1
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Oka Y, Inoue K. Time-resolved EPR observation of blue-light-induced radical ion pairs in a flavin-Trp dyad. Phys Chem Chem Phys 2024; 26:16444-16448. [PMID: 38808575 DOI: 10.1039/d3cp06219h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
A dyad of flavin and Trp bridged by a p-phenylamide linker was synthesized as an artificial model system to investigate molecular-based magnetic-field sensors relevant to blue-light photoreceptor proteins. The results demonstrated that intramolecular electron transfer generates a radical pair, only the triplet-born one of which has a microsecond lifetime at room temperature.
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Affiliation(s)
- Yoshimi Oka
- Frontier Research Core for Life Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
- Research Promotion Institute, Oita University, 700 Dannoharu, Oita 870-1192, Japan
- Graduate School of Advanced Science and Engineering, Chirality Research Center (CResCent), and International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2), Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima 739-8526, Japan.
| | - Katsuya Inoue
- Graduate School of Advanced Science and Engineering, Chirality Research Center (CResCent), and International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2), Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima 739-8526, Japan.
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2
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Kretschmer K, Frederiksen A, Reinholdt P, Kongsted J, Solov’yov IA. Understanding the Red Shift in the Absorption Spectrum of the FAD Cofactor in ClCry4 Protein. J Phys Chem B 2024; 128:5320-5326. [PMID: 38805723 PMCID: PMC11163422 DOI: 10.1021/acs.jpcb.4c00710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 05/03/2024] [Accepted: 05/16/2024] [Indexed: 05/30/2024]
Abstract
It is still a puzzle that has not been entirely solved how migratory birds utilize the Earth's magnetic field for biannual migration. The most consistent explanation thus far is rooted in the modulation of the biological function of the cryptochrome 4 (Cry4) protein by an external magnetic field. This phenomenon is closely linked with the flavin adenine dinucleotide (FAD) cofactor that is noncovalently bound in the protein. Cry4 is activated by blue light, which is absorbed by the FAD cofactor. Subsequent electron and proton transfers trigger radical pair formation in the protein, which is sensitive to the external magnetic field. An important long-lasting redox state of the FAD cofactor is the signaling (FADH•) state, which is present after the transient electron transfer steps have been completed. Recent experimental efforts succeeded in crystallizing the Cry4 protein from Columbia livia (ClCry4) with all of the important residues needed for protein photoreduction. This specific crystallization of Cry4 protein so far is the only avian cryptochrome crystal structure available, which, however, has great similarity to the Cry4 proteins of night migratory birds. The previous experimental studies of the ClCry4 protein included the absorption properties of the protein in its different redox states. The absorption spectrum of the FADH• state demonstrated a peculiar red shift compared to the photoabsorption properties of the FAD cofactor in its FADH• state in other Cry proteins from other species. The aim of this study is to understand this red shift by employing the tools of computational microscopy and, in particular, a QM/MM approach that relies on the polarizable embedding approximation.
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Affiliation(s)
- Katarina Kretschmer
- Institute of Physics, Carl von Ossietzky Universität Oldenburg, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
| | - Anders Frederiksen
- Institute of Physics, Carl von Ossietzky Universität Oldenburg, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
| | - Peter Reinholdt
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK 5230 Odense, Denmark
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK 5230 Odense, Denmark
| | - Ilia A. Solov’yov
- Institute of Physics, Carl von Ossietzky Universität Oldenburg, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
- Research Centre for Neurosensory
Science, Carl von Ossietzky Universität
Oldenburg, Carl-von-Ossietzky
Str. 9-11, 26129 Oldenburg, Germany
- Center
for Nanoscale Dynamics (CENAD), Carl von
Ossietzky Universität Oldenburg, Ammerländer Heerstr. 114-118, 26129 Oldenburg, Germany
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3
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Romanova N, Utvenko G, Prokshina A, Cellarius F, Fedorishcheva A, Pakhomov A. Migratory birds are able to choose the appropriate migratory direction under dim yellow narrowband light. Proc Biol Sci 2023; 290:20232499. [PMID: 38113940 PMCID: PMC10730290 DOI: 10.1098/rspb.2023.2499] [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: 11/06/2023] [Accepted: 11/21/2023] [Indexed: 12/21/2023] Open
Abstract
Currently, it is generally assumed that migratory birds are oriented in the appropriate migratory direction under UV, blue and green light (short-wavelength) and are unable to use their magnetic compass in total darkness and under yellow and red light (long-wavelength). However, it has also been suggested that the magnetic compass has two sensitivity peaks: in the short and long wavelengths, but with different intensities. In this project, we aimed to study the orientation of long-distance migrants, pied flycatchers (Ficedula hypoleuca), under different narrowband light conditions during autumn and spring migrations. The birds were tested in the natural magnetic field (NMF) and a changed magnetic field (CMF) rotated counterclockwise by 120° under dim green (autumn) and yellow (spring and autumn) light, which are on the 'threshold' between the short-wavelength and long-wavelength light. We showed that pied flycatchers (i) were completely disoriented under green light both in the NMF and CMF but (ii) showed the migratory direction in the NMF and the appropriate response to CMF under yellow light. Our data contradict the results of previous experiments under narrowband green and yellow light and raise doubts about the existence of only short-wavelength magnetoreception. The parameters of natural light change dramatically in spectral composition and intensity after local sunset, and the avian magnetic compass should be adapted to function properly under such constantly changing light conditions.
