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Stierschneider A, Wiesner C. Shedding light on the molecular and regulatory mechanisms of TLR4 signaling in endothelial cells under physiological and inflamed conditions. Front Immunol 2023; 14:1264889. [PMID: 38077393 PMCID: PMC10704247 DOI: 10.3389/fimmu.2023.1264889] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 11/08/2023] [Indexed: 12/18/2023] Open
Abstract
Toll-like receptor 4 (TLR4) are part of the innate immune system. They are capable of recognizing pathogen-associated molecular patterns (PAMPS) of microbes, and damage-associated molecular patterns (DAMPs) of damaged tissues. Activation of TLR4 initiates downstream signaling pathways that trigger the secretion of cytokines, type I interferons, and other pro-inflammatory mediators that are necessary for an immediate immune response. However, the systemic release of pro-inflammatory proteins is a powerful driver of acute and chronic inflammatory responses. Over the past decades, immense progress has been made in clarifying the molecular and regulatory mechanisms of TLR4 signaling in inflammation. However, the most common strategies used to study TLR4 signaling rely on genetic manipulation of the TLR4 or the treatment with agonists such as lipopolysaccharide (LPS) derived from the outer membrane of Gram-negative bacteria, which are often associated with the generation of irreversible phenotypes in the target cells or unintended cytotoxicity and signaling crosstalk due to off-target or pleiotropic effects. Here, optogenetics offers an alternative strategy to control and monitor cellular signaling in an unprecedented spatiotemporally precise, dose-dependent, and non-invasive manner. This review provides an overview of the structure, function and signaling pathways of the TLR4 and its fundamental role in endothelial cells under physiological and inflammatory conditions, as well as the advances in TLR4 modulation strategies.
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Affiliation(s)
| | - Christoph Wiesner
- Department Science & Technology, Institute Biotechnology, IMC Krems University of Applied Sciences, Krems, Austria
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2
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Maia RNA, Ehrenberg D, Oldemeyer S, Knieps-Grünhagen E, Krauss U, Heberle J. Real-Time Tracking of Proton Transfer from the Reactive Cysteine to the Flavin Chromophore of a Photosensing Light Oxygen Voltage Protein. J Am Chem Soc 2021; 143:12535-12542. [PMID: 34347468 DOI: 10.1021/jacs.1c03409] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
LOV (light oxygen voltage) proteins are photosensors ubiquitous to all domains of life. A variant of the short LOV protein from Dinoroseobacter shibae (DsLOV) exhibits an exceptionally fast photocycle. We performed time-resolved molecular spectroscopy on DsLOV-M49S and characterized the formation of the thio-adduct state with a covalent bond between the reactive cysteine (C72) and C4a of the FMN. By use of a tunable quantum cascade laser, the weak absorption change of the vibrational band of S-H stretching vibration of C57 was resolved with a time resolution of 10 ns. Deprotonation of C72 proceeded with a time constant of 12 μs which tallies the rise of the thio-adduct state. These results provide valuable information for the mechanistic interpretation of light-induced structural changes in LOV domains, which involves the choreographed sequence of proton transfers, changes in electron density distributions, spin alterations of the latter, and transient bond formation and breakage. Such molecular insight will help develop new optogenetic tools based on flavin photoreceptors.
