1
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Broser M, Andruniów T, Kraskov A, Palombo R, Katz S, Kloz M, Dostál J, Bernardo C, Kennis JTM, Hegemann P, Olivucci M, Hildebrandt P. Experimental Assessment of the Electronic and Geometrical Structure of a Near-Infrared Absorbing and Highly Fluorescent Microbial Rhodopsin. J Phys Chem Lett 2023; 14:9291-9295. [PMID: 37815402 DOI: 10.1021/acs.jpclett.3c02167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/11/2023]
Abstract
The recently discovered Neorhodopsin (NeoR) exhibits absorption and emission maxima in the near-infrared spectral region, which together with the high fluorescence quantum yield makes it an attractive retinal protein for optogenetic applications. The unique optical properties can be rationalized by a theoretical model that predicts a high charge transfer character in the electronic ground state (S0) which is otherwise typical of the excited state S1 in canonical retinal proteins. The present study sets out to assess the electronic structure of the NeoR chromophore by resonance Raman (RR) spectroscopy since frequencies and relative intensities of RR bands are controlled by the ground and excited state's properties. The RR spectra of NeoR differ dramatically from those of canonical rhodopsins but can be reliably reproduced by the calculations carried out within two different structural models. The remarkable agreement between the experimental and calculated spectra confirms the consistency and robustness of the theoretical approach.
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Affiliation(s)
- Matthias Broser
- Institut für Biologie, Experimentelle Biophysik, Humboldt-Universität zu Berlin, Invalidenstr. 42, D-10115 Berlin, Germany
| | - Tadeusz Andruniów
- Department of Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Anastasia Kraskov
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Riccardo Palombo
- Dipartimento di Biotecnologie, Chimica e Farmacia, Universitâ di Siena, via A. Moro 2, 53100 Siena, Italy
| | - Sagie Katz
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Miroslav Kloz
- ELI Beamlines Facility, The Extreme Light Infrastructure ERIC, Za Radnicí 835, 25241 Dolní Břežany, Czech Republic
| | - Jakub Dostál
- ELI Beamlines Facility, The Extreme Light Infrastructure ERIC, Za Radnicí 835, 25241 Dolní Břežany, Czech Republic
| | - César Bernardo
- ELI Beamlines Facility, The Extreme Light Infrastructure ERIC, Za Radnicí 835, 25241 Dolní Břežany, Czech Republic
| | - John T M Kennis
- Department of Physics and Astronomy, Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands
| | - Peter Hegemann
- Institut für Biologie, Experimentelle Biophysik, Humboldt-Universität zu Berlin, Invalidenstr. 42, D-10115 Berlin, Germany
| | - Massimo Olivucci
- Dipartimento di Biotecnologie, Chimica e Farmacia, Universitâ di Siena, via A. Moro 2, 53100 Siena, Italy
- Department of Chemistry, Bowling Green State University, Overman Hall, Bowling Green, Ohio 43403, United States
| | - Peter Hildebrandt
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany
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2
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Ostrovsky MA, Smitienko OA, Bochenkova AV, Feldman TB. Similarities and Differences in Photochemistry of Type I and Type II Rhodopsins. BIOCHEMISTRY. BIOKHIMIIA 2023; 88:1528-1543. [PMID: 38105022 DOI: 10.1134/s0006297923100097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 07/20/2023] [Accepted: 08/12/2023] [Indexed: 12/19/2023]
Abstract
The diversity of the retinal-containing proteins (rhodopsins) in nature is extremely large. Fundamental similarity of the structure and photochemical properties unites them into one family. However, there is still a debate about the origin of retinal-containing proteins: divergent or convergent evolution? In this review, based on the results of our own and literature data, a comparative analysis of the similarities and differences in the photoconversion of the rhodopsin of types I and II is carried out. The results of experimental studies of the forward and reverse photoreactions of the bacteriorhodopsin (type I) and visual rhodopsin (type II) rhodopsins in the femto- and picosecond time scale, photo-reversible reaction of the octopus rhodopsin (type II), photovoltaic reactions, as well as quantum chemical calculations of the forward photoreactions of bacteriorhodopsin and visual rhodopsin are presented. The issue of probable convergent evolution of type I and type II rhodopsins is discussed.
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Affiliation(s)
- Mikhail A Ostrovsky
- Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
- Emanuel Institute of Biochemical Physics, Moscow, 119334, Russia
| | - Olga A Smitienko
- Emanuel Institute of Biochemical Physics, Moscow, 119334, Russia
| | | | - Tatiana B Feldman
- Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
- Emanuel Institute of Biochemical Physics, Moscow, 119334, Russia
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3
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Mim MS, Knight C, Zartman JJ. Quantitative insights in tissue growth and morphogenesis with optogenetics. Phys Biol 2023; 20:061001. [PMID: 37678266 PMCID: PMC10594237 DOI: 10.1088/1478-3975/acf7a1] [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: 01/20/2023] [Revised: 08/15/2023] [Accepted: 09/07/2023] [Indexed: 09/09/2023]
Abstract
Cells communicate with each other to jointly regulate cellular processes during cellular differentiation and tissue morphogenesis. This multiscale coordination arises through the spatiotemporal activity of morphogens to pattern cell signaling and transcriptional factor activity. This coded information controls cell mechanics, proliferation, and differentiation to shape the growth and morphogenesis of organs. While many of the molecular components and physical interactions have been identified in key model developmental systems, there are still many unresolved questions related to the dynamics involved due to challenges in precisely perturbing and quantitatively measuring signaling dynamics. Recently, a broad range of synthetic optogenetic tools have been developed and employed to quantitatively define relationships between signal transduction and downstream cellular responses. These optogenetic tools can control intracellular activities at the single cell or whole tissue scale to direct subsequent biological processes. In this brief review, we highlight a selected set of studies that develop and implement optogenetic tools to unravel quantitative biophysical mechanisms for tissue growth and morphogenesis across a broad range of biological systems through the manipulation of morphogens, signal transduction cascades, and cell mechanics. More generally, we discuss how optogenetic tools have emerged as a powerful platform for probing and controlling multicellular development.
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Affiliation(s)
- Mayesha Sahir Mim
- Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, United States of America
| | - Caroline Knight
- Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, United States of America
| | - Jeremiah J Zartman
- Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, United States of America
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4
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de Grip WJ, Ganapathy S. Rhodopsins: An Excitingly Versatile Protein Species for Research, Development and Creative Engineering. Front Chem 2022; 10:879609. [PMID: 35815212 PMCID: PMC9257189 DOI: 10.3389/fchem.2022.879609] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Accepted: 05/16/2022] [Indexed: 01/17/2023] Open
Abstract
The first member and eponym of the rhodopsin family was identified in the 1930s as the visual pigment of the rod photoreceptor cell in the animal retina. It was found to be a membrane protein, owing its photosensitivity to the presence of a covalently bound chromophoric group. This group, derived from vitamin A, was appropriately dubbed retinal. In the 1970s a microbial counterpart of this species was discovered in an archaeon, being a membrane protein also harbouring retinal as a chromophore, and named bacteriorhodopsin. Since their discovery a photogenic panorama unfolded, where up to date new members and subspecies with a variety of light-driven functionality have been added to this family. The animal branch, meanwhile categorized as type-2 rhodopsins, turned out to form a large subclass in the superfamily of G protein-coupled receptors and are essential to multiple elements of light-dependent animal sensory physiology. The microbial branch, the type-1 rhodopsins, largely function as light-driven ion pumps or channels, but also contain sensory-active and enzyme-sustaining subspecies. In this review we will follow the development of this exciting membrane protein panorama in a representative number of highlights and will present a prospect of their extraordinary future potential.
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Affiliation(s)
- Willem J. de Grip
- Leiden Institute of Chemistry, Department of Biophysical Organic Chemistry, Leiden University, Leiden, Netherlands
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Srividya Ganapathy
- Department of Imaging Physics, Delft University of Technology, Netherlands
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5
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Chow WY, De Paëpe G, Hediger S. Biomolecular and Biological Applications of Solid-State NMR with Dynamic Nuclear Polarization Enhancement. Chem Rev 2022; 122:9795-9847. [PMID: 35446555 DOI: 10.1021/acs.chemrev.1c01043] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Solid-state NMR spectroscopy (ssNMR) with magic-angle spinning (MAS) enables the investigation of biological systems within their native context, such as lipid membranes, viral capsid assemblies, and cells. However, such ambitious investigations often suffer from low sensitivity due to the presence of significant amounts of other molecular species, which reduces the effective concentration of the biomolecule or interaction of interest. Certain investigations requiring the detection of very low concentration species remain unfeasible even with increasing experimental time for signal averaging. By applying dynamic nuclear polarization (DNP) to overcome the sensitivity challenge, the experimental time required can be reduced by orders of magnitude, broadening the feasible scope of applications for biological solid-state NMR. In this review, we outline strategies commonly adopted for biological applications of DNP, indicate ongoing challenges, and present a comprehensive overview of biological investigations where MAS-DNP has led to unique insights.
