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Utschig LM, Brahmachari U, Mulfort KL, Niklas J, Poluektov OG. Biohybrid photosynthetic charge accumulation detected by flavin semiquinone formation in ferredoxin-NADP + reductase. Chem Sci 2022; 13:6502-6511. [PMID: 35756516 PMCID: PMC9172293 DOI: 10.1039/d2sc01546c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 05/02/2022] [Indexed: 11/21/2022] Open
Abstract
Flavin chemistry is ubiquitous in biological systems with flavoproteins engaged in important redox reactions. In photosynthesis, flavin cofactors are used as electron donors/acceptors to facilitate charge transfer and accumulation for ultimate use in carbon fixation. Following light-induced charge separation in the photosynthetic transmembrane reaction center photosystem I (PSI), an electron is transferred to one of two small soluble shuttle proteins, a ferredoxin (Fd) or a flavodoxin (Fld) (the latter in the condition of Fe-deficiency), followed by electron transfer to the ferredoxin-NADP+ reductase (FNR) enzyme. FNR accepts two of these sequential one electron transfers, with its flavin adenine dinucleotide (FAD) cofactor becoming doubly reduced, forming a hydride which is then passed onto the substrate NADP+ to form NADPH. The two one-electron potentials (oxidized/semiquinone and semiquinone/hydroquinone) are similar to each other with the FNR protein stabilizing the hydroquinone, making spectroscopic detection of the intermediate semiquinone state difficult. We employed a new biohybrid-based strategy that involved truncating the native three-protein electron transfer cascade PSI → Fd → FNR to a two-protein cascade by replacing PSI with a molecular Ru(ii) photosensitizer (RuPS) which is covalently bound to Fd and Fld to form biohybrid complexes that successfully mimic PSI in light-driven NADPH formation. RuFd → FNR and RuFld → FNR electron transfer experiments revealed a notable distinction in photosynthetic charge accumulation that we attribute to the different protein cofactors [2Fe2S] and flavin. After freeze quenching the two-protein systems under illumination, an intermediate semiquinone state of FNR was readily observed with cw X-band EPR spectroscopy. The increased spectral resolution from selective deuteration allowed EPR detection of inter-flavoprotein electron transfer. This work establishes a biohybrid experimental approach for further studies of photosynthetic light-driven electron transfer chain that culminates at FNR and highlights nature's mechanisms that couple single electron transfer chemistry to charge accumulation, providing important insight for the development of photon-to-fuel schemes.
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Affiliation(s)
- Lisa M Utschig
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Udita Brahmachari
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Karen L Mulfort
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
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Santabarbara S, Galuppini L, Casazza AP. Bidirectional electron transfer in the reaction centre of photosystem I. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2010; 52:735-749. [PMID: 20666929 DOI: 10.1111/j.1744-7909.2010.00977.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In the past decade light-induced electron transfer reactions in photosystem I have been the subject of intensive investigations that have led to the elucidation of some unique characteristics, the most striking of which is the existence of two parallel, functional, redox active cofactors chains. This process is generally referred to as bidirectional electron transfer. Here we present a review of the principal evidences that have led to the uncovering of bidirectionality in the reaction centre of photosystem I. A special focus is dedicated to the results obtained combining time-resolved spectroscopic techniques, either difference absorption or electron paramagnetic resonance, with molecular genetics, which allows, through modification of the binding of redox active cofactors with the reaction centre subunits, an effect on their physical-chemical properties.