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Affiliation(s)
- Raiza N A Maia
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - David Ehrenberg
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Sabine Oldemeyer
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Esther Knieps-Grünhagen
- Institut für Molekulare Enzymtechnologie, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52426 Jülich, Germany
| | - Ulrich Krauss
- Institut für Molekulare Enzymtechnologie, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52426 Jülich, Germany.,Institute of Bio- and Geosciences (IBG-1): Biotechnology, Forschungszentrum Jülich, D-52426 Jülich, Germany
| | - Joachim Heberle
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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3
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Bannister S, Böhm E, Zinn T, Hellweg T, Kottke T. Arguments for an additional long-lived intermediate in the photocycle of the full-length aureochrome 1c receptor: A time-resolved small-angle X-ray scattering study. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2019; 6:034701. [PMID: 31263739 PMCID: PMC6588521 DOI: 10.1063/1.5095063] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 06/05/2019] [Indexed: 06/09/2023]
Abstract
Aureochromes (AUREO) act as blue-light photoreceptors in algae. They consist of a light-, oxygen-, voltage-sensitive (LOV) domain and a DNA-binding basic region/leucine zipper. Illumination of the flavin cofactor in LOV leads to the formation of an adduct, followed by global structural changes. Here, we first applied UV/vis spectroscopy to characterize the photocycle of full-length aureochrome 1c (PtAUREO1c) from the diatom Phaeodactylum tricornutum. With a time constant of 850 s and a quantum yield of 23%, PtAUREO1c reveals a faster recovery time and a much lower sensitivity toward light than PtAUREO1a, pointing to its role as a high light sensor in vivo. UV/vis spectroscopy offers details on the local recovery of the flavin chromophore. However, kinetic information on the global structural recovery of full-length AUREO or any other multidomain LOV protein is missing. This information is essential not least for the photoreceptors' applications as optogenetic devices. Therefore, we established a procedure to apply small-angle X-ray scattering on PtAUREO1c in a time-resolved manner employing an in-house setup. In combination with UV/vis spectroscopy under similar conditions, we revealed a discrepancy between the recovery of the global protein structure and the adduct lifetime. Accordingly, we propose to supplement the photocycle by an intermediate state (I447), which decays with a time constant of about 800 s and prolongs the lifetime of the signaling state.
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Affiliation(s)
- Saskia Bannister
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, Universitaetsstr. 25, 33615 Bielefeld, Germany
| | - Elena Böhm
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, Universitaetsstr. 25, 33615 Bielefeld, Germany
| | - Thomas Zinn
- ESRF–The European Synchrotron, 71, Avenue des Martyrs, 38043 Grenoble Cedex 9, France
| | - Thomas Hellweg
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, Universitaetsstr. 25, 33615 Bielefeld, Germany
| | - Tilman Kottke
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, Universitaetsstr. 25, 33615 Bielefeld, Germany
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4
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Tateyama S, Kobayashi I, Hisatomi O. Target Sequence Recognition by a Light-Activatable Basic Leucine Zipper Factor, Photozipper. Biochemistry 2018; 57:6615-6623. [PMID: 30388362 DOI: 10.1021/acs.biochem.8b00995] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photozipper (PZ) is a light-activatable basic leucine zipper (bZIP) protein composed of a bZIP domain and a light-oxygen-voltage-sensing domain of aureochrome-1. Blue light induces dimerization and subsequently increases the affinity of PZ for the target DNA sequence. We prepared site-directed PZ mutants in which Asn131 (N131) in the basic region was substituted with Ala and Gln. N131 mutants showed spectroscopic and dimerization properties almost identical to those of wild-type PZ and an increase in helical content in the presence of the target sequence. Quantitative analyses by an electrophoretic mobility shift assay and quartz crystal microbalance (QCM) measurements demonstrated that the half-maximal effective concentrations of N131 mutants to bind to the target sequence were significantly higher than those of PZ. QCM data also revealed that N131 substitutions accelerated the dissociation without affecting the association, suggesting that a base-specific interaction of N131 occurred after the association between PZ and DNA. Activation of PZ by illumination decreased both the standard errors and the unstable period of QCM data. Optical control of transcription factors will provide new knowledge of the recognition of the target sequence.
