51
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Biskup T, Schleicher E, Okafuji A, Link G, Hitomi K, Getzoff ED, Weber S. Direct observation of a photoinduced radical pair in a cryptochrome blue-light photoreceptor. Angew Chem Int Ed Engl 2009; 48:404-7. [PMID: 19058271 DOI: 10.1002/anie.200803102] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Till Biskup
- Department of Physics, Free University Berlin, Germany
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52
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Rodgers CT, Hore PJ. Chemical magnetoreception in birds: the radical pair mechanism. Proc Natl Acad Sci U S A 2009; 106:353-60. [PMID: 19129499 PMCID: PMC2626707 DOI: 10.1073/pnas.0711968106] [Citation(s) in RCA: 314] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Indexed: 11/18/2022] Open
Abstract
Migratory birds travel vast distances each year, finding their way by various means, including a remarkable ability to perceive the Earth's magnetic field. Although it has been known for 40 years that birds possess a magnetic compass, avian magnetoreception is poorly understood at all levels from the primary biophysical detection events, signal transduction pathways and neurophysiology, to the processing of information in the brain. It has been proposed that the primary detector is a specialized ocular photoreceptor that plays host to magnetically sensitive photochemical reactions having radical pairs as fleeting intermediates. Here, we present a physical chemist's perspective on the "radical pair mechanism" of compass magnetoreception in birds. We outline the essential chemical requirements for detecting the direction of an Earth-strength approximately 50 microT magnetic field and comment on the likelihood that these might be satisfied in a biologically plausible receptor. Our survey concludes with a discussion of cryptochrome, the photoactive protein that has been put forward as the magnetoreceptor molecule.
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Affiliation(s)
- Christopher T. Rodgers
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, United Kingdom; and
- Oxford Centre for Clinical Magnetic Resonance Research, Level 0, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom
| | - P. J. Hore
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, United Kingdom; and
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53
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Biskup T, Schleicher E, Okafuji A, Link G, Hitomi K, Getzoff E, Weber S. Direkte Detektion eines lichtinduzierten Radikalpaars in einem Cryptochrom-Blaulichtrezeptor. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200803102] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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54
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Shafaat HS, Leigh BS, Tauber MJ, Kim JE. Resonance Raman Characterization of a Stable Tryptophan Radical in an Azurin Mutant. J Phys Chem B 2008; 113:382-8. [PMID: 19072535 DOI: 10.1021/jp809329a] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Hannah S. Shafaat
- Department of Chemistry & Biochemistry, University of California at San Diego, La Jolla, California 92093
| | - Brian S. Leigh
- Department of Chemistry & Biochemistry, University of California at San Diego, La Jolla, California 92093
| | - Michael J. Tauber
- Department of Chemistry & Biochemistry, University of California at San Diego, La Jolla, California 92093
| | - Judy E. Kim
- Department of Chemistry & Biochemistry, University of California at San Diego, La Jolla, California 92093
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55
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Costentin C, Louault C, Robert M. Evidence for Concerted Proton−Electron Transfer in the Electrochemical Oxidation of Phenols with Water As Proton Acceptor. Tri-tert-butylphenol. J Am Chem Soc 2008; 130:15817-9. [DOI: 10.1021/ja8064914] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Cyrille Costentin
- Contribution from the Laboratoire d’Electrochimie Moléculaire, Unité Mixte de Recherche Université - CNRS No 7591, Université Paris - Diderot, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France
| | - Cyril Louault
- Contribution from the Laboratoire d’Electrochimie Moléculaire, Unité Mixte de Recherche Université - CNRS No 7591, Université Paris - Diderot, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France
| | - Marc Robert
- Contribution from the Laboratoire d’Electrochimie Moléculaire, Unité Mixte de Recherche Université - CNRS No 7591, Université Paris - Diderot, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France
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56
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Lukacs A, Eker APM, Byrdin M, Brettel K, Vos MH. Electron hopping through the 15 A triple tryptophan molecular wire in DNA photolyase occurs within 30 ps. J Am Chem Soc 2008; 130:14394-5. [PMID: 18850708 DOI: 10.1021/ja805261m] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
DNA photolyase is a photoactive flavoprotein that contains three tryptophan residues between the FAD cofactor and the protein surface, the solvent-exposed Trp being located 14.8 A from the flavin. Photoreduction of the neutral radical FADH. form to the catalytically active FADH- form occurs via electron transfer through this chain. The first step in this chain takes 30 ps, the second less than 4 ps. Using a combination of site-directed mutagenesis and femtosecond polarization spectroscopy to discriminate the spectroscopically indistinguishable Trp residues, we show that the third step occurs in less than 30 ps. This implies that the first photoreduction step is rate limiting and that the Trp chain effectively acts as molecular "wire" ensuring rapid and directed long-range charge translocation across the protein. This finding is important for the functioning of the large class of cryptochrome blue-light receptors, where the Trp chain is conserved. In DNA photolyase we make use of the natural photoactivation of the process, but more generally chains of aromatic amino acids may allow very fast long-range electron transfer also in nonphotoactive proteins.