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Lester GE, Makus DJ, Hodges DM. Relationship between fresh-packaged spinach leaves exposed to continuous light or dark and bioactive contents: effects of cultivar, leaf size, and storage duration. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2010; 58:2980-7. [PMID: 20131793 DOI: 10.1021/jf903596v] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Current retail marketing conditions allow produce to receive artificial light 24 h per day during its displayed shelf life. Essential human-health vitamins [ascorbic acid (vit C), folate (vit B(9)), phylloquinone (vit K(1)), alpha-tocopherol (vit E), and the carotenoids lutein, violaxanthin, zeaxanthin, and beta-carotene (provit A)] also are essential for photosynthesis and are biosynthesized in plants by light conditions even under chilling temperatures. Spinach leaves, notably abundant in the aforementioned human-health compounds, were harvested from flat-leaf 'Lazio' and crinkle-leafed 'Samish' cultivars at peak whole-plant maturity as baby (top- and midcanopy) and larger (lower-canopy) leaves. Leaves were placed as a single layer in commercial, clear-polymer retail boxes and stored at 4 degrees C for up to 9 days under continuous light (26.9 micromol.m(2 ).s) or dark. Top-canopy, baby-leaf spinach generally had higher concentrations of all bioactive compounds, on a dry weight basis, with the exception of carotenoids, than bottom-canopy leaves. All leaves stored under continuous light generally had higher levels of all bioactive compounds, except beta-carotene and violaxanthin, and were more prone to wilting, especially the flat-leafed cultivar. All leaves stored under continuous darkness had declining or unchanged levels of the aforementioned bioactive compounds. Findings from this study revealed that spinach leaves exposed to simulated retail continuous light at 4 degrees C, in clear plastic containers, were overall more nutritionally dense (enriched) than leaves exposed to continuous darkness.
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Affiliation(s)
- Gene E Lester
- Kika de la Garza Subtropical Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Weslaco, Texas 78596, USA.
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Link G, Heinen U, Berthold T, Ohmes E, Weidner JU, Kothe G. High Time Resolution Multifrequency EPR of Radical Pair Intermediates in Photosynthetic Reaction Centers: Structure Determination on a Nanosecond Time Scale. ACTA ACUST UNITED AC 2009. [DOI: 10.1524/zpch.218.1.171.25391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
The primary steps of photosynthesis proceed via light-induced radical pairs as short-lived intermediates. In this paper we discuss novel coherence phenomena which can be observed for these species. It is demonstrated that the analysis of quantum beat oscillations in combination with multifrequency EPR and a magnetically oriented sample represents a powerful structural tool. We expect that this is of general interest, since the detailed structure of radical pair intermediates can be determined on a nanosecond time scale.
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Srinivasan N, Golbeck JH. Protein–cofactor interactions in bioenergetic complexes: The role of the A1A and A1B phylloquinones in Photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1057-88. [DOI: 10.1016/j.bbabio.2009.04.010] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 04/14/2009] [Accepted: 04/22/2009] [Indexed: 10/20/2022]
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Bender SL, Keough JM, Boesch SE, Wheeler RA, Barry BA. The Vibrational Spectrum of the Secondary Electron Acceptor, A1, in Photosystem I. J Phys Chem B 2008; 112:3844-52. [DOI: 10.1021/jp0775146] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shana L. Bender
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, and Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
| | - James M. Keough
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, and Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
| | - Scott E. Boesch
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, and Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
| | - Ralph A. Wheeler
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, and Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
| | - Bridgette A. Barry
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, and Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
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Link G, Poluektov OG, Utschig LM, Lalevée J, Yago T, Weidner JU, Thurnauer MC, Kothe G. Structural organization in photosynthetic proteins as studied by high-field EPR of spin-correlated radical pair states. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2005; 43 Spec no.:S103-9. [PMID: 16235208 DOI: 10.1002/mrc.1678] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We demonstrate the potential of high-field (HF) time-resolved electron paramagnetic resonance (EPR) spectroscopy to reveal unique information about electron transfer processes and the structure of photosynthetic systems. The lineshapes and electron spin polarization (ESP) of spin-correlated radical pair (SCRP) spectra recorded with HF-EPR are very sensitive to the magnetic parameters, interactions, and geometry of the radicals in the pair. This sensitivity facilitates an analysis of more sophisticated models and methods to reveal the important relationship between structural organization and light-induced electron transfer of the photosynthetic proteins. In this review, we report on a new time-resolved HF and multi-frequency EPR approach developed in the Freiburg laboratory in cooperation with the Argonne Photosynthesis group. The method is designed to probe the geometric structure of charge separated states in the photosynthetic membrane. First, we discuss the magneto-orientation of photosynthetic cyanobacteria as revealed by time-resolved HF-EPR of SCRPs. Then, we demonstrate how the three-dimensional structure of the SCRP P700(+)A1 from photosystem I of oxygenic photosynthesis and its arrangement in the membrane is obtained from application of multi-frequency including time-resolved HF-EPR techniques.
