aindrila Mukhopadhyay
- Biological Systems and Engineering DivisionLawrence Berkeley National LaboratoryBerkeleyCA94720USA
- Department of Comparative BiochemistryUniversity of CaliforniaBerkeleyCA94720USA
- Environmental Genomics and Systems Biology DivisionLawrence Berkeley National LaboratoryBerkeleyCA94720USA
| |
Collapse
|
7
|
Fiebig A, Varesio LM, Alejandro Navarreto X, Crosson S. Regulation of the Erythrobacter litoralis DSM 8509 general stress response by visible light. Mol Microbiol 2019; 112:442-460. [PMID: 31125464 DOI: 10.1111/mmi.14310] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/20/2019] [Indexed: 01/23/2023]
Abstract
Extracytoplasmic function (ECF) sigma factors are environmentally responsive transcriptional regulators. In Alphaproteobacteria, σEcfG activates general stress response (GSR) transcription and protects cells from multiple stressors. A phosphorylation-dependent protein partner switching mechanism, involving HWE/HisKA_2-family histidine kinases, underlies σEcfG activation. The identity of these sensor kinases and the signals that regulate them remain largely uncharacterized. We have developed the aerobic anoxygenic photoheterotroph (AAP), Erythrobacter litoralis DSM 8509, as a comparative genetic model to investigate GSR. Using this system, we sought to define the role of visible light and a photosensory HWE kinase, LovK, in regulation of GSR transcription. We identified three HWE kinase genes that collectively control GSR: gsrK and lovK are activators, while gsrP is a repressor. In wild-type cells, GSR transcription is activated in the dark and nearly off in the light, and the opposing activities of gsrK and gsrP are sufficient to modulate GSR transcription in response to illumination. In the absence of gsrK and gsrP, lovK alone is sufficient to activate GSR transcription. lovK is a more robust activator in the dark, and light-dependent regulation by LovK requires that its N-terminal LOV domain be photochemically active. Our studies establish a role for visible light and an ensemble of HWE kinases in light-dependent regulation of GSR transcription in E. litoralis.
Collapse
Affiliation(s)
- Aretha Fiebig
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA
| | - Lydia M Varesio
- The Committee on Microbiology, The University of Chicago, Chicago, IL, 60637, USA
| | | | - Sean Crosson
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.,The Committee on Microbiology, The University of Chicago, Chicago, IL, 60637, USA
| |
Collapse
|
8
|
Dikiy I, Gardner KH. Shining light on the alphaproteobacterial general stress response: Comment on: Fiebig et al., Mol Microbiol, 2019. Mol Microbiol 2019; 112:438-441. [PMID: 31120626 DOI: 10.1111/mmi.14311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/20/2019] [Indexed: 11/26/2022]
Abstract
The general stress response (GSR) allows many bacterial species to react to myriad different stressors. In Alphaproteobacteria, this signaling pathway proceeds through the partner-switching PhyR-EcfG sigma-factor mechanism and is involved in multiple life processes, including virulence in Brucella abortus. To date, details of the alphaproteobacterial GSR signaling pathway have been determined using genetic and biochemical work on a diverse set of species distributed throughout the clade. Fiebig and co-workers establish Erythrobacter litoralis DSM 8509 as a genetically tractable lab strain and use it to both directly and indirectly delineate photoresponsive GSR pathways mediated by multiple HWE/HisKA_2 histidine kinases. The existence of a new phototrophic lab strain allows researchers to compare the GSR across different Alphaproteobacteria, as well as study the interplay between the GSR and phototrophy. Additionally, the discovery of new HWE/HisKA_2 kinases regulating the GSR poses new questions about how different stimuli feed into this widespread stress pathway.
