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Kanda T, Saito K, Ishikita H. Electron Acceptor-Donor Iron Sites in the Iron-Sulfur Cluster of Photosynthetic Electron-Transfer Pathways. J Phys Chem Lett 2021; 12:7431-7438. [PMID: 34338530 DOI: 10.1021/acs.jpclett.1c01896] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In photosystem I, two electron-transfer pathways via quinones (A1A and A1B) are merged at the iron-sulfur Fe4S4 cluster FX into a single pathway toward the other two Fe4S4 clusters FA and FB. Using a quantum mechanical/molecular mechanical approach, we identify the redox-active Fe sites in the clusters. In FA and FB, the Fe site, which does not belong to the CxxCxxCxxxCP motif, serves as an electron acceptor/donor. FX has two independent electron acceptor Fe sites for A- and B-branch electron transfers, depending on the Asp-B575 protonation state, which causes the A1A-to-FX electron transfer to be uphill and the A1B-to-FX electron transfer to be downhill. The two asymmetric electron-transfer pathways from A1 to FX and the separation of the electron acceptor and donor Fe sites are likely associated with the specific role of FX in merging the two electron transfer pathways into the single pathway.
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Affiliation(s)
- Tomoki Kanda
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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2
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Kondo T, Matsuoka M, Azai C, Itoh S, Oh-oka H. Orientations of Iron–Sulfur Clusters FA and FB in the Homodimeric Type-I Photosynthetic Reaction Center of Heliobacterium modesticaldum. J Phys Chem B 2016; 120:4204-12. [DOI: 10.1021/acs.jpcb.6b01112] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Toru Kondo
- Division
of Material Science (Physics), Graduate School of Science, Nagoya University, Furocho, Chikusa, Nagoya 464-8602, Japan
| | - Masahiro Matsuoka
- Department
of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Chihiro Azai
- Department
of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Shigeru Itoh
- Center
for Gene Research, Nagoya University, Furocho, Chikusa, Nagoya 464-8602, Japan
| | - Hirozo Oh-oka
- Department
of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
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3
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Schlodder E, Lendzian F, Meyer J, Çetin M, Brecht M, Renger T, Karapetyan N. Long-wavelength limit of photochemical energy conversion in Photosystem I. J Am Chem Soc 2014; 136:3904-18. [PMID: 24517238 PMCID: PMC3959156 DOI: 10.1021/ja412375j] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Indexed: 11/30/2022]
Abstract
In Photosystem I (PS I) long-wavelength chlorophylls (LWC) of the core antenna are known to extend the spectral region up to 750 nm for absorbance of light that drives photochemistry. Here we present clear evidence that even far-red light with wavelengths beyond 800 nm, clearly outside the LWC absorption bands, can still induce photochemical charge separation in PS I throughout the full temperature range from 295 to 5 K. At room temperature, the photoaccumulation of P700(+•) was followed by the absorbance increase at 826 nm. At low temperatures (T < 100 K), the formation of P700(+•)FA/B(-•) was monitored by the characteristic EPR signals of P700(+•) and FA/B(-•) and by the characteristic light-minus-dark absorbance difference spectrum in the QY region. P700 oxidation was observed upon selective excitation at 754, 785, and 808 nm, using monomeric and trimeric PS I core complexes of Thermosynechococcus elongatus and Arthrospira platensis, which differ in the amount of LWC. The results show that the LWC cannot be responsible for the long-wavelength excitation-induced charge separation at low temperatures, where thermal uphill energy transfer is frozen out. Direct energy conversion of the excitation energy from the LWC to the primary radical pair, e.g., via a superexchange mechanism, is excluded, because no dependence on the content of LWC was observed. Therefore, it is concluded that electron transfer through PS I is induced by direct excitation of a proposed charge transfer (CT) state in the reaction center. A direct signature of this CT state is seen in absorbance spectra of concentrated PS I samples, which reveal a weak and featureless absorbance band extending beyond 800 nm, in addition to the well-known bands of LWC (C708, C719 and C740) in the range between 700 and 750 nm. The present findings suggest that nature can exploit CT states for extending the long wavelength limit in PSI even beyond that of LWC. Similar mechanisms may work in other photosynthetic systems and in chemical systems capable of photoinduced electron transfer processes in general.