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Affiliation(s)
- Gerhard Link
- Department of Physical Chemistry, University of Freiburg, Albertstr. 21, D-79104 Freiburg, Germany
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Santabarbara S, Heathcote P, Evans MCW. Modelling of the electron transfer reactions in Photosystem I by electron tunnelling theory: The phylloquinones bound to the PsaA and the PsaB reaction centre subunits of PS I are almost isoenergetic to the iron–sulfur cluster FX. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1708:283-310. [PMID: 15975545 DOI: 10.1016/j.bbabio.2005.05.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2004] [Revised: 04/12/2005] [Accepted: 05/03/2005] [Indexed: 10/25/2022]
Abstract
Photosystem I is a large macromolecular complex located in the thylakoid membranes of chloroplasts and in cyanobacteria that catalyses the light driven reduction of ferredoxin and oxidation of plastocyanin. Due to the very negative redox potential of the primary electron transfer cofactors accepting electrons, direct estimation by redox titration of the energetics of the system is hampered. However, the rates of electron transfer reactions are related to the thermodynamic properties of the system. Hence, several spectroscopic and biochemical techniques have been employed, in combination with the classical Marcus theory for electron transfer tunnelling, in order to access these parameters. Nevertheless, the values which have been presented are very variable. In particular, for the case of the tightly bound phylloquinone molecule A(1), the values of the redox potentials reported in the literature vary over a range of about 350 mV. Previous models of Photosystem I have assumed a unidirectional electron transfer model. In the present study, experimental evidence obtained by means of time resolved absorption, photovoltage, and electron paramagnetic resonance measurements are reviewed and analysed in terms of a bi-directional kinetic model for electron transfer reactions. This model takes into consideration the thermodynamic equilibrium between the iron-sulfur centre F(X) and the phylloquinone bound to either the PsaA (A(1A)) or the PsaB (A(1B)) subunit of the reaction centre and the equilibrium between the iron-sulfur centres F(A) and F(B). The experimentally determined decay lifetimes in the range of sub-picosecond to the microsecond time domains can be satisfactorily simulated, taking into consideration the edge-to-edge distances between redox cofactors and driving forces reported in the literature. The only exception to this general behaviour is the case of phylloquinone (A(1)) reoxidation. In order to describe the reported rates of the biphasic decay, of about 20 and 200 ns, associated with this electron transfer step, the redox potentials of the quinones are estimated to be almost isoenergetic with that of the iron sulfur centre F(X). A driving force in the range of 5 to 15 meV is estimated for these reactions, being slightly exergonic in the case of the A(1B) quinone and slightly endergonic, in the case of the A(1A) quinone. The simulation presented in this analysis not only describes the kinetic data obtained for the wild type samples at room temperature and is consistent with estimates of activation energy by the analysis of temperature dependence, but can also explain the effect of the mutations around the PsaB quinone binding pocket. A model of the overall energetics of the system is derived, which suggests that the only substantially irreversible electron transfer reactions are the reoxidation of A(0) on both electron transfer branches and the reduction of F(A) by F(X).