Collapse
Affiliation(s)
- Igor Dikiy
- Structural Biology Initiative, CUNY Advanced Science Research Center, New York, NY, USA
| | - Kevin H Gardner
- Department of Chemistry and Biochemistry, City College of New York, New York, NY, USA.,Programs in Biochemistry, Biology and Chemistry, CUNY Graduate Center, New York, NY, USA
| |
Collapse
|
9
|
Insights into histidine kinase activation mechanisms from the monomeric blue light sensor EL346. Proc Natl Acad Sci U S A 2019; 116:4963-4972. [PMID: 30808807 DOI: 10.1073/pnas.1813586116] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Translation of environmental cues into cellular behavior is a necessary process in all forms of life. In bacteria, this process frequently involves two-component systems in which a sensor histidine kinase (HK) autophosphorylates in response to a stimulus before subsequently transferring the phosphoryl group to a response regulator that controls downstream effectors. Many details of the molecular mechanisms of HK activation are still unclear due to complications associated with the multiple signaling states of these large, multidomain proteins. To address these challenges, we combined complementary solution biophysical approaches to examine the conformational changes upon activation of a minimal, blue-light-sensing histidine kinase from Erythrobacter litoralis HTCC2594, EL346. Our data show that multiple conformations coexist in the dark state of EL346 in solution, which may explain the enzyme's residual dark-state activity. We also observe that activation involves destabilization of the helices in the dimerization and histidine phosphotransfer-like domain, where the phosphoacceptor histidine resides, and their interactions with the catalytic domain. Similar light-induced changes occur to some extent even in constitutively active or inactive mutants, showing that light sensing can be decoupled from activation of kinase activity. These structural changes mirror those inferred by comparing X-ray crystal structures of inactive and active HK fragments, suggesting that they are at the core of conformational changes leading to HK activation. More broadly, our findings uncover surprising complexity in this simple system and allow us to outline a mechanism of the multiple steps of HK activation.
Collapse
|
10
|
Nishino K, Takahashi S, Nishida H. Comparison of gene expression levels of appA, ppsR, and EL368 in Erythrobacter litoralis spheroplasts under aerobic and anaerobic conditions, and under blue light, red light, and dark conditions. J GEN APPL MICROBIOL 2018; 64:117-120. [PMID: 29607875 DOI: 10.2323/jgam.2017.09.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We compared the gene expression levels of the blue-light-responsive genes, appA (encoding photosynthesis promoting protein AppA), ppsR (encoding photosynthesis suppressing protein PpsR), and EL368 (encoding a blue-light-activated histidine kinase with a light, oxygen, or voltage domain) between aerobic and anaerobic conditions in spheroplasts of the aerobic photosynthetic bacterium Erythrobacter litoralis. The spheroplasts conducted photosynthesis under red light but not under blue light. All three blue-light-responsive genes showed higher expression under aerobic conditions than under anaerobic conditions under blue light. In contrast, under red light, although the expression level of appA was higher in the presence of oxygen than in the absence of oxygen, the expression levels of ppsR and EL368 were similar in the presence and absence of oxygen. Our findings demonstrate that the expression of blue-light-responsive genes is strongly affected by oxygen in E. litoralis spheroplasts.
Collapse
Affiliation(s)
- Koki Nishino
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University
| | - Sawako Takahashi
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University
| | - Hiromi Nishida
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University
| |
Collapse
|
11
|
Abstract
Sensory photoreceptors underpin light-dependent adaptations of organismal physiology, development, and behavior in nature. Adapted for optogenetics, sensory photoreceptors become genetically encoded actuators and reporters to enable the noninvasive, spatiotemporally accurate and reversible control by light of cellular processes. Rooted in a mechanistic understanding of natural photoreceptors, artificial photoreceptors with customized light-gated function have been engineered that greatly expand the scope of optogenetics beyond the original application of light-controlled ion flow. As we survey presently, UV/blue-light-sensitive photoreceptors have particularly allowed optogenetics to transcend its initial neuroscience applications by unlocking numerous additional cellular processes and parameters for optogenetic intervention, including gene expression, DNA recombination, subcellular localization, cytoskeleton dynamics, intracellular protein stability, signal transduction cascades, apoptosis, and enzyme activity. The engineering of novel photoreceptors benefits from powerful and reusable design strategies, most importantly light-dependent protein association and (un)folding reactions. Additionally, modified versions of these same sensory photoreceptors serve as fluorescent proteins and generators of singlet oxygen, thereby further enriching the optogenetic toolkit. The available and upcoming UV/blue-light-sensitive actuators and reporters enable the detailed and quantitative interrogation of cellular signal networks and processes in increasingly more precise and illuminating manners.
