1
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Chen X, Bi S, Ma X, Sourjik V, Lai L. Discovery of a New Chemoeffector for Escherichia coli Chemoreceptor Tsr and Identification of a Molecular Mechanism of Repellent Sensing. ACS BIO & MED CHEM AU 2022; 2:386-394. [PMID: 37102165 PMCID: PMC10125284 DOI: 10.1021/acsbiomedchemau.1c00055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Motile bacteria use chemotaxis to search for nutrients and escape from harmful chemicals. While the sensing mechanisms for chemical attractants are well established, the molecular details of chemorepellent detection are poorly understood. Here, by using combined computational and experimental approaches to screen potential chemoeffectors for the Escherichia coli chemoreceptor Tsr, we identified a specific chemorepellent, 1-aminocyclohexanecarboxylic acid (ACHC). Our study strongly suggests that ACHC directly binds to the periplasmic sensory domain of Tsr and competes with l-serine, the amino acid attractant of Tsr. We further characterized the binding features of l-serine, ACHC, and l-leucine (a natural repellent that binds Tsr) and found that Asn68 plays a key role in mediating chemotactic response. Mutating Asn68 to Ala inverted the response to l-leucine from a repellent to an attractant. Our study provides important insights into the molecular mechanisms of ligand sensing via bacterial chemoreceptors.
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Affiliation(s)
- Xi Chen
- BNLMS,
Peking-Tsinghua Center for Life Sciences at College of Chemistry and
Molecular Engineering, Peking University, Beijing 100871, China
- Center
for Quantitative Biology, Academy of Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Shuangyu Bi
- Max
Planck Institute for Terrestrial Microbiology & LOEWE Center for
Synthetic Microbiology (SYNMIKRO), Marburg 35043, Germany
- State
Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Xiaomin Ma
- BNLMS,
Peking-Tsinghua Center for Life Sciences at College of Chemistry and
Molecular Engineering, Peking University, Beijing 100871, China
- Center
for Quantitative Biology, Academy of Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Victor Sourjik
- Max
Planck Institute for Terrestrial Microbiology & LOEWE Center for
Synthetic Microbiology (SYNMIKRO), Marburg 35043, Germany
| | - Luhua Lai
- BNLMS,
Peking-Tsinghua Center for Life Sciences at College of Chemistry and
Molecular Engineering, Peking University, Beijing 100871, China
- Center
for Quantitative Biology, Academy of Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
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2
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Mensa B, Polizzi NF, Molnar KS, Natale AM, Lemmin T, DeGrado WF. Allosteric mechanism of signal transduction in the two-component system histidine kinase PhoQ. eLife 2021; 10:73336. [PMID: 34904568 PMCID: PMC8719878 DOI: 10.7554/elife.73336] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 12/13/2021] [Indexed: 12/05/2022] Open
Abstract
Transmembrane signaling proteins couple extracytosolic sensors to cytosolic effectors. Here, we examine how binding of Mg2+ to the sensor domain of an E. coli two component histidine kinase (HK), PhoQ, modulates its cytoplasmic kinase domain. We use cysteine-crosslinking and reporter-gene assays to simultaneously and independently probe the signaling state of PhoQ’s sensor and autokinase domains in a set of over 30 mutants. Strikingly, conservative single-site mutations distant from the sensor or catalytic site strongly influence PhoQ’s ligand-sensitivity as well as the magnitude and direction of the signal. Data from 35 mutants are explained by a semi-empirical three-domain model in which the sensor, intervening HAMP, and catalytic domains can adopt kinase-promoting or inhibiting conformations that are in allosteric communication. The catalytic and sensor domains intrinsically favor a constitutively ‘kinase-on’ conformation, while the HAMP domain favors the ‘off’ state; when coupled, they create a bistable system responsive to physiological concentrations of Mg2+. Mutations alter signaling by locally modulating domain intrinsic equilibrium constants and interdomain couplings. Our model suggests signals transmit via interdomain allostery rather than propagation of a single concerted conformational change, explaining the diversity of signaling structural transitions observed in individual HK domains.