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Affiliation(s)
- Nadezhda Romanova
- Moscow State Pedagogical University, 1/1 M. Pirogovskaya St., Moscow 119991, Russia
| | - Gleb Utvenko
- Department of Vertebrate Zoology, St. Petersburg State University, 199034 St. Petersburg, Russia
- Biological Station Rybachy, Zoological Institute RAS, Kaliningrad Region, Rybachy 238535, Russia
| | - Anisia Prokshina
- Department of Vertebrate Zoology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Fyodor Cellarius
- Department of Vertebrate Zoology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | | | - Alexander Pakhomov
- Biological Station Rybachy, Zoological Institute RAS, Kaliningrad Region, Rybachy 238535, Russia
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4
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Krischer J, König S, Weisheit W, Mittag M, Büchel C. The C-terminus of a diatom plant-like cryptochrome influences the FAD redox state and binding of interaction partners. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:1934-1948. [PMID: 35034113 DOI: 10.1093/jxb/erac012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
A plant-like cryptochrome of diatom microalgae, CryP, acts as a photoreceptor involved in transcriptional regulation. It contains FAD and 5,10-methenyltetrahydrofolate as chromophores. Here, we demonstrate that the unstructured C-terminal extension (CTE) of CryP has an influence on the redox state of the flavin. In CryP lacking the CTE, the flavin is in the oxidized state (FADox), whereas it is a neutral radical (FADH•) in the full-length protein. When the CTE of CryP is coupled to another diatom cryptochrome that naturally binds FADox, this chimera also binds FADH•. In full-length CryP, FADH• is the most stable redox state and oxidation to FADox is extremely slow, whereas reduction to FADH2 is reversible in the dark in approximately 1 h. We also identified novel interaction partners of this algal CRY and characterized two of them in depth regarding their binding activities. BolA, a putative transcription factor, binds to monomeric and to dimeric CryP via the CTE, independent of the redox state of the flavin. In contrast, an unknown protein, ID42612, which occurs solely in heterokont algae, binds only to CryP dimers. This binding is independent of the CTE and shows slight differences in strength depending on the flavin's redox state.
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Affiliation(s)
- Julia Krischer
- Institute of Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany
| | - Sarah König
- Institute of Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany
| | - Wolfram Weisheit
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University, Jena, Germany
| | - Maria Mittag
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University, Jena, Germany
| | - Claudia Büchel
- Institute of Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany
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5
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Babcock N, Kattnig DR. Radical Scavenging Could Answer the Challenge Posed by Electron-Electron Dipolar Interactions in the Cryptochrome Compass Model. JACS AU 2021; 1:2033-2046. [PMID: 34841416 PMCID: PMC8611662 DOI: 10.1021/jacsau.1c00332] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Indexed: 06/13/2023]
Abstract
Many birds are endowed with a visual magnetic sense that may exploit magnetosensitive radical recombination processes in the protein cryptochrome. In this widely accepted but unproven model, geomagnetic sensitivity is suggested to arise from variations in the recombination rate of a pair of radicals, whose unpaired electron spins undergo coherent singlet-triplet interconversion in the geomagnetic field by coupling to nuclear spins via hyperfine interactions. However, simulations of this conventional radical pair mechanism (RPM) predicted only tiny magnetosensitivities for realistic conditions because the RPM's directional sensitivity is strongly suppressed by the intrinsic electron-electron dipolar (EED) interactions, casting doubt on its viability as a magnetic sensor. We show how this RPM-suppression problem is overcome in a three-radical system in which a third "scavenger" radical reacts with one member of the primary pair. We use this finding to predict substantial magnetic field effects that exceed those of the RPM in the presence of EED interactions in animal cryptochromes.
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Affiliation(s)
- Nathan
Sean Babcock
- Quantum
Biology Laboratory, Howard University, 2400 Sixth Street NW, Washington District of Columbia, 20059, United States of America
- Living
Systems Institute and Department of Physics University of Exeter, Stocker Road, Exeter, EX4 4QD, United Kingdom
| | - Daniel R. Kattnig
- Living
Systems Institute and Department of Physics University of Exeter, Stocker Road, Exeter, EX4 4QD, United Kingdom
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6
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Netušil R, Tomanová K, Chodáková L, Chvalová D, Doležel D, Ritz T, Vácha M. Cryptochrome-dependent magnetoreception in a heteropteran insect continues even after 24 h in darkness. J Exp Biol 2021; 224:272037. [PMID: 34477876 DOI: 10.1242/jeb.243000] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 08/26/2021] [Indexed: 11/20/2022]
Abstract
Sensitivity to magnetic fields is dependent on the intensity and color of light in several animal species. The light-dependent magnetoreception working model points to cryptochrome (Cry) as a protein cooperating with its co-factor flavin, which possibly becomes magnetically susceptible upon excitation by light. The type of Cry involved and what pair of magnetosensitive radicals are responsible is still elusive. Therefore, we developed a conditioning assay for the firebug Pyrrhocoris apterus, an insect species that possesses only the mammalian cryptochrome (Cry II). Here, using the engineered Cry II null mutant, we show that: (i) vertebrate-like Cry II is an essential component of the magnetoreception response, and (ii) magnetic conditioning continues even after 25 h in darkness. The light-dependent and dark-persisting magnetoreception based on Cry II may inspire new perspectives in magnetoreception and cryptochrome research.
