1
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Guo H, Liu S, Liu X, Zhang L. Lightening flavin by amination for fluorescent sensing. Phys Chem Chem Phys 2024; 26:19554-19563. [PMID: 38979978 DOI: 10.1039/d4cp01525h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Monitoring of reactive oxygen species (ROS), such as O2˙-, etc., in organisms is of great significance, not only for their essential role in biological processes, but their excessive production may also result in many diseases. Flavin (FL) is a fluorophore that naturally exists in flavoenzymes, and its fluorescent emission (FE) becomes negligible when reduced. This enables the application of FL derivatives as fluorescent sensors for ROS. We presented a theoretical investigation to address the impact of amino substitution on the photophysical properties of aminoflavins (AmFLs). Resulting from the interplay of electronic and positional effects, amination at C8 enhances the electronic coupling between the ground state and the first singlet excited state by enlarging the adiabatic energy change of the electronic transitions and the emission transition dipole moments, weakens the vibronic coupling by decreasing the contribution of isoalloxazine to the frontier molecular orbitals, redshifts the absorption band, and enhances the fluorescent emission drastically in 8AmFL. The theoretically estimated fluorescent emission intensity of 8AmFL is ∼40 times that of FL, suggesting its potential application as a fluorescent sensor.
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Affiliation(s)
- Huimin Guo
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Siyu Liu
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Xin Liu
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Lijun Zhang
- Department of Ophthalmology, The Third People's Hospital of Dalian and Faculty of Medicine, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China
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2
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Panter S, Ayekoi A, Tesche J, Chen J, Illarionov B, Bacher A, Fischer M, Weber S. Shining a Spotlight on Methyl Groups: Photochemically Induced Dynamic Nuclear Polarization Spectroscopy of 5-Deazariboflavin and Its Nor Analogs. Int J Mol Sci 2024; 25:848. [PMID: 38255921 PMCID: PMC10815406 DOI: 10.3390/ijms25020848] [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: 12/08/2023] [Revised: 01/07/2024] [Accepted: 01/08/2024] [Indexed: 01/24/2024] Open
Abstract
5-Deazaflavins are analogs of naturally occurring flavin cofactors. They serve as substitutes for natural flavin cofactors to investigate and modify the reaction pathways of flavoproteins. Demethylated 5-deazaflavins are potential candidates for artificial cofactors, allowing us to fine-tune the reaction kinetics and absorption characteristics of flavoproteins. In this contribution, demethylated 5-deazariboflavin radicals are investigated (1) to assess the influence of the methyl groups on the electronic structure of the 5-deazaflavin radical and (2) to explore their photophysical properties with regard to their potential as artificial cofactors. We determined the proton hyperfine structure of demethylated 5-deazariboflavins using photochemically induced dynamic nuclear polarization (photo-CIDNP) spectroscopy, as well as density functional theory (DFT). To provide context, we compare our findings to a study of flavin mononucleotide (FMN) derivatives. We found a significant influence of the methylation pattern on the absorption properties, as well as on the proton hyperfine coupling ratios of the xylene moiety, which appears to be solvent-dependent. This effect is enhanced by the replacement of N5 by C5-H in 5-deazaflavin derivatives compared to their respective flavin counterparts.
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Affiliation(s)
- Sabrina Panter
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany; (S.P.); (A.A.)
| | - Audrey Ayekoi
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany; (S.P.); (A.A.)
| | - Jannis Tesche
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany; (S.P.); (A.A.)
| | - Jing Chen
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany; (S.P.); (A.A.)
| | - Boris Illarionov
- Institut für Lebensmittelchemie, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany; (B.I.); (M.F.)
| | - Adelbert Bacher
- TUM School of Natural Sciences, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany;
| | - Markus Fischer
- Institut für Lebensmittelchemie, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany; (B.I.); (M.F.)
| | - Stefan Weber
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany; (S.P.); (A.A.)