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Affiliation(s)
- Samu Tateyama
- Department of Earth and Space Science, Graduate School of Science , Osaka University , Toyonaka , Osaka 560-0043 , Japan
| | - Itsuki Kobayashi
- Department of Earth and Space Science, Graduate School of Science , Osaka University , Toyonaka , Osaka 560-0043 , Japan
| | - Osamu Hisatomi
- Department of Earth and Space Science, Graduate School of Science , Osaka University , Toyonaka , Osaka 560-0043 , Japan
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5
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Kerruth S, Langner P, Raffelberg S, Gärtner W, Heberle J. Characterization of the Blue-Light-Activated Adenylyl Cyclase mPAC by Flash Photolysis and FTIR Spectroscopy. Photochem Photobiol 2018; 93:857-864. [PMID: 28500710 DOI: 10.1111/php.12746] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 01/08/2017] [Indexed: 11/29/2022]
Abstract
The recently discovered photo-activated adenylyl cyclase (mPAC from Microcoleus chthonoplastes) is the first PAC that owes a light-, oxygen- and voltage-sensitive (LOV) domain for blue-light sensing. The photoreaction of the mPAC receptor was studied by time-resolved UV/vis and light-induced Fourier transform infrared (FTIR) absorption difference spectroscopy. The photocycle comprises of the typical triplet state LOV715 and the thio-adduct state LOV390 . While the adduct state decays with a time constant of 8 s, the lifetime of the triplet state is with 656 ns significantly shorter than in all other reported LOV domains. The light-induced FTIR difference spectrum shows the typical bands of the LOV390 and LOV450 intermediates. The negative S-H stretching vibration at 2573 cm-1 is asymmetric suggesting two rotamer configurations of the protonated side chain of C194. A positive band at 3632 cm-1 is observed, which is assigned to an internal water molecule. In contrast to other LOV domains, mPAC exhibits a second positive feature at 3674 cm-1 which is due to the O-H stretch of a second intrinsic water molecule and the side chain of Y476. We conclude that the latter might be involved in the dimerization of the cyclase domain which is crucial for ATP binding.
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Affiliation(s)
- Silke Kerruth
- Experimental Molecular Biophysics, Freie Universität Berlin, Berlin, Germany
| | - Pit Langner
- Experimental Molecular Biophysics, Freie Universität Berlin, Berlin, Germany
| | - Sarah Raffelberg
- Department of Botany and Plant Biology, University of Geneva, Geneva, Switzerland
| | - Wolfgang Gärtner
- Max Planck Institute for Chemical Energy Conversion, Mülheim a. d. Ruhr, Germany
| | - Joachim Heberle
- Experimental Molecular Biophysics, Freie Universität Berlin, Berlin, Germany
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6
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Affiliation(s)
- Mareike Daniela Hoffmann
- Department of Theoretical Bioinformatics; German Cancer Research Center (DKFZ); Im Neuenheimer Feld 280 69120 Heidelberg Germany
- Synthetic Biology Group; Institute for Pharmacy and Biotechnology (IPMB) and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant); University of Heidelberg; Im Neuenheimer Feld 267 69120 Heidelberg Germany
| | - Felix Bubeck
- Synthetic Biology Group; Institute for Pharmacy and Biotechnology (IPMB) and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant); University of Heidelberg; Im Neuenheimer Feld 267 69120 Heidelberg Germany
| | - Roland Eils
- Department of Theoretical Bioinformatics; German Cancer Research Center (DKFZ); Im Neuenheimer Feld 280 69120 Heidelberg Germany
- Synthetic Biology Group; Institute for Pharmacy and Biotechnology (IPMB) and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant); University of Heidelberg; Im Neuenheimer Feld 267 69120 Heidelberg Germany
- Digital Health Center; Berlin Institute of Health (BIH) and Charité-University Medicine Berlin; 10117 Berlin Germany
- Health Data Science Unit; University Hospital Heidelberg; 10117 Heidelberg Germany
| | - Dominik Niopek
- Department of Theoretical Bioinformatics; German Cancer Research Center (DKFZ); Im Neuenheimer Feld 280 69120 Heidelberg Germany
- Synthetic Biology Group; Institute for Pharmacy and Biotechnology (IPMB) and Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant); University of Heidelberg; Im Neuenheimer Feld 267 69120 Heidelberg Germany
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Essen LO, Franz S, Banerjee A. Structural and evolutionary aspects of algal blue light receptors of the cryptochrome and aureochrome type. JOURNAL OF PLANT PHYSIOLOGY 2017; 217:27-37. [PMID: 28756992 DOI: 10.1016/j.jplph.2017.07.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Revised: 07/05/2017] [Accepted: 07/05/2017] [Indexed: 06/07/2023]
Abstract
Blue-light reception plays a pivotal role for algae to adapt to changing environmental conditions. In this review we summarize the current structural and mechanistic knowledge about flavin-dependent algal photoreceptors. We especially focus on the cryptochrome and aureochrome type photoreceptors in the context of their evolutionary divergence. Despite similar photochemical characteristics to orthologous photoreceptors from higher plants and animals the algal blue-light photoreceptors have developed a set of unique structural and mechanistic features that are summarized below.