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Affiliation(s)
- Stefano Santabarbara
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
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Bittl R, Weber S. Transient radical pairs studied by time-resolved EPR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1707:117-26. [PMID: 15721610 DOI: 10.1016/j.bbabio.2004.03.012] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Accepted: 03/05/2004] [Indexed: 12/20/2022]
Abstract
Photogenerated short-lived radical pairs (RP) are common in biological photoprocesses such as photosynthesis and enzymatic DNA repair. They can be favorably probed by time-resolved electron paramagnetic resonance (EPR) methods with adequate time resolution. Two EPR techniques have proven to be particularly useful to extract information on the working states of photoinduced biological processes that is only difficult or sometimes even impossible to obtain by other types of spectroscopy. Firstly, transient EPR yields crucial information on the chemical nature and the geometry of the individual RP halves in a doublet-spin pair generated by a short laser pulse. This time-resolved method is applicable in all magnetic field/microwave frequency regimes that are used for continuous-wave EPR, and is nowadays routinely utilized with a time resolution reaching about 10 ns. Secondly, a pulsed EPR method named out-of-phase electron spin echo envelope modulation (OOP-ESEEM) is increasingly becoming popular. By this pulsed technique, the mutual spin-spin interaction between the RP halves in a doublet-spin pair manifests itself as an echo modulation detected as a function of the microwave-pulse spacing of a two-pulse echo sequence subsequent to a laser pulse. From the dipolar coupling, the distance between the radicals is readily derived. Since the spin-spin interaction parameters are typically not observable by transient EPR, the two techniques complement each other favorably. Both EPR methods have recently been applied to a variety of light-induced RPs in photobiology. This review summarizes the results obtained from such studies in the fields of plant and bacterial photosynthesis and DNA repair mediated by the enzyme DNA photolyase.
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Affiliation(s)
- Robert Bittl
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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Time-Resolved High-Frequency and Multifrequency EPR Studies of Spin-Correlated Radical Pairs in Photosynthetic Reaction Center Proteins. ACTA ACUST UNITED AC 2004. [DOI: 10.1007/978-1-4757-4379-1_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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11
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Fairclough WV, Forsyth A, Evans MCW, Rigby SEJ, Purton S, Heathcote P. Bidirectional electron transfer in photosystem I: electron transfer on the PsaA side is not essential for phototrophic growth in Chlamydomonas. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1606:43-55. [PMID: 14507426 DOI: 10.1016/s0005-2728(03)00083-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We have used pulsed electron paramagnetic resonance (EPR) measurements of the electron spin polarised (ESP) signals arising from the geminate radical pair P700(z.rad;+)/A(1)(z.rad;-) to detect electron transfer on both the PsaA and PsaB branches of redox cofactors in the photosystem I (PSI) reaction centre of Chlamydomonas reinhardtii. We have also used electron nuclear double resonance (ENDOR) spectroscopy to monitor the electronic structure of the bound phyllosemiquinones on both the PsaA and PsaB polypeptides. Both these spectroscopic assays have been used to analyse the effects of site-directed mutations to the axial ligands of the primary chlorophyll electron acceptor(s) A(0) and the conserved tryptophan in the PsaB phylloquinone (A(1)) binding pocket. Substitution of histidine for the axial ligand methionine on the PsaA branch (PsaA-M684H) blocks electron transfer to the PsaA-branch phylloquinone, and blocks photoaccumulation of the PsaA-branch phyllosemiquinone. However, this does not prevent photoautotrophic growth, indicating that electron transfer via the PsaB branch must take place and is alone sufficient to support growth. The corresponding substitution on the PsaB branch (PsaB-M664H) blocks kinetic electron transfer to the PsaB phylloquinone at 100 K, but does not block the photoaccumulation of the phyllosemiquinone. This transformant is unable to grow photoautotrophically although PsaA-branch electron transfer to and from the phyllosemiquinone is functional, indicating that the B branch of electron transfer may be essential for photoautotrophic growth. Mutation of the conserved tryptophan PsaB-W673 to leucine affects the electronic structure of the PsaB phyllosemiquinone, and also prevents photoautotrophic growth.