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3
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Bracker M, Kubitz MK, Czekelius C, Marian CM, Kleinschmidt M. Computer‐Aided Design of Fluorinated Flavin Derivatives by Modulation of Intersystem Crossing and Fluorescence. CHEMPHOTOCHEM 2022. [DOI: 10.1002/cptc.202200040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mario Bracker
- Institute of Theoretical and Computational Chemistry Heinrich-Heine-University Düsseldorf D-40204 Düsseldorf Germany
| | - Mira K. Kubitz
- Institute of Organic and Macromolecular Chemistry Heinrich-Heine-University Düsseldorf D-40204 Düsseldorf Germany
| | - Constantin Czekelius
- Institute of Organic and Macromolecular Chemistry Heinrich-Heine-University Düsseldorf D-40204 Düsseldorf Germany
| | - Christel M. Marian
- Institute of Theoretical and Computational Chemistry Heinrich-Heine-University Düsseldorf D-40204 Düsseldorf Germany
| | - Martin Kleinschmidt
- Institute of Theoretical and Computational Chemistry Heinrich-Heine-University Düsseldorf D-40204 Düsseldorf Germany
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4
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Lafaye C, Aumonier S, Torra J, Signor L, von Stetten D, Noirclerc-Savoye M, Shu X, Ruiz-González R, Gotthard G, Royant A, Nonell S. Riboflavin-binding proteins for singlet oxygen production. Photochem Photobiol Sci 2022; 21:1545-1555. [PMID: 35041199 DOI: 10.1007/s43630-021-00156-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 12/07/2021] [Indexed: 12/27/2022]
Abstract
miniSOG, developed as the first fully genetically encoded singlet oxygen photosensitiser, has found various applications in cell imaging and functional studies. Yet, miniSOG has suboptimal properties, including a low yield of singlet oxygen generation, which can nevertheless be improved tenfold upon blue light irradiation. In a previous study, we showed that this improvement was due to the photolysis of the miniSOG chromophore, flavin mononucleotide (FMN), into lumichrome, with concomitant removal of the phosphoribityl tail, thereby improving oxygen access to the alloxazine ring. We thus reasoned that a chromophore with a shorter tail would readily improve the photosensitizing properties of miniSOG. In this work, we show that the replacement of FMN by riboflavin (RF), which lacks the bulky phosphate group, significantly improves the singlet oxygen quantum yield (ΦΔ). We then proceeded to mutagenize the residues stabilizing the phosphate group of FMN to alter the chromophore specificity. We identified miniSOG-R57Q as a flavoprotein that selectively binds RF in cellulo, with a modestly improved ΦΔ. Our results show that it is possible to modify the flavin specificity of a given flavoprotein, thus providing a new option to tune its photophysical properties, including those leading to photosensitization. We also determined the structure of miniSOG-Q103L, a mutant with a much increased ΦΔ, which allowed us to postulate the existence of another access channel to FMN for molecular oxygen.
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Affiliation(s)
- Céline Lafaye
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), 71 Avenue des Martyrs, 38044, Grenoble Cedex 9, France
| | - Sylvain Aumonier
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38043, Grenoble Cedex 9, France
| | - Joaquim Torra
- Institut Químic de Sarrià, Universitat Ramon Llull, Via Augusta 390, 08017, Barcelona, Spain
| | - Luca Signor
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), 71 Avenue des Martyrs, 38044, Grenoble Cedex 9, France
| | - David von Stetten
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38043, Grenoble Cedex 9, France
| | - Marjolaine Noirclerc-Savoye
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), 71 Avenue des Martyrs, 38044, Grenoble Cedex 9, France
| | - Xiaokun Shu
- Department of Pharmaceutical Chemistry, University of California-San Francisco, San Francisco, CA, 94158-9001, USA.,Cardiovascular Research Institute, University of California-San Francisco, San Francisco, CA, 94158-9001, USA
| | - Rubén Ruiz-González
- Institut Químic de Sarrià, Universitat Ramon Llull, Via Augusta 390, 08017, Barcelona, Spain
| | - Guillaume Gotthard
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38043, Grenoble Cedex 9, France
| | - Antoine Royant
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), 71 Avenue des Martyrs, 38044, Grenoble Cedex 9, France. .,European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38043, Grenoble Cedex 9, France.
| | - Santi Nonell
- Institut Químic de Sarrià, Universitat Ramon Llull, Via Augusta 390, 08017, Barcelona, Spain.
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5
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Smolentseva A, Goncharov IM, Yudenko A, Bogorodskiy A, Semenov O, Nazarenko VV, Borshchevskiy V, Fonin AV, Remeeva A, Jaeger KE, Krauss U, Gordeliy V, Gushchin I. Extreme dependence of Chloroflexus aggregans LOV domain thermo- and photostability on the bound flavin species. Photochem Photobiol Sci 2021; 20:1645-1656. [PMID: 34796467 DOI: 10.1007/s43630-021-00138-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 11/08/2021] [Indexed: 01/10/2023]
Abstract
Light-oxygen-voltage (LOV) domains are common photosensory modules that found many applications in fluorescence microscopy and optogenetics. Here, we show that the Chloroflexus aggregans LOV domain can bind different flavin species (lumichrome, LC; riboflavin, RF; flavin mononucleotide, FMN; flavin adenine dinucleotide, FAD) during heterologous expression and that its physicochemical properties depend strongly on the nature of the bound flavin. We show that whereas the dissociation constants for different chromophores are similar, the melting temperature of the protein reconstituted with single flavin species varies from ~ 60 °C for LC to ~ 81 °C for FMN, and photobleaching half-times vary almost 100-fold. These observations serve as a caution for future studies of LOV domains in non-native conditions yet raise the possibility of fine-tuning various properties of LOV-based fluorescent probes and optogenetic tools by manipulating the chromophore composition.