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Affiliation(s)
- Wing Ying Chow
- Univ. Grenoble Alpes, CEA, CNRS, Interdisciplinary Research Institute of Grenoble (IRIG), Modeling and Exploration of Materials Laboratory (MEM), 38054 Grenoble, France.,Univ. Grenoble Alpes, CEA, CNRS, Inst. Biol. Struct. IBS, 38044 Grenoble, France
| | - Gaël De Paëpe
- Univ. Grenoble Alpes, CEA, CNRS, Interdisciplinary Research Institute of Grenoble (IRIG), Modeling and Exploration of Materials Laboratory (MEM), 38054 Grenoble, France
| | - Sabine Hediger
- Univ. Grenoble Alpes, CEA, CNRS, Interdisciplinary Research Institute of Grenoble (IRIG), Modeling and Exploration of Materials Laboratory (MEM), 38054 Grenoble, France
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6
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Xin Q, Cheng J, Wang H, Zhang W, Lu H, Zhou J, Lo GV, Dou Y, Yuan S. Modeling the syn-cycle in the light activated opening of the channelrhodopsin-2 ion channel. RSC Adv 2022; 12:6515-6524. [PMID: 35424642 PMCID: PMC8981705 DOI: 10.1039/d1ra08521b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Accepted: 02/14/2022] [Indexed: 11/21/2022] Open
Abstract
The ion channel of channelrhodopsin-2 (ChR2) is activated by absorbing light. The light stimulates retinal to isomerize to start the photocycle. There are two pathways for photocycles, which are caused by isomerization of the retinal from all-trans, 15-anti to 13-cis, 15-anti in the dark-adapted state (anti-cycle) and from 13-cis, 15-syn to all-trans, 15-syn in the light-adapted state (syn-cycle). In this work, the structure of the syn-cycle intermediate and mechanism of channel opening were studied by molecular dynamics (MD) and steered molecular dynamics (SMD) simulations. Due to the lack of crystal structure of intermediates in the syn-cycle of ChR2, the intermediate models were constructed from the homologous intermediates in the anti-cycle. The isomerization of retinal was shown to cause the central gate (CG) hydrogen bond network to rearrange, cutting the link between TM2 and TM7. TM2 is moved by the intrahelical hydrogen bond of E90 and K93, and induced the intracellular gate (ICG) to expand. The ion penetration pathway between TM1, TM2, TM3 and TM7 in the P500* state was observed by MD simulations. However, this channel is not fully opened compared with the homologous P500 state in the anti-cycle. In addition, the protons on Schiff bases were found to be unable to form hydrogen bonds with the counter residues (E123 and D253) in the P500* state, preventing an evolution of the P500* state to a P390-like state in the syn-cycle. Modelling the syn-cycle is a series of operations on the ChR2 crystal structure (PDB ID: 6EID). By replacement and isomerization, we obtained P500* and P480 intermediates. A feasible explanation that no P390* was observed in experiment was inferred.![]()
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Affiliation(s)
- Qi Xin
- Chongqing Key Laboratory of Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing 40065, China
| | - Jie Cheng
- Chongqing Key Laboratory of Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing 40065, China
| | - Hongwei Wang
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane St Lucia, QLD 4072, Australia
| | - Wenying Zhang
- Chongqing Key Laboratory of Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing 40065, China
| | - Hong Lu
- Chongqing Key Laboratory of Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing 40065, China
| | - Junpeng Zhou
- Chongqing Key Laboratory of Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing 40065, China
| | - Glenn V. Lo
- Department of Chemistry and Physical Sciences, Nicholls State University, P.O. Box 2022, Thibodaux, LA 70310, USA
| | - Yusheng Dou
- Department of Chemistry and Physical Sciences, Nicholls State University, P.O. Box 2022, Thibodaux, LA 70310, USA
| | - Shuai Yuan
- Chongqing Key Laboratory of Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing 40065, China
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7
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Lu H, Gallinaro JV, Normann C, Rotter S, Yalcin I. Time Course of Homeostatic Structural Plasticity in Response to Optogenetic Stimulation in Mouse Anterior Cingulate Cortex. Cereb Cortex 2021; 32:1574-1592. [PMID: 34607362 DOI: 10.1093/cercor/bhab281] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 07/09/2021] [Accepted: 07/12/2021] [Indexed: 11/13/2022] Open
Abstract
Plasticity is the mechanistic basis of development, aging, learning, and memory, both in healthy and pathological brains. Structural plasticity is rarely accounted for in computational network models due to a lack of insight into the underlying neuronal mechanisms and processes. Little is known about how the rewiring of networks is dynamically regulated. To inform such models, we characterized the time course of neural activity, the expression of synaptic proteins, and neural morphology employing an in vivo optogenetic mouse model. We stimulated pyramidal neurons in the anterior cingulate cortex of mice and harvested their brains at 1.5 h, 24 h, and $48\,\mathrm{h}$ after stimulation. Stimulus-induced cortical hyperactivity persisted up to 1.5 h and decayed to baseline after $24\,\mathrm{h}$ indicated by c-Fos expression. The synaptic proteins VGLUT1 and PSD-95, in contrast, were upregulated at $24\,\mathrm{h}$ and downregulated at $48\,\mathrm{h}$, respectively. Spine density and spine head volume were also increased at $24\,\mathrm{h}$ and decreased at $48\,\mathrm{h}$. This specific sequence of events reflects a continuous joint evolution of activity and connectivity that is characteristic of the model of homeostatic structural plasticity. Our computer simulations thus corroborate the observed empirical evidence from our animal experiments.
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Affiliation(s)
- Han Lu
- Bernstein Center Freiburg and Faculty of Biology, University of Freiburg, Freiburg 79104, Germany.,Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives UPR3212, Strasbourg 67000, France.,Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Freiburg 79104, Germany
| | - Júlia V Gallinaro
- Bernstein Center Freiburg and Faculty of Biology, University of Freiburg, Freiburg 79104, Germany.,Bioengineering Department, Imperial College London, London SW7 2AZ, United Kingdom
| | - Claus Normann
- Department of Psychiatry and Psychotherapy, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg 79104, Germany.,Center for Basics in Neuromodulation, Faculty of Medicine, University of Freiburg, Freiburg 79104, Germany
| | - Stefan Rotter
- Bernstein Center Freiburg and Faculty of Biology, University of Freiburg, Freiburg 79104, Germany
| | - Ipek Yalcin
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives UPR3212, Strasbourg 67000, France.,Department of Psychiatry and Neuroscience, Université Laval, Québec QC G1V 0A6, Canada
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8
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Becker‐Baldus J, Leeder A, Brown LJ, Brown RCD, Bamann C, Glaubitz C. The Desensitized Channelrhodopsin‐2 Photointermediate Contains 13 ‐
cis
, 15 ‐
syn
Retinal Schiff Base. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202015797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Johanna Becker‐Baldus
- Institute of Biophysical Chemistry and Centre for Biomolecular Magnetic Resonance Goethe University Frankfurt Max-von-Laue-Str. 9 60438 Frankfurt Germany
| | - Alexander Leeder
- Department of Chemistry University of Southampton Southampton SO17 1BJ UK
| | - Lynda J. Brown
- Department of Chemistry University of Southampton Southampton SO17 1BJ UK
| | | | - Christian Bamann
- Max-Planck-Institute of Biophysics Max-von-Laue-Str. 3 60438 Frankfurt Germany
| | - Clemens Glaubitz
- Institute of Biophysical Chemistry and Centre for Biomolecular Magnetic Resonance Goethe University Frankfurt Max-von-Laue-Str. 9 60438 Frankfurt Germany
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9
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Becker-Baldus J, Leeder A, Brown LJ, Brown RCD, Bamann C, Glaubitz C. The Desensitized Channelrhodopsin-2 Photointermediate Contains 13 -cis, 15 -syn Retinal Schiff Base. Angew Chem Int Ed Engl 2021; 60:16442-16447. [PMID: 33973334 PMCID: PMC8362212 DOI: 10.1002/anie.202015797] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 03/18/2021] [Indexed: 11/13/2022]
Abstract
Channelrhodopsin‐2 (ChR2) is a light‐gated cation channel and was used to lay the foundations of optogenetics. Its dark state X‐ray structure has been determined in 2017 for the wild‐type, which is the prototype for all other ChR variants. However, the mechanistic understanding of the channel function is still incomplete in terms of structural changes after photon absorption by the retinal chromophore and in the framework of functional models. Hence, detailed information needs to be collected on the dark state as well as on the different photointermediates. For ChR2 detailed knowledge on the chromophore configuration in the different states is still missing and a consensus has not been achieved. Using DNP‐enhanced solid‐state MAS NMR spectroscopy on proteoliposome samples, we unambiguously determined the chromophore configuration in the desensitized state, and we show that this state occurs towards the end of the photocycle.
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Affiliation(s)
- Johanna Becker-Baldus
- Institute of Biophysical Chemistry and Centre for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438, Frankfurt, Germany
| | - Alexander Leeder
- Department of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK
| | - Lynda J Brown
- Department of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK
| | - Richard C D Brown
- Department of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK
| | - Christian Bamann
- Max-Planck-Institute of Biophysics, Max-von-Laue-Str. 3, 60438, Frankfurt, Germany
| | - Clemens Glaubitz
- Institute of Biophysical Chemistry and Centre for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438, Frankfurt, Germany
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10
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Schoeters R, Tarnaud T, Martens L, Joseph W, Raedt R, Tanghe E. Double Two-State Opsin Model With Autonomous Parameter Inference. Front Comput Neurosci 2021; 15:688331. [PMID: 34220478 PMCID: PMC8243001 DOI: 10.3389/fncom.2021.688331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 05/21/2021] [Indexed: 11/13/2022] Open
Abstract
Optogenetics has a lot of potential to become an effective neuromodulative therapy for clinical applications. Selecting the correct opsin is crucial to have an optimal optogenetic tool. With computational modeling, the neuronal response to the current dynamics of an opsin can be extensively and systematically tested. Unlike electrical stimulation where the effect is directly defined by the applied field, the stimulation in optogenetics is indirect, depending on the selected opsin's non-linear kinetics. With the continuous expansion of opsin possibilities, computational studies are difficult due to the need for an accurate model of the selected opsin first. To this end, we propose a double two-state opsin model as alternative to the conventional three and four state Markov models used for opsin modeling. Furthermore, we provide a fitting procedure, which allows for autonomous model fitting starting from a vast parameter space. With this procedure, we successfully fitted two distinctive opsins (ChR2(H134R) and MerMAID). Both models are able to represent the experimental data with great accuracy and were obtained within an acceptable time frame. This is due to the absence of differential equations in the fitting procedure, with an enormous reduction in computational cost as result. The performance of the proposed model with a fit to ChR2(H134R) was tested, by comparing the neural response in a regular spiking neuron to the response obtained with the non-instantaneous, four state Markov model (4SB), derived by Williams et al. (2013). Finally, a computational speed gain was observed with the proposed model in a regular spiking and sparse Pyramidal-Interneuron-Network-Gamma (sPING) network simulation with respect to the 4SB-model, due to the former having two differential equations less. Consequently, the proposed model allows for computationally efficient optogenetic neurostimulation and with the proposed fitting procedure will be valuable for further research in the field of optogenetics.