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Affiliation(s)
- Lars-Oliver Essen
- Department of Biochemistry, Philipps-University, 35043 Marburg, Germany; LOEWE Center for Synthetic Microbiology, Philipps-University, 35043 Marburg, Germany.
| | - Sophie Franz
- Department of Biochemistry, Philipps-University, 35043 Marburg, Germany
| | - Ankan Banerjee
- Department of Biochemistry, Philipps-University, 35043 Marburg, Germany
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8
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Kroth PG, Wilhelm C, Kottke T. An update on aureochromes: Phylogeny - mechanism - function. JOURNAL OF PLANT PHYSIOLOGY 2017; 217:20-26. [PMID: 28797596 DOI: 10.1016/j.jplph.2017.06.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 06/21/2017] [Accepted: 06/23/2017] [Indexed: 05/20/2023]
Abstract
Light is important for algae, as it warrants metabolic independence via photosynthesis. In addition to the absorption of light by the photosystems, algae possess a variety of specific photoreceptors that allow the quantification of the light fluxes as well as the assessment of light qualities. About a decade ago, aureochromes have been described in the xanthophyte alga Vaucheria frigida. These proteins represent a new type of blue light photoreceptor as they possess both a light-oxygen-voltage (LOV) domain for light reception as well as a basic region leucine zipper (bZIP) domain for DNA binding, indicating that they represent light-driven transcription factors. Aureochromes so far have been detected only in a single group of algae, photosynthetic stramenopiles, but not in any other prokaryotic or eukaryotic organisms. Recent biophysical work on aureochromes in the absence and the presence of DNA revealed the mechanism of allosteric communication between the sensor and effector domains despite their unusual inversed arrangement. Different molecular models have been proposed to describe the effect of light on DNA binding. Functional characterization of mutants of the diatom Phaeodactylum tricornutum, in which the aureochrome genes have been silenced or deleted, indicate that different aureochromes may have different functions, being involved in central processes like light acclimation and regulation of the cell cycle.
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Affiliation(s)
- Peter G Kroth
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
| | - Christian Wilhelm
- Institute of Biology, University of Leipzig, Johannisallee 21-23, 04103 Leipzig, Germany
| | - Tilman Kottke
- Department of Chemistry, Physical and Biophysical Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
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9
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Sequential conformational transitions and α-helical supercoiling regulate a sensor histidine kinase. Nat Commun 2017; 8:284. [PMID: 28819239 PMCID: PMC5561222 DOI: 10.1038/s41467-017-00300-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 06/20/2017] [Indexed: 12/13/2022] Open
Abstract
Sensor histidine kinases are central to sensing in bacteria and in plants. They usually contain sensor, linker, and kinase modules and the structure of many of these components is known. However, it is unclear how the kinase module is structurally regulated. Here, we use nano- to millisecond time-resolved X-ray scattering to visualize the solution structural changes that occur when the light-sensitive model histidine kinase YF1 is activated by blue light. We find that the coiled coil linker and the attached histidine kinase domains undergo a left handed rotation within microseconds. In a much slower second step, the kinase domains rearrange internally. This structural mechanism presents a template for signal transduction in sensor histidine kinases. Sensor histidine kinases (SHK) consist of sensor, linker and kinase modules and different models for SHK signal transduction have been proposed. Here the authors present nano- to millisecond time-resolved X-ray scattering measurements, which reveal a structural mechanism for kinase domain activation in SHK.