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Affiliation(s)
- Anastasia Smolentseva
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Ivan M Goncharov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Anna Yudenko
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Andrey Bogorodskiy
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Oleg Semenov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Vera V Nazarenko
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Valentin Borshchevskiy
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia.,Institute of Biological Information Processing IBI-7: Structural Biochemistry, Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Alexander V Fonin
- Institute of Cytology, Russian Academy of Sciences, 194064, Saint Petersburg, Russia
| | - Alina Remeeva
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Karl-Erich Jaeger
- Institute of Molecular Enzyme Technology, Heinrich Heine University Düsseldorf, Forschungszentrum Jülich, Jülich, Germany.,Institute of Bio- and Geosciences IBG-1: Biotechnology, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Ulrich Krauss
- Institute of Molecular Enzyme Technology, Heinrich Heine University Düsseldorf, Forschungszentrum Jülich, Jülich, Germany.,Institute of Bio- and Geosciences IBG-1: Biotechnology, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Valentin Gordeliy
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia.,Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-CEA-CNRS, 38000, Grenoble, France.,Institute of Biological Information Processing IBI-7: Structural Biochemistry, Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Ivan Gushchin
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia.
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6
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Arinkin V, Granzin J, Krauss U, Jaeger KE, Willbold D, Batra-Safferling R. Structural determinants underlying the adduct lifetime in the LOV proteins of Pseudomonas putida. FEBS J 2021; 288:4955-4972. [PMID: 33621443 DOI: 10.1111/febs.15785] [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: 10/04/2020] [Revised: 01/22/2021] [Accepted: 02/22/2021] [Indexed: 11/30/2022]
Abstract
The primary photochemistry is similar among the flavin-bound sensory domains of light-oxygen-voltage (LOV) photoreceptors, where upon blue-light illumination a covalent adduct is formed on the microseconds time scale between the flavin chromophore and a strictly conserved cysteine residue. In contrast, the adduct-state decay kinetics vary from seconds to days or longer. The molecular basis for this variation among structurally conserved LOV domains is not fully understood. Here, we selected PpSB2-LOV, a fast-cycling (τrec 3.5 min, 20 °C) short LOV protein from Pseudomonas putida that shares 67% sequence identity with a slow-cycling (τrec 2467 min, 20 °C) homologous protein PpSB1-LOV. Based on the crystal structure of the PpSB2-LOV in the dark state reported here, we used a comparative approach, in which we combined structure and sequence information with molecular dynamic (MD) simulations to address the mechanistic basis for the vastly different adduct-state lifetimes in the two homologous proteins. MD simulations pointed toward dynamically distinct structural region, which were subsequently targeted by site-directed mutagenesis of PpSB2-LOV, where we introduced single- and multisite substitutions exchanging them with the corresponding residues from PpSB1-LOV. Collectively, the data presented identify key amino acids on the Aβ-Bβ, Eα-Fα loops, and the Fα helix, such as E27 and I66, that play a decisive role in determining the adduct lifetime. Our results additionally suggest a correlation between the solvent accessibility of the chromophore pocket and adduct-state lifetime. The presented results add to our understanding of LOV signaling and will have important implications in tuning the signaling behavior (on/off kinetics) of LOV-based optogenetic tools.
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Affiliation(s)
- Vladimir Arinkin
- IBI-7: Structural Biochemistry, Forschungszentrum Jülich, Germany
| | - Joachim Granzin
- IBI-7: Structural Biochemistry, Forschungszentrum Jülich, Germany
| | - Ulrich Krauss
- Institut für Molekulare Enzymtechnologie, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich GmbH, Germany.,IBG-1: Biotechnologie, Forschungszentrum Jülich GmbH, Germany
| | - Karl-Erich Jaeger
- Institut für Molekulare Enzymtechnologie, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich GmbH, Germany.,IBG-1: Biotechnologie, Forschungszentrum Jülich GmbH, Germany
| | - Dieter Willbold
- IBI-7: Structural Biochemistry, Forschungszentrum Jülich, Germany.,Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Germany.,Jülich Centre for Structural Biology (JuStruct), Forschungszentrum Jülich, Germany
| | - Renu Batra-Safferling
- IBI-7: Structural Biochemistry, Forschungszentrum Jülich, Germany.,Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Germany
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7
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Pompe N, Chen J, Illarionov B, Panter S, Fischer M, Bacher A, Weber S. Methyl groups matter: Photo-CIDNP characterizations of the semiquinone radicals of FMN and demethylated FMN analogs. J Chem Phys 2019; 151:235103. [PMID: 31864274 DOI: 10.1063/1.5130557] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this contribution, the relative hyperfine couplings are determined for the 1H nuclei of the flavin mononucleotide (FMN) radical in an aqueous environment. In addition, three structural analogs with different methylation patterns are characterized and the influence of the substituents at the isoalloxazine moiety on the electronic structure of the radicals is explored. By exploiting nuclear hyperpolarization generated via the photo-CIDNP (chemically induced dynamic nuclear polarization) effect, it is possible to study the short-lived radical species generated by in situ light excitation. Experimental data are extracted by least-squares fitting and supported by quantum chemical calculations and published values from electron paramagnetic resonance and electron-nuclear double resonance. Furthermore, mechanistic details of the photoreaction of the investigated flavin analogs with l-tryptophan are derived from the photo-CIDNP spectra recorded at different pH values. Thereby, the neutral and anionic radicals of FMN and three structural analogs are, for the first time, characterized in terms of their electronic structure in an aqueous environment.