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Affiliation(s)
- Radek Netušil
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno 62500, Czech Republic
| | - Kateřina Tomanová
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno 62500, Czech Republic
| | - Lenka Chodáková
- Biology Centre of the Czech Academy of Sciences, České Budějovice 37005, Czech Republic
| | - Daniela Chvalová
- Biology Centre of the Czech Academy of Sciences, České Budějovice 37005, Czech Republic
| | - David Doležel
- Biology Centre of the Czech Academy of Sciences, České Budějovice 37005, Czech Republic
| | - Thorsten Ritz
- Department of Physics and Astronomy, University of California Irvine, Irvine, CA 92697, USA
| | - Martin Vácha
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno 62500, Czech Republic
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7
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Giacomozzi L, Kjær C, Brøndsted Nielsen S, Ashworth EK, Bull JN, Stockett MH. Non-statistical fragmentation in photo-activated flavin mononucleotide anions. J Chem Phys 2021; 155:044305. [PMID: 34340366 DOI: 10.1063/5.0056415] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The spectroscopy and photo-induced dissociation of flavin mononucleotide anions in vacuo are investigated over the 300-500 nm wavelength range. Comparison of the dependence of fragment ion yields as a function of deposited photon energy with calculated dissociation energies and collision-induced dissociation measurements performed under single-collision conditions suggests that a substantial fraction of photo-activated ions decompose through non-statistical fragmentation pathways. Among these pathways is the dominant photo-induced fragmentation channel, the loss of a fragment identified as formylmethylflavin. The fragment ion specific action spectra reveal electronic transition energies close to those for flavins in solution and previously published gas-phase measurements, although the photo-fragment yield upon excitation of the S2 ← S0 transition appears to be suppressed.
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Affiliation(s)
| | - Christina Kjær
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | | | - Eleanor K Ashworth
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - James N Bull
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Mark H Stockett
- Department of Physics, Stockholm University, Stockholm, Sweden
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8
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Wiltschko R, Nießner C, Wiltschko W. The Magnetic Compass of Birds: The Role of Cryptochrome. Front Physiol 2021; 12:667000. [PMID: 34093230 PMCID: PMC8171495 DOI: 10.3389/fphys.2021.667000] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/08/2021] [Indexed: 12/28/2022] Open
Abstract
The geomagnetic field provides directional information for birds. The avian magnetic compass is an inclination compass that uses not the polarity of the magnetic field but the axial course of the field lines and their inclination in space. It works in a flexible functional window, and it requires short-wavelength light. These characteristics result from the underlying sensory mechanism based on radical pair processes in the eyes, with cryptochrome suggested as the receptor molecule. The chromophore of cryptochrome, flavin adenine dinucleotide (FAD), undergoes a photocycle, where radical pairs are formed during photo-reduction as well as during re-oxidation; behavioral data indicate that the latter is crucial for detecting magnetic directions. Five types of cryptochromes are found in the retina of birds: cryptochrome 1a (Cry1a), cryptochrome 1b, cryptochrome 2, cryptochrome 4a, and cryptochrome 4b. Because of its location in the outer segments of the ultraviolet cones with their clear oil droplets, Cry1a appears to be the most likely receptor molecule for magnetic compass information.
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Affiliation(s)
- Roswitha Wiltschko
- FB Biowissenschaften, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
| | - Christine Nießner
- FB Biowissenschaften, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
| | - Wolfgang Wiltschko
- FB Biowissenschaften, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
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9
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Karki N, Vergish S, Zoltowski BD. Cryptochromes: Photochemical and structural insight into magnetoreception. Protein Sci 2021; 30:1521-1534. [PMID: 33993574 DOI: 10.1002/pro.4124] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/10/2021] [Accepted: 05/11/2021] [Indexed: 12/21/2022]
Abstract
Cryptochromes (CRYs) function as blue light photoreceptors in diverse physiological processes in nearly all kingdoms of life. Over the past several decades, they have emerged as the most likely candidates for light-dependent magnetoreception in animals, however, a long history of conflicts between in vitro photochemistry and in vivo behavioral data complicate validation of CRYs as a magnetosensor. In this review, we highlight the origins of conflicts regarding CRY photochemistry and signal transduction, and identify recent data that provides clarity on potential mechanisms of signal transduction in magnetoreception. The review primarily focuses on examining differences in photochemistry and signal transduction in plant and animal CRYs, and identifies potential modes of convergent evolution within these independent lineages that may identify conserved signaling pathways.
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Affiliation(s)
- Nischal Karki
- Department of Chemistry, Southern Methodist University, Dallas, Texas, USA
| | - Satyam Vergish
- Department of Chemistry, Southern Methodist University, Dallas, Texas, USA
| | - Brian D Zoltowski
- Department of Chemistry, Southern Methodist University, Dallas, Texas, USA
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10
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Abstract
Species throughout the animal kingdom use the Earth's magnetic field (MF) to navigate using either or both of two mechanisms. The first relies on magnetite crystals in tissue where their magnetic moments align with the MF to transduce a signal transmitted to the central nervous system. The second and the subject of this paper involves cryptochrome (CRY) proteins located in cone photoreceptors distributed across the retina, studied most extensively in birds. According to the "Radical Pair Mechanism" (RPM), blue/UV light excites CRY's flavin cofactor (FAD) to generate radical pairs whose singlet-to-triplet interconversion rate is modulated by an external MF. The signaling product of the RPM produces an impression of the field across the retinal surface. In birds, the resulting signal on the optic nerve is transmitted along the thalamofugal pathway to the primary visual cortex, which projects to brain regions concerned with image processing, memory, and executive function. The net result is a bird's orientation to the MF's inclination: its vector angle relative to the Earth's surface. The quality of ambient light (e.g., polarization) provides additional input to the compass. In birds, the Type IV CRY isoform appears pivotal to the compass, given its positioning within retinal cones; a cytosolic location therein indicating no role in the circadian clock; relatively steady diurnal levels (unlike Type II CRY's cycling); and a full complement of FAD (essential for photosensitivity). The evidence indicates that mammalian Type II CRY isoforms play a light-independent role in the cellular molecular clock without a photoreceptive function.