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Affiliation(s)
- Ruben Schoeters
- WAVES, Department of Information Technology (INTEC), Ghent University/IMEC, Ghent, Belgium
| | - Thomas Tarnaud
- WAVES, Department of Information Technology (INTEC), Ghent University/IMEC, Ghent, Belgium
| | - Luc Martens
- WAVES, Department of Information Technology (INTEC), Ghent University/IMEC, Ghent, Belgium
| | - Wout Joseph
- WAVES, Department of Information Technology (INTEC), Ghent University/IMEC, Ghent, Belgium
| | - Robrecht Raedt
- 4BRAIN, Department of Neurology, Institute for Neuroscience, Ghent University, Ghent, Belgium
| | - Emmeric Tanghe
- WAVES, Department of Information Technology (INTEC), Ghent University/IMEC, Ghent, Belgium
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11
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Hontani Y, Broser M, Luck M, Weißenborn J, Kloz M, Hegemann P, Kennis JTM. Dual Photoisomerization on Distinct Potential Energy Surfaces in a UV-Absorbing Rhodopsin. J Am Chem Soc 2020; 142:11464-11473. [PMID: 32475117 PMCID: PMC7315636 DOI: 10.1021/jacs.0c03229] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
![]()
UV-absorbing rhodopsins are essential
for UV vision and sensing
in all kingdoms of life. Unlike the well-known visible-absorbing rhodopsins,
which bind a protonated retinal Schiff base for light absorption,
UV-absorbing rhodopsins bind an unprotonated retinal Schiff base.
Thus far, the photoreaction dynamics and mechanisms of UV-absorbing
rhodopsins have remained essentially unknown. Here, we report the
complete excited- and ground-state dynamics of the UV form of histidine
kinase rhodopsin 1 (HKR1) from eukaryotic algae, using femtosecond
stimulated Raman spectroscopy (FSRS) and transient absorption spectroscopy,
covering time scales from femtoseconds to milliseconds. We found that
energy-level ordering is inverted with respect to visible-absorbing
rhodopsins, with an optically forbidden low-lying S1 excited
state that has Ag– symmetry and a higher-lying UV-absorbing
S2 state of Bu+ symmetry. UV-photoexcitation
to the S2 state elicits a unique dual-isomerization reaction:
first, C13=C14 cis–trans isomerization occurs during S2–S1 evolution
in <100 fs. This very fast reaction features the remarkable property
that the newly formed isomer appears in the excited state rather than
in the ground state. Second, C15=N16 anti–syn isomerization occurs on the S1–S0 evolution to the ground state in 4.8 ps. We detected two
ground-state unprotonated retinal photoproducts, 13-trans/15-anti (all-trans) and 13-cis/15-syn, after relaxation to the ground
state. These isomers become protonated in 58 μs and 3.2 ms,
respectively, resulting in formation of the blue-absorbing form of
HKR1. Our results constitute a benchmark of UV-induced photochemistry
of animal and microbial rhodopsins.
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Affiliation(s)
- Yusaku Hontani
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan, Amsterdam 1081 HV, The Netherlands
| | - Matthias Broser
- Institut für Biologie, Experimentelle Biophysik, Humboldt Universität zu Berlin, Invalidenstrasse 42, D-10115 Berlin, Germany
| | - Meike Luck
- Institut für Biologie, Experimentelle Biophysik, Humboldt Universität zu Berlin, Invalidenstrasse 42, D-10115 Berlin, Germany
| | - Jörn Weißenborn
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan, Amsterdam 1081 HV, The Netherlands
| | - Miroslav Kloz
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan, Amsterdam 1081 HV, The Netherlands.,ELI-Beamlines, Institute of Physics, Na Slovance 2, 182 21 Praha 8, Czech Republic
| | - Peter Hegemann
- Institut für Biologie, Experimentelle Biophysik, Humboldt Universität zu Berlin, Invalidenstrasse 42, D-10115 Berlin, Germany
| | - John T M Kennis
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan, Amsterdam 1081 HV, The Netherlands
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12
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Buhrke D, Hildebrandt P. Probing Structure and Reaction Dynamics of Proteins Using Time-Resolved Resonance Raman Spectroscopy. Chem Rev 2019; 120:3577-3630. [PMID: 31814387 DOI: 10.1021/acs.chemrev.9b00429] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The mechanistic understanding of protein functions requires insight into the structural and reaction dynamics. To elucidate these processes, a variety of experimental approaches are employed. Among them, time-resolved (TR) resonance Raman (RR) is a particularly versatile tool to probe processes of proteins harboring cofactors with electronic transitions in the visible range, such as retinal or heme proteins. TR RR spectroscopy offers the advantage of simultaneously providing molecular structure and kinetic information. The various TR RR spectroscopic methods can cover a wide dynamic range down to the femtosecond time regime and have been employed in monitoring photoinduced reaction cascades, ligand binding and dissociation, electron transfer, enzymatic reactions, and protein un- and refolding. In this account, we review the achievements of TR RR spectroscopy of nearly 50 years of research in this field, which also illustrates how the role of TR RR spectroscopy in molecular life science has changed from the beginning until now. We outline the various methodological approaches and developments and point out current limitations and potential perspectives.
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Affiliation(s)
- David Buhrke
- Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17, Juni 135, D-10623 Berlin, Germany
| | - Peter Hildebrandt
- Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17, Juni 135, D-10623 Berlin, Germany
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13
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Oppermann J, Fischer P, Silapetere A, Liepe B, Rodriguez-Rozada S, Flores-Uribe J, Schiewer E, Keidel A, Vierock J, Kaufmann J, Broser M, Luck M, Bartl F, Hildebrandt P, Wiegert JS, Béjà O, Hegemann P, Wietek J. MerMAIDs: a family of metagenomically discovered marine anion-conducting and intensely desensitizing channelrhodopsins. Nat Commun 2019; 10:3315. [PMID: 31346176 PMCID: PMC6658528 DOI: 10.1038/s41467-019-11322-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 06/24/2019] [Indexed: 01/07/2023] Open
Abstract
Channelrhodopsins (ChRs) are algal light-gated ion channels widely used as optogenetic tools for manipulating neuronal activity. ChRs desensitize under continuous bright-light illumination, resulting in a significant decline of photocurrents. Here we describe a metagenomically identified family of phylogenetically distinct anion-conducting ChRs (designated MerMAIDs). MerMAIDs almost completely desensitize during continuous illumination due to accumulation of a late non-conducting photointermediate that disrupts the ion permeation pathway. MerMAID desensitization can be fully explained by a single photocycle in which a long-lived desensitized state follows the short-lived conducting state. A conserved cysteine is the critical factor in desensitization, as its mutation results in recovery of large stationary photocurrents. The rapid desensitization of MerMAIDs enables their use as optogenetic silencers for transient suppression of individual action potentials without affecting subsequent spiking during continuous illumination. Our results could facilitate the development of optogenetic tools from metagenomic databases and enhance general understanding of ChR function.
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Affiliation(s)
- Johannes Oppermann
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Paul Fischer
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Arita Silapetere
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Bernhard Liepe
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Silvia Rodriguez-Rozada
- Research Group Synaptic Wiring and Information Processing, Center for Molecular Neurobiology Hamburg, Falkenried 94, 20251, Hamburg, Germany
| | - José Flores-Uribe
- Technion-Israel Institute of Technology, 32000, Haifa, Israel
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, 50829, Germany
| | - Enrico Schiewer
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Anke Keidel
- Institute for Chemistry, Physical Chemistry/Biophysical Chemistry, Technische Universität Berlin, Straße des 17. Juni 135, 10623, Berlin, Germany
| | - Johannes Vierock
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Joel Kaufmann
- Institute for Biology, Biophysical Chemistry, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Matthias Broser
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Meike Luck
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Franz Bartl
- Institute for Biology, Biophysical Chemistry, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany
| | - Peter Hildebrandt
- Institute for Chemistry, Physical Chemistry/Biophysical Chemistry, Technische Universität Berlin, Straße des 17. Juni 135, 10623, Berlin, Germany
| | - J Simon Wiegert
- Research Group Synaptic Wiring and Information Processing, Center for Molecular Neurobiology Hamburg, Falkenried 94, 20251, Hamburg, Germany
| | - Oded Béjà
- Technion-Israel Institute of Technology, 32000, Haifa, Israel
| | - Peter Hegemann
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany.
| | - Jonas Wietek
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115, Berlin, Germany.
- Department of Neurobiology, Weizmann Institute of Science, 7610001, Rehovot, Israel.
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14
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Hontani Y, Ganapathy S, Frehan S, Kloz M, de Grip WJ, Kennis JTM. Photoreaction Dynamics of Red-Shifting Retinal Analogues Reconstituted in Proteorhodopsin. J Phys Chem B 2019; 123:4242-4250. [PMID: 30998011 PMCID: PMC6526469 DOI: 10.1021/acs.jpcb.9b01136] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
![]()
Microbial rhodopsins
constitute a key protein family in optobiotechnological
applications such as optogenetics and voltage imaging. Spectral tuning
of rhodopsins into the deep-red and near-infrared spectral regions
is of great demand in such applications because more bathochromic
light into the near-infrared range penetrates deeper in living tissue.