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Affiliation(s)
- Nils Pompe
- Institute of Physical Chemistry, University of Freiburg, 79104 Freiburg, Germany
| | - Jing Chen
- Institute of Physical Chemistry, University of Freiburg, 79104 Freiburg, Germany
| | - Boris Illarionov
- Hamburg School of Food Science, Institute of Food Chemistry, University of Hamburg, 20146 Hamburg, Germany
| | - Sabrina Panter
- Institute of Physical Chemistry, University of Freiburg, 79104 Freiburg, Germany
| | - Markus Fischer
- Hamburg School of Food Science, Institute of Food Chemistry, University of Hamburg, 20146 Hamburg, Germany
| | - Adelbert Bacher
- Department of Chemistry, Technical University of Munich, 85748 Garching, Germany
| | - Stefan Weber
- Institute of Physical Chemistry, University of Freiburg, 79104 Freiburg, Germany
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8
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Kalvaitis ME, Johnson LA, Mart RJ, Rizkallah P, Allemann RK. A Noncanonical Chromophore Reveals Structural Rearrangements of the Light-Oxygen-Voltage Domain upon Photoactivation. Biochemistry 2019; 58:2608-2616. [PMID: 31082213 PMCID: PMC7007005 DOI: 10.1021/acs.biochem.9b00255] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
![]()
Light-oxygen-voltage
(LOV) domains are increasingly used to engineer
photoresponsive biological systems. While the photochemical cycle
is well documented, the allosteric mechanism by which formation of
a cysteinyl-flavin adduct leads to activation is unclear. Via replacement
of flavin mononucleotide (FMN) with 5-deazaflavin mononucleotide (5dFMN)
in the Aureochrome1a (Au1a) transcription factor from Ochromonas
danica, a thermally stable cysteinyl-5dFMN adduct was generated.
High-resolution crystal structures (<2 Å) under different
illumination conditions with either FMN or 5dFMN chromophores reveal
three conformations of the highly conserved glutamine 293. An allosteric
hydrogen bond network linking the chromophore via Gln293 to the auxiliary
A′α helix is observed. With FMN, a “flip”
of the Gln293 side chain occurs between dark and lit states. 5dFMN
cannot hydrogen bond through the C5 position and proved to be unable
to support Au1a domain dimerization. Under blue light, the Gln293
side chain instead “swings” away in a conformation distal
to the chromophore and not previously observed in existing LOV domain
structures. Together, the multiple side chain conformations of Gln293
and functional analysis of 5dFMN provide new insight into the structural
requirements for LOV domain activation.
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Affiliation(s)
- Mindaugas E Kalvaitis
- School of Chemistry , Cardiff University , Park Place , Cardiff CF10 3AT , United Kingdom
| | - Luke A Johnson
- School of Chemistry , Cardiff University , Park Place , Cardiff CF10 3AT , United Kingdom
| | - Robert J Mart
- School of Chemistry , Cardiff University , Park Place , Cardiff CF10 3AT , United Kingdom
| | - Pierre Rizkallah
- School of Medicine , University Hospital Wales , Main Building, Heath Park , Cardiff CF14 4XN , United Kingdom
| | - Rudolf K Allemann
- School of Chemistry , Cardiff University , Park Place , Cardiff CF10 3AT , United Kingdom
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9
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Gregor C, Sidenstein SC, Andresen M, Sahl SJ, Danzl JG, Hell SW. Novel reversibly switchable fluorescent proteins for RESOLFT and STED nanoscopy engineered from the bacterial photoreceptor YtvA. Sci Rep 2018; 8:2724. [PMID: 29426833 PMCID: PMC5807511 DOI: 10.1038/s41598-018-19947-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 01/10/2018] [Indexed: 01/05/2023] Open
Abstract
The reversibly switchable fluorescent proteins (RSFPs) commonly used for RESOLFT nanoscopy have been developed from fluorescent proteins of the GFP superfamily. These proteins are bright, but exhibit several drawbacks such as relatively large size, oxygen-dependence, sensitivity to low pH, and limited switching speed. Therefore, RSFPs from other origins with improved properties need to be explored. Here, we report the development of two RSFPs based on the LOV domain of the photoreceptor protein YtvA from Bacillus subtilis. LOV domains obtain their fluorescence by association with the abundant cellular cofactor flavin mononucleotide (FMN). Under illumination with blue and ultraviolet light, they undergo a photocycle, making these proteins inherently photoswitchable. Our first improved variant, rsLOV1, can be used for RESOLFT imaging, whereas rsLOV2 proved useful for STED nanoscopy of living cells with a resolution of down to 50 nm. In addition to their smaller size compared to GFP-related proteins (17 kDa instead of 27 kDa) and their usability at low pH, rsLOV1 and rsLOV2 exhibit faster switching kinetics, switching on and off 3 times faster than rsEGFP2, the fastest-switching RSFP reported to date. Therefore, LOV-domain-based RSFPs have potential for applications where the switching speed of GFP-based proteins is limiting.