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Affiliation(s)
- Bruk Mensa
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States.,Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States.,Chemistry and Chemical Biology PhD program, University of California, San Francisco, San Francisco, United States
| | - Nicholas F Polizzi
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | | | - Andrew M Natale
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States.,Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States.,Biophysics PhD program, University of California, San Francisco, San Francisco, United States
| | - Thomas Lemmin
- Euler Institute, Università della Svizzera Italiana, Lugano, Switzerland
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States.,Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States
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3
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Bi S, Jin F, Sourjik V. Inverted signaling by bacterial chemotaxis receptors. Nat Commun 2018; 9:2927. [PMID: 30050034 PMCID: PMC6062612 DOI: 10.1038/s41467-018-05335-w] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 07/02/2018] [Indexed: 11/09/2022] Open
Abstract
Microorganisms use transmembrane sensory receptors to perceive a wide range of environmental factors. It is unclear how rapidly the sensory properties of these receptors can be modified when microorganisms adapt to novel environments. Here, we demonstrate experimentally that the response of an Escherichia coli chemotaxis receptor to its chemical ligands can be easily inverted by mutations at several sites along receptor sequence. We also perform molecular dynamics simulations to shed light on the mechanism of the transmembrane signaling by E. coli chemoreceptors. Finally, we use receptors with inverted signaling to map determinants that enable the same receptor to sense multiple environmental factors, including metal ions, aromatic compounds, osmotic pressure, and salt ions. Our findings demonstrate high plasticity of signaling and provide further insights into the mechanisms of stimulus sensing and processing by bacterial chemoreceptors. Bacteria use chemotaxis receptors to perceive environmental factors. Here, the authors show that mutations in a chemotaxis receptor can invert the sensory response, e.g. from attractant to repellent, and use these mutants to map regions that enable the receptor to sense multiple environmental factors.
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Affiliation(s)
- Shuangyu Bi
- Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, 35043, Germany
| | - Fan Jin
- Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, 35043, Germany
| | - Victor Sourjik
- Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, 35043, Germany.
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4
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Yusuf R, Lawrence RJ, Eke LV, Draheim RR. Tuning Chemoreceptor Signaling by Positioning Aromatic Residues at the Lipid-Aqueous Interface. Methods Mol Biol 2018; 1729:147-158. [PMID: 29429090 DOI: 10.1007/978-1-4939-7577-8_14] [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] [Indexed: 06/08/2023]
Abstract
Aromatic tuning facilitates stimulus-independent modulation of receptor output. The methodology is based upon the affinity of amphipathic aromatic residues, namely Trp and Tyr, for the polar-hydrophobic interfaces found within biological membranes. Here, we describe the application of aromatic tuning within the aspartate chemoreceptor of Escherichia coli (Tar). We have also employed the method within other related proteins, such as sensor histidine kinases (SHKs), and therefore hope that other research groups find it useful to modulate signal output from their receptor of interest.
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Affiliation(s)
- Rahmi Yusuf
- School of Pharmacy and Biomedical Sciences, Institute of Biological and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - Robert J Lawrence
- School of Pharmacy and Biomedical Sciences, Institute of Biological and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - Lucy V Eke
- School of Pharmacy and Biomedical Sciences, Institute of Biological and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - Roger R Draheim
- School of Pharmacy and Biomedical Sciences, Institute of Biological and Biomedical Sciences, University of Portsmouth, Portsmouth, UK.