Collapse
Affiliation(s)
- Aba Losi
- Department of Mathematical, Physical and Computer Sciences , University of Parma , Parco Area delle Scienze 7/A-43124 Parma , Italy
| | - Kevin H Gardner
- Structural Biology Initiative, CUNY Advanced Science Research Center , New York , New York 10031 , United States.,Department of Chemistry and Biochemistry, City College of New York , New York , New York 10031 , United States.,Ph.D. Programs in Biochemistry, Chemistry, and Biology , The Graduate Center of the City University of New York , New York , New York 10016 , United States
| | - Andreas Möglich
- Lehrstuhl für Biochemie , Universität Bayreuth , 95447 Bayreuth , Germany.,Research Center for Bio-Macromolecules , Universität Bayreuth , 95447 Bayreuth , Germany.,Bayreuth Center for Biochemistry & Molecular Biology , Universität Bayreuth , 95447 Bayreuth , Germany
| |
Collapse
|
12
|
Luebke JL, Eaton DS, Sachleben JR, Crosson S. Allosteric control of a bacterial stress response system by an anti-σ factor. Mol Microbiol 2018; 107:164-179. [PMID: 29052909 PMCID: PMC5760481 DOI: 10.1111/mmi.13868] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/2017] [Indexed: 11/28/2022]
Abstract
Bacterial signal transduction systems commonly use receiver (REC) domains, which regulate adaptive responses to the environment as a function of their phosphorylation state. REC domains control cell physiology through diverse mechanisms, many of which remain understudied. We have defined structural features that underlie activation of the multi-domain REC protein, PhyR, which functions as an anti-anti-σ factor and regulates transcription of genes required for stress adaptation and host-microbe interactions in Alphaproteobacteria. Though REC phosphorylation is necessary for PhyR function in vivo, we did not detect expected changes in inter-domain interactions upon phosphorylation by solution X-ray scattering. We sought to understand this result by defining additional molecular requirements for PhyR activation. We uncovered specific interactions between unphosphorylated PhyR and an intrinsically disordered region (IDR) of the anti-σ factor, NepR, by solution NMR spectroscopy. Our data support a model whereby nascent NepR(IDR)-PhyR interactions and REC phosphorylation coordinately impart the free energy to shift PhyR to an open, active conformation that binds and inhibits NepR. This mechanism ensures PhyR is activated only when NepR and an activating phosphoryl signal are present. Our study provides new structural understanding of the molecular regulatory logic underlying a conserved environmental response system.
Collapse
Affiliation(s)
- Justin L. Luebke
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA
| | - Daniel S. Eaton
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA
| | - Joseph R. Sachleben
- Biomolecular NMR Core Facility, Biological Sciences Division, The University of Chicago, Chicago, Illinois, USA
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA
- Department of Microbiology, The University of Chicago, Chicago, Illinois, USA
| |
Collapse
|
13
|
Herrou J, Crosson S, Fiebig A. Structure and function of HWE/HisKA2-family sensor histidine kinases. Curr Opin Microbiol 2017; 36:47-54. [PMID: 28193573 DOI: 10.1016/j.mib.2017.01.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/12/2017] [Accepted: 01/19/2017] [Indexed: 02/01/2023]
Abstract
Sensor histidine kinases regulate adaptive cellular responses to changes in the chemical or physical state of the environment. HWE/HisKA2-family kinases comprise a subset of histidine kinases that is defined by unique sequence motifs in both the catalytic and non-catalytic regions. Recent crystal structures have defined conserved intramolecular interactions that inform models of kinase regulation that are unique to the HWE/HisKA2 superfamily. Emerging genetic, biochemical and genomic data indicate that, unlike typical histidine kinases, HWE/HisKA2 kinases do not generally signal via classical DNA-binding response regulators. Rather, these unusual kinases are often part of atypical regulatory pathways that control changes in gene expression via modulation of protein-protein interactions or transcription anti-termination.
Collapse
Affiliation(s)
- Julien Herrou
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA; Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Aretha Fiebig
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.
| |
Collapse
|
14
|
Losi A, Gärtner W. Solving Blue Light Riddles: New Lessons from Flavin-binding LOV Photoreceptors. Photochem Photobiol 2017; 93:141-158. [PMID: 27861974 DOI: 10.1111/php.12674] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Accepted: 10/22/2016] [Indexed: 12/15/2022]
Abstract
Detection of blue light (BL) via flavin-binding photoreceptors (Fl-Blues) has evolved throughout all three domains of life. Although the main BL players, that is light, oxygen and voltage (LOV), blue light sensing using flavins (BLUF) and Cry (cryptochrome) proteins, have been characterized in great detail with respect to structure and function, still several unresolved issues at different levels of complexity remain and novel unexpected findings were reported. Here, we review the most prevailing riddles of LOV-based photoreceptors, for example: the relevance of water and/or small metabolites for the dynamics of the photocycle; molecular details of light-to-signal transduction events; the interplay of BL sensing by LOV domains with other environmental stimuli, such as BL plus oxygen-mediating photodamage and its impact on microbial lifestyles; the importance of the cell or chromophore redox state in determining the fate of BL-driven reactions; the evolutionary pathways of LOV-based BL sensing and associated functions through the diverse phyla. We will discuss major novelties emerged during the last few years on these intriguing aspects of LOV proteins by presenting paradigmatic examples from prokaryotic photosensors that exhibit the largest complexity and richness in associated functions.