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Affiliation(s)
- Andras Lukacs
- Laboratoire d'Optique et Biosciences, CNRS, Ecole Polytechnique, F-91128 Palaiseau, France
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57
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Absorption and fluorescence spectroscopic characterisation of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry). Chem Phys 2008. [DOI: 10.1016/j.chemphys.2008.06.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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58
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Byrdin M, Villette S, Espagne A, Eker APM, Brettel K. Polarized Transient Absorption To Resolve Electron Transfer between Tryptophans in DNA Photolyase. J Phys Chem B 2008; 112:6866-71. [DOI: 10.1021/jp711435y] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Martin Byrdin
- Laboratoire de Photocatalyse et Biohydrogène, iBiTecS, CEA, 91191 Gif sur Yvette, France, URA 2096, CNRS, 91191 Gif sur Yvette, France, and Department of Cell Biology and Genetics, MGC, Erasmus University Medical Centre, PO Box 2040, Rotterdam, 3000 CA, The Netherlands
| | - Sandrine Villette
- Laboratoire de Photocatalyse et Biohydrogène, iBiTecS, CEA, 91191 Gif sur Yvette, France, URA 2096, CNRS, 91191 Gif sur Yvette, France, and Department of Cell Biology and Genetics, MGC, Erasmus University Medical Centre, PO Box 2040, Rotterdam, 3000 CA, The Netherlands
| | - Agathe Espagne
- Laboratoire de Photocatalyse et Biohydrogène, iBiTecS, CEA, 91191 Gif sur Yvette, France, URA 2096, CNRS, 91191 Gif sur Yvette, France, and Department of Cell Biology and Genetics, MGC, Erasmus University Medical Centre, PO Box 2040, Rotterdam, 3000 CA, The Netherlands
| | - Andre P. M. Eker
- Laboratoire de Photocatalyse et Biohydrogène, iBiTecS, CEA, 91191 Gif sur Yvette, France, URA 2096, CNRS, 91191 Gif sur Yvette, France, and Department of Cell Biology and Genetics, MGC, Erasmus University Medical Centre, PO Box 2040, Rotterdam, 3000 CA, The Netherlands
| | - Klaus Brettel
- Laboratoire de Photocatalyse et Biohydrogène, iBiTecS, CEA, 91191 Gif sur Yvette, France, URA 2096, CNRS, 91191 Gif sur Yvette, France, and Department of Cell Biology and Genetics, MGC, Erasmus University Medical Centre, PO Box 2040, Rotterdam, 3000 CA, The Netherlands
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59
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Discrimination of class I cyclobutane pyrimidine dimer photolyase from blue light photoreceptors by single methionine residue. Biophys J 2007; 94:2194-203. [PMID: 18055535 DOI: 10.1529/biophysj.107.119248] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DNA photolyase recognizes ultraviolet-damaged DNA and breaks improperly formed covalent bonds within the cyclobutane pyrimidine dimer by a light-activated electron transfer reaction between the flavin adenine dinucleotide, the electron donor, and cyclobutane pyrimidine dimer, the electron acceptor. Theoretical analysis of the electron-tunneling pathways of the DNA photolyase derived from Anacystis nidulans can reveal the active role of the protein environment in the electron transfer reaction. Here, we report the unexpectedly important role of the single methionine residue, Met-353, where busy trafficking of electron-tunneling currents is observed. The amino acid conservation pattern of Met-353 in the homologous sequences perfectly correlates with experimentally verified annotation as photolyases. The bioinformatics sequence analysis also suggests that the residue plays a pivotal role in biological function. Consistent findings from different disciplines of computational biology strongly suggest the pivotal role of Met-353 in the biological function of DNA photolyase.