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Affiliation(s)
| | - Joseph Brain
- Environmental Physiology, Molecular, and Integrative Physiological Sciences Program, Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
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11
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Oka Y, Miura T, Ikoma T. Photogenerated Radical Pair between Flavin and a Tryptophan-Containing Transmembrane-Type Peptide in a Large Unilamellar Vesicle. J Phys Chem B 2021; 125:4057-4066. [PMID: 33858138 DOI: 10.1021/acs.jpcb.1c01231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electron-transfer (ET) reactions in biological systems, such as those with magnetic sensors based on flavoproteins and electron transport at biomembrane interfaces, are interesting and important issues that require understanding. As a model system of flavoproteins in biomimetic environments, we report the dynamics of the radical pair generated by photoinduced ET between riboflavin tetrabutylate (RFTB) and tryptophan (Trp) residues in a transmembrane-type polypeptide, both of which are distributed in a large unilamellar vesicle of 1,2-dimyristoyl-sn-glycero-3-phosphocholine. The Trp residues locate near the hydrophilic membrane interface, as confirmed by a dual-fluorescence quenching assay. The fluorescence and transient absorption upon photoexcitation of RFTB indicate that ET from both the singlet and triplet excited states occurs at the hydrophilic interface, whereas the RFTB in the hydrophobic region does not contribute to ET. The ET efficiency and the magnetic field effect (MFE) on the RFTB anion increase significantly above the gel-to-liquid crystal phase transition temperature due to a decrease in microviscosity. The MFE analysis indicates that the radical pair generated from the triplet ET channel exhibits a long lifetime as those in micellar systems due to the strong cage effect of the vesicle.
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Affiliation(s)
- Yoshimi Oka
- Frontier Research Core for Life Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Tomoaki Miura
- Department of Chemistry, Faculty of Science, Niigata University, 2-8050 Ikarashi, Nishi-ku, Niigata 950-2181, Japan
| | - Tadaaki Ikoma
- Department of Chemistry, Faculty of Science, Niigata University, 2-8050 Ikarashi, Nishi-ku, Niigata 950-2181, Japan
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12
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The Role of Hp-NCL Network in Goal-Directed Routing Information Encoding of Bird: A Review. Brain Sci 2020; 10:brainsci10090617. [PMID: 32906650 PMCID: PMC7563516 DOI: 10.3390/brainsci10090617] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/02/2020] [Accepted: 09/02/2020] [Indexed: 12/26/2022] Open
Abstract
Goal-directed navigation is a crucial behavior for the survival of animals, especially for the birds having extraordinary spatial navigation ability. In the studies of the neural mechanism of the goal-directed behavior, especially involving the information encoding mechanism of the route, the hippocampus (Hp) and nidopallium caudalle (NCL) of the avian brain are the famous regions that play important roles. Therefore, they have been widely concerned and a series of studies surrounding them have increased our understandings of the navigation mechanism of birds in recent years. In this paper, we focus on the studies of the information encoding mechanism of the route in the avian goal-directed behavior. We first summarize and introduce the related studies on the role of the Hp and NCL for goal-directed behavior comprehensively. Furthermore, we review the related cooperative interaction studies about the Hp-NCL local network and other relevant brain regions supporting the goal-directed routing information encoding. Finally, we summarize the current situation and prospect the existing important questions in this field. We hope this paper can spark fresh thinking for the following research on routing information encoding mechanism of birds.
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13
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Zoltowski BD, Chelliah Y, Wickramaratne A, Jarocha L, Karki N, Xu W, Mouritsen H, Hore PJ, Hibbs RE, Green CB, Takahashi JS. Chemical and structural analysis of a photoactive vertebrate cryptochrome from pigeon. Proc Natl Acad Sci U S A 2019; 116:19449-19457. [PMID: 31484780 PMCID: PMC6765304 DOI: 10.1073/pnas.1907875116] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Computational and biochemical studies implicate the blue-light sensor cryptochrome (CRY) as an endogenous light-dependent magnetosensor enabling migratory birds to navigate using the Earth's magnetic field. Validation of such a mechanism has been hampered by the absence of structures of vertebrate CRYs that have functional photochemistry. Here we present crystal structures of Columba livia (pigeon) CRY4 that reveal evolutionarily conserved modifications to a sequence of Trp residues (Trp-triad) required for CRY photoreduction. In ClCRY4, the Trp-triad chain is extended to include a fourth Trp (W369) and a Tyr (Y319) residue at the protein surface that imparts an unusually high quantum yield of photoreduction. These results are consistent with observations of night migratory behavior in animals at low light levels and could have implications for photochemical pathways allowing magnetosensing.