Collapse
Affiliation(s)
- Aba Losi
- Department of Physics and Earth Sciences, University of Parma, Parma, Italy
| | - Wolfgang Gärtner
- Max-Planck-Institute for Chemical Energy Conversion, Mülheim, Germany
| |
Collapse
|
15
|
Corrêa F, Gardner KH. Basis of Mutual Domain Inhibition in a Bacterial Response Regulator. Cell Chem Biol 2016; 23:945-954. [PMID: 27524295 DOI: 10.1016/j.chembiol.2016.07.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 06/12/2016] [Accepted: 07/08/2016] [Indexed: 01/12/2023]
Abstract
Information transmission in biological signaling networks is commonly considered to be a unidirectional flow of information between protein partners. According to this view, many bacterial response regulator proteins utilize input receiver (REC) domains to "switch" functional outputs, using REC phosphorylation to shift pre-existing equilibria between inactive and active conformations. However, recent data indicate that output domains themselves also shift such equilibria, implying a "mutual inhibition" model. Here we use solution nuclear magnetic resonance to provide a mechanistic basis for such control in a PhyR-type response regulator. Our structure of the isolated, non-phosphorylated REC domain surprisingly reveals a fully active conformation, letting us identify structural and dynamic changes imparted by the output domain to inactivate the full-length protein. Additional data reveal transient structural changes within the full-length protein, facilitating activation. Our data provide a basis for understanding the changes that REC and output domains undergo to set a default "inactive" state.
Collapse
Affiliation(s)
- Fernando Corrêa
- Structural Biology Initiative, CUNY Advanced Science Research Center, New York, NY 10031, USA
| | - Kevin H Gardner
- Structural Biology Initiative, CUNY Advanced Science Research Center, New York, NY 10031, USA; Department of Chemistry and Biochemistry, City College of New York, New York, NY 10031, USA; Biochemistry, Chemistry and Biology PhD Programs, Graduate Center, The City University of New York, New York, NY 10016, USA.
| |
Collapse
|
16
|
Glantz ST, Carpenter EJ, Melkonian M, Gardner KH, Boyden ES, Wong GKS, Chow BY. Functional and topological diversity of LOV domain photoreceptors. Proc Natl Acad Sci U S A 2016; 113:E1442-51. [PMID: 26929367 PMCID: PMC4801262 DOI: 10.1073/pnas.1509428113] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Light-oxygen-voltage sensitive (LOV) flavoproteins are ubiquitous photoreceptors that mediate responses to environmental cues. Photosensory inputs are transduced into signaling outputs via structural rearrangements in sensor domains that consequently modulate the activity of an effector domain or multidomain clusters. Establishing the diversity in effector function and sensor-effector topology will inform what signaling mechanisms govern light-responsive behaviors across multiple kingdoms of life and how these signals are transduced. Here, we report the bioinformatics identification of over 6,700 candidate LOV domains (including over 4,000 previously unidentified sequences from plants and protists), and insights from their annotations for ontological function and structural arrangements. Motif analysis identified the sensors from ∼42 million ORFs, with strong statistical separation from other flavoproteins and non-LOV members of the structurally related Per-aryl hydrocarbon receptor nuclear translocator (ARNT)-Sim family. Conserved-domain analysis determined putative light-regulated function and multidomain topologies. We found that for certain effectors, sensor-effector linker length is discretized based on both phylogeny and the preservation of α-helical heptad repeats within an extended coiled-coil linker structure. This finding suggests that preserving sensor-effector orientation is a key determinant of linker length, in addition to ancestry, in LOV signaling structure-function. We found a surprisingly high prevalence of effectors with functions previously thought to be rare among LOV proteins, such as regulators of G protein signaling, and discovered several previously unidentified effectors, such as lipases. This work highlights the value of applying genomic and transcriptomic technologies to diverse organisms to capture the structural and functional variation in photosensory proteins that are vastly important in adaptation, photobiology, and optogenetics.