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60
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Role of exchange and dipolar interactions in the radical pair model of the avian magnetic compass. Biophys J 2007; 94:1565-74. [PMID: 17981903 DOI: 10.1529/biophysj.107.119362] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
It is not yet understood how migratory birds sense the Earth's magnetic field as a source of compass information. One suggestion is that the magnetoreceptor involves a photochemical reaction whose product yields are sensitive to external magnetic fields. Specifically, a flavin-tryptophan radical pair is supposedly formed by photoinduced sequential electron transfer along a chain of three tryptophan residues in a cryptochrome flavoprotein immobilized in the retina. The electron Zeeman interaction with the Earth's magnetic field ( approximately 50 microT), modulated by anisotropic magnetic interactions within the radicals, causes the product yields to depend on the orientation of the receptor. According to well-established theory, the radicals would need to be separated by >3.5 nm in order that interradical spin-spin interactions are weak enough to permit a approximately 50 microT field to have a significant effect. Using quantum mechanical simulations, it is shown here that substantial changes in product yields can nevertheless be expected at the much smaller separation of 2.0 +/- 0.2 nm where the effects of exchange and dipolar interactions partially cancel. The terminal flavin-tryptophan radical pair in cryptochrome has a separation of approximately 1.9 nm and is thus ideally placed to act as a magnetoreceptor for the compass mechanism.
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61
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Das S, Mukhopadhyay S. Oxidation of N
III
and N
–I
by an {Mn
4
O
6
}
4+
Core in Aqueous Media: Proton‐Coupled Electron Transfer. Eur J Inorg Chem 2007. [DOI: 10.1002/ejic.200700363] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Suranjana Das
- Department of Chemistry, Jadavpur University, Calcutta 700 032, India
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62
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Lukacs A, Eker APM, Byrdin M, Villette S, Pan J, Brettel K, Vos MH. Role of the middle residue in the triple tryptophan electron transfer chain of DNA photolyase: ultrafast spectroscopy of a Trp-->Phe mutant. J Phys Chem B 2007; 110:15654-8. [PMID: 16898706 DOI: 10.1021/jp063686b] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Photoreduction of the semi-reduced flavin adenine dinucleotide cofactor FADH* in DNA photolyase from Escherichia coli into FADH- involves three tryptophan (W) residues that form a closely spaced electron-transfer chain FADH*-W382-W359-W306. To investigate this process, we have constructed a mutant photolyase in which W359 is replaced by phenylalanine (F). Monitoring its photoproducts by femtosecond spectroscopy, the excited-state FADH* was found to decay in approximately 30 ps, similar as in wild type (WT) photolyase. In contrast to WT, however, in W359F mutant photolyase the ground-state FADH* fully recovered virtually concomitantly with the decay of its excited state and, despite the presence of the primary electron donor W382, no measurable flavin reduction was observed at any time. Thus, W359F photolyase appears to behave like many other flavoproteins, where flavin excited states are quenched by very short-lived oxidation of aromatic residues. Our analysis indicates that both charge recombination of the primary charge separation state FADH-W382*+ and (in WT) electron transfer from W359 to W382*+ occur with time constants <4 ps, considerably faster than the initial W382-->FADH* electron-transfer step. Our results provide a first experimental indication that electron transfer between aromatic residues can take place on the time scale of approximately 10(-12) s.