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Affiliation(s)
- Brian D Zoltowski
- Department of Chemistry, Southern Methodist University, Dallas, TX 75275
- Center for Drug Discovery, Design, and Delivery, Southern Methodist University, Dallas, TX 75275
| | - Yogarany Chelliah
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Anushka Wickramaratne
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Lauren Jarocha
- Department of Chemistry, University of Oxford, OX1 3QZ Oxford, United Kingdom
| | - Nischal Karki
- Department of Chemistry, Southern Methodist University, Dallas, TX 75275
- Center for Drug Discovery, Design, and Delivery, Southern Methodist University, Dallas, TX 75275
| | - Wei Xu
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Henrik Mouritsen
- Institute for Biology and Environmental Sciences, Carl von Ossietzky University of Oldenburg, DE-26111 Oldenburg, Germany
- Research Center for Neurosensory Sciences, University of Oldenburg, DE-26111 Oldenburg, Germany
| | - Peter J Hore
- Department of Chemistry, University of Oxford, OX1 3QZ Oxford, United Kingdom
| | - Ryan E Hibbs
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Carla B Green
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Joseph S Takahashi
- Department of Neuroscience, Peter O'Donnell Jr. Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390;
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
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14
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Atkins C, Bajpai K, Rumball J, Kattnig DR. On the optimal relative orientation of radicals in the cryptochrome magnetic compass. J Chem Phys 2019. [DOI: 10.1063/1.5115445] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chadsley Atkins
- Institute and Department of Physics, University of Exeter, North Park Road, Exeter EX4 4QL, United Kingdom
| | - Kieran Bajpai
- Institute and Department of Physics, University of Exeter, North Park Road, Exeter EX4 4QL, United Kingdom
| | - Jeremy Rumball
- Institute and Department of Physics, University of Exeter, North Park Road, Exeter EX4 4QL, United Kingdom
| | - Daniel R. Kattnig
- Institute and Department of Physics, University of Exeter, North Park Road, Exeter EX4 4QL, United Kingdom
- Living Systems Institute and Department of Physics, University of Exeter, Stocker Road, Exeter EX4 4QD, United Kingdom
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15
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Nießner C, Denzau S, Peichl L, Wiltschko W, Wiltschko R. Magnetoreception: activation of avian cryptochrome 1a in various light conditions. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2018; 204:977-984. [DOI: 10.1007/s00359-018-1296-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Revised: 07/26/2018] [Accepted: 09/26/2018] [Indexed: 12/24/2022]
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16
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Kimø SM, Friis I, Solov'yov IA. Atomistic Insights into Cryptochrome Interprotein Interactions. Biophys J 2018; 115:616-628. [PMID: 30078611 DOI: 10.1016/j.bpj.2018.06.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/11/2018] [Accepted: 06/29/2018] [Indexed: 11/30/2022] Open
Abstract
It is striking that the mechanism by which birds sense geomagnetic fields during the biannual migration seasons is not entirely understood. A protein believed to be responsible for avian magnetoreception is the flavoprotein cryptochrome (CRY), which fulfills many of the criteria for a magnetic field sensor. Some experiments, however, indicate that magnetoreception in birds may be disturbed by extremely weak radio frequency fields, an effect that likely cannot be described by an isolated CRY protein. An explanation can possibly be delivered if CRY binds to another protein inside a cell that would possess certain biochemical properties, and it is, therefore, important to identify possible intracellular CRY interaction partners. The goal of this study is to investigate a possible interaction between CRY4 and the iron-sulfur-containing assembly protein (ISCA1) from Erithacus rubecula (European robin), which has recently been proposed to be relevant for magnetic field sensing. The interaction between the proteins is established through classical molecular dynamics simulations for several possible protein-docking modes. The analysis of these simulations concludes that the ISCA1 complex and CRY4 are capable of binding; however, the peculiarities of this binding argue strongly against ISCA1 as relevant for magnetoreception.
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Affiliation(s)
- Sarafina M Kimø
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M, Denmark
| | - Ida Friis
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M, Denmark
| | - Ilia A Solov'yov
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M, Denmark.
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17
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Giacomozzi L, Kjær C, Langeland Knudsen J, Andersen LH, Brøndsted Nielsen S, Stockett MH. Absorption and luminescence spectroscopy of mass-selected flavin adenine dinucleotide mono-anions. J Chem Phys 2018; 148:214309. [PMID: 29884035 DOI: 10.1063/1.5024028] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We report the absorption profile of isolated Flavin Adenine Dinucleotide (FAD) mono-anions recorded using photo-induced dissociation action spectroscopy. In this charge state, one of the phosphoric acid groups is deprotonated and the chromophore itself is in its neutral oxidized state. These measurements cover the first four optical transitions of FAD with excitation energies from 2.3 to 6.0 eV (210-550 nm). The S0 → S2 transition is strongly blue shifted relative to aqueous solution, supporting the view that this transition has a significant charge-transfer character. The remaining bands are close to their solution-phase positions. This confirms that the large discrepancy between quantum chemical calculations of vertical transition energies and solution-phase band maxima cannot be explained by solvent effects. We also report the luminescence spectrum of FAD mono-anions in vacuo. The gas-phase Stokes shift for S1 is 3000 cm-1, which is considerably larger than any previously reported for other molecular ions and consistent with a significant displacement of the ground and excited state potential energy surfaces. Consideration of the vibronic structure is thus essential for simulating the absorption and luminescence spectra of flavins.
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Affiliation(s)
- L Giacomozzi
- Department of Physics, Stockholm University, Stockholm, Sweden
| | - C Kjær
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | | | - L H Andersen
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | | | - M H Stockett
- Department of Physics, Stockholm University, Stockholm, Sweden
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18
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Myklatun A, Lauri A, Eder SHK, Cappetta M, Shcherbakov D, Wurst W, Winklhofer M, Westmeyer GG. Zebrafish and medaka offer insights into the neurobehavioral correlates of vertebrate magnetoreception. Nat Commun 2018; 9:802. [PMID: 29476093 PMCID: PMC5824813 DOI: 10.1038/s41467-018-03090-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2017] [Accepted: 01/18/2018] [Indexed: 11/12/2022] Open
Abstract
An impediment to a mechanistic understanding of how some species sense the geomagnetic field ("magnetoreception") is the lack of vertebrate genetic models that exhibit well-characterized magnetoreceptive behavior and are amenable to whole-brain analysis. We investigated the genetic model organisms zebrafish and medaka, whose young stages are transparent and optically accessible. In an unfamiliar environment, adult fish orient according to the directional change of a magnetic field even in darkness. To enable experiments also in juveniles, we applied slowly oscillating magnetic fields, aimed at generating conflicting sensory inputs during exploratory behavior. Medaka (but not zebrafish) increase their locomotor activity in this assay. Complementary brain activity mapping reveals neuronal activation in the lateral hindbrain during magnetic stimulation. These comparative data support magnetoreception in teleosts, provide evidence for a light-independent mechanism, and demonstrate the usefulness of zebrafish and medaka as genetic vertebrate models for studying the biophysical and neuronal mechanisms underlying magnetoreception.