Collapse
Affiliation(s)
- Spencer T Glantz
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104
| | - Eric J Carpenter
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9
| | - Michael Melkonian
- Institute of Botany, Cologne Biocenter, University of Cologne, 50674 Cologne, Germany
| | - Kevin H Gardner
- Structural Biology Initiative, CUNY Advanced Science Research Center, City College of New York, New York, NY 10031; Department of Chemistry and Biochemistry, City College of New York, New York, NY 10031; Biochemistry, Chemistry and Biology Programs, Graduate Center, The City University of New York, New York, NY 10031
| | - Edward S Boyden
- The Media Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139; Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139; McGovern Institute for Brain Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Gane Ka-Shu Wong
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9; Department of Medicine, University of Alberta, Edmonton, AB, Canada T6G 2E1; BGI-Shenzhen, Beishan Industrial Zone, Yantian District, Shenzhen 518083, China
| | - Brian Y Chow
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104;
| |
Collapse
|
17
|
Abstract
The Alphaproteobacteria uniquely integrate features of two-component signal transduction and alternative σ factor regulation to control transcription of genes that ensure growth and survival across a range of stress conditions. Research over the past decade has led to the discovery of the key molecular players of this general stress response (GSR) system, including the sigma factor σ(EcfG), its anti-σ factor NepR, and the anti-anti-σ factor PhyR. The central molecular event of GSR activation entails aspartyl phosphorylation of PhyR, which promotes its binding to NepR and thereby releases σ(EcfG) to associate with RNAP and direct transcription. Recent studies are providing a new understanding of complex, multilayered sensory networks that activate and repress this central protein partner switch. This review synthesizes our structural and functional understanding of the core GSR regulatory proteins and highlights emerging data that are defining the systems that regulate GSR transcription in a variety of species.
Collapse
Affiliation(s)
- Aretha Fiebig
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - Julien Herrou
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - Jonathan Willett
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| |
Collapse
|
18
|
Losi A, Mandalari C, Gärtner W. The Evolution and Functional Role of Flavin-based Prokaryotic Photoreceptors. Photochem Photobiol 2015; 91:1021-31. [DOI: 10.1111/php.12489] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 06/15/2015] [Indexed: 12/12/2022]
Affiliation(s)
- Aba Losi
- Department of Physics and Earth Sciences; University of Parma; Parma Italy
| | - Carmen Mandalari
- Department of Physics and Earth Sciences; University of Parma; Parma Italy
| | - Wolfgang Gärtner
- Max-Planck-Institute for Chemical Energy Conversion; Mülheim Germany
| |
Collapse
|
19
|
Abstract
The anti-σ factor NepR plays a central role in regulation of the general stress response (GSR) in alphaproteobacteria. This small protein has two known interaction partners: its cognate extracytoplasmic function (ECF) σ factor and the anti-anti-σ factor, PhyR. Stress-dependent phosphorylation of PhyR initiates a protein partner switch that promotes phospho-PhyR binding to NepR, which frees ECF σ to activate transcription of genes required for cell survival under adverse or fluctuating conditions. We have defined key functional roles for structured and intrinsically disordered domains of Caulobacter crescentus NepR in partner binding and activation of GSR transcription. We further demonstrate that NepR strongly stimulates the rate of PhyR phosphorylation in vitro and that this effect requires the structured and disordered domains of NepR. This result provides evidence for an additional layer of GSR regulation in which NepR directly influences activation of its binding partner, PhyR, as an anti-anti-σ factor. We conclude that structured and intrinsically disordered domains of NepR coordinately control multiple functions in the GSR signaling pathway, including core protein partner switch interactions and pathway activation by phosphorylation. Anti-σ factors are key molecular participants in a range of adaptive responses in bacteria. The anti-σ factor NepR plays a vital role in a multiprotein partner switch that governs general stress response (GSR) transcription in alphaproteobacteria. We have defined conserved and unconserved features of NepR structure that determine its function as an anti-σ factor and uncovered a functional role for intrinsically disordered regions of NepR in partner binding events required for GSR activation. We further demonstrate a novel function for NepR as an enhancer of PhyR phosphorylation; this activity also requires the disordered domains of NepR. Our results provide evidence for a new layer of GSR regulatory control in which NepR directly modulates PhyR phosphorylation and, hence, activation of the GSR.