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63
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Solov'yov IA, Chandler DE, Schulten K. Magnetic field effects in Arabidopsis thaliana cryptochrome-1. Biophys J 2007; 92:2711-26. [PMID: 17259272 PMCID: PMC1831705 DOI: 10.1529/biophysj.106.097139] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Accepted: 01/04/2007] [Indexed: 11/18/2022] Open
Abstract
The ability of some animals, most notably migratory birds, to sense magnetic fields is still poorly understood. It has been suggested that this "magnetic sense" may be mediated by the blue light receptor protein cryptochrome, which is known to be localized in the retinas of migratory birds. Cryptochromes are a class of photoreceptor signaling proteins that are found in a wide variety of organisms and that primarily perform regulatory functions, such as the entrainment of circadian rhythm in mammals and the inhibition of hypocotyl growth in plants. Recent experiments have shown that the activity of cryptochrome-1 in Arabidopsis thaliana is enhanced by the presence of a weak external magnetic field, confirming the ability of cryptochrome to mediate magnetic field responses. Cryptochrome's signaling is tied to the photoreduction of an internally bound chromophore, flavin adenine dinucleotide. The spin chemistry of this photoreduction process, which involves electron transfer from a chain of three tryptophans, can be modulated by the presence of a magnetic field in an effect known as the radical-pair mechanism. Here we present and analyze a model of the flavin-adenine-dinucleotide-tryptophan chain system that incorporates realistic hyperfine coupling constants and reaction rate constants. Our calculations show that the radical-pair mechanism in cryptochrome can produce an increase in the protein's signaling activity of approximately 10% for magnetic fields on the order of 5 G, which is consistent with experimental results. These calculations, in view of the similarity between bird and plant cryptochromes, provide further support for a cryptochrome-based model of avian magnetoreception.
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Affiliation(s)
- Ilia A Solov'yov
- Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
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64
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Thoma F. Repair of UV lesions in nucleosomes--intrinsic properties and remodeling. DNA Repair (Amst) 2007; 4:855-69. [PMID: 15925550 DOI: 10.1016/j.dnarep.2005.04.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/18/2005] [Indexed: 11/28/2022]
Abstract
Nucleotide excision repair and reversal of pyrimidine dimers by photolyase (photoreactivation) are two major pathways to remove UV-lesions from DNA. Here, it is discussed how lesions are recognized and removed when the DNA is condensed into nucleosomes. During the recent years it was shown that nucleosomes inhibit photolyase and excision repair in vitro and slow down repair in vivo. The correlation of DNA-repair rates with nucleosome positions in yeast suggests that intrinsic properties of nucleosomes such as mobility and transient unwrapping of nucleosomal DNA facilitate damage recognition. Moreover, it was shown that nucleosome remodeling activities can act on UV-damaged DNA in vitro and facilitate repair suggesting that random remodeling of chromatin might contribute to damage recognition in vivo. Recent work on nucleosome structure and mobility is included to evaluate how nucleosomes accommodate DNA lesions and how nucleosome mobility and remodeling can take place on damaged DNA.
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Affiliation(s)
- Fritz Thoma
- Institut für Zellbiologie, ETH-Hönggerberg, CH-8093 Zürich, Switzerland.
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65
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Bouly JP, Schleicher E, Dionisio-Sese M, Vandenbussche F, Van Der Straeten D, Bakrim N, Meier S, Batschauer A, Galland P, Bittl R, Ahmad M. Cryptochrome blue light photoreceptors are activated through interconversion of flavin redox states. J Biol Chem 2007; 282:9383-9391. [PMID: 17237227 DOI: 10.1074/jbc.m609842200] [Citation(s) in RCA: 272] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cryptochromes are blue light-sensing photoreceptors found in plants, animals, and humans. They are known to play key roles in the regulation of the circadian clock and in development. However, despite striking structural similarities to photolyase DNA repair enzymes, cryptochromes do not repair double-stranded DNA, and their mechanism of action is unknown. Recently, a blue light-dependent intramolecular electron transfer to the excited state flavin was characterized and proposed as the primary mechanism of light activation. The resulting formation of a stable neutral flavin semiquinone intermediate enables the photoreceptor to absorb green/yellow light (500-630 nm) in addition to blue light in vitro. Here, we demonstrate that Arabidopsis cryptochrome activation by blue light can be inhibited by green light in vivo consistent with a change of the cofactor redox state. We further characterize light-dependent changes in the cryptochrome1 (cry1) protein in living cells, which match photoreduction of the purified cry1 in vitro. These experiments were performed using fluorescence absorption/emission and EPR on whole cells and thereby represent one of the few examples of the active state of a known photoreceptor being monitored in vivo. These results indicate that cry1 activation via blue light initiates formation of a flavosemiquinone signaling state that can be converted by green light to an inactive form. In summary, cryptochrome activation via flavin photoreduction is a reversible mechanism novel to blue light photoreceptors. This photocycle may have adaptive significance for sensing the quality of the light environment in multiple organisms.