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Affiliation(s)
- Wendy V Fairclough
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
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Rigby SEJ, Muhiuddin IP, Evans MCW, Purton S, Heathcote P. Photoaccumulation of the PsaB phyllosemiquinone in photosystem I of Chlamydomonas reinhardtii. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1556:13-20. [PMID: 12351214 DOI: 10.1016/s0005-2728(02)00281-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photoaccumulation of membrane preparations of Chlamydomonas reinhardtii at pH 8 and 220 K reduces the primary and secondary electron acceptors in the Photosystem I (PSI) reaction centre, and produces a maximum of two spins per P700(z.rad;+). Proton electron nuclear double resonance (ENDOR) spectra demonstrate that the phyllosemiquinone produced is that attributed to the PsaA branch of electron transfer. Photoaccumulation at pH 10 and 220 K produces a maximum of four spins per P700(z.rad;+), and proton ENDOR spectra indicate that a second phyllosemiquinone is being photoaccumulated, with markedly different proton hyperfine couplings (hfcs). This phyllosemiquinone is unaffected by mutation of PsaAW693, confirming that it does not arise from the PsaA branch of electron transfer, and we therefore attribute it to the PsaB phyllosemiquinone.
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Affiliation(s)
- Stephen E J Rigby
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, E1 4NS, London, UK
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van der Est A. Light-induced spin polarization in type I photosynthetic reaction centres. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1507:212-25. [PMID: 11687216 DOI: 10.1016/s0005-2728(01)00204-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The use of light-induced spin polarization to study the structure and function of type I reaction centres is reviewed. The absorption of light by these systems generates a series of sequential radical pairs, which exhibit spin polarization as a result of the correlation of the unpaired electron spins. A description of how the polarization patterns can be used to deduce the relative orientation of the radicals is given and the most important structural results from such studies on photosystem I (PS I) are summarized. Quinone exchange experiments which demonstrate the influence of protein-cofactor interactions on the polarization patterns are discussed. The results show that there are significant differences between the binding sites of the primary quinone acceptors in PS I and purple bacterial reaction centres and suggest that pi-pi interactions probably play a more important role in PS I. Studies using spin-polarized EPR transients and spectra to investigate the electron transfer pathway and kinetics are also reviewed. The results from PS I, green-sulphur bacteria and Heliobacteria are compared and the controversy surrounding the role of a quinone in the electron transfer in the latter two systems is discussed.
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Affiliation(s)
- A van der Est
- Department of Chemistry, Brock University, 500 Glenridge Avenue, L2S 3A1, St. Catharines, ON, Canada.
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Bittl R, Zech SG. Pulsed EPR spectroscopy on short-lived intermediates in Photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1507:194-211. [PMID: 11687215 DOI: 10.1016/s0005-2728(01)00210-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The application of pulsed electron paramagnetic resonance spectroscopy on short-lived intermediates in Photosystem I is reviewed. The spin polarization in light-induced radical pairs gives rise to a phase shifted 'out-of-phase' electron spin echo signal. This echo signal shows a prominent modulation of its intensity as a function of the spacing between the two microwave pulses. Its modulation frequency is determined by the electron-electron spin couplings within the radical pair. Thereby, the measurement of the dipolar coupling gives direct information about the spin-spin distance and can therefore be used to determine cofactor distances with high precision. Application of this technique to the radical pair P(*+)(700)A(*-)(1) in Photosystem I is discussed. Moreover, if oriented samples (e.g. single crystals) are used, the angular dependence of the dipolar coupling can be used to derive the orientation of the axis connecting donor and acceptor with respect to an external (crystal) axes system. Using out-of-phase electron spin echo envelope modulation spectroscopy, the localization of the secondary acceptor quinone A(1) has become possible.
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Affiliation(s)
- R Bittl
- Max-Volmer-Institut, Technische Universität Berlin, Germany.