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Affiliation(s)
- Carola Gregor
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany.
| | - Sven C Sidenstein
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany.,Abberior Instruments GmbH, Hans-Adolf-Krebs-Weg 1, 37077, Göttingen, Germany
| | - Martin Andresen
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Steffen J Sahl
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Johann G Danzl
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany.,Institute of Science and Technology Austria (IST Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Stefan W Hell
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany. .,Max Planck Institute for Medical Research, Department of Optical Nanoscopy, Jahnstraße 29, 69120, Heidelberg, Germany.
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10
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Sommer C, Dietz MS, Patschkowski T, Mathes T, Kottke T. Light-Induced Conformational Changes in the Plant Cryptochrome Photolyase Homology Region Resolved by Selective Isotope Labeling and Infrared Spectroscopy. Photochem Photobiol 2017; 93:881-887. [DOI: 10.1111/php.12750] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 02/10/2017] [Indexed: 11/28/2022]
Affiliation(s)
- Constanze Sommer
- Physical and Biophysical Chemistry; Department of Chemistry; Bielefeld University; Bielefeld Germany
| | - Marina S. Dietz
- Physical and Biophysical Chemistry; Department of Chemistry; Bielefeld University; Bielefeld Germany
| | - Thomas Patschkowski
- Proteome and Metabolome Research (Bio 27); Department of Biology; Bielefeld University; Bielefeld Germany
| | - Tilo Mathes
- Department of Biology; Experimental Biophysics; Humboldt-Universität zu Berlin; Berlin Germany
| | - Tilman Kottke
- Physical and Biophysical Chemistry; Department of Chemistry; Bielefeld University; Bielefeld Germany
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11
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Structure of a LOV protein in apo-state and implications for construction of LOV-based optical tools. Sci Rep 2017; 7:42971. [PMID: 28211532 PMCID: PMC5314338 DOI: 10.1038/srep42971] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 01/17/2017] [Indexed: 12/29/2022] Open
Abstract
Unique features of Light-Oxygen-Voltage (LOV) proteins like relatively small size (~12–19 kDa), inherent modularity, highly-tunable photocycle and oxygen-independent fluorescence have lately been exploited for the generation of optical tools. Structures of LOV domains reported so far contain a flavin chromophore per protein molecule. Here we report two new findings on the short LOV protein W619_1-LOV from Pseudomonas putida. First, the apo-state crystal structure of W619_1-LOV at 2.5 Å resolution reveals conformational rearrangements in the secondary structure elements lining the chromophore pocket including elongation of the Fα helix, shortening of the Eα-Fα loop and partial unfolding of the Eα helix. Second, the apo W619_1-LOV protein binds both natural and structurally modified flavin chromophores. Remarkably different photophysical and photochemical properties of W619_1-LOV bound to 7-methyl-8-chloro-riboflavin (8-Cl-RF) and lumichrome imply application of these variants as novel optical tools as they offer advantages such as no adduct state formation, and a broader choice of wavelengths for in vitro studies.
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12
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Eichhof I, Ernst JF. Oxygen-independent FbFP: Fluorescent sentinel and oxygen sensor component in Saccharomyces cerevisiae and Candida albicans. Fungal Genet Biol 2016; 92:14-25. [PMID: 27126475 DOI: 10.1016/j.fgb.2016.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 04/22/2016] [Accepted: 04/23/2016] [Indexed: 02/06/2023]
Abstract
FMN-binding fluorescent proteins (FbFPs) outperform GFP and its derivatives because of their oxygen-independence, small size and rapid maturation. FbFPs have been used successfully as reliable reporters of gene expression in the cytoplasm of pro- and eukaryotes. Here we extend previous findings on the codon-adapted CaFbFP variant, which functions in the apathogenic yeast Saccharomyces cerevisiae and the human fungal pathogen Candida albicans. In both fungal species, CaFbFP could be targeted to the nucleus and the cell wall by endogenous signals (H2B-/Aga2-fusions) demonstrating its use as a fluorescent beacon in these relevant cellular locations. Transformants of both fungal species producing a CaFbFP-YFP fusion (YFOS) showed variable energy transfer from CaFbFP to YFP (FRET) that depended in its extent on external O2 concentrations. Applications as fluorescent sentinel and oxygen biosensor expand the FbFP toolbox to study oxygen-independent cellular processes under hypoxia.
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Affiliation(s)
- Isabel Eichhof
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Joachim F Ernst
- Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
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13
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Lee R, Gam J, Moon J, Lee SG, Suh YG, Lee BJ, Lee J. A critical element of the light-induced quaternary structural changes in YtvA-LOV. Protein Sci 2015; 24:1997-2007. [PMID: 26402155 DOI: 10.1002/pro.2810] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/18/2015] [Accepted: 09/19/2015] [Indexed: 01/27/2023]
Abstract
YtvA, a photosensory LOV (light-oxygen-voltage) protein from Bacillus subtilis, exists as a dimer that previously appeared to undergo surprisingly small structural changes after light illumination compared with other light-sensing proteins. However, we now report that light induces significant structural perturbations in a series of YtvA-LOV domain derivatives in which the Jα helix has been truncated or replaced. Results from native gel analysis showed significant mobility changes in these derivatives after light illumination; YtvA-LOV without the Jα helix dimerized in the dark state but existed as a monomer in the light state. The absence of the Jα helix also affected the dark regeneration kinetics and the stability of the flavin mononucleotide (FMN) binding to its binding site. Our results demonstrate an alternative way of photo-induced signal propagation that leads to a bigger functional response through dimer/monomer conversions of the YtvA-LOV than the local disruption of Jα helix in the As-LOV domain.