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5
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Gushchin I, Gordeliy V. Transmembrane Signal Transduction in Two-Component Systems: Piston, Scissoring, or Helical Rotation? Bioessays 2017; 40. [PMID: 29280502 DOI: 10.1002/bies.201700197] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Revised: 11/30/2017] [Indexed: 11/10/2022]
Abstract
Allosteric and transmembrane (TM) signaling are among the major questions of structural biology. Here, we review and discuss signal transduction in four-helical TM bundles, focusing on histidine kinases and chemoreceptors found in two-component systems. Previously, piston, scissors, and helical rotation have been proposed as the mechanisms of TM signaling. We discuss theoretically possible conformational changes and examine the available experimental data, including the recent crystallographic structures of nitrate/nitrite sensor histidine kinase NarQ and phototaxis system NpSRII:NpHtrII. We show that TM helices can flex at multiple points and argue that the various conformational changes are not mutually exclusive, and often are observed concomitantly, throughout the TM domain or in its part. The piston and scissoring motions are the most prominent motions in the structures, but more research is needed for definitive conclusions.
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Affiliation(s)
- Ivan Gushchin
- Moscow Institute of Physics and Technology, 141700, Dolgoprudniy, Russia
| | - Valentin Gordeliy
- Moscow Institute of Physics and Technology, 141700, Dolgoprudniy, Russia.,Université Grenoble Alpes, CEA, CNRS, IBS, F-38000, Grenoble, France.,Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425, Jülich, Germany
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6
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Lehning CE, Heidelberger JB, Reinhard J, Nørholm MHH, Draheim RR. A Modular High-Throughput In Vivo Screening Platform Based on Chimeric Bacterial Receptors. ACS Synth Biol 2017; 6:1315-1326. [PMID: 28372360 DOI: 10.1021/acssynbio.6b00288] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Multidrug resistance (MDR) is a globally relevant problem that requires novel approaches. Two-component systems are a promising, yet untapped target for novel antibacterials. They are prevalent in bacteria and absent in mammals, and their activity can be modulated upon perception of various stimuli. Screening pre-existing compound libraries could reveal small molecules that inhibit stimulus-perception by virulence-modulating receptors, reduce signal output from essential receptors or identify artificial stimulatory ligands for novel SHKs that are involved in virulence. Those small molecules could possess desirable therapeutic properties to combat MDR. We propose that a modular screening platform in which the periplasmic domain of the targeted receptors are fused to the cytoplasmic domain of a well-characterized receptor that governs fluorescence reporter genes could be employed to rapidly screen currently existing small molecule libraries. Here, we have examined two previously created Tar-EnvZ chimeras and a novel NarX-EnvZ chimera. We demonstrate that it is possible to couple periplasmic stimulus-perceiving domains to an invariable cytoplasmic domain that governs transcription of a dynamic fluorescent reporter system. Furthermore, we show that aromatic tuning, or repositioning the aromatic residues at the end of the second transmembrane helix (TM2), modulates baseline signal output from the tested chimeras and even restores output from a nonfunctional NarX-EnvZ chimera. Finally, we observe an inverse correlation between baseline signal output and the degree of response to cognate stimuli. In summary, we propose that the platform described here, a fluorescent Escherichia coli reporter strain with plasmid-based expression of the aromatically tuned chimeric receptors, represents a synthetic biology approach to rapidly screen pre-existing compound libraries for receptor-modulating activities.