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Affiliation(s)
- Eberhard Schlodder
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Friedhelm Lendzian
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Jenny Meyer
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Marianne Çetin
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Marc Brecht
- Institut für
Physikalische und Theoretische Physik, Eberhard-Karls-Universität
Tübingen, Auf
der Morgenstelle 14, 71976 Tübingen, Germany
| | - Thomas Renger
- Institut
für Theoretische Physik, Johannes
Kepler Universität, Abteilung Theoretische
Biophysik, Altenberger
Str. 69, Linz, Austria
| | - Navasard
V. Karapetyan
- A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky Prospect 33, 119071 Moscow, Russia
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Kamidaki C, Kondo T, Noji T, Itoh T, Yamaguchi A, Itoh S. Alumina Plate Containing Photosystem I Reaction Center Complex Oriented inside Plate-Penetrating Silica Nanopores. J Phys Chem B 2013; 117:9785-92. [DOI: 10.1021/jp406589u] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Chihiro Kamidaki
- Division of Material Science
(Physics), Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku Nagoya, Ai-chi 464-8602, Japan
| | - Toru Kondo
- Division of Material Science
(Physics), Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku Nagoya, Ai-chi 464-8602, Japan
| | - Tomoyasu Noji
- Division of Material Science
(Physics), Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku Nagoya, Ai-chi 464-8602, Japan
| | - Tetsuji Itoh
- Research Center for Compact
Chemical System, National Institute of Advanced Industrial Science and Technology (AIST), Nigatake 4-2-1, Miyagino-ku,
Sendai 983-8551, Japan
| | - Akira Yamaguchi
- College
of Science and Frontier
Research Center for Applied Atomic Sciences, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
| | - Shigeru Itoh
- Division of Material Science
(Physics), Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku Nagoya, Ai-chi 464-8602, Japan
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5
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Roessler MM, King MS, Robinson AJ, Armstrong FA, Harmer J, Hirst J. Direct assignment of EPR spectra to structurally defined iron-sulfur clusters in complex I by double electron-electron resonance. Proc Natl Acad Sci U S A 2010; 107:1930-5. [PMID: 20133838 PMCID: PMC2808219 DOI: 10.1073/pnas.0908050107] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In oxidative phosphorylation, complex I (NADH:quinone oxidoreductase) couples electron transfer to proton translocation across an energy-transducing membrane. Complex I contains a flavin mononucleotide to oxidize NADH, and an unusually long series of iron-sulfur (FeS) clusters, in several subunits, to transfer the electrons to quinone. Understanding coupled electron transfer in complex I requires a detailed knowledge of the properties of individual clusters and of the cluster ensemble, and so it requires the correlation of spectroscopic and structural data: This has proved a challenging task. EPR studies on complex I from Bos taurus have established that EPR signals N1b, N2 and N3 arise, respectively, from the 2Fe cluster in the 75 kDa subunit, and from 4Fe clusters in the PSST and 51 kDa subunits (positions 2, 7, and 1 along the seven-cluster chain extending from the flavin). The other clusters have either evaded detection or definitive signal assignments have not been established. Here, we combine double electron-electron resonance (DEER) spectroscopy on B. taurus complex I with the structure of the hydrophilic domain of Thermus thermophilus complex I. By considering the magnetic moments of the clusters and the orientation selectivity of the DEER experiment explicitly, signal N4 is assigned to the first 4Fe cluster in the TYKY subunit (position 5), and N5 to the all-cysteine ligated 4Fe cluster in the 75 kDa subunit (position 3). The implications of our assignment for the mechanisms of electron transfer and energy transduction by complex I are discussed.
