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Shibata Y, Yamagishi A, Kawamoto S, Noji T, Itoh S. Kinetically Distinct Three Red Chlorophylls in Photosystem I of Thermosynechococcus elongatus Revealed by Femtosecond Time-Resolved Fluorescence Spectroscopy at 15 K. J Phys Chem B 2010; 114:2954-63. [DOI: 10.1021/jp909583r] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yutaka Shibata
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
| | - Atsushi Yamagishi
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
| | - Shunsuke Kawamoto
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
| | - Tomoyasu Noji
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
| | - Shigeru Itoh
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
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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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Srinivasan N, Karyagina I, Bittl R, van der Est A, Golbeck JH. Role of the Hydrogen Bond from Leu722 to the A1A Phylloquinone in Photosystem I. Biochemistry 2009; 48:3315-24. [DOI: 10.1021/bi802340s] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nithya Srinivasan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Irina Karyagina
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Robert Bittl
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Art van der Est
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - John H. Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, Institut für Experimental Physik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D14195 Berlin, Germany, Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada, and Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
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Agalarov R, Byrdin M, Rappaport F, Shen G, Bryant DA, van der Est A, Golbeck JH. Removal of the PsaF Polypeptide Biases Electron Transfer in Favor of the PsaB Branch of Cofactors in Triton X-100 Photosystem I Complexes fromSynechococcussp. PCC 7002†. Photochem Photobiol 2008; 84:1371-80. [DOI: 10.1111/j.1751-1097.2008.00457.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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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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6
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Proton ENDOR spectroscopy of the anion radicals of the chlorophyll primary electron acceptors in type I photosynthetic reaction centres. Chem Phys 2003. [DOI: 10.1016/s0301-0104(03)00284-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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7
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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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Rigby SE, Evans MC, Heathcote P. Electron nuclear double resonance (ENDOR) spectroscopy of radicals in photosystem I and related Type 1 photosynthetic reaction centres. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1507:247-59. [PMID: 11687218 DOI: 10.1016/s0005-2728(01)00211-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- S E Rigby
- School of Biological Sciences, University of London, UK.
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11
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Abstract
This mini-review focuses on recent experimental results and questions, which came up since the last more comprehensive reviews on the subject. We include a brief discussion of the different techniques used for time-resolved studies of electron transfer in photosystem I (PS I) and relate the kinetic results to new structural data of the PS I reaction centre.
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Affiliation(s)
- K Brettel
- Section de Bioénergétique and CNRS URA 2096, Département de Biologie Cellulaire et Moléculaire, CEA Saclay, 91191 Cedex, Gif-sur-Yvette, France.
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12
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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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Guergova-Kuras M, Boudreaux B, Joliot A, Joliot P, Redding K. Evidence for two active branches for electron transfer in photosystem I. Proc Natl Acad Sci U S A 2001; 98:4437-42. [PMID: 11274371 PMCID: PMC31853 DOI: 10.1073/pnas.081078898] [Citation(s) in RCA: 222] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
All photosynthetic reaction centers share a common structural theme. Two related, integral membrane polypeptides sequester electron transfer cofactors into two quasi-symmetrical branches, each of which incorporates a quinone. In type II reaction centers [photosystem (PS) II and proteobacterial reaction centers], electron transfer proceeds down only one of the branches, and the mobile quinone on the other branch is used as a terminal acceptor. PS I uses iron-sulfur clusters as terminal acceptors, and the quinone serves only as an intermediary in electron transfer. Much effort has been devoted to understanding the unidirectionality of electron transport in type II reaction centers, and it was widely thought that PS I would share this feature. We have tested this idea by examining in vivo kinetics of electron transfer from the quinone in mutant PS I reaction centers. This transfer is associated with two kinetic components, and we show that mutation of a residue near the quinone in one branch specifically affects the faster component, while the corresponding mutation in the other branch specifically affects the slower component. We conclude that both electron transfer branches in PS I are active.