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Affiliation(s)
- Rang Lee
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, 151-742, Korea
| | - Jongsik Gam
- Department of Medicinal Bioscience, College of Interdisciplinary & Creative Studies, Konyang University, Nonsan-Si, 320-711, Korea
| | - Jayoung Moon
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, 151-742, Korea
| | - Seung-Goo Lee
- Synthetic Biology and Bioengineering Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, 305-806, Korea
| | - Young-Ger Suh
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, 151-742, Korea
| | - Bong-Jin Lee
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, 151-742, Korea
| | - Jeeyeon Lee
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, 151-742, Korea
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14
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Kraiselburd I, Gutt A, Losi A, Gärtner W, Orellano EG. Functional Characterization of a LOV-Histidine Kinase Photoreceptor from Xanthomonas citri subsp. citri. Photochem Photobiol 2015; 91:1123-32. [PMID: 26172037 DOI: 10.1111/php.12493] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 06/18/2015] [Indexed: 01/30/2023]
Abstract
The blue-light (BL) absorbing protein Xcc-LOV from Xanthomonas citri subsp. citri is composed of a LOV-domain, a histidine kinase (HK) and a response regulator. Spectroscopic characterization of Xcc-LOV identified intermediates and kinetics of the protein's photocycle. Measurements of steady state and time-resolved fluorescence allowed determination of quantum yields for triplet (ΦT = 0.68 ± 0.03) and photoproduct formation (Φ390 = 0.46 ± 0.05). The lifetime for triplet decay was determined as τT = 2.4-2.8 μs. Fluorescence of tryptophan and tyrosine residues was unchanged upon light-to-dark conversion, emphasizing the absence of significant conformational changes. Photochemistry was blocked upon cysteine C76 (C76S) mutation, causing a seven-fold longer lifetime of the triplet state (τT = 16-18.5 μs). Optoacoustic spectroscopy yielded the energy content of the triplet state. Interestingly, Xcc-LOV did not undergo the volume contraction reported for other LOV domains within the observation time window, although the back-conversion into the dark state was accompanied by a volume expansion. A radioactivity-based enzyme function assay revealed a larger HK activity in the lit than in the dark state. The C76S mutant showed a still lower enzyme function, indicating the dark state activity being corrupted by a remaining portion of the long-lived lit state.
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Affiliation(s)
- Ivana Kraiselburd
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Universidad Nacional de Rosario, Rosario, Argentina
| | - Alexander Gutt
- Max-Planck-Institute for Chemical Energy Conversion, Mülheim, Germany
| | - Aba Losi
- Department of Physics and Earth Sciences, University of Parma, Parma, Italy
| | - Wolfgang Gärtner
- Max-Planck-Institute for Chemical Energy Conversion, Mülheim, Germany
| | - Elena G Orellano
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Universidad Nacional de Rosario, Rosario, Argentina
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15
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Pudasaini A, El-Arab KK, Zoltowski BD. LOV-based optogenetic devices: light-driven modules to impart photoregulated control of cellular signaling. Front Mol Biosci 2015; 2:18. [PMID: 25988185 PMCID: PMC4428443 DOI: 10.3389/fmolb.2015.00018] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 04/27/2015] [Indexed: 12/31/2022] Open
Abstract
The Light-Oxygen-Voltage domain family of proteins is widespread in biology where they impart sensory responses to signal transduction domains. The small, light responsive LOV modules offer a novel platform for the construction of optogenetic tools. Currently, the design and implementation of these devices is partially hindered by a lack of understanding of how light drives allosteric changes in protein conformation to activate diverse signal transduction domains. Further, divergent photocycle properties amongst LOV family members complicate construction of highly sensitive devices with fast on/off kinetics. In the present review we discuss the history of LOV domain research with primary emphasis on tuning LOV domain chemistry and signal transduction to allow for improved optogenetic tools.
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Affiliation(s)
- Ashutosh Pudasaini
- Department of Chemistry, Center for Drug Discovery, Design and Delivery at Dedman College, Southern Methodist University Dallas, TX, USA
| | - Kaley K El-Arab
- Department of Chemistry, Center for Drug Discovery, Design and Delivery at Dedman College, Southern Methodist University Dallas, TX, USA
| | - Brian D Zoltowski
- Department of Chemistry, Center for Drug Discovery, Design and Delivery at Dedman College, Southern Methodist University Dallas, TX, USA
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16
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Lee J. Light-Controlled Chemical Reactions and Their Applications in Biological Systems. ASIAN J ORG CHEM 2014. [DOI: 10.1002/ajoc.201402054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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17
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Abstract
Most biological photoreceptors are protein/cofactor complexes that induce a physiological reaction upon absorption of a photon. Therefore, these proteins represent signal converters that translate light into biological information. Researchers use this property to stimulate and study various biochemical processes conveniently and non-invasively by the application of light, an approach known as optogenetics. Here, we summarize the recent experimental progress on the family of blue light receptors using FAD (BLUF) receptors. Several BLUF photoreceptors modulate second messenger levels and thus represent highly interesting tools for optogenetic application. In order to activate a coupled effector protein, the flavin-binding pocket of the BLUF domain undergoes a subtle rearrangement of the hydrogen network upon blue light absorption. The hydrogen bond switch is facilitated by the ultrafast light-induced proton-coupled electron transfer (PCET) between a tyrosine and the flavin in less than a nanosecond and remains stable on a long enough timescale for biochemical reactions to take place. The cyclic nature of the photoinduced reaction makes BLUF domains powerful model systems to study protein/cofactor interaction, protein-modulated PCET and novel mechanisms of biological signalling. The ultrafast nature of the photoconversion as well as the subtle structural rearrangement requires sophisticated spectroscopic and molecular biological methods to study and understand this highly intriguing signalling process.