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Affiliation(s)
- Ahne Myklatun
- Institute of Biological and Medical Imaging, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany
- Institute of Developmental Genetics, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany
- Department of Nuclear Medicine, Technical University of Munich, Ismaninger Strasse 22, 81675, Munich, Germany
| | - Antonella Lauri
- Institute of Biological and Medical Imaging, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany
- Institute of Developmental Genetics, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany
- Department of Nuclear Medicine, Technical University of Munich, Ismaninger Strasse 22, 81675, Munich, Germany
| | - Stephan H K Eder
- Department of Earth- and Environmental Sciences Section Geophysics, Ludwig Maximilian University of Munich, Theresienstrasse 41, 80333, Munich, Germany
| | - Michele Cappetta
- Institute of Biological and Medical Imaging, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany
- Institute of Developmental Genetics, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany
- Department of Nuclear Medicine, Technical University of Munich, Ismaninger Strasse 22, 81675, Munich, Germany
| | - Denis Shcherbakov
- Institute of Zoology 220, University of Hohenheim, 70593, Stuttgart, Germany
| | - Wolfgang Wurst
- Institute of Developmental Genetics, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany
| | - Michael Winklhofer
- Institute for Biology and Environmental Sciences IBU, Carl von Ossietzky University of Oldenburg, Carl-von-Ossietzky-Strasse 9-11, 26129, Oldenburg, Germany
- Research Center Neurosensory Science, Carl von Ossietzky Universität Oldenburg, Oldenburg, D-26111, Germany
| | - Gil G Westmeyer
- Institute of Biological and Medical Imaging, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany.
- Institute of Developmental Genetics, Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany.
- Department of Nuclear Medicine, Technical University of Munich, Ismaninger Strasse 22, 81675, Munich, Germany.
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19
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Stockett MH. Photo-induced proton-coupled electron transfer and dissociation of isolated flavin adenine dinucleotide mono-anions. Phys Chem Chem Phys 2018; 19:25829-25833. [PMID: 28745349 DOI: 10.1039/c7cp04068g] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The intrinsic optical absorption spectrum and photo-dissociation pathways of flavin adenine dinucleotide (FAD) mono-anions isolated in vacuo are probed using photo-induced dissociation (PID) action spectroscopy. The main photo-products are lumichrome and formylmethylflavin. Evidence is presented that the dissociation pathway leading to these products is non-statistical i.e. occurs during the excited state lifetime. This suggests that the stacking of the adenine and alloxazine chromophores, which enables ultra-fast quenching of the flavin excited state by photo-induced electron transfer in aqueous solution, is inhibited in vacuo. These results provide firm experimental confirmation that lumichrome formation from flavins proceeds via photo-induced, intra-molecular proton-coupled electron transfer.
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Affiliation(s)
- Mark H Stockett
- Stockholm University Department of Physics, Stockholm, Sweden.
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20
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Thoss F, Bartsch B. A model of the FAD redox cycle describes the dynamics of the effect of the geomagnetic field on the human visual system. BIOLOGICAL CYBERNETICS 2017; 111:347-352. [PMID: 28776258 DOI: 10.1007/s00422-017-0725-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 07/27/2017] [Indexed: 06/07/2023]
Abstract
In experimental studies, we could show that the visual threshold of man is influenced by the geomagnetic field. One of the results was that the threshold shows periodic fluctuations when the vertical component of the field is reversed periodically. The maximum of these oscillations occurred at a period duration of 110 s. To explain this phenomenon, we chose the process that likely underlies the navigation of birds in the geomagnetic field: the light reaction of the FAD component of cryptochrome in the retina. The human retina contains cryptpochrome like the bird retina. Based on the investigations of Müller and Ahmad (J Biol Chem 286:21033-21040, 2011) and Solov'yov and Schulten (J Phys Chem B 116:1089-1099, 2012), we designed a model of the light-induced reduction and subsequent reoxidation of FAD. This model contains a radical pair, whose interconversion dynamics are affected by the geomagnetic field. The parameters of the model were partly calculated from the data of our experimental investigation and partly taken from the results of other authors. These parameters were then optimized by adjusting the model behaviour to the experimental results. The simulation of the finished model shows that the concentrations of all substances included show really oscillations with the frequency of the modelled magnetic field. After optimization of the parameters, the oscillations of FAD and FADH* show maximal amplitude at a period duration of 110 s, as was observed in the experiment. This makes it most likely that the signal, which influences the visual system, originates from FADH* (signalling state).
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Affiliation(s)
- Franz Thoss
- Carl-Ludwig-Institute of Physiology, University of Leipzig, Liebigstr. 27, 04103, Leipzig, Germany.
| | - Bengt Bartsch
- Carl-Ludwig-Institute of Physiology, University of Leipzig, Liebigstr. 27, 04103, Leipzig, Germany
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21
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Kattnig DR. Radical-Pair-Based Magnetoreception Amplified by Radical Scavenging: Resilience to Spin Relaxation. J Phys Chem B 2017; 121:10215-10227. [DOI: 10.1021/acs.jpcb.7b07672] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Daniel R. Kattnig
- Living Systems Institute
and Department of Physics, University of Exeter, Stocker Road, Exeter, Devon, EX4 4QD, United Kingdom
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22
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Wiltschko R, Ahmad M, Nießner C, Gehring D, Wiltschko W. Light-dependent magnetoreception in birds: the crucial step occurs in the dark. J R Soc Interface 2017; 13:rsif.2015.1010. [PMID: 27146685 PMCID: PMC4892254 DOI: 10.1098/rsif.2015.1010] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 04/12/2016] [Indexed: 11/24/2022] Open
Abstract
The Radical Pair Model proposes that the avian magnetic compass is based on spin-chemical processes: since the ratio between the two spin states singlet and triplet of radical pairs depends on their alignment in the magnetic field, it can provide information on magnetic directions. Cryptochromes, blue light-absorbing flavoproteins, with flavin adenine dinucleotide as chromophore, are suggested as molecules forming the radical pairs underlying magnetoreception. When activated by light, cryptochromes undergo a redox cycle, in the course of which radical pairs are generated during photo-reduction as well as during light-independent re-oxidation. This raised the question as to which radical pair is crucial for mediating magnetic directions. Here, we present the results from behavioural experiments with intermittent light and magnetic field pulses that clearly show that magnetoreception is possible in the dark interval, pointing to the radical pair formed during flavin re-oxidation. This differs from the mechanism considered for cryptochrome signalling the presence of light and rules out most current models of an avian magnetic compass based on the radical pair generated during photo-reduction. Using the radical pair formed during re-oxidation may represent a specific adaptation of the avian magnetic compass.