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Affiliation(s)
- Jean-Pierre Bouly
- Université Paris VI, FRE-CNRS 2846, Casier 156, 4 Place Jussieu, 75005 Paris, France
| | - Erik Schleicher
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
| | - Maribel Dionisio-Sese
- FB Biologie-Pflanzenphysiologie, Philipps-Universität, Karl-von-Frisch-Strasse 8, 35032 Marburg, Germany
| | - Filip Vandenbussche
- Université Paris VI, FRE-CNRS 2846, Casier 156, 4 Place Jussieu, 75005 Paris, France; Unit Plant Hormone Signaling and Bio-imaging, Department of Molecular Genetics, Ghent University, Ledeganckstraat 35, B-9000 Ghent, Belgium
| | | | - Nadia Bakrim
- Université Paris VI, FRE-CNRS 2846, Casier 156, 4 Place Jussieu, 75005 Paris, France
| | - Stefan Meier
- FB Biologie-Pflanzenphysiologie, Philipps-Universität, Karl-von-Frisch-Strasse 8, 35032 Marburg, Germany
| | - Alfred Batschauer
- FB Biologie-Pflanzenphysiologie, Philipps-Universität, Karl-von-Frisch-Strasse 8, 35032 Marburg, Germany
| | - Paul Galland
- FB Biologie-Pflanzenphysiologie, Philipps-Universität, Karl-von-Frisch-Strasse 8, 35032 Marburg, Germany
| | - Robert Bittl
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
| | - Margaret Ahmad
- Université Paris VI, FRE-CNRS 2846, Casier 156, 4 Place Jussieu, 75005 Paris, France; Pennsylvania State University, Media, Pennsylvania 19063.
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66
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Prytkova TR, Beratan DN, Skourtis SS. Photoselected electron transfer pathways in DNA photolyase. Proc Natl Acad Sci U S A 2007; 104:802-7. [PMID: 17209014 PMCID: PMC1783394 DOI: 10.1073/pnas.0605319104] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Indexed: 11/18/2022] Open
Abstract
Cyclobutane dimer photolyases are proteins that bind to UV-damaged DNA containing cyclobutane pyrimidine dimer lesions. They repair these lesions by photo-induced electron transfer. The electron donor cofactor of a photolyase is a two-electron-reduced flavin adenine dinucleotide (FADH(-)). When FADH(-) is photo-excited, it transfers an electron from an excited pi --> pi* singlet state to the pyrimidine dimer lesion of DNA. We compute the lowest excited singlet states of FADH(-) using ab initio (time-dependent density functional theory and time-dependent Hartree-Fock), and semiempirical (INDO/S configuration interaction) methods. The calculations show that the two lowest pi --> pi* singlet states of FADH(-) are localized on the side of the flavin ring that is proximal to the dimer lesion of DNA. For the lowest-energy donor excited state of FADH(-), we compute the conformationally averaged electronic coupling to acceptor states of the thymine dimer. The coupling calculations are performed at the INDO/S level, on donor-acceptor cofactor conformations obtained from molecular dynamics simulations of the solvated protein with a thymine dimer docked in its active site. These calculations demonstrate that the localization of the (1)FADH(-)* donor state on the flavin ring enhances the electronic coupling between the flavin and the dimer by permitting shorter electron-transfer pathways to the dimer that have single through-space jumps. Therefore, in photolyase, the photo-excitation itself enhances the electron transfer rate by moving the electron towards the dimer.