Collapse
|
20
|
The general stress response in Alphaproteobacteria. Trends Microbiol 2015; 23:164-71. [DOI: 10.1016/j.tim.2014.12.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 12/08/2014] [Accepted: 12/09/2014] [Indexed: 11/18/2022]
|
21
|
Ocasio VJ, Corrêa F, Gardner KH. Ligand-induced folding of a two-component signaling receiver domain. Biochemistry 2015; 54:1353-63. [PMID: 25629646 DOI: 10.1021/bi501143b] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
To survive and adapt to environmental changes, bacteria commonly use two-component signaling systems. Minimally, these pathways use histidine kinases (HKs) to detect environmental signals, harnessing these to control phosphorylation levels of receiver (REC) domains of downstream response regulators that convert this signal into physiological responses. Studies of several prototypical REC domains suggest that phosphorylation shifts these proteins between inactive and active structures that are globally similar and well-folded. However, it is unclear how globally these findings hold within REC domains in general, particularly when they are considered within full-length proteins. Here, we present EL_LovR, a full-length REC-only protein that is phosphorylated in response to blue light in the marine α-proteobacterium, Erythrobacter litoralis HTCC2594. Notably, EL_LovR is similar to comparable REC-only proteins used in bacterial general stress responses, where genetic evidence suggests that their potent phosphatase activity is important to shut off such systems. Size exclusion chromatography, light scattering, and solution NMR experiments show that EL_LovR is monomeric and unfolded in solution under conditions routinely used for other REC structure determinations. Addition of Mg(2+) and phosphorylation induce progressively greater degrees of tertiary structure stabilization, with the solution structure of the fully activated EL_LovR adopting the canonical receiver domain fold. Parallel functional assays show that EL_LovR has a fast dephosphorylation rate, consistent with its proposed function as a phosphate sink that depletes the HK phosphoryl group, promoting the phosphatase activity of this enzyme. Our findings demonstrate that EL_LovR undergoes substantial ligand-dependent conformational changes that have not been reported for other RRs, expanding the scope of conformational changes and regulation used by REC domains, critical components of bacterial signaling systems.
Collapse
Affiliation(s)
- Victor J Ocasio
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center , Dallas, Texas 75390-8816, United States
| | | | | |
Collapse
|
22
|
Sycz G, Carrica MC, Tseng TS, Bogomolni RA, Briggs WR, Goldbaum FA, Paris G. LOV Histidine Kinase Modulates the General Stress Response System and Affects the virB Operon Expression in Brucella abortus. PLoS One 2015; 10:e0124058. [PMID: 25993430 PMCID: PMC4438053 DOI: 10.1371/journal.pone.0124058] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 03/05/2015] [Indexed: 12/31/2022] Open
Abstract
Brucella is the causative agent of the zoonotic disease brucellosis, and its success as an intracellular pathogen relies on its ability to adapt to the harsh environmental conditions that it encounters inside the host. The Brucella genome encodes a sensor histidine kinase containing a LOV domain upstream from the kinase, LOVHK, which plays an important role in light-regulated Brucella virulence. In this report we study the intracellular signaling pathway initiated by the light sensor LOVHK using an integrated biochemical and genetic approach. From results of bacterial two-hybrid assays and phosphotransfer experiments we demonstrate that LOVHK functionally interacts with two response regulators: PhyR and LovR, constituting a functional two-component signal-transduction system. LOVHK contributes to the activation of the General Stress Response (GSR) system in Brucella via PhyR, while LovR is proposed to be a phosphate-sink for LOVHK, decreasing its phosphorylation state. We also show that in the absence of LOVHK the expression of the virB operon is down-regulated. In conclusion, our results suggest that LOVHK positively regulates the GSR system in vivo, and has an effect on the expression of the virB operon. The proposed regulatory network suggests a similar role for LOVHK in other microorganisms.