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Affiliation(s)
- Roswitha Wiltschko
- FB Biowissenschaften, Goethe-Universität Frankfurt, Max-von-Laue-Straße 13, 60438 Frankfurt am Main, Germany
| | - Margaret Ahmad
- Université Pierre et Marie Curie, Casier 156, 4 Place Jussieu, 75005 Paris, France
| | - Christine Nießner
- FB Biowissenschaften, Goethe-Universität Frankfurt, Max-von-Laue-Straße 13, 60438 Frankfurt am Main, Germany
| | - Dennis Gehring
- FB Biowissenschaften, Goethe-Universität Frankfurt, Max-von-Laue-Straße 13, 60438 Frankfurt am Main, Germany
| | - Wolfgang Wiltschko
- FB Biowissenschaften, Goethe-Universität Frankfurt, Max-von-Laue-Straße 13, 60438 Frankfurt am Main, Germany
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23
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Pakhomov A, Bojarinova J, Cherbunin R, Chetverikova R, Grigoryev PS, Kavokin K, Kobylkov D, Lubkovskaja R, Chernetsov N. Very weak oscillating magnetic field disrupts the magnetic compass of songbird migrants. J R Soc Interface 2017; 14:20170364. [PMID: 28794163 PMCID: PMC5582129 DOI: 10.1098/rsif.2017.0364] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 07/13/2017] [Indexed: 11/12/2022] Open
Abstract
Previously, it has been shown that long-distance migrants, garden warblers (Sylvia borin), were disoriented in the presence of narrow-band oscillating magnetic field (1.403 MHz OMF, 190 nT) during autumn migration. This agrees with the data of previous experiments with European robins (Erithacus rubecula). In this study, we report the results of experiments with garden warblers tested under a 1.403 MHz OMF with various amplitudes (∼0.4, 1, ∼2.4, 7 and 20 nT). We found that the ability of garden warblers to orient in round arenas using the magnetic compass could be disrupted by a very weak oscillating field, such as an approximate 2.4, 7 and 20 nT OMF, but not by an OMF with an approximate 0.4 nT amplitude. The results of the present study indicate that the sensitivity threshold of the magnetic compass to the OMF lies around 2-3 nT, while in experiments with European robins the birds were disoriented in a 15 nT OMF but could choose the appropriate migratory direction when a 5 nT OMF was added to the stationary magnetic field. The radical-pair model, one of the mainstream theories of avian magnetoreception, cannot explain the sensitivity to such a low-intensity OMF, and therefore, it needs further refinement.
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Affiliation(s)
- Alexander Pakhomov
- Biological Station Rybachy, Zoological Institute RAS, 238535 Rybachy, Kaliningrad Region, Russia
- Sechenov Institute of Evolutionary Physiology and Biochemistry, 44 Thorez Ave, 194223 St Petersburg, Russia
| | - Julia Bojarinova
- Sechenov Institute of Evolutionary Physiology and Biochemistry, 44 Thorez Ave, 194223 St Petersburg, Russia
- St Petersburg State University, 7-9 Universitetskaya Emb., St Petersburg 199034, Russia
| | - Roman Cherbunin
- Sechenov Institute of Evolutionary Physiology and Biochemistry, 44 Thorez Ave, 194223 St Petersburg, Russia
- St Petersburg State University, 7-9 Universitetskaya Emb., St Petersburg 199034, Russia
| | - Raisa Chetverikova
- St Petersburg State University, 7-9 Universitetskaya Emb., St Petersburg 199034, Russia
- AG Neurosensorik (Animal Navigation), Institut für Biologie und Umweltwissenschaften (IBU), University of Oldenburg, 26111 Oldenburg, Germany
| | - Philipp S Grigoryev
- St Petersburg State University, 7-9 Universitetskaya Emb., St Petersburg 199034, Russia
| | - Kirill Kavokin
- Sechenov Institute of Evolutionary Physiology and Biochemistry, 44 Thorez Ave, 194223 St Petersburg, Russia
- St Petersburg State University, 7-9 Universitetskaya Emb., St Petersburg 199034, Russia
- A.F. Ioffe Physical Technical Institute, 26 Polytechnicheskaya, St Petersburg 194021, Russia
| | - Dmitry Kobylkov
- AG Neurosensorik (Animal Navigation), Institut für Biologie und Umweltwissenschaften (IBU), University of Oldenburg, 26111 Oldenburg, Germany
| | - Regina Lubkovskaja
- St Petersburg State University, 7-9 Universitetskaya Emb., St Petersburg 199034, Russia
| | - Nikita Chernetsov
- Biological Station Rybachy, Zoological Institute RAS, 238535 Rybachy, Kaliningrad Region, Russia
- Sechenov Institute of Evolutionary Physiology and Biochemistry, 44 Thorez Ave, 194223 St Petersburg, Russia
- St Petersburg State University, 7-9 Universitetskaya Emb., St Petersburg 199034, Russia
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24
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Nießner C, Winklhofer M. Radical-pair-based magnetoreception in birds: radio-frequency experiments and the role of cryptochrome. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2017; 203:499-507. [PMID: 28612234 PMCID: PMC5522499 DOI: 10.1007/s00359-017-1189-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/28/2017] [Accepted: 05/29/2017] [Indexed: 11/30/2022]
Abstract
The radical-pair hypothesis of magnetoreception has gained a lot of momentum, since the flavoprotein cryptochrome was postulated as a structural candidate to host magnetically sensitive chemical reactions. Here, we first discuss behavioral tests using radio-frequency magnetic fields (0.1-10 MHz) to specifically disturb a radical-pair-based avian magnetic compass sense. While disorienting effects of broadband RF magnetic fields have been replicated independently in two competing labs, the effects of monochromatic RF magnetic fields administered at the electronic Larmor frequency (~1.3 MHz) are disparate. We give technical recommendations for future RF experiments. We then focus on two candidate magnetoreceptor proteins in birds, Cry1a and Cry1b, two splice variants of the same gene (Cry1). Immunohistochemical studies have identified Cry1a in the outer segments of the ultraviolet/violet-sensitive cone photoreceptors and Cry1b in the cytosol of retinal ganglion cells. The identification of the host neurons of these cryptochromes and their subcellular expression patterns presents an important advance, but much work lies ahead to gain some functional understanding. In particular, interaction partners of cryptochrome Cry1a and Cry1b remain to be identified. A candidate partner for Cry4 was previously suggested, but awaits independent replication.