Recently, retinal analogues have been successfully used in ion transporting
and fluorescent rhodopsins to achieve red-shifted absorption, activity,
and emission properties. Understanding their photochemical mechanism
is essential for further design of appropriate retinal analogues but
is yet only poorly understood for most retinal analogue pigments.
Here, we report the photoreaction dynamics of red-shifted analogue
pigments of the proton pump proteorhodopsin (PR) containing A2 (all-trans-3,4-dehydroretinal), MOA2 (all-trans-3-methoxy-3,4-dehydroretinal), or DMAR (all-trans-3-dimethylamino-16-nor-1,2,3,4-didehydroretinal), utilizing femto-
to submillisecond transient absorption spectroscopy. We found that
the A2 analogue photoisomerizes in 1.4, 3.0, and/or 13 ps upon 510
nm light illumination, which is comparable to the native retinal (A1)
in PR. On the other hand, the deprotonation of the A2 pigment Schiff
base was observed with a dominant time constant of 67 μs, which
is significantly slower than the A1 pigment. In the MOA2 pigment,
no isomerization or photoproduct formation was detected upon 520 nm
excitation, implying that all the excited molecules returned to the
initial ground state in 2.0 and 4.2 ps. The DMAR pigment showed very
slow excited state dynamics similar to the previously studied MMAR
pigment, but only very little photoproduct was formed. The low efficiency
of the photoproduct formation likely is the reason why DMAR analogue
pigments of PR showed very weak proton pumping activity.
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Affiliation(s)
- Yusaku Hontani
- Department of Physics and Astronomy , Vrije Universiteit , Amsterdam 1081 HV , The Netherlands
| | - Srividya Ganapathy
- Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories , Leiden University , Leiden 2300 RA , The Netherlands
| | - Sean Frehan
- Department of Physics and Astronomy , Vrije Universiteit , Amsterdam 1081 HV , The Netherlands
| | - Miroslav Kloz
- ELI-Beamlines , Institute of Physics , Na Slovance 2 , Praha 8 182 21 , Czech Republic
| | - Willem J de Grip
- Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories , Leiden University , Leiden 2300 RA , The Netherlands.,Department of Biochemistry , Radboud University Medical Center , Nijmegen 6500 HB , The Netherlands
| | - John T M Kennis
- Department of Physics and Astronomy , Vrije Universiteit , Amsterdam 1081 HV , The Netherlands
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15
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Unifying photocycle model for light adaptation and temporal evolution of cation conductance in channelrhodopsin-2. Proc Natl Acad Sci U S A 2019; 116:9380-9389. [PMID: 31004059 PMCID: PMC6510988 DOI: 10.1073/pnas.1818707116] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Although channelrhodopsin (ChR) is a widely applied light-activated ion channel, important properties such as light adaptation, photocurrent inactivation, and alteration of the ion selectivity during continuous illumination are not well understood from a molecular perspective. Herein, we address these open questions using single-turnover electrophysiology, time-resolved step-scan FTIR, and Raman spectroscopy of fully dark-adapted ChR2. This yields a unifying parallel photocycle model integrating now all so far controversial discussed data. In dark-adapted ChR2, the protonated retinal Schiff base chromophore (RSBH+) adopts an all-trans,C=N-anti conformation only. Upon light activation, a branching reaction into either a 13-cis,C=N-anti or a 13-cis,C=N-syn retinal conformation occurs. The anti-cycle features sequential H+ and Na+ conductance in a late M-like state and an N-like open-channel state. In contrast, the 13-cis,C=N-syn isomer represents a second closed-channel state identical to the long-lived P480 state, which has been previously assigned to a late intermediate in a single-photocycle model. Light excitation of P480 induces a parallel syn-photocycle with an open-channel state of small conductance and high proton selectivity. E90 becomes deprotonated in P480 and stays deprotonated in the C=N-syn cycle. Deprotonation of E90 and successive pore hydration are crucial for late proton conductance following light adaptation. Parallel anti- and syn-photocycles now explain inactivation and ion selectivity changes of ChR2 during continuous illumination, fostering the future rational design of optogenetic tools.
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16
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Luck M, Velázquez Escobar F, Glass K, Sabotke MI, Hagedorn R, Corellou F, Siebert F, Hildebrandt P, Hegemann P. Photoreactions of the Histidine Kinase Rhodopsin Ot-HKR from the Marine Picoalga Ostreococcus tauri. Biochemistry 2019; 58:1878-1891. [PMID: 30768260 DOI: 10.1021/acs.biochem.8b01200] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The tiny picoalga, Ostreococcus tauri, originating from the Thau Lagoon is a member of the marine phytoplankton. Because of its highly reduced genome and small cell size, while retaining the fundamental requirements of a eukaryotic photosynthetic cell, it became a popular model organism for studying photosynthesis or circadian clock-related processes. We analyzed the spectroscopic properties of the photoreceptor domain of the histidine kinase rhodopsin Ot-HKR that is suggested to be involved in the light-induced entrainment of the Ostreococcus circadian clock. We found that the rhodopsin, Ot-Rh, dark state absorbs maximally at 505 nm. Exposure to green-orange light led to the accumulation of a blue-shifted M-state-like absorbance form with a deprotonated Schiff base. This Ot-Rh P400 state had an unusually long lifetime of several minutes. A second long-living photoproduct with a red-shifted absorbance, P560, accumulated upon illumination with blue/UVA light. The resulting photochromicity of the rhodopsin is expected to be advantageous to its function as a molecular control element of the signal transducing HKR domains. The light intensity and the ratio of blue vs green light are reflected by the ratio of rhodopsin molecules in the long-living absorbance forms. Furthermore, dark-state absorbance and the photocycle kinetics vary with the salt content of the environment substantially. This observation is attributed to anion binding in the dark state and a transient anion release during the photocycle, indicating that the salinity affects the photoinduced processes.
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Affiliation(s)
- Meike Luck
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Berlin 10115 , Germany
| | | | - Kathrin Glass
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Berlin 10115 , Germany
| | - Mareike-Isabel Sabotke
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Berlin 10115 , Germany
| | - Rolf Hagedorn
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Berlin 10115 , Germany
| | - Florence Corellou
- Laboratoire d'Oceanographie Microbienne , Université Pierre et Marie Curie (Paris 6), Centre National de la Recherche Scientifique, Unité Mixte de Recherche , 7621 , Observatoire Oceanologique, Banyuls/mer , France
| | - Friedrich Siebert
- Institute of Chemistry, Technische Universität Berlin , Berlin 10623 , Germany.,Institut für Molekulare Medizin und Zellforschung, Sektion Biophysik , Albert-Ludwigs-Universität Freiburg , Freiburg 79104 , Germany
| | - Peter Hildebrandt
- Institute of Chemistry, Technische Universität Berlin , Berlin 10623 , Germany
| | - Peter Hegemann
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Berlin 10115 , Germany
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17
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Böhm M, Boness D, Fantisch E, Erhard H, Frauenholz J, Kowalzyk Z, Marcinkowski N, Kateriya S, Hegemann P, Kreimer G. Channelrhodopsin-1 Phosphorylation Changes with Phototactic Behavior and Responds to Physiological Stimuli in Chlamydomonas. THE PLANT CELL 2019; 31:886-910. [PMID: 30862615 PMCID: PMC6501600 DOI: 10.1105/tpc.18.00936] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 02/25/2019] [Accepted: 03/11/2019] [Indexed: 05/26/2023]
Abstract
The unicellular alga Chlamydomonas (Chlamydomonas reinhardtii) exhibits oriented movement responses (phototaxis) to light over more than three log units of intensity. Phototaxis thus depends on the cell's ability to adjust the sensitivity of its photoreceptors to ambient light conditions. In Chlamydomonas, the photoreceptors for phototaxis are the channelrhodopsins (ChR)1 and ChR2; these light-gated cation channels are located in the plasma membrane. Although ChRs are widely used in optogenetic studies, little is known about ChR signaling in algae. We characterized the in vivo phosphorylation of ChR1. Its reversible phosphorylation occurred within seconds as a graded response to changes in the light intensity and ionic composition of the medium and depended on an elevated cytosolic Ca2+ concentration. Changes in the phototactic sign were accompanied by alterations in the phosphorylation status of ChR1. Furthermore, compared with the wild type, a permanently negative phototactic mutant required higher light intensities to evoke ChR1 phosphorylation. C-terminal truncation of ChR1 disturbed its reversible phosphorylation, whereas it was normal in ChR2-knockout and eyespot-assembly mutants. The identification of phosphosites in regions important for ChR1 function points to their potential regulatory role(s). We propose that multiple ChR1 phosphorylation, regulated via a Ca2+-based feedback loop, is an important component in the adaptation of phototactic sensitivity in Chlamydomonas.