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10
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Endo M, Ozawa T. Strategies for development of optogenetic systems and their applications. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2017. [DOI: 10.1016/j.jphotochemrev.2016.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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11
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Kottke T, Lórenz-Fonfría VA, Heberle J. The Grateful Infrared: Sequential Protein Structural Changes Resolved by Infrared Difference Spectroscopy. J Phys Chem B 2016; 121:335-350. [PMID: 28100053 DOI: 10.1021/acs.jpcb.6b09222] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The catalytic activity of proteins is a function of structural changes. Very often these are as minute as protonation changes, hydrogen bonding changes, and amino acid side chain reorientations. To resolve these, a methodology is afforded that not only provides the molecular sensitivity but allows for tracing the sequence of these hierarchical reactions at the same time. This feature article showcases results from time-resolved IR spectroscopy on channelrhodopsin (ChR), light-oxygen-voltage (LOV) domain protein, and cryptochrome (CRY). All three proteins are activated by blue light, but their biological role is drastically different. Channelrhodopsin is a transmembrane retinylidene protein which represents the first light-activated ion channel of its kind and which is involved in primitive vision (phototaxis) of algae. LOV and CRY are flavin-binding proteins acting as photoreceptors in a variety of signal transduction mechanisms in all kingdoms of life. Beyond their biological relevance, these proteins are employed in exciting optogenetic applications. We show here how IR difference absorption resolves crucial structural changes of the protein after photonic activation of the chromophore. Time-resolved techniques are introduced that cover the time range from nanoseconds to minutes along with some technical considerations. Finally, we provide an outlook toward novel experimental approaches that are currently developed in our laboratories or are just in our minds ("Gedankenexperimente"). We believe that some of them have the potential to provide new science.
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Affiliation(s)
- Tilman Kottke
- Department of Chemistry, Physical and Biophysical Chemistry, Bielefeld University , Universitätsstraße 25, 33615 Bielefeld, Germany
| | | | - Joachim Heberle
- Experimental Molecular Biophysics, Freie Universität Berlin , Arnimalle 14, 14195 Berlin, Germany
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Banerjee A, Herman E, Serif M, Maestre-Reyna M, Hepp S, Pokorny R, Kroth PG, Essen LO, Kottke T. Allosteric communication between DNA-binding and light-responsive domains of diatom class I aureochromes. Nucleic Acids Res 2016; 44:5957-70. [PMID: 27179025 PMCID: PMC4937327 DOI: 10.1093/nar/gkw420] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 05/04/2016] [Indexed: 12/20/2022] Open
Abstract
The modular architecture of aureochrome blue light receptors, found in several algal groups including diatoms, is unique by having the LOV-type photoreceptor domain fused to the C-terminus of its putative effector, an N-terminal DNA-binding bZIP module. The structural and functional understanding of aureochromes’ light-dependent signaling mechanism is limited, despite their promise as an optogenetic tool. We show that class I aureochromes 1a and 1c from the diatom Phaeodactylum tricornutum are regulated in a light-independent circadian rhythm. These aureochromes are capable to form functional homo- and heterodimers, which recognize the ACGT core sequence within the canonical ‘aureo box’, TGACGT, in a light-independent manner. The bZIP domain holds a more folded and less flexible but extended conformation in the duplex DNA-bound state. FT-IR spectroscopy in the absence and the presence of DNA shows light-dependent helix unfolding in the LOV domain, which leads to conformational changes in the bZIP region. The solution structure of DNA bound to aureochrome points to a tilted orientation that was further validated by molecular dynamics simulations. We propose that aureochrome signaling relies on an allosteric pathway from LOV to bZIP that results in conformational changes near the bZIP-DNA interface without major effects on the binding affinity.