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Affiliation(s)
- Christine Nießner
- Ernst Strüngmann Institute for Neuroscience, Deutschordenstr 46, 60528, Frankfurt am Main, Germany
| | - Michael Winklhofer
- Institute for Biology and Environmental Sciences IBU, School of Mathematics and Science, University of Oldenburg, 26111, Oldenburg, Germany.
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25
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Affiliation(s)
- Alex R. Jones
- School of Chemistry, Photon Science Institute and Manchester Institute of Biotechnology, The University of Manchester, Manchester, UK
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26
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Abstract
The ability to perceive geomagnetic fields (GMFs) represents a fascinating biological phenomenon. Studies on transgenic flies have provided evidence that photosensitive Cryptochromes (Cry) are involved in the response to magnetic fields (MFs). However, none of the studies tackled the problem of whether the Cry-dependent magnetosensitivity is coupled to the sole MF presence or to the direction of MF vector. In this study, we used gene silencing and a directional MF to show that mammalian-like Cry2 is necessary for a genuine directional response to periodic rotations of the GMF vector in two insect species. Longer wavelengths of light required higher photon fluxes for a detectable behavioral response, and a sharp detection border was present in the cyan/green spectral region. Both observations are consistent with involvement of the FADox, FAD(•-) and FADH(-) redox forms of flavin. The response was lost upon covering the eyes, demonstrating that the signal is perceived in the eye region. Immunohistochemical staining detected Cry2 in the hemispherical layer of laminal glia cells underneath the retina. Together, these findings identified the eye-localized Cry2 as an indispensable component and a likely photoreceptor of the directional GMF response. Our study is thus a clear step forward in deciphering the in vivo effects of GMF and supports the interaction of underlying mechanism with the visual system.
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27
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Nießner C, Denzau S, Peichl L, Wiltschko W, Wiltschko R. Magnetoreception in birds: I. Immunohistochemical studies concerning the cryptochrome cycle. ACTA ACUST UNITED AC 2015; 217:4221-4. [PMID: 25472972 PMCID: PMC4254396 DOI: 10.1242/jeb.110965] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cryptochrome 1a, located in the UV/violet-sensitive cones in the avian retina, is discussed as receptor molecule for the magnetic compass of birds. Our previous immunohistochemical studies of chicken retinae with an antiserum that labelled only activated cryptochrome 1a had shown activation of cryptochrome 1a under 373 nm UV, 424 nm blue, 502 nm turquoise and 565 nm green light. Green light, however, does not allow the first step of photoreduction of oxidized cryptochromes to the semiquinone. As the chickens had been kept under 'white' light before, we suggested that there was a supply of the semiquinone present at the beginning of the exposure to green light, which could be further reduced and then re-oxidized. To test this hypothesis, we exposed chickens to various wavelengths (1) for 30 min after being kept in daylight, (2) for 30 min after a 30 min pre-exposure to total darkness, and (3) for 1 h after being kept in daylight. In the first case, we found activated cryptochrome 1a under UV, blue, turquoise and green light; in the second two cases we found activated cryptochrome 1a only under UV to turquoise light, where the complete redox cycle of cryptochrome can run, but not under green light. This observation is in agreement with the hypothesis that activated cryptochrome 1a is found as long as there is some of the semiquinone left, but not when the supply is depleted. It supports the idea that the crucial radical pair for magnetoreception is generated during re-oxidation.
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Affiliation(s)
- Christine Nießner
- Goethe-Universität Frankfurt, FB Biowissenschaften, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany
| | - Susanne Denzau
- Goethe-Universität Frankfurt, FB Biowissenschaften, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany
| | - Leo Peichl
- Max-Planck-Institute for Brain Research, Max-von-Laue-Straße 4, D-60438 Frankfurt am Main, Germany
| | - Wolfgang Wiltschko
- Goethe-Universität Frankfurt, FB Biowissenschaften, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany
| | - Roswitha Wiltschko
- Goethe-Universität Frankfurt, FB Biowissenschaften, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany
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28
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Knight K. Migrating birds use fully reduced FADH− for navigation. J Exp Biol 2014. [DOI: 10.1242/jeb.116939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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