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Affiliation(s)
- John T M Kennis
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences , Vrije Universiteit , De Boelelaan 1081, 1081 HV Amsterdam , The Netherlands
| | - Tilo Mathes
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences , Vrije Universiteit , De Boelelaan 1081, 1081 HV Amsterdam , The Netherlands
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18
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Moon J, Gam J, Lee SG, Suh YG, Lee J. Light-regulated tetracycline binding to the Tet repressor. Chemistry 2014; 20:2508-14. [PMID: 24478132 DOI: 10.1002/chem.201304027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Indexed: 01/21/2023]
Abstract
Elucidation of the signal-transmission pathways between distant sites within proteins is of great importance in medical and bioengineering sciences. The use of optical methods to redesign protein functions is emerging as a general approach for the control of biological systems with high spatiotemporal precision. Here we report the detailed thermodynamic and kinetic characterization of novel chimeric light-regulated Tet repressor (TetR) switches in which light modulates the TetR function. Light absorbed by flavin mononucleotide (FMN) generates a signal that is transmitted to As-LOV and YtvA-LOV fused TetR proteins (LOV=light-oxygen-voltage), in which it alters the binding to tetracycline, the TetR ligand. The engineering of light-sensing protein modules with TetR is a valuable tool that deepens our understanding of the mechanism of signal transmission within proteins. In addition, the light-regulated changes of drug binding that we describe here suggest that engineered light-sensitive proteins may be used for the development of novel therapeutic strategies.
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Affiliation(s)
- Jayoung Moon
- College of Pharmacy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-742 (Korea), Fax: (+82) 2-884-8334
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19
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Dorn M, Jurk M, Wartenberg A, Hahn A, Schmieder P. LOV takes a pick: thermodynamic and structural aspects of the flavin-LOV-interaction of the blue-light sensitive photoreceptor YtvA from Bacillus subtilis. PLoS One 2013; 8:e81268. [PMID: 24278408 PMCID: PMC3836802 DOI: 10.1371/journal.pone.0081268] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 10/10/2013] [Indexed: 11/29/2022] Open
Abstract
LOV domains act as versatile photochromic switches servicing multiple effector domains in a variety of blue light sensing photoreceptors abundant in a multitude of organisms from all kingdoms of life. The perception of light is realized by a flavin chromophore that upon illumination reversibly switches from the non-covalently bound dark-state to a covalently linked flavin-LOV adduct. It is usually assumed that most LOV domains preferably bind FMN, but heterologous expression frequently results in the incorporation of all natural occurring flavins, i.e. riboflavin, FMN and FAD. Over recent years, the structures, photochemical properties, activation mechanisms and physiological functions of a multitude of LOV proteins have been studied intensively, but little is known about its affinities to physiologically relevant flavins or the thermodynamics of the flavin-LOV interaction. We have investigated the interaction of the LOV domain of the well characterized bacterial photoreceptor YtvA with riboflavin, FMN and FAD by ITC experiments providing binding constants and thermodynamic profiles of these interactions. For this purpose, we have developed a protocol for the production of the apo forms of YtvA and its isolated LOV domain and we demonstrate that the latter can be used as a molecular probe for free flavins in cell lysates. Furthermore, we show here using NMR spectroscopic techniques and Analytical Ultracentrifugation that the flavin moiety stabilizes the conformation of the LOV domain and that dimerization of YtvA is caused not only by intermolecular LOV-LOV but also by STAS-STAS contacts.