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Affiliation(s)
- Christina E. Lehning
- Novo
Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Building 220, Kemitorvet, DK-2800, Kgs. Lyngby, Denmark
| | | | - John Reinhard
- Buchmann
Institute for Molecular Life Sciences, Goethe University Frankfurt, Max-von-Laue-Straße 15, D-60438, Frankfurt, Germany
| | - Morten H. H. Nørholm
- Novo
Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Building 220, Kemitorvet, DK-2800, Kgs. Lyngby, Denmark
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7
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Ames P, Hunter S, Parkinson JS. Evidence for a Helix-Clutch Mechanism of Transmembrane Signaling in a Bacterial Chemoreceptor. J Mol Biol 2016; 428:3776-88. [PMID: 27019297 PMCID: PMC5023463 DOI: 10.1016/j.jmb.2016.03.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/14/2016] [Accepted: 03/15/2016] [Indexed: 11/19/2022]
Abstract
The Escherichia coli Tsr protein contains a periplasmic serine-binding domain that transmits ligand occupancy information to a cytoplasmic kinase-control domain to regulate the cell's flagellar motors. The Tsr input and output domains communicate through conformational changes transmitted through a transmembrane helix (TM2), a five-residue control cable helix at the membrane-cytoplasm interface, and a four-helix HAMP bundle. Changes in serine occupancy are known to promote TM2 piston displacements in one subunit of the Tsr homodimer. We explored how such piston motions might be relayed through the control cable to reach the input AS1 helix of HAMP by constructing and characterizing mutant receptors that had one-residue insertions or deletions in the TM2-control cable segment of Tsr. TM2 deletions caused kinase-off output shifts; TM2 insertions caused kinase-on shifts. In contrast, control cable deletions caused kinase-on output, whereas insertions at the TM2-control cable junction caused kinase-off output. These findings rule out direct mechanical transmission of TM2 conformational changes to HAMP. Instead, we suggest that the Tsr control cable transmits input signals to HAMP by modulating the intensity of structural clashes between out-of-register TM2 and AS1 helices. Inward displacement of TM2 might alter the sidechain environment of control cable residues at the membrane core-headgroup interface, causing a break in the control cable helix to attenuate the register mismatch and enhance HAMP packing stability, leading to a kinase-off output response. This helix-clutch model offers a new perspective on the mechanism of transmembrane signaling in chemoreceptors.
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Affiliation(s)
- Peter Ames
- Biology Department, University of Utah, Salt Lake City, Utah 84112, USA
| | - Samuel Hunter
- Biology Department, University of Utah, Salt Lake City, Utah 84112, USA
| | - John S Parkinson
- Biology Department, University of Utah, Salt Lake City, Utah 84112, USA.
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8
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Mise T. Structural Analysis of the Ligand-Binding Domain of the Aspartate Receptor Tar from Escherichia coli. Biochemistry 2016; 55:3708-13. [DOI: 10.1021/acs.biochem.6b00160] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Takeshi Mise
- 2-19-3 Misato, Okinawa-shi, Okinawa 904-2153, Japan
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9
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Heininger A, Yusuf R, Lawrence RJ, Draheim RR. Identification of transmembrane helix 1 (TM1) surfaces important for EnvZ dimerisation and signal output. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1868-75. [PMID: 27155567 DOI: 10.1016/j.bbamem.2016.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 04/12/2016] [Accepted: 05/03/2016] [Indexed: 02/06/2023]
Abstract
The Escherichia coli sensor kinase EnvZ modulates porin expression in response to various stimuli, including extracellular osmolarity, the presence of procaine and interaction with an accessory protein, MzrA. Two major outer membrane porins, OmpF and OmpC, act as passive diffusion-limited pores that allow compounds, including certain classes of antibiotics such as β-lactams and fluoroquinolones, to enter the bacterial cell. Even though the mechanisms by which EnvZ detects and processes the presence of various stimuli are a fundamental component of microbial physiology, they are not yet fully understood. Here, we assess the role of TM1 during signal transduction in response to the presence of extracellular osmolarity. Various mechanisms of transmembrane communication have been proposed including rotation of individual helices within the transmembrane domain, dynamic movement of the membrane-distal portion of the cytoplasmic domain and regulated intra-protein unfolding. To assess these possibilities, we have created a library of single-Cys-containing EnvZ proteins in order to facilitate sulfhydryl-reactivity experimentation. Our results demonstrate that the major TM1-TM1' interface falls along a single surface consisting of residue positions 19, 23, 26, 30 and 34. In addition, we show that Cys substitutions within the N- and C-terminal regions of TM1 result in drastic changes to EnvZ signal output. Finally, we demonstrate that core residues within TM1 are responsible for both TM1 dimerisation and maintenance of steady-state signal output. Overall, our results suggest that no major rearrangement of the TM1-TM1' interface occurs during transmembrane communication in response to extracellular osmolarity. We conclude by discussing these results within the frameworks of several proposed models for transmembrane communication.