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Affiliation(s)
- M Guergova-Kuras
- Institut de Biologie Physico-Chimique, Centre National de la Recherche Scientifique, UPR 1261, 13 Rue Pierre et Marie Curie, 75005 Paris, France
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Mi D, Lin S, Blankenship RE. Picosecond transient absorption spectroscopy in the blue spectral region of photosystem I. Biochemistry 1999; 38:15231-7. [PMID: 10563806 DOI: 10.1021/bi991139t] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Picosecond transient absorption difference spectroscopy in the blue wavelength region (380-500 nm) was used to study the early electron acceptors in photosystem I. Samples were photosystem I core particles with about 100 chlorophylls per reaction center isolated from the cyanobacterium Synechocystis sp. PCC 6803. After excitation at 590 nm at room temperature, decay-associated spectra (DAS) were determined from global analysis in the blue region, yielding two transient components and one nondecaying component. A 3 ps decay phase is interpreted as primarily due to antenna excited-state redistribution. A 28 ps decay phase is interpreted as due to overall excited-state decay by electron transfer. The nondecaying component is ascribed to the difference spectrum of P(700) and the quinone or A(1) electron acceptor (P(700)(+)A(1)(-) - P(700)A(1)). Decay curves on the millisecond time scale at different wavelengths were measured with an autoxidizable artificial electron acceptor, benzyl viologen, and the (P(700)(+) - P(700)) difference spectrum was constructed. The (A(1)(-) - A(1)) difference spectrum was obtained by taking the difference between the above two difference spectra. A parallel picosecond experiment under strongly reducing conditions was also done as a control experiment. These conditions stabilize the electron on an earlier acceptor, A(0). The nondecaying component of the DAS at low potential was assigned to (P(700)(+)A(0)(-) - P(700)A(0)) since the electron-transfer pathway from A(0) to A(1) was blocked. The [(P(700)(+)A(0)(-) - P(700)A(0)) - (P(700)(+) - P(700))] subtraction gives a spectrum, interpreted as the (A(0)(-) - A(0)) difference spectrum of a chlorophyll a molecule, consistent with previous studies. The (A(1)(-) - A(1)) spectrum resolved on the picosecond time scale shows significant differences with similar spectra measured on longer time scales. These differences may be due to electrochromic effects and spectral evolution.
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Affiliation(s)
- D Mi
- Department of Chemistry and Biochemistry, Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe 85287-1604, USA
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Yang F, Shen G, Schluchter WM, Zybailov BL, Ganago AO, Vassiliev IR, Bryant DA, Golbeck JH. Deletion of the PsaF Polypeptide Modifies the Environment of the Redox-Active Phylloquinone (A1). Evidence for Unidirectionality of Electron Transfer in Photosystem I. J Phys Chem B 1998. [DOI: 10.1021/jp981952i] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Fan Yang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Gaozhong Shen
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Wendy M. Schluchter
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Boris L. Zybailov
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Alexander O. Ganago
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Ilya R. Vassiliev
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Donald A. Bryant
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - John H. Golbeck
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, and Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
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Schubert WD, Klukas O, Krauss N, Saenger W, Fromme P, Witt HT. Photosystem I of Synechococcus elongatus at 4 A resolution: comprehensive structure analysis. J Mol Biol 1997; 272:741-69. [PMID: 9368655 DOI: 10.1006/jmbi.1997.1269] [Citation(s) in RCA: 224] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
An improved structural model of the photosystem I complex from the thermophilic cyanobacterium Synechococcus elongatus is described at 4 A resolution. This represents the most complete model of a photosystem presently available, uniting both a photosynthetic reaction centre domain and a core antenna system. Most constituent elements of the electron transfer system have been located and their relative centre-to-centre distances determined at an accuracy of approximately 1 A. These include three pseudosymmetric pairs of Chla and three iron-sulphur centres, FX, FA and FB. The first pair, a Chla dimer, has been assigned to the primary electron donor P700. One or both Chla of the second pair, eC2 and eC'2, presumably functionally link P700 to the corresponding Chla of the third pair, eC3 and eC'3, which is assumed to constitute the spectroscopically-identified primary electron acceptor(s), A0, of PSI. A likely location of the subsequent phylloquinone electron acceptor, QK, in relation to the properties of the spectroscopically identified electron acceptor A1 is discussed. The positions of a total of 89 Chla, 83 of which constitute the core antenna system, are presented. The maximal centre-to-centre distance between antenna Chla is < or = 16 A; 81 Chla are grouped into four clusters comprising 21, 23, 17 and 20 Chla, respectively. Two "connecting" Chla are positioned to structurally (and possibly functionally) link the Chla of the core antenna to those of the electron transfer system. Thus the second and third Chla pairs of the electron transfer system may have a dual function both in energy transfer and electron transport. A total of 34 transmembrane and nine surface alpha-helices have been identified and assigned to the 11 subunits of the PSI complex. The connectivity of the nine C-terminal (seven transmembrane, two "surface") alpha-helices of each of the large core subunits PsaA and PsaB is described. The assignment of the amino acid sequence to the transmembrane alpha-helices is proposed and likely residues involved in co-ordinating the Chla of the electron transfer system discussed.