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Affiliation(s)
- Matthias Dorn
- Department of Structural Biology, Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
- Department of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Marcel Jurk
- Department of Structural Biology, Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
| | - Anne Wartenberg
- Department of Structural Biology, Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
- Department of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Aaron Hahn
- Department of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Peter Schmieder
- Department of Structural Biology, Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
- * E-mail:
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20
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Silva MR, Mansurova M, Gärtner W, Thiel W. Photophysics of structurally modified flavin derivatives in the blue-light photoreceptor YtvA: a combined experimental and theoretical study. Chembiochem 2013; 14:1648-61. [PMID: 23940057 DOI: 10.1002/cbic.201300217] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Indexed: 11/10/2022]
Abstract
The light-induced processes of two flavin mononucleotide derivatives (1- and 5-deaza flavin mononucleotide, 1DFMN and 5DFMN), incorporated into the LOV domain of YtvA protein from Bacillus subtilis, were studied by a combination of experimental and computational methods. Quantum mechanics/molecular mechanics (QM/MM) calculations were carried out in which the QM part was treated by density functional theory (DFT) using the B3LYP functional for geometry optimizations and the DFT/MRCI method for spectroscopic properties, whereas the MM part was described by the CHARMM force field. 1DFMN is incorporated into the protein binding site, yielding a red-shifted absorption band (λ(max) =530 nm compared to YtvA wild-type λ(max) =445 nm), but does not undergo any LOV-typical photoreactions such as triplet and photoadduct formation. QM/MM computations confirmed the absence of a channel for triplet formation and located a radiation-free channel (through an S₁/S₀ conical intersection) along a hydrogen transfer path that might allow for fast deactivation. By contrast, 5DFMN-YtvA-LOV shows a blue-shifted absorption (λ(max) =410 nm) and undergoes similar photochemical processes to FMN in the wild-type protein, both with regard to the photophysics and the formation of a photoadduct with a flavin-cysteinyl covalent bond. The QM/MM calculations predict a mechanism that involves hydrogen transfer in the T₁ state, followed by intersystem crossing and adduct formation in the S₀ state for the forward reaction. Experimentally, in contrast to wild-type YtvA, dark-state recovery in 5DFMN-YtvA-LOV is not thermally driven but can only be accomplished after absorption of a second photon by the photoadduct, again via the triplet state. The QM/MM calculations suggest a photochemical mechanism for dark-state recovery that is accessible only for the adduct with a C4a--S bond but not for alternative adducts with a C5--S bond.
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Affiliation(s)
- Mario R Silva
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr (Germany)
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Mansurova M, Simon J, Salzmann S, Marian CM, Gärtner W. Spectroscopic and Theoretical Study on Electronically Modified Chromophores in LOV Domains: 8-Bromo- and 8-Trifluoromethyl-Substituted Flavins. Chembiochem 2013; 14:645-54. [DOI: 10.1002/cbic.201200670] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Indexed: 11/11/2022]
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Abstract
LOV (light, oxygen or voltage) domains are protein photosensors that are conserved in bacteria, archaea, plants and fungi, and detect blue light via a flavin cofactor. LOV domains are present in both chemotrophic and phototrophic bacterial species, in which they are found amino-terminally of signalling and regulatory domains such as sensor histidine kinases, diguanylate cyclases-phosphodiesterases, DNA-binding domains and regulators of RNA polymerase σ-factors. In this Review, we describe the current state of knowledge about the function of bacterial LOV proteins, the structural basis of LOV domain-mediated signal transduction, and the use of LOV domains as genetically encoded photoswitches in synthetic biology.
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Losi A, Gärtner W. Old Chromophores, New Photoactivation Paradigms, Trendy Applications: Flavins in Blue Light-Sensing Photoreceptors†. Photochem Photobiol 2011; 87:491-510. [DOI: 10.1111/j.1751-1097.2011.00913.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Raffelberg S, Mansurova M, Gärtner W, Losi A. Modulation of the photocycle of a LOV domain photoreceptor by the hydrogen-bonding network. J Am Chem Soc 2011; 133:5346-56. [PMID: 21410163 DOI: 10.1021/ja1097379] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An extended hydrogen-bonding (HB) network stabilizes the isoalloxazine ring of the flavin mononucleotide (FMN) chromophore within the photosensing LOV domain of blue-light protein receptors, via interactions between the C(2)═O, N(3)H, C(4)═O, and N(5) groups and conserved glutamine and asparagine residues. In this work we studied the influence of the HB network on the efficiency, kinetics, and energetics of a LOV protein photocycle, involving the reversible formation of a FMN-cysteine covalent adduct. The following results were found for mutations of the conserved amino acids N94, N104, and Q123 in the Bacillus subtilis LOV protein YtvA: (i) Increased (N104D, N94D) or strongly reduced (N94A) rate of adduct formation; this latter mutation extends the lifetime of the flavin triplet state, i.e., adduct formation, more than 60-fold, from 2 μs for the wild-type (WT) protein to 129 μs. (ii) Acceleration of the overall photocycle for N94S, N94A, and Q123N, with recovery lifetimes 20, 45, and 85 times faster than for YtvA-WT, respectively. (iii) Slight modifications of FMN spectral features, correlated with the polarization of low-energy transitions. (iv) Strongly reduced (N94S) or suppressed (Q123N) structural volume changes accompanying adduct formation, as determined by optoacoustic spectroscopy. (v) Minor effects on the quantum yield, with the exception of a considerable reduction for Q123N, i.e., 0.22 vs 0.49 for YtvA-WT. The data stress the importance of the HB network in modulating the photocycle of LOV domains, while at the same time establishing a link with functional responses.
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Affiliation(s)
- Sarah Raffelberg
- Max-Planck-Institute for Bioinorganic Chemistry, Stiftstrasse 34-36, 45470 Mülheim, Germany
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