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Affiliation(s)
- Annika Heininger
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, D-60438 Frankfurt, Germany.
| | - Rahmi Yusuf
- School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth PO1 2DT, England, UK.
| | - Robert J Lawrence
- School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth PO1 2DT, England, UK.
| | - Roger R Draheim
- School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth PO1 2DT, England, UK; Institute of Biomedical and Biomolecular Science, University of Portsmouth, Portsmouth PO1 2DT, England, UK.
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10
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A Trigger Residue for Transmembrane Signaling in the Escherichia coli Serine Chemoreceptor. J Bacteriol 2015; 197:2568-79. [PMID: 26013490 DOI: 10.1128/jb.00274-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 05/18/2015] [Indexed: 01/10/2023] Open
Abstract
UNLABELLED The transmembrane Tsr protein of Escherichia coli mediates chemotactic responses to environmental serine gradients. Serine binds to the periplasmic domain of the homodimeric Tsr molecule, promoting a small inward displacement of one transmembrane helix (TM2). TM2 piston displacements, in turn, modulate the structural stability of the Tsr-HAMP domain on the cytoplasmic side of the membrane to control the autophosphorylation activity of the signaling CheA kinase bound to the membrane-distal cytoplasmic tip of Tsr. A five-residue control cable segment connects TM2 to the AS1 helix of HAMP and transmits stimulus and sensory adaptation signals between them. To explore the possible role of control cable helicity in transmembrane signaling by Tsr, we characterized the signaling properties of mutant receptors with various control cable alterations. An all-alanine control cable shifted Tsr output toward the kinase-on state, whereas an all-glycine control cable prevented Tsr from reaching either a fully on or fully off output state. Restoration of the native isoleucine (I214) in these synthetic control cables largely alleviated their signaling defects. Single amino acid replacements at Tsr-I214 shifted output toward the kinase-off (L, N, H, and R) or kinase-on (A and G) states, whereas other control cable residues tolerated most amino acid replacements with little change in signaling behavior. These findings indicate that changes in control cable helicity might mediate transitions between the kinase-on and kinase-off states during transmembrane signaling by chemoreceptors. Moreover, the Tsr-I214 side chain plays a key role, possibly through interaction with the membrane interfacial environment, in triggering signaling changes in response to TM2 piston displacements. IMPORTANCE The Tsr protein of E. coli mediates chemotactic responses to environmental serine gradients. Stimulus signals from the Tsr periplasmic sensing domain reach its cytoplasmic kinase control domain through piston displacements of a membrane-spanning helix and an adjoining five-residue control cable segment. We characterized the signaling properties of Tsr variants to elucidate the transmembrane signaling role of the control cable, an element present in many microbial sensory proteins. Both the kinase-on and kinase-off output states of Tsr depended on control cable helicity, but only one residue, I214, was critical for triggering responses to attractant inputs. These findings suggest that signal transmission in Tsr involves modulation of control cable helicity through interaction of the I214 side chain with the cytoplasmic membrane.
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11
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Yusuf R, Draheim RR. Employing aromatic tuning to modulate output from two-component signaling circuits. J Biol Eng 2015; 9:7. [PMID: 26000034 PMCID: PMC4440246 DOI: 10.1186/s13036-015-0003-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 05/01/2015] [Indexed: 11/10/2022] Open
Abstract
Two-component signaling circuits (TCSs) govern the majority of environmental, pathogenic and industrial processes undertaken by bacteria. Therefore, controlling signal output from these circuits in a stimulus-independent manner is of central importance to synthetic microbiologists. Aromatic tuning, or repositioning the aromatic residues commonly found at the cytoplasmic end of the final TM helix has been shown to modulate signal output from the aspartate chemoreceptor (Tar) and the major osmosensor (EnvZ) of Escherichia coli. Aromatic residues are found in a similar location within other bacterial membrane-spanning receptors, suggesting that aromatic tuning could be harnessed for a wide-range of applications. Here, a brief synopsis of the data underpinning aromatic tuning, the initial successes with the method and the inherent advantages over those previously employed for modulating TCS signal output are presented.