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Affiliation(s)
- Michaela Böhm
- Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
| | - David Boness
- Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
| | - Elisabeth Fantisch
- Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
| | - Hanna Erhard
- Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
| | - Julia Frauenholz
- Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
| | - Zarah Kowalzyk
- Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
| | - Nadin Marcinkowski
- Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
| | - Suneel Kateriya
- School of Biotechnology, Jawaharlal Nehru University, 110067 New Delhi, India
| | - Peter Hegemann
- Institute for Experimental Biophysics, Humboldt University, 10115 Berlin, Germany
| | - Georg Kreimer
- Department of Biology, Friedrich-Alexander University, 91058 Erlangen, Germany
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18
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Hontani Y, Ganapathy S, Frehan S, Kloz M, de Grip WJ, Kennis JTM. Strong pH-Dependent Near-Infrared Fluorescence in a Microbial Rhodopsin Reconstituted with a Red-Shifting Retinal Analogue. J Phys Chem Lett 2018; 9:6469-6474. [PMID: 30376338 PMCID: PMC6240888 DOI: 10.1021/acs.jpclett.8b02780] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 10/30/2018] [Indexed: 06/08/2023]
Abstract
Near-infrared (NIR)-driven rhodopsins are of great interest in optogenetics and other optobiotechnological developments such as artificial photosynthesis and deep-tissue voltage imaging. Here we report that the proton pump proteorhodopsin (PR) containing a NIR-active retinal analogue (PR:MMAR) exhibits intense NIR fluorescence at a quantum yield of 3.3%. This is 130 times higher than native PR ( Lenz , M. O. ; Biophys J. 2006 , 91 , 255 - 262 ) and 3-8 times higher than the QuasAr and PROPS voltage sensors ( Kralj , J. ; Science 2011 , 333 , 345 - 348 ; Hochbaum , D. R. ; Nat. Methods 2014 , 11 , 825 - 833 ). The NIR fluorescence strongly depends on the pH in the range of 6-8.5, suggesting potential application of MMAR-binding proteins as ultrasensitive NIR-driven pH and/or voltage sensors. Femtosecond transient absorption spectroscopy showed that upon near-IR excitation, PR:MMAR features an unusually long fluorescence lifetime of 310 ps and the absence of isomerized photoproducts, consistent with the high fluorescence quantum yield. Stimulated Raman analysis indicates that the NIR-absorbing species develops upon protonation of a conserved aspartate, which promotes charge delocalization and bond length leveling due to an additional methylamino group in MMAR, in essence providing a secondary protonated Schiff base. This results in much smaller bond length alteration along the conjugated backbone, thereby conferring significant single-bond character to the C13═C14 bond and structural deformation of the chromophore, which interferes with photoinduced isomerization and extends the lifetime for fluorescence. Hence, our studies allow for a molecular understanding of the relation between absorption/emission wavelength, isomerization, and fluorescence in PR:MMAR. As acidification enhances the resonance state, this explains the strong pH dependence of the NIR emission.
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Affiliation(s)
- Yusaku Hontani
- Department
of Physics and Astronomy, Vrije Universiteit, Amsterdam 1081 HV, The Netherlands
| | - Srividya Ganapathy
- Department
of Biophysical Organic Chemistry, Leiden Institute of
Chemistry, Gorlaeus Laboratories, Leiden University, Leiden 2300 RA, The Netherlands
| | - Sean Frehan
- Department
of Physics and Astronomy, Vrije Universiteit, Amsterdam 1081 HV, The Netherlands
| | - Miroslav Kloz
- Department
of Physics and Astronomy, Vrije Universiteit, Amsterdam 1081 HV, The Netherlands
- ELI-Beamlines,
Institute of Physics, Na Slovance 2, 182 21 Praha 8, Czech Republic
| | - Willem J. de Grip
- Department
of Biophysical Organic Chemistry, Leiden Institute of
Chemistry, Gorlaeus Laboratories, Leiden University, Leiden 2300 RA, The Netherlands
- Department
of Biochemistry, Radboud University Medical
Center, Nijmegen 6500 HB, The Netherlands
| | - John T. M. Kennis
- Department
of Physics and Astronomy, Vrije Universiteit, Amsterdam 1081 HV, The Netherlands
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19
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Kim YS, Kato HE, Yamashita K, Ito S, Inoue K, Ramakrishnan C, Fenno LE, Evans KE, Paggi JM, Dror RO, Kandori H, Kobilka BK, Deisseroth K. Crystal structure of the natural anion-conducting channelrhodopsin GtACR1. Nature 2018; 561:343-348. [PMID: 30158696 PMCID: PMC6340299 DOI: 10.1038/s41586-018-0511-6] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 08/13/2018] [Indexed: 01/08/2023]
Abstract
The naturally occurring channelrhodopsin variant anion channelrhodopsin-1 (ACR1), discovered in the cryptophyte algae Guillardia theta, exhibits large light-gated anion conductance and high anion selectivity when expressed in heterologous settings, properties that support its use as an optogenetic tool to inhibit neuronal firing with light. However, molecular insight into ACR1 is lacking owing to the absence of structural information underlying light-gated anion conductance. Here we present the crystal structure of G. theta ACR1 at 2.9 Å resolution. The structure reveals unusual architectural features that span the extracellular domain, retinal-binding pocket, Schiff-base region, and anion-conduction pathway. Together with electrophysiological and spectroscopic analyses, these findings reveal the fundamental molecular basis of naturally occurring light-gated anion conductance, and provide a framework for designing the next generation of optogenetic tools.
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Affiliation(s)
- Yoon Seok Kim
- Department of Bioengineering, Department of Psychiatry and Behavioral Sciences, and Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Hideaki E Kato
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.
- PRESTO, Japan Science and Technology Agency, Honcho, Kawaguchi, Japan.
| | | | - Shota Ito
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Japan
| | - Keiichi Inoue
- PRESTO, Japan Science and Technology Agency, Honcho, Kawaguchi, Japan
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Japan
- OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya, Japan
| | - Charu Ramakrishnan
- Department of Bioengineering, Department of Psychiatry and Behavioral Sciences, and Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Lief E Fenno
- Department of Bioengineering, Department of Psychiatry and Behavioral Sciences, and Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Kathryn E Evans
- Department of Bioengineering, Department of Psychiatry and Behavioral Sciences, and Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Joseph M Paggi
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA
| | - Ron O Dror
- Department of Computer Science, Stanford University, Stanford, CA, USA
- Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Japan
- OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya, Japan
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Karl Deisseroth
- Department of Bioengineering, Department of Psychiatry and Behavioral Sciences, and Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA.
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20
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Saita M, Pranga-Sellnau F, Resler T, Schlesinger R, Heberle J, Lorenz-Fonfria VA. Photoexcitation of the P4480 State Induces a Secondary Photocycle That Potentially Desensitizes Channelrhodopsin-2. J Am Chem Soc 2018; 140:9899-9903. [DOI: 10.1021/jacs.8b03931] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Mattia Saita
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Franziska Pranga-Sellnau
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Tom Resler
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Ramona Schlesinger
- Genetic Biophysics, Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Joachim Heberle
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Victor A. Lorenz-Fonfria
- Institute of Molecular Science, Universitat de València, 46980 Paterna, Spain
- Department of Biochemistry and Molecular Biology, Universitat de València, 46100 Burjassot, Spain
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21
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Scheib U, Broser M, Constantin OM, Yang S, Gao S, Mukherjee S, Stehfest K, Nagel G, Gee CE, Hegemann P. Rhodopsin-cyclases for photocontrol of cGMP/cAMP and 2.3 Å structure of the adenylyl cyclase domain. Nat Commun 2018; 9:2046. [PMID: 29799525 PMCID: PMC5967339 DOI: 10.1038/s41467-018-04428-w] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 04/26/2018] [Indexed: 12/17/2022] Open
Abstract
The cyclic nucleotides cAMP and cGMP are important second messengers that orchestrate fundamental cellular responses. Here, we present the characterization of the rhodopsin-guanylyl cyclase from Catenaria anguillulae (CaRhGC), which produces cGMP in response to green light with a light to dark activity ratio >1000. After light excitation the putative signaling state forms with τ = 31 ms and decays with τ = 570 ms. Mutations (up to 6) within the nucleotide binding site generate rhodopsin-adenylyl cyclases (CaRhACs) of which the double mutated YFP-CaRhAC (E497K/C566D) is the most suitable for rapid cAMP production in neurons. Furthermore, the crystal structure of the ligand-bound AC domain (2.25 Å) reveals detailed information about the nucleotide binding mode within this recently discovered class of enzyme rhodopsin. Both YFP-CaRhGC and YFP-CaRhAC are favorable optogenetic tools for non-invasive, cell-selective, and spatio-temporally precise modulation of cAMP/cGMP with light. Cyclic AMP and cGMP orchestrate a variety of cellular responses. Here, authors characterize the cGMP producing rhodopsin-guanylyl cyclase from C. anguillulae and derived adenylyl cyclase by a biochemical and structural approach which demonstrates the usability of these cyclases for optogenetic applications.
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Affiliation(s)
- Ulrike Scheib
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, 10115, Berlin, Germany
| | - Matthias Broser
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, 10115, Berlin, Germany
| | - Oana M Constantin
- Institute for Synaptic Physiology, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany
| | - Shang Yang
- Department of Biology, Institute for Molecular Plant Physiology and Biophysics, Biocenter, Julius-Maximilians-University of Würzburg, Julius-von-Sachs-Platz 2, 97082, Würzburg, Germany
| | - Shiqiang Gao
- Department of Biology, Institute for Molecular Plant Physiology and Biophysics, Biocenter, Julius-Maximilians-University of Würzburg, Julius-von-Sachs-Platz 2, 97082, Würzburg, Germany
| | - Shatanik Mukherjee
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, 10115, Berlin, Germany
| | - Katja Stehfest
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, 10115, Berlin, Germany
| | - Georg Nagel
- Department of Biology, Institute for Molecular Plant Physiology and Biophysics, Biocenter, Julius-Maximilians-University of Würzburg, Julius-von-Sachs-Platz 2, 97082, Würzburg, Germany
| | - Christine E Gee
- Institute for Synaptic Physiology, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, 20251, Hamburg, Germany.
| | - Peter Hegemann
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, 10115, Berlin, Germany.
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22
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Abstract
The first stage in biological signaling is based on changes in the functional state of a receptor protein triggered by interaction of the receptor with its ligand(s). The light-triggered nature of photoreceptors allows studies on the mechanism of such changes in receptor proteins using a wide range of biophysical methods and with superb time resolution. Here, we critically evaluate current understanding of proton and electron transfer in photosensory proteins and their involvement both in primary photochemistry and subsequent processes that lead to the formation of the signaling state. An insight emerging from multiple families of photoreceptors is that ultrafast primary photochemistry is followed by slower proton transfer steps that contribute to triggering large protein conformational changes during signaling state formation. We discuss themes and principles for light sensing shared by the six photoreceptor families: rhodopsins, phytochromes, photoactive yellow proteins, light-oxygen-voltage proteins, blue-light sensors using flavin, and cryptochromes.