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Affiliation(s)
- Ankan Banerjee
- Structural Biochemistry - Department of Chemistry, Philipps University Marburg, Hans-Meerwein Straße 4, 35032 Marburg, Germany
| | - Elena Herman
- Physical and Biophysical Chemistry - Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Manuel Serif
- Plant Ecophysiology - Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Manuel Maestre-Reyna
- Institute of Biological Chemistry, Academia Sinica, 128 Academia Road, Sec. 2 Nankang, Taipei 11529, Taiwan
| | - Sebastian Hepp
- Structural Biochemistry - Department of Chemistry, Philipps University Marburg, Hans-Meerwein Straße 4, 35032 Marburg, Germany
| | - Richard Pokorny
- Faculty of Biology, Department of Plant Physiology and Photobiology, Philipps-University Marburg, 35043 Marburg, Germany
| | - Peter G Kroth
- Plant Ecophysiology - Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Lars-Oliver Essen
- Structural Biochemistry - Department of Chemistry, Philipps University Marburg, Hans-Meerwein Straße 4, 35032 Marburg, Germany
| | - Tilman Kottke
- Physical and Biophysical Chemistry - Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
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Takahashi F. Blue-light-regulated transcription factor, Aureochrome, in photosynthetic stramenopiles. JOURNAL OF PLANT RESEARCH 2016; 129:189-197. [PMID: 26781435 DOI: 10.1007/s10265-016-0784-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 12/23/2015] [Indexed: 06/05/2023]
Abstract
During the course of evolution through various endosymbiotic processes, diverse photosynthetic eukaryotes acquired blue light (BL) responses that do not use photosynthetic pathways. Photosynthetic stramenopiles, which have red algae-derived chloroplasts through secondary symbiosis, are principal primary producers in aquatic environments, and play important roles in ecosystems and aquaculture. Through secondary symbiosis, these taxa acquired BL responses, such as phototropism, chloroplast photo-relocation movement, and photomorphogenesis similar to those which green plants acquired through primary symbiosis. Photosynthetic stramenopile BL receptors were undefined until the discovery in 2007, of a new type of BL receptor, the aureochrome (AUREO), from the photosynthetic stramenopile alga, Vaucheria. AUREO has a bZIP domain and a LOV domain, and thus BL-responsive transcription factor. AUREO orthologs are only conserved in photosynthetic stramenopiles, such as brown algae, diatoms, and red tide algae. Here, a brief review is presented of the role of AUREOs as photoreceptors for these diverse BL responses and their biochemical properties in photosynthetic stramenopiles.
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Affiliation(s)
- Fumio Takahashi
- College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan.
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Herman E, Kottke T. Allosterically regulated unfolding of the A'α helix exposes the dimerization site of the blue-light-sensing aureochrome-LOV domain. Biochemistry 2015; 54:1484-92. [PMID: 25621532 DOI: 10.1021/bi501509z] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Aureochromes have been shown to act as blue-light-regulated transcription factors in algae in the absence of phototropins. Aureochromes comprise a light-, oxygen-, or voltage-sensitive (LOV) domain as a sensory module binding the flavin chromophore and a basic region leucine zipper (bZIP) domain as an effector. The domain arrangement in aureochromes with an N-terminal effector is inversed to other LOV proteins. To clarify the role of the linking A'α helix in signaling, we have investigated the LOV domain of aureochrome1a from the diatom alga Phaeodactylum tricornutum without the N-terminal A'α helix but with the C-terminal Jα helix. Results were analyzed in comparison to those previously obtained on the LOV domain with both flanking helices and on the LOV domain with the A'α helix but without the Jα helix. Fourier transform infrared difference spectroscopy provides evidence by a band at 1656 cm(-1) that the A'α helix unfolds in response to light. This unfolding takes place only in the presence and as a consequence of the unfolding of the Jα helix, which points to an allosteric regulation. Size exclusion chromatography shows the LOV domain to be dimeric in the absence and monomeric in the presence of the A'α helix, implying that the folded helix covers the dimerization site. Therefore, the A'α helix directly modulates the oligomerization state of the LOV domain, whereas the Jα helix acts as an allosteric regulator. Both the allosteric control and the light-induced dimerization have not been observed in phototropin-LOV2 and point to a different signaling mechanism within the full-length proteins.
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Affiliation(s)
- Elena Herman
- Department of Chemistry, Physical and Biophysical Chemistry, Bielefeld University , Universitätsstraße 25, 33615 Bielefeld, Germany
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