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Affiliation(s)
- Rahmi Yusuf
- Division of Pharmacy, Durham University, Queen's Campus, Stockton-on-Tees, TS17 6BH England UK
| | - Roger R Draheim
- School of Pharmacy and Biomedical Sciences, University of Portsmouth, St. Michael's Building, White Swan Road, Portsmouth, PO1 2DT, England UK
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12
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Nørholm MHH, von Heijne G, Draheim RR. Forcing the issue: aromatic tuning facilitates stimulus-independent modulation of a two-component signaling circuit. ACS Synth Biol 2015; 4:474-81. [PMID: 25162177 PMCID: PMC4410910 DOI: 10.1021/sb500261t] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two-component signaling circuits allow bacteria to detect and respond to external stimuli. Unfortunately, the input stimulus remains unidentified for the majority of these circuits. Therefore, development of a synthetic method for stimulus-independent modulation of these circuits is highly desirable because particular physiological or developmental processes could be controlled for biotechnological purposes without the need to identify the stimulus itself. Here, we demonstrate that aromatic tuning, i.e., repositioning the aromatic residues commonly found at the cytoplasmic end of the receptor (EnvZ) transmembrane domain, facilitates stimulus-independent modulation of signal output from the EnvZ/OmpR osmosensing circuit of Escherichia coli. We found that these osmosensing circuits retained the ability to respond appropriately to increased external osmolarity, suggesting that the tuned receptors were not locked in a single conformation. We also noted that circuits containing aromatically tuned variants became more sensitive to changes in the receptor concentration than their wild-type counterpart, suggesting a new way to study mechanisms underpinning receptor concentration-dependent robustness. We believe that aromatic tuning has several advantages compared to previous methods aimed at stimulus-independent modulation of receptors and that it will be generally applicable to a wide-range of two-component circuits.
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Affiliation(s)
- Morten H. H. Nørholm
- Novo
Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kogle Alle 6, DK-2970 Hørsholm, Denmark
| | - Gunnar von Heijne
- Department
of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius
väg 16C, SE-10691 Stockholm, Sweden
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13
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Parkinson JS, Hazelbauer GL, Falke JJ. Signaling and sensory adaptation in Escherichia coli chemoreceptors: 2015 update. Trends Microbiol 2015; 23:257-66. [PMID: 25834953 DOI: 10.1016/j.tim.2015.03.003] [Citation(s) in RCA: 253] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Revised: 03/03/2015] [Accepted: 03/04/2015] [Indexed: 11/25/2022]
Abstract
Motile Escherichia coli cells track gradients of attractant and repellent chemicals in their environment with transmembrane chemoreceptor proteins. These receptors operate in cooperative arrays to produce large changes in the activity of a signaling kinase, CheA, in response to small changes in chemoeffector concentration. Recent research has provided a much deeper understanding of the structure and function of core receptor signaling complexes and the architecture of higher-order receptor arrays, which, in turn, has led to new insights into the molecular signaling mechanisms of chemoreceptor networks. Current evidence supports a new view of receptor signaling in which stimulus information travels within receptor molecules through shifts in the dynamic properties of adjoining structural elements rather than through a few discrete conformational states.