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Affiliation(s)
- Tilman Kottke
- Department of Chemistry, Bielefeld University, 33615 Bielefeld, Germany
| | - Aihua Xie
- Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078, USA
| | - Delmar S. Larsen
- Department of Chemistry, University of California, Davis, California 95616, USA
| | - Wouter D. Hoff
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma 74078, USA
- Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, USA
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23
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Deisseroth K, Hegemann P. The form and function of channelrhodopsin. Science 2018; 357:357/6356/eaan5544. [PMID: 28912215 PMCID: PMC5723383 DOI: 10.1126/science.aan5544] [Citation(s) in RCA: 155] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Accepted: 07/25/2017] [Indexed: 12/22/2022]
Abstract
Channelrhodopsins are light-gated ion channels that, via regulation of flagellar function, enable single-celled motile algae to seek ambient light conditions suitable for photosynthesis and survival. These plant behavioral responses were initially investigated more than 150 years ago. Recently, major principles of function for light-gated ion channels have been elucidated by creating channelrhodopsins with kinetics that are accelerated or slowed over orders of magnitude, by discovering and designing channelrhodopsins with altered spectral properties, by solving the high-resolution channelrhodopsin crystal structure, and by structural model-guided redesign of channelrhodopsins for altered ion selectivity. Each of these discoveries not only revealed basic principles governing the operation of light-gated ion channels, but also enabled the creation of new proteins for illuminating, via optogenetics, the fundamentals of brain function.
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Affiliation(s)
- Karl Deisseroth
- Department of Bioengineering, Stanford University, Stanford, CA, USA. .,Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA.,Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Peter Hegemann
- Institute for Biology, Humboldt Universität zu Berlin, D-10115 Berlin, Germany. .,Experimental Biophysics, Humboldt Universität zu Berlin, D-10115 Berlin, Germany
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24
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Jagtap AP, Geiger MA, Stöppler D, Orwick-Rydmark M, Oschkinat H, Sigurdsson ST. bcTol : a highly water-soluble biradical for efficient dynamic nuclear polarization of biomolecules. Chem Commun (Camb) 2018; 52:7020-3. [PMID: 27161650 DOI: 10.1039/c6cc01813k] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Dynamic nuclear polarization (DNP) is an efficient method to overcome the inherent low sensitivity of magic-angle spinning (MAS) solid-state NMR. We report a new polarizing agent (), designed for biological applications, that yielded an enhancement value of 244 in a microcrystalline SH3 domain sample at 110 K.
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Affiliation(s)
- Anil P Jagtap
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland.
| | - Michel-Andreas Geiger
- NMR supported structural biology, Leibniz-Institut for Molecular Biology (FMP), Robert-Roessle-Str. 10, 13125 Berlin, Germany.
| | - Daniel Stöppler
- NMR supported structural biology, Leibniz-Institut for Molecular Biology (FMP), Robert-Roessle-Str. 10, 13125 Berlin, Germany.
| | - Marcella Orwick-Rydmark
- NMR supported structural biology, Leibniz-Institut for Molecular Biology (FMP), Robert-Roessle-Str. 10, 13125 Berlin, Germany.
| | - Hartmut Oschkinat
- NMR supported structural biology, Leibniz-Institut for Molecular Biology (FMP), Robert-Roessle-Str. 10, 13125 Berlin, Germany.
| | - Snorri Th Sigurdsson
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland.
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25
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Itin B, Sergeyev IV. Strategies for Efficient Sample Preparation for Dynamic Nuclear Polarization Solid-State NMR of Biological Macromolecules. Methods Mol Biol 2018; 1688:133-154. [PMID: 29151208 DOI: 10.1007/978-1-4939-7386-6_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Solid-state NMR (SSNMR) is a powerful tool for the elucidation of structure and dynamics in biological macromolecules. Over the years, SSNMR spectroscopists have developed an array of techniques enabling the measurement of internuclear correlations, distances, and torsional angles; these have been applied to the study of a number of biological systems that are difficult to study by X-ray crystallography and solution NMR, including key biological targets such as membrane proteins and amyloid fibrils. Applications of SSNMR to other topic areas, including materials science, pharmaceuticals, and small molecules, have also flourished in recent years. These studies, however, have always been hampered by the low inherent sensitivity of SSNMR, requiring large amounts of both sample and time for data collection. By taking advantage of unpaired electrons doped into a sample as a ready source of additional nuclear polarization, dynamic nuclear polarization (DNP) has brought about large improvements in SSNMR sensitivity. These, in turn, have enabled structural studies of previously inaccessible targets, such as large protein complexes, nucleic acids, viral capsids, and membrane proteins in vivo. Herein, we focus on sample preparation strategies and considerations for scientists interested in applying DNP to challenging systems.
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Affiliation(s)
- Boris Itin
- New York Structural Biology Center, 89 Convent Avenue, New York, NY, 10027, USA.
| | - Ivan V Sergeyev
- Bruker Biospin Corporation, 15 Fortune Drive, Billerica, MA, 01821, USA
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26
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Absorption and Emission Spectroscopic Investigation of Thermal Dynamics and Photo-Dynamics of the Rhodopsin Domain of the Rhodopsin-Guanylyl Cyclase from the Nematophagous Fungus Catenaria anguillulae. Int J Mol Sci 2017; 18:ijms18102099. [PMID: 28981475 PMCID: PMC5666781 DOI: 10.3390/ijms18102099] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 09/27/2017] [Accepted: 09/28/2017] [Indexed: 11/16/2022] Open
Abstract
The rhodopsin-guanylyl cyclase from the nematophagous fungus Catenaria anguillulae belongs to a recently discovered class of enzymerhodopsins and may find application as a tool in optogenetics. Here the rhodopsin domain CaRh of the rhodopsin-guanylyl cyclase from Catenaria anguillulae was studied by absorption and emission spectroscopic methods. The absorption cross-section spectrum and excitation wavelength dependent fluorescence quantum distributions of CaRh samples were determined (first absorption band in the green spectral region). The thermal stability of CaRh was studied by long-time attenuation measurements at room temperature (20.5 °C) and refrigerator temperature of 3.5 °C. The apparent melting temperature of CaRh was determined by stepwise sample heating up and cooling down (obtained apparent melting temperature: 62 ± 2 °C). The photocycle dynamics of CaRh was investigated by sample excitation to the first inhomogeneous absorption band of the CaRhda dark-adapted state around 590 nm (long-wavelength tail), 530 nm (central region) and 470 nm (short-wavelength tail) and following the absorption spectra development during exposure and after exposure (time resolution 0.0125 s). The original protonated retinal Schiff base PRSBall-trans in CaRhda photo-converted reversibly to protonated retinal Schiff base PRSBall-trans,la1 with restructured surroundings (CaRhla₁ light-adapted state, slightly blue-shifted and broadened first absorption band, recovery to CaRhda with time constant of 0.8 s) and deprotonated retinal Schiff base RSB13-cis (CaRhla₂ light-adapted state, first absorption band in violet to near ultraviolet spectral region, recovery to CaRhda with time constant of 0.35 s). Long-time light exposure of light-adapted CaRhla₁ around 590, 530 and 470 nm caused low-efficient irreversible degradation to photoproducts CaRhprod. Schemes of the primary photocycle dynamics of CaRhda and the secondary photocycle dynamics of CaRhla1 are developed.
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27
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Luck M, Hegemann P. The two parallel photocycles of the Chlamydomonas sensory photoreceptor histidine kinase rhodopsin 1. JOURNAL OF PLANT PHYSIOLOGY 2017; 217:77-84. [PMID: 28784569 DOI: 10.1016/j.jplph.2017.07.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 07/10/2017] [Accepted: 07/11/2017] [Indexed: 06/07/2023]
Abstract
Histidine kinase rhodopsins (HKRs) belong to a class of unexplored sensory photoreceptors that share a similar modular architecture. The light sensing rhodopsin domain is covalently linked to signal-transducing modules and in some cases to a C-terminal guanylyl-cyclase effector. In spite of their wide distribution in unicellular organisms, very little is known about their physiological role and mechanistic functioning. We investigated the photochemical properties of the recombinant rhodopsin-fragment of Cr-HKR1 originating from Chlamydomonas reinhardtii. Our spectroscopic studies revealed an unusual thermal stability of the photoproducts with the deprotonated retinal Schiff base (RSB). Upon UV-irradiation these Rh-UV states with maximal absorbance in the UVA-region (Rh-UV) photochemically convert to stable blue light absorbing rhodopsin (Rh-Bl) with protonated chromophore. The heterogeneity of the sample is based on two parallel photocycles with the chromophore in C15=N-syn- or -anti-configuration. This report represents an attempt to decipher the underlying reaction schemes and interconversions of the two coexisting photocycles.