Collapse
Affiliation(s)
- Gabriela Sycz
- Laboratorio de Inmunología y Microbiología Molecular, Fundación Instituto Leloir (IIBBA-CONICET), Buenos Aires, Argentina
| | - Mariela Carmen Carrica
- Laboratorio de Inmunología y Microbiología Molecular, Fundación Instituto Leloir (IIBBA-CONICET), Buenos Aires, Argentina
| | - Tong-Seung Tseng
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California, United States of America
| | - Roberto A. Bogomolni
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Winslow R. Briggs
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California, United States of America
| | - Fernando A. Goldbaum
- Laboratorio de Inmunología y Microbiología Molecular, Fundación Instituto Leloir (IIBBA-CONICET), Buenos Aires, Argentina
| | - Gastón Paris
- Laboratorio de Inmunología y Microbiología Molecular, Fundación Instituto Leloir (IIBBA-CONICET), Buenos Aires, Argentina
- * E-mail:
| |
Collapse
|
23
|
Full-length structure of a monomeric histidine kinase reveals basis for sensory regulation. Proc Natl Acad Sci U S A 2014; 111:17839-44. [PMID: 25468971 DOI: 10.1073/pnas.1413983111] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Although histidine kinases (HKs) are critical sensors of external stimuli in prokaryotes, the mechanisms by which their sensor domains control enzymatic activity remain unclear. Here, we report the full-length structure of a blue light-activated HK from Erythrobacter litoralis HTCC2594 (EL346) and the results of biochemical and biophysical studies that explain how it is activated by light. Contrary to the standard view that signaling occurs within HK dimers, EL346 functions as a monomer. Its structure reveals that the light-oxygen-voltage (LOV) sensor domain both controls kinase activity and prevents dimerization by binding one side of a dimerization/histidine phosphotransfer-like (DHpL) domain. The DHpL domain also contacts the catalytic/ATP-binding (CA) domain, keeping EL346 in an inhibited conformation in the dark. Upon light stimulation, interdomain interactions weaken to facilitate activation. Our data suggest that the LOV domain controls kinase activity by affecting the stability of the DHpL/CA interface, releasing the CA domain from an inhibited conformation upon photoactivation. We suggest parallels between EL346 and dimeric HKs, with sensor-induced movements in the DHp similarly remodeling the DHp/CA interface as part of activation.
Collapse
|
24
|
Complex two-component signaling regulates the general stress response in Alphaproteobacteria. Proc Natl Acad Sci U S A 2014; 111:E5196-204. [PMID: 25404331 DOI: 10.1073/pnas.1410095111] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The general stress response (GSR) in Alphaproteobacteria was recently shown to be controlled by a partner-switching mechanism that is triggered by phosphorylation of the response regulator PhyR. Activation of PhyR ultimately results in release of the alternative extracytoplasmic function sigma factor σ(EcfG), which redirects transcription toward the GSR. Little is known about the signal transduction pathway(s) controlling PhyR phosphorylation. Here, we identified the single-domain response regulator (SDRR) SdrG and seven histidine kinases, PakA to PakG, belonging to the HWE/HisKA2 family as positive modulators of the GSR in Sphingomonas melonis Fr1. Phenotypic analyses, epistasis experiments, and in vitro phosphorylation assays indicate that Paks directly phosphorylate PhyR and SdrG, and that SdrG acts upstream of or in concert with PhyR, modulating its activity in a nonlinear pathway. Furthermore, we found that additional SDRRs negatively affect the GSR in a way that strictly requires PhyR and SdrG. Finally, analysis of GSR activation by thermal, osmotic, and oxidative stress indicates that Paks display different degrees of redundancy and that a specific kinase can sense multiple stresses, suggesting that the GSR senses a particular condition as a combination of, rather than individual, molecular cues. This study thus establishes the alphaproteobacterial GSR as a complex and interlinked network of two-component systems, in which multiple histidine kinases converge to PhyR, the phosphorylation of which is, in addition, subject to regulation by several SDRRs. Our finding that most HWE/HisKA2 kinases contribute to the GSR in S. melonis Fr1 opens the possibility that this notion might also be true for other Alphaproteobacteria.