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Affiliation(s)
- Tatiana R. Prytkova
- Departments of Chemistry and Biochemistry, Duke University, Durham, NC 27708; and
| | - David N. Beratan
- Departments of Chemistry and Biochemistry, Duke University, Durham, NC 27708; and
| | - Spiros S. Skourtis
- Department of Physics, University of Cyprus, P.O. Box 20537, Nicosia 1678, Cyprus
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67
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Plaza P, Mahet M, Martin MM, Checcucci G, Lenci F. Target Analysis of Primary Photoprocesses Involved in the Oxyblepharismin-Binding Protein. J Phys Chem B 2007; 111:690-6. [PMID: 17249812 DOI: 10.1021/jp0642591] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Target analysis is performed on previously published transient absorption spectra of the 200-kDa oxyblepharismin-binding protein (OBIP) thought to trigger the photophobic response of the ciliate Blepharisma japonicum. The OBIP sample is considered as heterogeneous and made of two distinct classes of chromophore-protein complexes. A so-called nonreactive class is seen to be comparable to free oxyblepharismin in organic solution. Another, reactive, class is shown to undergo a fast picosecond photocycle involving the formation in 4 ps of an intermediate state noted Y1. The spectrum associated to Y1 bears striking similarities with that of the oxyblepharismin radical cation. This element favors the hypothesis that an excited-state intermolecular electron-transfer could be the primary step of the sensory transduction chain of B. japonicum. Proton release is also considered as a possible secondary step. These possibilities support the idea that reactive OBIP functions like an electron or proton pump. We alternatively propose a new hypothesis stating that the fast photocycle of reactive OBIP actually does not generate any photoproduct or protein change of conformation but is involved in another biological function. It would act as a kind of solar screen, providing additional protection to the light-adapted form of B. japonicum in case of excessive illumination.
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Affiliation(s)
- Pascal Plaza
- Département de Chimie, UMR 8640 CNRS-ENS, Ecole Normale Supérieure, 24 rue Lhomond, 75005 Paris, France.
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68
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Schleicher E, Hitomi K, Kay CWM, Getzoff ED, Todo T, Weber S. Electron nuclear double resonance differentiates complementary roles for active site histidines in (6-4) photolyase. J Biol Chem 2006; 282:4738-4747. [PMID: 17164245 DOI: 10.1074/jbc.m604734200] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
(6-4) photolyase catalyzes the light-dependent repair of UV-damaged DNA containing (6-4) photoproducts. Blue light excitation of the enzyme generates the neutral FAD radical, FADH., which is believed to be transiently formed during the enzymatic DNA repair. Here (6-4) photolyase has been examined by optical spectroscopy, electron paramagnetic resonance, and pulsed electron nuclear double resonance spectroscopy. Characterization of selected proton hyperfine couplings of FADH., namely those of H(8alpha) and H(1'), yields information on the micropolarity at the site where the DNA substrate is expected to bind. Shifts in the hyperfine couplings as a function of structural modifications induced by point mutations and pH changes distinguish the protonation states of two highly conserved histidines, His(354) and His(358), in Xenopus laevis (6-4) photolyase. These are proposed to catalyze formation of the oxetane intermediate that precedes light-initiated DNA repair. The results show that at pH 9.5, where the enzymatic repair activity is highest, His(358) is deprotonated, whereas His(354) is protonated. Hence, the latter is likely the proton donor that initiates oxetane formation from the (6-4) photoproduct.