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Affiliation(s)
- Meike Luck
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Germany.
| | - Peter Hegemann
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Germany
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28
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Kaufmann JCD, Krause BS, Grimm C, Ritter E, Hegemann P, Bartl FJ. Proton transfer reactions in the red light-activatable channelrhodopsin variant ReaChR and their relevance for its function. J Biol Chem 2017; 292:14205-14216. [PMID: 28659342 PMCID: PMC5572910 DOI: 10.1074/jbc.m117.779629] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 06/27/2017] [Indexed: 11/06/2022] Open
Abstract
Channelrhodopsins (ChRs) are light-gated ion channels widely used for activating selected cells in large cellular networks. ChR variants with a red-shifted absorption maximum, such as the modified Volvox carteri ChR1 red-activatable channelrhodopsin ("ReaChR," λmax = 527 nm), are of particular interest because longer wavelengths allow optical excitation of cells in deeper layers of organic tissue. In all ChRs investigated so far, proton transfer reactions and hydrogen bond changes are crucial for the formation of the ion-conducting pore and the selectivity for protons versus cations, such as Na+, K+, and Ca2+ (1). By using a combination of electrophysiological measurements and UV-visible and FTIR spectroscopy, we characterized the proton transfer events in the photocycle of ReaChR and describe their relevance for its function. 1) The central gate residue Glu130 (Glu90 in Chlamydomonas reinhardtii (Cr) ChR2) (i) undergoes a hydrogen bond change in D → K transition and (ii) deprotonates in K → M transition. Its negative charge in the open state is decisive for proton selectivity. 2) The counter-ion Asp293 (Asp253 in CrChR2) receives the retinal Schiff base proton during M-state formation. Starting from M, a photocycle branching occurs involving (i) a direct M → D transition and (ii) formation of late photointermediates N and O. 3) The DC pair residue Asp196 (Asp156 in CrChR2) deprotonates in N → O transition. Interestingly, the D196N mutation increases 15-syn-retinal at the expense of 15-anti, which is the predominant isomer in the wild type, and abolishes the peak current in electrophysiological measurements. This suggests that the peak current is formed by 15-anti species, whereas 15-syn species contribute only to the stationary current.
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Affiliation(s)
- Joel C D Kaufmann
- From the Institut für medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany,.
| | | | | | | | | | - Franz J Bartl
- From the Institut für medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany,; Institut für Biologie, Biophysikalische Chemie, Humboldt-Universität zu Berlin, Invalidenstrasse 42, 10115 Berlin, Germany.
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29
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Abstract
Channelrhodopsin (ChR) is a key protein of the optogenetic toolkit. C1C2, a functional chimeric protein of Chlamydomonas reinhardtii ChR1 and ChR2, is the only ChR whose crystal structure has been solved, and thus uniquely suitable for structure-based analysis. We report C1C2 photoreaction dynamics with ultrafast transient absorption and multi-pulse spectroscopy combined with target analysis and structure-based hybrid quantum mechanics/molecular mechanics calculations. Two relaxation pathways exist on the excited (S1) state through two conical intersections CI1 and CI2, that are reached via clockwise and counter-clockwise rotations: (i) the C13=C14 isomerization path with 450 fs via CI1 and (ii) a relaxation path to the initial ground state with 2.0 ps and 11 ps via CI2, depending on the hydrogen-bonding network, hence indicating active-site structural heterogeneity. The presence of the additional conical intersection CI2 rationalizes the relatively low quantum yield of photoisomerization (30 ± 3%), reported here. Furthermore, we show the photoreaction dynamics from picoseconds to seconds, characterizing the complete photocycle of C1C2.
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30
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Applications of solid-state NMR to membrane proteins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1577-1586. [PMID: 28709996 DOI: 10.1016/j.bbapap.2017.07.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 06/30/2017] [Accepted: 07/07/2017] [Indexed: 11/23/2022]
Abstract
Membrane proteins mediate flow of molecules, signals, and energy between cells and intracellular compartments. Understanding membrane protein function requires a detailed understanding of the structural and dynamic properties involved. Lipid bilayers provide a native-like environment for structure-function investigations of membrane proteins. In this review we give a general discourse on the recent progress in the field of solid-state NMR of membrane proteins. Solid-state NMR is a variation of NMR spectroscopy that is applicable to molecular systems with restricted mobility, such as high molecular weight proteins and protein complexes, supramolecular assemblies, or membrane proteins in a phospholipid environment. We highlight recent advances in applications of solid-state NMR to membrane proteins, specifically focusing on the recent developments in the field of Dynamic Nuclear Polarization, proton detection, and solid-state NMR applications in situ (in cell membranes). This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman.
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31
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Govorunova EG, Sineshchekov OA, Li H, Spudich JL. Microbial Rhodopsins: Diversity, Mechanisms, and Optogenetic Applications. Annu Rev Biochem 2017; 86:845-872. [PMID: 28301742 PMCID: PMC5747503 DOI: 10.1146/annurev-biochem-101910-144233] [Citation(s) in RCA: 229] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Microbial rhodopsins are a family of photoactive retinylidene proteins widespread throughout the microbial world. They are notable for their diversity of function, using variations of a shared seven-transmembrane helix design and similar photochemical reactions to carry out distinctly different light-driven energy and sensory transduction processes. Their study has contributed to our understanding of how evolution modifies protein scaffolds to create new protein chemistry, and their use as tools to control membrane potential with light is fundamental to optogenetics for research and clinical applications. We review the currently known functions and present more in-depth assessment of three functionally and structurally distinct types discovered over the past two years: (a) anion channelrhodopsins (ACRs) from cryptophyte algae, which enable efficient optogenetic neural suppression; (b) cryptophyte cation channelrhodopsins (CCRs), structurally distinct from the green algae CCRs used extensively for neural activation and from cryptophyte ACRs; and
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Affiliation(s)
- Elena G Govorunova
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030; , , ,
| | - Oleg A Sineshchekov
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030; , , ,
| | - Hai Li
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030; , , ,
| | - John L Spudich
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030; , , ,
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32
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Yi A, Li H, Mamaeva N, Fernandez De Cordoba RE, Lugtenburg J, DeGrip WJ, Spudich JL, Rothschild KJ. Structural Changes in an Anion Channelrhodopsin: Formation of the K and L Intermediates at 80 K. Biochemistry 2017; 56:2197-2208. [PMID: 28350445 DOI: 10.1021/acs.biochem.7b00002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A recently discovered natural family of light-gated anion channelrhodopsins (ACRs) from cryptophyte algae provides an effective means of optogenetically silencing neurons. The most extensively studied ACR is from Guillardia theta (GtACR1). Earlier studies of GtACR1 have established a correlation between formation of a blue-shifted L-like intermediate and the anion channel "open" state. To study structural changes of GtACR1 in the K and L intermediates of the photocycle, a combination of low-temperature Fourier transform infrared (FTIR) and ultraviolet-visible absorption difference spectroscopy was used along with stable-isotope retinal labeling and site-directed mutagenesis. In contrast to bacteriorhodopsin (BR) and other microbial rhodopsins, which form only a stable red-shifted K intermediate at 80 K, GtACR1 forms both stable K and L-like intermediates. Evidence includes the appearance of positive ethylenic and fingerprint vibrational bands characteristic of the L intermediate as well as a positive visible absorption band near 485 nm. FTIR difference bands in the carboxylic acid C═O stretching region indicate that several Asp/Glu residues undergo hydrogen bonding changes at 80 K. The Glu68 → Gln and Ser97 → Glu substitutions, residues located close to the retinylidene Schiff base, altered the K:L ratio and several of the FTIR bands in the carboxylic acid region. In the case of the Ser97 → Glu substitution, a significant red-shift of the absorption wavelength of the K and L intermediates occurs. Sequence comparisons suggest that L formation in GtACR1 at 80 K is due in part to the substitution of the highly conserved Leu or Ile at position 93 in helix 3 (BR sequence) with the homologous Met105 in GtACR1.
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Affiliation(s)
- Adrian Yi
- Molecular Biophysics Laboratory, Photonics Center, and Department of Physics, Boston University , Boston, Massachusetts 02215, United States
| | - Hai Li
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, McGovern Medical School , Houston, Texas 77030, United States
| | - Natalia Mamaeva
- Molecular Biophysics Laboratory, Photonics Center, and Department of Physics, Boston University , Boston, Massachusetts 02215, United States
| | - Roberto E Fernandez De Cordoba
- Molecular Biophysics Laboratory, Photonics Center, and Department of Physics, Boston University , Boston, Massachusetts 02215, United States
| | - Johan Lugtenburg
- Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden University , 2300 AR Leiden, The Netherlands
| | - Willem J DeGrip
- Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden University , 2300 AR Leiden, The Netherlands
| | - John L Spudich
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, McGovern Medical School , Houston, Texas 77030, United States
| | - Kenneth J Rothschild
- Molecular Biophysics Laboratory, Photonics Center, and Department of Physics, Boston University , Boston, Massachusetts 02215, United States
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33
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Krause BS, Grimm C, Kaufmann JCD, Schneider F, Sakmar TP, Bartl FJ, Hegemann P. Complex Photochemistry within the Green-Absorbing Channelrhodopsin ReaChR. Biophys J 2017; 112:1166-1175. [PMID: 28355544 PMCID: PMC5374998 DOI: 10.1016/j.bpj.2017.02.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 12/29/2016] [Accepted: 02/01/2017] [Indexed: 11/26/2022] Open
Abstract
Channelrhodopsins (ChRs) are light-activated ion channels widely employed for photostimulation of excitable cells. This study focuses on ReaChR, a chimeric ChR variant with optimal properties for optogenetic applications. We combined electrophysiological recordings with infrared and UV-visible spectroscopic measurements to investigate photocurrents and photochemical properties of ReaChR. Our data imply that ReaChR is green-light activated (λmax = 532 nm) with a non-rhodopsin-like action spectrum peaking at 610 nm for stationary photocurrents. This unusual spectral feature is associated with photoconversion of a previously unknown light-sensitive, blue-shifted photocycle intermediate L (λmax = 495 nm), which is accumulated under continuous illumination. To explain the complex photochemical reactions, we propose a symmetrical two-cycle-model based on the two C15=N isomers of the retinal cofactor with either syn- or anti-configuration, each comprising six consecutive states D, K, L, M, N, and O. Ion conduction involves two states per cycle, the late M- (M2) with a deprotonated retinal Schiff base and the consecutive green-absorbing N-state that both equilibrate via reversible reprotonation. In our model, a fraction of the deprotonated M-intermediate of the anti-cycle may be photoconverted-as the L-state-back to its inherent dark state, or to its M-state pendant (M') of the syn-cycle. The latter reaction pathway requires a C13=C14, C15=N double-isomerization of the retinal chromophore, whereas the intracircular photoconversion of M back to D involves only one C13=C14 double-bond isomerization.