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Affiliation(s)
- John S Parkinson
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA.
| | - Gerald L Hazelbauer
- Department of Biochemistry, University of Missouri Columbia, Columbia, MO 65211, USA
| | - Joseph J Falke
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA
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14
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Bi S, Lai L. Bacterial chemoreceptors and chemoeffectors. Cell Mol Life Sci 2015; 72:691-708. [PMID: 25374297 PMCID: PMC11113376 DOI: 10.1007/s00018-014-1770-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 10/05/2014] [Accepted: 10/23/2014] [Indexed: 01/11/2023]
Abstract
Bacteria use chemotaxis signaling pathways to sense environmental changes. Escherichia coli chemotaxis system represents an ideal model that illustrates fundamental principles of biological signaling processes. Chemoreceptors are crucial signaling proteins that mediate taxis toward a wide range of chemoeffectors. Recently, in deep study of the biochemical and structural features of chemoreceptors, the organization of higher-order clusters in native cells, and the signal transduction mechanisms related to the on-off signal output provides us with general insights to understand how chemotaxis performs high sensitivity, precise adaptation, signal amplification, and wide dynamic range. Along with the increasing knowledge, bacterial chemoreceptors can be engineered to sense novel chemoeffectors, which has extensive applications in therapeutics and industry. Here we mainly review recent advances in the E. coli chemotaxis system involving structure and organization of chemoreceptors, discovery, design, and characterization of chemoeffectors, and signal recognition and transduction mechanisms. Possible strategies for changing the specificity of bacterial chemoreceptors to sense novel chemoeffectors are also discussed.
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Affiliation(s)
- Shuangyu Bi
- Center for Quantitative Biology, Peking University, Beijing, 100871 China
- Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Luhua Lai
- Center for Quantitative Biology, Peking University, Beijing, 100871 China
- BNLMS, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, and Peking-Tsinghua Center for Life Sciences at College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871 China
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15
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Botelho SC, Enquist K, von Heijne G, Draheim RR. Differential repositioning of the second transmembrane helices from E. coli Tar and EnvZ upon moving the flanking aromatic residues. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:615-21. [PMID: 25445668 DOI: 10.1016/j.bbamem.2014.11.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 10/29/2014] [Accepted: 11/17/2014] [Indexed: 01/04/2023]
Abstract
Aromatic tuning, i.e. repositioning aromatic residues found at the cytoplasmic end of transmembrane (TM) domains within bacterial receptors, has been previously shown to modulate signal output from the aspartate chemoreceptor (Tar) and the major osmosensor EnvZ of Escherichia coli. In the case of Tar, changes in signal output consistent with the vertical position of the native Trp-Tyr aromatic tandem within TM2 were observed. In contrast, within EnvZ, where a Trp-Leu-Phe aromatic triplet was repositioned, the surface that the triplet resided upon was the major determinant governing signal output. However, these studies failed to determine whether moving the aromatic residues was sufficient to physically reposition the TM helix within a membrane. Recent coarse-grained molecular dynamics (CG-MD) simulations predicted displacement of Tar TM2 upon moving the aromatic residues at the cytoplasmic end of the helix. Here, we demonstrate that repositioning the Trp-Tyr tandem within Tar TM2 displaces the C-terminal boundary of the helix relative to the membrane. In a similar analysis of EnvZ, an abrupt initial displacement of TM2 was observed but no subsequent movement was seen, suggesting that the vertical position of TM2 is not governed by the location of the Trp-Leu-Phe triplet. Our results also provide another set of experimental data, i.e. the resistance of EnvZ TM2 to being displaced upon aromatic tuning, which could be useful for subsequent refinement of the initial CG-MD simulations. Finally, we discuss the limitations of these methodologies, how moving flanking aromatic residues might impact steady-state signal output and the potential to employ aromatic tuning in other bacterial membrane-spanning receptors.
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Affiliation(s)
- Salomé C Botelho
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Karl Enquist
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Gunnar von Heijne
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Roger R Draheim
- Division of Pharmacy, Durham University, Queen's Campus, Stockton-on-Tees TS17 6BH, England, UK; Wolfson Research Institute for Health and Wellbeing, Durham University, Queen's Campus, Stockton-on-Tees, TS17 6BH, England, UK.
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