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Affiliation(s)
- Maxie M. Roessler
- Center for Advanced Electron Spin Resonance, and
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom; and
| | - Martin S. King
- Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/Medical Research Council Building, Hills Road, Cambridge, CB2 0XY, United Kingdom
| | - Alan J. Robinson
- Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/Medical Research Council Building, Hills Road, Cambridge, CB2 0XY, United Kingdom
| | - Fraser A. Armstrong
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom; and
| | | | - Judy Hirst
- Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/Medical Research Council Building, Hills Road, Cambridge, CB2 0XY, United Kingdom
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7
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Fromme P, Bottin H, Krauss N, Sétif P. Crystallization and electron paramagnetic resonance characterization of the complex of photosystem I with its natural electron acceptor ferredoxin. Biophys J 2002; 83:1760-73. [PMID: 12324399 PMCID: PMC1302270 DOI: 10.1016/s0006-3495(02)73942-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The formation of a transient complex between photosystem I and ferredoxin is involved in the process of ferredoxin photoreduction in oxygenic photosynthetic organisms. Reduced ferredoxin is an essential redox intermediate involved in many assimilatory processes and is necessary for the reduction of NADP(+) to NADPH. Single crystals from a complex of photosystem I with ferredoxin were grown using PEG 400 and CaCl(2) as precipitation agents. The crystals diffract x-rays to a resolution of 7-8 A. The space group was determined to be orthorhombic with the unit cell dimensions a = 194 A, b = 208 A, and c = 354 A. The crystals contain photosystem I and ferredoxin in a 1:1 ratio. Electron paramagnetic resonance (EPR) measurements on these crystals are reported, where EPR signals of the three [4Fe-4S] clusters F(A), F(B), F(X), and the [2Fe-2S] cluster of ferredoxin were detected. From the EPR spectra observed at three particular orientations of the crystal in the magnetic field, the full orientation pattern of the F g-tensor was simulated. This simulation is consistent with the presence of 12 magnetically inequivalent F clusters per unit cell with the C(3) axis of the PSI trimers oriented at (23 degrees, 72 degrees, 77 degrees ) to the unit cell axes.
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Affiliation(s)
- Petra Fromme
- Max Volmer Laboratorium, Institut für Chemie, Fakultät II, Technische Universität Berlin, Germany
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Lakshmi KV, Brudvig GW. Electron Paramagnetic Resonance Distance Measurements in Photosystems. DISTANCE MEASUREMENTS IN BIOLOGICAL SYSTEMS BY EPR 2002. [DOI: 10.1007/0-306-47109-4_12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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9
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Vassiliev IR, Antonkine ML, Golbeck JH. Iron-sulfur clusters in type I reaction centers. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1507:139-60. [PMID: 11687212 DOI: 10.1016/s0005-2728(01)00197-9] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Type I reaction centers (RCs) are multisubunit chlorophyll-protein complexes that function in photosynthetic organisms to convert photons to Gibbs free energy. The unique feature of Type I RCs is the presence of iron-sulfur clusters as electron transfer cofactors. Photosystem I (PS I) of oxygenic phototrophs is the best-studied Type I RC. It is comprised of an interpolypeptide [4Fe-4S] cluster, F(X), that bridges the PsaA and PsaB subunits, and two terminal [4Fe-4S] clusters, F(A) and F(B), that are bound to the PsaC subunit. In this review, we provide an update on the structure and function of the bound iron-sulfur clusters in Type I RCs. The first new development in this area is the identification of F(A) as the cluster proximal to F(X) and the resolution of the electron transfer sequence as F(X)-->F(A)-->F(B)-->soluble ferredoxin. The second new development is the determination of the three-dimensional NMR solution structure of unbound PsaC and localization of the equal- and mixed-valence pairs in F(A)(-) and F(B)(-). We provide a survey of the EPR properties and spectra of the iron-sulfur clusters in Type I RCs of cyanobacteria, green sulfur bacteria, and heliobacteria, and we summarize new information about the kinetics of back-reactions involving the iron-sulfur clusters.