Collapse
|
25
|
Kim HS, Willett JW, Jain-Gupta N, Fiebig A, Crosson S. The Brucella abortus virulence regulator, LovhK, is a sensor kinase in the general stress response signalling pathway. Mol Microbiol 2014; 94:913-25. [PMID: 25257300 DOI: 10.1111/mmi.12809] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2014] [Indexed: 12/11/2022]
Abstract
In the intracellular pathogen Brucella abortus, the general stress response (GSR) signalling system determines survival under acute stress conditions in vitro, and is required for long-term residence in a mammalian host. To date, the identity of the Brucella sensor kinase(s) that function to perceive stress and directly activate GSR signalling have remained undefined. We demonstrate that the flavin-binding sensor histidine kinase, LovhK (bab2_0652), functions as a primary B. abortus GSR sensor. LovhK rapidly and specifically phosphorylates the central GSR regulator, PhyR, and activates transcription of a set of genes that closely overlaps the known B. abortus GSR regulon. Deletion of lovhK severely compromises cell survival under defined oxidative and acid stress conditions. We further show that lovhK is required for cell survival during the early phase of mammalian cell infection and for establishment of long-term residence in a mouse infection model. Finally, we present evidence that particular regions of primary structure within the two N-terminal PAS domains of LovhK have distinct sensory roles under specific environmental conditions. This study elucidates new molecular components of a conserved signalling pathway that regulates B. abortus stress physiology and infection biology.
Collapse
Affiliation(s)
- Hye-Sook Kim
- The Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA; Howard Taylor Ricketts Laboratory, University of Chicago, Argonne National Laboratory, Argonne, IL, USA
| | | | | | | | | |
Collapse
|
26
|
A putative bifunctional histidine kinase/phosphatase of the HWE family exerts positive and negative control on the Sinorhizobium meliloti general stress response. J Bacteriol 2014; 196:2526-35. [PMID: 24794560 DOI: 10.1128/jb.01623-14] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The EcfG-type sigma factor RpoE2 is the regulator of the general stress response in Sinorhizobium meliloti. RpoE2 activity is negatively regulated by two NepR-type anti-sigma factors (RsiA1/A2), themselves under the control of two anti-anti-sigma factors (RsiB1/B2) belonging to the PhyR family of response regulators. The current model of RpoE2 activation suggests that in response to stress, RsiB1/B2 are activated by phosphorylation of an aspartate residue in their receiver domain. Once activated, RsiB1/B2 become able to interact with the anti-sigma factors and release RpoE2, which can then associate with the RNA polymerase to transcribe its target genes. The purpose of this work was to identify and characterize proteins involved in controlling the phosphorylation status of RsiB1/B2. Using in vivo approaches, we show that the putative histidine kinase encoded by the rsiC gene (SMc01507), located downstream from rpoE2, is able to both positively and negatively regulate the general stress response. In addition, our data suggest that the negative action of RsiC results from inhibition of RsiB1/B2 phosphorylation. From these observations, we propose that RsiC is a bifunctional histidine kinase/phosphatase responsible for RsiB1/B2 phosphorylation or dephosphorylation in the presence or absence of stress, respectively. Two proteins were previously proposed to control PhyR phosphorylation in Caulobacter crescentus and Sphingomonas sp. strain FR1. However, these proteins contain a Pfam:HisKA_2 domain of dimerization and histidine phosphotransfer, whereas S. meliloti RsiC harbors a Pfam:HWE_HK domain instead. Therefore, this is the first report of an HWE_HK-containing protein controlling the general stress response in Alphaproteobacteria.
Collapse
|
27
|
From Plant Infectivity to Growth Patterns: The Role of Blue-Light Sensing in the Prokaryotic World. PLANTS 2014; 3:70-94. [PMID: 27135492 PMCID: PMC4844311 DOI: 10.3390/plants3010070] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 01/14/2014] [Accepted: 01/15/2014] [Indexed: 01/15/2023]
Abstract
Flavin-based photoreceptor proteins of the LOV (Light, Oxygen, and Voltage) and BLUF (Blue Light sensing Using Flavins) superfamilies are ubiquitous among the three life domains and are essential blue-light sensing systems, not only in plants and algae, but also in prokaryotes. Here we review their biological roles in the prokaryotic world and their evolution pathways. An unexpected large number of bacterial species possess flavin-based photosensors, amongst which are important human and plant pathogens. Still, few cases are reported where the activity of blue-light sensors could be correlated to infectivity and/or has been shown to be involved in the activation of specific genes, resulting in selective growth patterns. Metagenomics and bio-informatic analysis have only recently been initiated, but signatures are beginning to emerge that allow definition of a bona fide LOV or BLUF domain, aiming at better selection criteria for novel blue-light sensors. We also present here, for the first time, the phylogenetic tree for archaeal LOV domains that have reached a statistically significant number but have not at all been investigated thus far.
Collapse
|