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Boudreaux B, MacMillan F, Teutloff C, Agalarov R, Gu F, Grimaldi S, Bittl R, Brettel K, Redding K. Mutations in both sides of the photosystem I reaction center identify the phylloquinone observed by electron paramagnetic resonance spectroscopy. J Biol Chem 2001; 276:37299-306. [PMID: 11489879 DOI: 10.1074/jbc.m102327200] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The core of photosystem I (PS1) is composed of the two related integral membrane polypeptides, PsaA and PsaB, which bind two symmetrical branches of cofactors, each consisting of two chlorophylls and a phylloquinone, that potentially link the primary electron donor and the tertiary acceptor. In an effort to identify amino acid residues near the phylloquinone binding sites, all tryptophans and histidines that are conserved between PsaA and PsaB in the region of the 10th and 11th transmembrane alpha-helices were mutated in Chlamydomonas reinhardtii. The mutant PS1 reaction centers appear to assemble normally and possess photochemical activity. An electron paramagnetic resonance (EPR) signal attributed to the phylloquinone anion radical (A(1)(-)) can be observed either transiently or after illumination of reaction centers with pre-reduced iron-sulfur clusters. Mutation of PsaA-Trp(693) to Phe resulted in an inability to photo-accumulate A(1)(-), whereas mutation of the analogous tryptophan in PsaB (PsaB-Trp(673)) did not produce this effect. The PsaA-W693F mutation also produced spectral changes in the time-resolved EPR spectrum of the P(700)(+) A(1)(-) radical pair, whereas the analogous mutation in PsaB had no observable effect. These observations indicate that the A(1)(-) phylloquinone radical observed by EPR occupies the phylloquinone-binding site containing PsaA-Trp(693). However, mutation of either tryptophan accelerated charge recombination from the terminal Fe-S clusters.
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Affiliation(s)
- B Boudreaux
- Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487, USA
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Ostafin AE, Weber S. Quinone exchange at the A1 site in Photosystem I in spinach and cyanobacteria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1997. [DOI: 10.1016/s0005-2728(97)00023-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Electron transfer and arrangement of the redox cofactors in photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1997. [DOI: 10.1016/s0005-2728(96)00112-0] [Citation(s) in RCA: 380] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Rigby SE, Evans MC, Heathcote P. ENDOR and special triple resonance spectroscopy of A1.- of photosystem 1. Biochemistry 1996; 35:6651-6. [PMID: 8639614 DOI: 10.1021/bi952619x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The photoaccumulated radical state of the photosystem 1 secondary electron acceptor A1, A1.-, has been studied in spinach and the cyanobacterium Anabaena variabilis strain Met27 using electron nuclear double resonance (ENDOR) and electron--nuclear--nuclear special triple (ST) resonance spectroscopies. Spectra of A1.- in both these species are very similar. ENDOR spectra of the phylloquinone anion radical in solvent glass were also obtained. Comparison of the spectra of the in vivo and in vitro radicals shows that A1.- is a phylloquinone anion radical with a distorted electron spin density distribution. Hyperfine couplings to the A1.- methyl group and to two protons hydrogen bonded to the quinone oxygens have been identified using biosynthetic deuteration in A. variabilis. Possible hyperfine coupling to a methylene proton of the phytyl side chain of the quinone has also been identified. These results are compared with those from previous studies of protein-bound semiquinones in the light of the unusual redox potential of A1.
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Affiliation(s)
- S E Rigby
- Department of Biology, University College London, University of London, U.K
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Weber S, Ohmes E, Thurnauer MC, Norris JR, Kothe G. Light-generated nuclear quantum beats: a signature of photosynthesis. Proc Natl Acad Sci U S A 1995; 92:7789-93. [PMID: 11607572 PMCID: PMC41231 DOI: 10.1073/pnas.92.17.7789] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Light-induced radical pairs in deuterated and deuterated plus 15N-substituted Synechococcus lividus cyanobacteria have been studied by transient EPR following pulsed laser excitation. Nuclear quantum beats are observed in the transverse electron magnetization at lower temperatures. Model calculations for the time profiles, evaluated at the high-field emissive maximum of the spectrum, indicate assignment of these coherences to nitrogen nuclei in the primary donor. Thorough investigation of the nuclear modulation patterns can provide detailed information on the electronic structure of the primary donor, providing insight into the mechanism of the primary events of plant photosynthesis.