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Affiliation(s)
- I R Vassiliev
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, 310 South Frear Building, University Park, PA 16802, USA
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10
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Antonkine ML, Bentrop D, Bertini I, Luchinat C, Shen G, Bryant DA, Stehlik D, Golbeck JH. Paramagnetic 1H NMR spectroscopy of the reduced, unbound photosystem I subunit PsaC: sequence-specific assignment of contact-shifted resonances and identification of mixed- and equal-valence Fe-Fe pairs in [4Fe-4S] centers FA- and FB-. J Biol Inorg Chem 2000; 5:381-92. [PMID: 10907749 DOI: 10.1007/pl00010667] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The PsaC subunit of Photosystem I (PS I) is a 9.3-kDa protein that binds two important cofactors in photosynthetic electron transfer: the [4Fe-4S] clusters FA and FB. The g-tensor orientation of FA- and FB- is believed to be correlated to the preferential localization of the mixed-valence and equal-valence (ferrous) iron pairs in each [4Fe-4S]+ cluster. The preferential position of the mixed-valence and equal-valence pairs, in turn. can be inferred from the study of the temperature dependence of contact-shifted resonances by 1H NMR spectroscopy. For this, a sequence-specific assignment of these signals is required. The 1H NMR spectrum of reduced, unbound PsaC from Synechococcus sp. PCC 7002 at 280.4 K in 99% D2O solution shows 18 hyperfine-shifted resonances. The non-solvent-exchangeable, hyperfine-shifted resonances of reduced PsaC are clearly identified as belonging to the cysteines coordinating the clusters FA- and FB- by their downfield chemical shifts, by their temperature dependencies, and by their short T1 relaxation times. The usual fast method of assigning the 1H NMR spectra of reduced [4Fe-4S] proteins through magnetization transfer from the oxidized to the reduced state was not feasible in the case of reduced PsaC. Therefore, a de novo self-consistent sequence-specific assignment of the hyperfine-shifted resonances was obtained based on dipolar connectivities from 1D NOE difference spectra and on longitudinal relaxation times using the X-ray structure of Clostridium acidi urici 2[4Fe-4S] cluster ferredoxin at 0.94 A resolution as a model. The results clearly show the same sequence-specific distribution of Curie and anti-Curie cysteines for unbound, reduced PsaC as established for other [4Fe-4S]-containing proteins; therefore, the mixed-valence and equal-valence (ferrous) Fe-Fe pairs in FA- and FB- have the same preferential positions relative to the protein. The analysis reveals that the magnetic properties of the two [4Fe-4S] clusters are essentially indistinguishable in unbound PsaC, in contrast to the PsaC that is bound as a component of the PS I complex.
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Affiliation(s)
- M L Antonkine
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park 16802, USA
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11
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Klukas O, Schubert WD, Jordan P, Krau N, Fromme P, Witt HT, Saenger W. Localization of two phylloquinones, QK and QK', in an improved electron density map of photosystem I at 4-A resolution. J Biol Chem 1999; 274:7361-7. [PMID: 10066800 DOI: 10.1074/jbc.274.11.7361] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An improved electron density map of photosystem I from Synechococcus elongatus calculated at 4-A resolution for the first time reveals a second phylloquinone molecule and thereby completes the set of cofactors constituting the electron transfer system of this iron-sulfur type photosynthetic reaction center: six chlorophyll a, two phylloquinones, and three Fe4S4 clusters. The location of the newly identified phylloquinone pair, the individual plane orientations of these molecules, and the resulting distances to other cofactors of the electron transfer system are discussed and compared with those determined by magnetic resonance techniques.
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Affiliation(s)
- O Klukas
- Institut für Kristallographie, Freie Universität Berlin, Takustrasse 6, D-14195 Berlin, Germany
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12
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Schoepp B, Brugna M, Lebrun E, Nitschke W. Iron-Sulfur Centers Involved in Photosynthetic Light Reactions. ADVANCES IN INORGANIC CHEMISTRY 1999. [DOI: 10.1016/s0898-8838(08)60082-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Guigliarelli B, Bertrand P. Application of EPR Spectroscopy to the Structural and Functional Study of Iron-Sulfur Proteins. ADVANCES IN INORGANIC CHEMISTRY 1999. [DOI: 10.1016/s0898-8838(08)60084-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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14
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Sticht H, Rösch P. The structure of iron-sulfur proteins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1998; 70:95-136. [PMID: 9785959 DOI: 10.1016/s0079-6107(98)00027-3] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ferredoxins are a group of iron-sulfur proteins for which a wealth of structural and mutational data have recently become available. Previously unknown structures of ferredoxins which are adapted to halophilic, acidophilic or hyperthermophilic environments and new cysteine patterns for cluster ligation and non-cysteine cluster ligation have been described. Site-directed mutagenesis experiments have given insight into factors that influence the geometry, stability, redox potential, electronic properties and electron-transfer reactivity of iron-sulfur clusters.