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Affiliation(s)
- W D Schubert
- Institut für Kristallographie, Freie Universität Berlin, Germany
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MacMillan F, Hanley J, van der Weerd L, Knüpling M, Un S, Rutherford AW. Orientation of the phylloquinone electron acceptor anion radical in photosystem I. Biochemistry 1997; 36:9297-303. [PMID: 9280439 DOI: 10.1021/bi971097d] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The photosynthetic reaction center of photosystem I (PS I) contains a phylloquinone molecule (A1) which acts as a transient electron acceptor. In PS I form the cyanobacterium Synechocystis PCC 6803 under reducing conditions, we have photoaccumulated an EPR signal assigned to the phylloquinone radical anion. The phylloquinone EPR spectrum has been studied in oriented multilayers of PS I using EPR at 9 GHz. In addition, the phyllosemiquinone spectrum has been obtained at 283 GHz using high-field, high-frequency EPR spectroscopy. From the orientation dependence of the spectrum at 9 GHz and the resolved g values obtained at 283 GHz, the phyllosemiquinone ring plane was determined to be almost perpendicular to the membrane (76 degrees) while the oxygen-oxygen (O-O) axis of the quinone was found to make an approximate 63 degrees angle to the membrane plane. The orientation of the ring plane is similar to that determined for the quinone electron acceptor (QA) in the purple bacterial reaction center, while the orientation of the O-O axis is significantly different. The new orientation information, when taken with data in the literature, allows the position of the phylloquinone in the reaction center to be better defined.
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Affiliation(s)
- F MacMillan
- Département de Biologie Cellulaire et Molécularie, CNRS URA 2096, CEA Saclay, F-91191 Gif-sur-Yvette, France
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18
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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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19
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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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Klughammer C, Pace RJ. Photoreduction of the secondary Photosystem I electron acceptor vitamin K1 in intact spinach chloroplasts and Cyanobacteria in vivo. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1997. [DOI: 10.1016/s0005-2728(96)00129-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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White NTH, Beddard GS, Thorne JRG, Feehan TM, Keyes TE, Heathcote P. Primary Charge Separation and Energy Transfer in the Photosystem I Reaction Center of Higher Plants. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp9604709] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nigel T. H. White
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Godfrey S. Beddard
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Jonathan R. G. Thorne
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Tim M. Feehan
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Tia E. Keyes
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
| | - Peter Heathcote
- Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K., and School of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS, U.K
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Magnetic-field effects on primary reactions in Photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA (BBA) - BIOENERGETICS 1996. [DOI: 10.1016/0005-2728(96)00021-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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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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Nugent JH. Oxygenic photosynthesis. Electron transfer in photosystem I and photosystem II. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 237:519-31. [PMID: 8647094 DOI: 10.1111/j.1432-1033.1996.00519.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Photosystems I and II drive oxygenic photosynthesis. This requires biochemical systems with remarkable properties, allowing these membrane-bound pigment-protein complexes to oxidise water and produce NAD(P)H. The protein environment provides a scaffold in the membrane on which cofactors are placed at optimum distance and orientation, ensuring a rapid, efficient trapping and conversion of light energy. The polypeptide core also tunes the redox potentials of cofactors and provides for unidirectional progress of various reaction steps. The electron transfer pathways use a variety of inorganic and organic cofactors, including amino acids. This review sets out some of the current ideas and data on the cofactors and polypeptides of photosystems I and II.
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Affiliation(s)
- J H Nugent
- Department of Biology, University College London, UK
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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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