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Affiliation(s)
- S Weber
- Department of Physical Chemistry, University of Stuttgart, Stuttgart, Germany
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van der Est A, Sieckmann I, Lubitz W, Stehlik D. Differences in the binding of the primary quinone receptor in Photosystem I and reaction centres of Rhodobacter sphaeroides-R26 studied with transient EPR spectroscopy. Chem Phys 1995. [DOI: 10.1016/0301-0104(95)00046-q] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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22
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van der Est A, Bock C, Golbeck J, Brettel K, Sétif P, Stehlik D. Electron transfer from the acceptor A1 to the iron-sulfur centers in photosystem I as studied by transient EPR spectroscopy. Biochemistry 1994; 33:11789-97. [PMID: 7918396 DOI: 10.1021/bi00205a015] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The electron transfer in photosystem I (PS I) from the secondary acceptor A1 to the iron-sulfur centers is studied by X-band transient EPR with a time resolution of approximately 50 ns. Results are presented for a series of different PS I preparations from the cyanobacterium Synechococcus 6301 ranging from whole cells to core particles in which the iron-sulfur centers have been successively removed. In addition, results from PS I preparations from spinach and the cyanobacterium Synechocystis 6803 are presented. In all samples containing iron-sulfur centers, two consecutive spin-polarized EPR spectra are observed. The two signals have previously been assigned to the charge-separated states P700+.A1-. and P700+.(FeS)-, where (FeS) is one of the three iron-sulfur centers, FX, FA, or FB [Bock, C., van der Est, A., Brettel, K., & Stehlik, D. (1989) FEBS Lett. 247, 91-96]. In agreement with this, the second spectrum is not observed in the sample in which the iron-sulfur centers have been removed. For (P700-FX), core particles which do not contain FA and FB, the second spectrum can unambiguously be assigned to the pair P700+.FX-. In all samples containing FX, the transition from the first to the second spectrum occurs with t1/e approximately 280 ns (t1/2 approximately 190 ns) both in the presence and absence of FA and FB, which strongly suggests that this phase reflects electron transfer from A1-. to FX in intact PS I.(ABSTRACT TRUNCATED AT 250 WORDS)
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Double-reduction of A1 abolishes the EPR signal attributed to A−1: Evidence for C2 symmetry in the Photosystem I reaction centre. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1993. [DOI: 10.1016/0005-2728(93)90030-j] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Reconstitution and exchange of quinones in the A1 site of Photosystem I. An electron spin polarization electron paramagnetic resonance study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1992. [DOI: 10.1016/0005-2728(92)90087-i] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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25
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Trost JT, Brune DC, Blankenship RE. Protein sequences and redox titrations indicate that the electron acceptors in reaction centers from heliobacteria are similar to Photosystem I. PHOTOSYNTHESIS RESEARCH 1992; 32:11-22. [PMID: 24408151 DOI: 10.1007/bf00028794] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/1991] [Accepted: 12/02/1991] [Indexed: 06/03/2023]
Abstract
Photosynthetic reaction centers isolated from Heliobacillus mobilis exhibit a single major protein on SDS-PAGE of 47 000 Mr. Attempts to sequence the reaction center polypeptide indicated that the N-terminus is blocked. After enzymatic and chemical cleavage, four peptide fragments were sequenced from the Heliobacillus mobilis apoprotein. Only one of these sequences showed significant specific similarity to any of the protein and deduced protein sequences in the GenBank data base. This fragment is identical with 56% of the residues, including both cysteines, found in the highly conserved region that is proposed to bind iron-sulfur center FX in the Photosystem I reaction center peptide that is the psaB gene product. The similarity to the psaA gene product in this region is 48%.Redox titrations of laser-flash-induced photobleaching with millisecond decay kinetics on isolated reaction centers from Heliobacterium gestii indicate a midpoint potential of -414 mV with n=2 titration behavior. In membranes, the behavior is intermediate between n=1 and n=2, and the apparent midpoint potential is -444 mV. This is compared to the behavior in Photosystem I, where the intermediate electron acceptor A1, thought to be a phylloquinone molecule, has been proposed to undergo a double reduction at low redox potentials in the presence of viologen redox mediators.These results strongly suggest that the acceptor side electron transfer system in reaction centers from heliobacteria is indeed analogous to that found in Photosystem I. The sequence similarities indicate that the divergence of the heliobacteria from the Photosystem I line occurred before the gene duplication and subsequent divergence that lead to the heterodimeric protein core of the Photosystem I reaction center.