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Affiliation(s)
- Benjamin S Krause
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany.
| | - Christiane Grimm
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Joel C D Kaufmann
- Institute for Medical Physics and Biophysics, Charité Berlin, Berlin, Germany
| | - Franziska Schneider
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Thomas P Sakmar
- Laboratory of Chemical Biology and Signal Transduction, Rockefeller University, New York, New York
| | - Franz J Bartl
- Institute for Medical Physics and Biophysics, Charité Berlin, Berlin, Germany
| | - Peter Hegemann
- Institute of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany.
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34
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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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35
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Stöppler D, Song C, van Rossum BJ, Geiger MA, Lang C, Mroginski MA, Jagtap AP, Sigurdsson ST, Matysik J, Hughes J, Oschkinat H. Dynamic Nuclear Polarization Provides New Insights into Chromophore Structure in Phytochrome Photoreceptors. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201608119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Daniel Stöppler
- Leibniz-Institut für Molekulare Pharmakologie (FMP); NMR-supported Structural Biology; Robert-Rössle-Str. 10 13125 Berlin Germany
- Freie Universität Berlin; Fachbereich BCP; Takustr. 3 14195 Berlin Germany
| | - Chen Song
- Universität Leipzig; Institut für Analytische Chemie; Linnéstr. 3 04103 Leipzig Germany
| | - Barth-Jan van Rossum
- Leibniz-Institut für Molekulare Pharmakologie (FMP); NMR-supported Structural Biology; Robert-Rössle-Str. 10 13125 Berlin Germany
| | - Michel-Andreas Geiger
- Leibniz-Institut für Molekulare Pharmakologie (FMP); NMR-supported Structural Biology; Robert-Rössle-Str. 10 13125 Berlin Germany
- Freie Universität Berlin; Fachbereich BCP; Takustr. 3 14195 Berlin Germany
| | - Christina Lang
- Justus-Liebig-Universität Gießen; Institut für Pflanzenphysiologie; Senckenbergstr. 3 35390 Gießen Germany
| | - Maria-Andrea Mroginski
- Technische Universität Berlin; Institut für Chemie; Straße des 17. Juni 135 10623 Berlin Germany
| | | | | | - Jörg Matysik
- Universität Leipzig; Institut für Analytische Chemie; Linnéstr. 3 04103 Leipzig Germany
| | - Jon Hughes
- Justus-Liebig-Universität Gießen; Institut für Pflanzenphysiologie; Senckenbergstr. 3 35390 Gießen Germany
| | - Hartmut Oschkinat
- Leibniz-Institut für Molekulare Pharmakologie (FMP); NMR-supported Structural Biology; Robert-Rössle-Str. 10 13125 Berlin Germany
- Freie Universität Berlin; Fachbereich BCP; Takustr. 3 14195 Berlin Germany
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Stöppler D, Song C, van Rossum BJ, Geiger MA, Lang C, Mroginski MA, Jagtap AP, Sigurdsson ST, Matysik J, Hughes J, Oschkinat H. Dynamic Nuclear Polarization Provides New Insights into Chromophore Structure in Phytochrome Photoreceptors. Angew Chem Int Ed Engl 2016; 55:16017-16020. [DOI: 10.1002/anie.201608119] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 09/30/2016] [Indexed: 11/12/2022]
Affiliation(s)
- Daniel Stöppler
- Leibniz-Institut für Molekulare Pharmakologie (FMP); NMR-supported Structural Biology; Robert-Rössle-Str. 10 13125 Berlin Germany
- Freie Universität Berlin; Fachbereich BCP; Takustr. 3 14195 Berlin Germany
| | - Chen Song
- Universität Leipzig; Institut für Analytische Chemie; Linnéstr. 3 04103 Leipzig Germany
| | - Barth-Jan van Rossum
- Leibniz-Institut für Molekulare Pharmakologie (FMP); NMR-supported Structural Biology; Robert-Rössle-Str. 10 13125 Berlin Germany
| | - Michel-Andreas Geiger
- Leibniz-Institut für Molekulare Pharmakologie (FMP); NMR-supported Structural Biology; Robert-Rössle-Str. 10 13125 Berlin Germany
- Freie Universität Berlin; Fachbereich BCP; Takustr. 3 14195 Berlin Germany
| | - Christina Lang
- Justus-Liebig-Universität Gießen; Institut für Pflanzenphysiologie; Senckenbergstr. 3 35390 Gießen Germany
| | - Maria-Andrea Mroginski
- Technische Universität Berlin; Institut für Chemie; Straße des 17. Juni 135 10623 Berlin Germany
| | | | | | - Jörg Matysik
- Universität Leipzig; Institut für Analytische Chemie; Linnéstr. 3 04103 Leipzig Germany
| | - Jon Hughes
- Justus-Liebig-Universität Gießen; Institut für Pflanzenphysiologie; Senckenbergstr. 3 35390 Gießen Germany
| | - Hartmut Oschkinat
- Leibniz-Institut für Molekulare Pharmakologie (FMP); NMR-supported Structural Biology; Robert-Rössle-Str. 10 13125 Berlin Germany
- Freie Universität Berlin; Fachbereich BCP; Takustr. 3 14195 Berlin Germany
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Chan SK, Kawaguchi H, Kubo H, Murakami M, Ihara K, Maki K, Kouyama T. Crystal Structure of the 11-cis Isomer of Pharaonis Halorhodopsin: Structural Constraints on Interconversions among Different Isomeric States. Biochemistry 2016; 55:4092-104. [DOI: 10.1021/acs.biochem.6b00277] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Siu Kit Chan
- Department
of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Haruki Kawaguchi
- Department
of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Hiroki Kubo
- Department
of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Midori Murakami
- Department
of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Kunio Ihara
- Center
for Gene Research, Nagoya University, Nagoya 464-8602, Japan
| | - Kosuke Maki
- Department
of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Tsutomu Kouyama
- Department
of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
- RIKEN Harima Branch, 1-1-1, Kouto, Sayo, Hyogo, Japan
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38
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Guo Y, Beyle FE, Bold BM, Watanabe HC, Koslowski A, Thiel W, Hegemann P, Marazzi M, Elstner M. Active site structure and absorption spectrum of channelrhodopsin-2 wild-type and C128T mutant. Chem Sci 2016; 7:3879-3891. [PMID: 30155032 PMCID: PMC6013792 DOI: 10.1039/c6sc00468g] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 02/24/2016] [Indexed: 12/25/2022] Open
Abstract
We show by extensive ground state and absorption spectra simulations that the channelrhodopsin-2 active site samples three different hydrogen-bonding patterns.
In spite of considerable interest, the active site of channelrhodopsin still lacks a detailed atomistic description, the understanding of which could strongly enhance the development of novel optogenetics tools. We present a computational study combining different state-of-the-art techniques, including hybrid quantum mechanics/molecular mechanics schemes and high-level quantum chemical methods, to properly describe the hydrogen-bonding pattern between the retinal chromophore and its counterions in channelrhodopsin-2 Wild-Type and C128T mutant. Especially, we show by extensive ground state dynamics that the active site, containing a glutamic acid (E123) and a water molecule, is highly dynamic, sampling three different hydrogen-bonding patterns. This results in a broad absorption spectrum that is representative of the different structural motifs found. A comparison with bacteriorhodopsin, characterized by a pentagonal hydrogen-bonded active site structure, elucidates their different absorption properties.
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Affiliation(s)
- Yanan Guo
- Department of Theoretical Chemical Biology , Institute of Physical Chemistry , KIT , Kaiserstrasse 12 , 76131 Karlsruhe , Germany . ;
| | - Franziska E Beyle
- Department of Theoretical Chemical Biology , Institute of Physical Chemistry , KIT , Kaiserstrasse 12 , 76131 Karlsruhe , Germany . ;
| | - Beatrix M Bold
- Department of Theoretical Chemical Biology , Institute of Physical Chemistry , KIT , Kaiserstrasse 12 , 76131 Karlsruhe , Germany . ;
| | - Hiroshi C Watanabe
- Research Center for Advanced Science and Technology , The University of Tokyo , 4-6-1 Komaba, Meguro-ku , Tokyo 153-8904 , Japan
| | - Axel Koslowski
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , 45470 Mülheim an der Ruhr , Germany
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , 45470 Mülheim an der Ruhr , Germany
| | - Peter Hegemann
- Institute of Biology , Experimental Biophysics , Humboldt-Universität , Invalidenstraße 42 , D-10115 Berlin , Germany
| | - Marco Marazzi
- Department of Theoretical Chemical Biology , Institute of Physical Chemistry , KIT , Kaiserstrasse 12 , 76131 Karlsruhe , Germany . ;
| | - Marcus Elstner
- Department of Theoretical Chemical Biology , Institute of Physical Chemistry , KIT , Kaiserstrasse 12 , 76131 Karlsruhe , Germany . ;
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Abstract
After the discovery of Channelrhodopsin, a light-gated ion channel, only a few people saw the diverse range of applications for such a protein. Now, more than 10 years later Channelrhodopsins have become widely accepted as the ultimate tool to control the membrane potential of excitable cells via illumination. The demand for more application-specific Channelrhodopsin variants started a race between protein engineers to design improved variants. Even though many engineered variants have undisputable advantages compared to wild-type variants, many users are alienated by the tremendous amount of new variants and their perplexing names. Here, we review new variants whose efficacy has already been proven in neurophysiological experiments, or variants which are likely to extend the optogenetic toolbox. Variants are described based on their mechanistic and operational properties in terms of expression, kinetics, ion selectivity, and wavelength responsivity.
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Affiliation(s)
- Jonas Wietek
- Experimental Biophysics, Humboldt University Berlin, Invalidenstrasse 42, 10115, Berlin, Germany
| | - Matthias Prigge
- Department of Neurobiology, Weizmann Institute of Science, Herzel 234, 76100, Rehovot, Israel.
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