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Affiliation(s)
- Erik Schleicher
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Kenichi Hitomi
- Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Christopher W M Kay
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany; Department of Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom, and the
| | - Elizabeth D Getzoff
- Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Takeshi Todo
- Radiation Biology Center, Kyoto University, Yoshidakonoe-cho, Sakyoku, Kyoto 606-8501, Japan
| | - Stefan Weber
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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69
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Costentin C, Robert M, Savéant JM. Carboxylates as Proton-Accepting Groups in Concerted Proton−Electron Transfers. Electrochemistry of the 2,5-Dicarboxylate 1,4-Hydrobenzoquinone/2,5-Dicarboxy 1,4-Benzoquinone Couple. J Am Chem Soc 2006; 128:8726-7. [PMID: 16819855 DOI: 10.1021/ja0621750] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Concerted proton and electron transfers (CPET) currently attract considerable theoretical and experimental attention, notably in view of their likely involvement in many enzymatic reactions. The role of carboxylate groups as proton-accepting sites in CPET reactions is explored by means of a cyclic voltammetric investigation of the 2,5-dicarboxy 1,4-benzoquinone/2,5-dicarboxylate 1,4-hydrobenzoquinone couple in a nonaqueous medium. The presence of carboxylate groups ortho to the phenol groups induces the removal of an electron to be coupled with the transfer of the phenolic proton to a carboxylate oxygen. The kinetics of the electrochemical reaction and the observation of a significant hydrogen/deuterium kinetic isotope effect unambiguously indicate that electron transfer and proton transfer are concerted, thus providing an additional demonstration of the role of carboxylate groups as proton-accepting sites in concerted proton-electron transfer reactions.
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Affiliation(s)
- Cyrille Costentin
- Laboratoire d'Electrochimie Moléculaire, Unité Mixte de Recherche Université-CNRS 7591, Université de Paris 7-Denis Diderot, 2 place Jussieu, 75251 Paris Cedex 05, France
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70
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Zeugner A, Byrdin M, Bouly JP, Bakrim N, Giovani B, Brettel K, Ahmad M. Light-induced electron transfer in Arabidopsis cryptochrome-1 correlates with in vivo function. J Biol Chem 2005; 280:19437-40. [PMID: 15774475 DOI: 10.1074/jbc.c500077200] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cryptochromes are blue light-activated photoreceptors found in multiple organisms with significant similarity to photolyases, a class of light-dependent DNA repair enzymes. Unlike photolyases, cryptochromes do not repair DNA and instead mediate blue light-dependent developmental, growth, and/or circadian responses by an as yet unknown mechanism of action. It has recently been shown that Arabidopsis cryptochrome-1 retains photolyase-like photoreduction of its flavin cofactor FAD by intraprotein electron transfer from tryptophan and tyrosine residues. Here we demonstrate that substitution of two conserved tryptophans that are constituents of the flavin-reducing electron transfer chain in Escherichia coli photolyase impairs light-induced electron transfer in the Arabidopsis cryptochrome-1 photoreceptor in vitro. Furthermore, we show that these substitutions result in marked reduction of light-activated autophosphorylation of cryptochrome-1 in vitro and of its photoreceptor function in vivo, consistent with biological relevance of the electron transfer reaction. These data support the possibility that light-induced flavin reduction via the tryptophan chain is the primary step in the signaling pathway of plant cryptochrome.
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Wang H, Saxena C, Quan D, Sancar A, Zhong D. Femtosecond Dynamics of Flavin Cofactor in DNA Photolyase: Radical Reduction, Local Solvation, and Charge Recombination. J Phys Chem B 2005; 109:1329-33. [PMID: 16851098 DOI: 10.1021/jp044652b] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report here our femtosecond studies of the photoreduction dynamics of the neutral radical flavin (FADH) cofactor in E. coli photolyase, a process converting the inactive form to the biologically active one, a fully reduced deprotonated flavin FADH(-). The observed temporal absorption evolution revealed two initial electron-transfer reactions, occurring in 11 and 42 ps with the neighboring aromatic residues of W382 and F366, respectively. The new transient absorption, observed at 550 nm previously in photolyase, was found from the excited-state neutral radical and is probably caused by strong interactions with the adenine moiety through the flavin U-shaped configuration and the highly polar/charged surrounding residues. The solvation dynamics from the locally ordered water molecules in the active site was observed to occur in approximately 2 ps. These ultrafast ordered-water motions are critical to stabilizing the photoreduction product FADH(-) instantaneously to prevent fast charge recombination. The back electron-transfer reaction was found to occur in approximately 3 ns. This slow process, consistent with ultrafast stabilization of the catalytic cofactor, favors photoreduction in photolyase.
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Affiliation(s)
- Haiyu Wang
- Departments of Physics, Chemistry, and Biochemistry, OSU Biophysics, Chemical Physics, and Biochemistry Programs, 174 West 18th Avenue, The Ohio State University, Columbus, OH 43210, USA
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