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Affiliation(s)
- J T Trost
- Department of Chemistry and Biochemistry, Center for the Study of Early Events in Photosynthesis, Arizona State Univeristy, 85287-1604, Tempe, AZ, USA
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Transient EPR of weakly coupled spin-correlated radical pairs in photosynthetic reaction centres: increase spectral resolution from nutation analysis. Chem Phys Lett 1991. [DOI: 10.1016/s0009-2614(91)85135-j] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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27
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Snyder SW, Rustandi RR, Biggins J, Norris JR, Thurnauer MC. Direct assignment of vitamin K1 as the secondary acceptor A1 in photosystem I. Proc Natl Acad Sci U S A 1991; 88:9895-6. [PMID: 11607234 PMCID: PMC52828 DOI: 10.1073/pnas.88.21.9895] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The characteristic electron spin polarized electron paramagnetic resonance (ESP EPR) signal observed in photosystem I (PSI) has been previously assigned to a radical pair composed of the oxidized primary donor and a reduced vitamin K1. Under conditions in which Bottin, H. & Setif, P. [(1991), Biochim. Biophys. Acta 105, 331-336] proposed that A1 is doubly reduced, the ESP EPR signal was not observed. Therefore, the ESP EPR signal can be directly attributed to A-1, and vitamin K1 can be assigned as this PSI acceptor. The ESP EPR signal was partially restored by removal of the chemical reductants.
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Affiliation(s)
- S W Snyder
- Chemistry Division, Argonne National Laboratory, Argonne, IL 60439, USA
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Transient EPR of light-induced radical pairs in plant photosystem I: observation of quantum beats. Chem Phys Lett 1991. [DOI: 10.1016/0009-2614(91)90454-h] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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29
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Sieckman I, van der Est A, Bottin H, Sétif P, Stehlik D. Nanosecond electron transfer kinetics in photosystem I following substitution of quinones for vitamin K1 as studied by time resolved EPR. FEBS Lett 1991; 284:98-102. [PMID: 1647977 DOI: 10.1016/0014-5793(91)80771-t] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Room temperature transient EPR spectra of photosystem I (PS I) particles from Synechocystis 6803 are presented. Native PS I samples and preparations depleted in the A1-acceptor site by solvent extraction and then reconstituted with the quinones (Q) vitamin K1 (VK1), duroquinone (DQ and DQd12) and naphthoquinone (NQ) have been studied. Sequential electron transfer to P700+A1- (FeS) and P700+A1 (FeS)- is recovered only with VK1. With DQ and NQ electron transfer is restored to form the radical pair P700+Q- as specified by a characteristic electron spin polarization (ESP)-pattern, but further electron transfer is either slowed down or blocked. A qualitative analysis of the K-band spectrum suggests that the orientation of reconstituted NQ in PS I is different from the native acceptor A1 = VK1.
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Affiliation(s)
- I Sieckman
- Fachbereich Physik, Freie Universität Berlin, Germany
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Bittl R, Kothe G. Transient EPR of radical pairs in photosynthetic reaction centers: prediction of quantum beats. Chem Phys Lett 1991. [DOI: 10.1016/0009-2614(91)90082-k] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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