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Affiliation(s)
- H Sticht
- Lehrstuhl für Struktur und Chemie der Biopolymere, Universität Bayreuth, Germany.
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15
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Kamlowski A, Zech SG, Fromme P, Bittl R, Lubitz W, Witt HT, Stehlik D. The Radical Pair State in Photosystem I Single Crystals: Orientation Dependence of the Transient Spin-Polarized EPR Spectra. J Phys Chem B 1998. [DOI: 10.1021/jp9817022] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Andreas Kamlowski
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany, and Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - Stephan G. Zech
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany, and Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - Petra Fromme
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany, and Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - Robert Bittl
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany, and Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - Wolfgang Lubitz
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany, and Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - Horst T. Witt
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany, and Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
| | - Dietmar Stehlik
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany, and Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany
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16
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Fromme P, Witt HT. Improved isolation and crystallization of photosystem I for structural analysis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1998. [DOI: 10.1016/s0005-2728(98)00059-0] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Vassiliev IR, Jung YS, Yang F, Golbeck JH. PsaC subunit of photosystem I is oriented with iron-sulfur cluster F(B) as the immediate electron donor to ferredoxin and flavodoxin. Biophys J 1998; 74:2029-35. [PMID: 9545061 PMCID: PMC1299543 DOI: 10.1016/s0006-3495(98)77909-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The PsaC subunit of photosystem I (PS I) binds two [4Fe-4S] clusters, F(A) and F(B), functioning as electron carriers between F(X) and soluble ferredoxin. To resolve the issue whether F(A) or F(B) is proximal to F(X), we used single-turnover flashes to promote step-by-step electron transfer between electron carriers in control (both F(A) and F(B) present) and HgCl2-treated (F(B)-less) PS I complexes from Synechococcus sp. PCC 6301 and analyzed the kinetics of P700+ reduction by monitoring the absorbance changes at 832 nm in the presence of a fast electron donor (phenazine methosulfate (PMS)). In control PS I complexes exogenously added ferredoxin, or flavodoxin could be photoreduced on each flash, thus allowing P700+ to be reduced from PMS. In F(B)-less complexes, both in the presence and in the absence of ferredoxin or flavodoxin, P700+ was reduced from PMS only on the first flash and was reduced from F(X)- on the following flashes, indicating lack of electron transfer to ferredoxin or flavodoxin. In the F(B)-less complexes, a normal level of P700 photooxidation was detected accompanied by a high yield of charge recombination between P700+ and F(A)- in the presence of a slow donor, 2,6-dichlorophenol-indophenol. This recombination remained the only pathway of F(A)- reoxidation in the presence of added ferredoxin, consistent with the lack of forward electron transfer. F(A)- could be reoxidized by methyl viologen in F(B)-less PS I complexes, although at a concentration two orders of magnitude higher than is required in wild-type PS I complexes, thus implying the presence of a diffusion barrier. The inhibition of electron transfer to ferredoxin and flavodoxin was completely reversed after reconstituting the F(B) cluster. Using rate versus distance estimates for electron transfer rates from F(X) to ferredoxin for two possible orientations of PsaC, we conclude that the kinetic data are best compatible with PsaC being oriented with F(A) as the cluster proximal to F(X) and F(B) as the distal cluster that donates electrons to ferredoxin.
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Affiliation(s)
- I R Vassiliev
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park 16802, USA
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18
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[7] Comparison of in Vitro and in Vivo mutants of PsaC in photosystem I: Protocols for mutagenesis and techniques for analysis. Methods Enzymol 1998. [DOI: 10.1016/s0076-6879(98)97009-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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