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Gorka M, Charles P, Kalendra V, Baldansuren A, Lakshmi KV, Golbeck JH. A dimeric chlorophyll electron acceptor differentiates type I from type II photosynthetic reaction centers. iScience 2021; 24:102719. [PMID: 34278250 PMCID: PMC8267441 DOI: 10.1016/j.isci.2021.102719] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 05/17/2021] [Accepted: 06/09/2021] [Indexed: 01/09/2023] Open
Abstract
This research addresses one of the most compelling issues in the field of photosynthesis, namely, the role of the accessory chlorophyll molecules in primary charge separation. Using a combination of empirical and computational methods, we demonstrate that the primary acceptor of photosystem (PS) I is a dimer of accessory and secondary chlorophyll molecules, Chl2A and Chl3A, with an asymmetric electron charge density distribution. The incorporation of highly coupled donors and acceptors in PS I allows for extensive delocalization that prolongs the lifetime of the charge-separated state, providing for high quantum efficiency. The discovery of this motif has widespread implications ranging from the evolution of naturally occurring reaction centers to the development of a new generation of highly efficient artificial photosynthetic systems. Video abstract
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Affiliation(s)
- Michael Gorka
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Philip Charles
- Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Vidmantas Kalendra
- Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Amgalanbaatar Baldansuren
- Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - K V Lakshmi
- Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - John H Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.,Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
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2
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Kurashov V, Milanovsky G, Luo L, Martin A, Semenov AY, Savikhin S, Cherepanov DA, Golbeck JH, Xu W. Conserved residue PsaB-Trp673 is essential for high-efficiency electron transfer between the phylloquinones and the iron-sulfur clusters in Photosystem I. PHOTOSYNTHESIS RESEARCH 2021; 148:161-180. [PMID: 33991284 DOI: 10.1007/s11120-021-00839-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Accepted: 04/23/2021] [Indexed: 06/12/2023]
Abstract
Despite the high level of symmetry between the PsaA and PsaB polypeptides in Photosystem I, some amino acids pairs are strikingly different, such as PsaA-Gly693 and PsaB-Trp673, which are located near a cluster of 11 water molecules between the A1A and A1B quinones and the FX iron-sulfur cluster. In this work, we changed PsaB-Trp673 to PsaB-Phe673 in Synechocystis sp. PCC 6803. The variant contains ~ 85% of wild-type (WT) levels of Photosystem I but is unable to grow photoautotrophically. Both time-resolved and steady-state optical measurements show that in the PsaB-W673F variant less than 50% of the electrons reach the terminal iron-sulfur clusters FA and FB; the majority of the electrons recombine from A1A- and A1B-. However, in those reaction centers which pass electrons forward the transfer is heterogeneous: a minor population shows electron transfer rates from A1A- and A1B- to FX slightly slower than that of the WT, whereas a major population shows forward electron transfer rates to FX slowed to the ~ 10 µs time range. Competition between relatively similar forward and backward rates of electron transfer from the quinones to the FX cluster account for the relatively low yield of long-lived charge separation in the PsaB-W673F variant. A higher water content and its increased mobility observed in MD simulations in the interquinone cavity of the PsaB-W673F variant shifts the pK of PsaB-Asp575 and allows its deprotonation in situ. The heterogeneity found may be rooted in protonation state of PsaB-Asp575, which controls whether electron transfer can proceed beyond the phylloquinone cofactors.
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Affiliation(s)
- Vasily Kurashov
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - George Milanovsky
- A.N. Belozersky Institute of Physical-Chemical Biology, Moscow State University, Leninskie Gory, 1, Building 40, Moscow, Russia, 119992
| | - Lujun Luo
- Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA, 70504, USA
| | - Antoine Martin
- Department of Physics, Purdue University, West Lafayette, IN, USA
| | - Alexey Yu Semenov
- A.N. Belozersky Institute of Physical-Chemical Biology, Moscow State University, Leninskie Gory, 1, Building 40, Moscow, Russia, 119992
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Kosygina st, 4, Moscow, Russia, 117977
| | - Sergei Savikhin
- Department of Physics, Purdue University, West Lafayette, IN, USA
| | - Dmitry A Cherepanov
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Kosygina st, 4, Moscow, Russia, 117977.
| | - John H Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA.
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA.
| | - Wu Xu
- Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA, 70504, USA.
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Gorka M, Gruszecki E, Charles P, Kalendra V, Lakshmi KV, Golbeck JH. Two-dimensional HYSCORE spectroscopy reveals a histidine imidazole as the axial ligand to Chl 3A in the M688H PsaA genetic variant of Photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2021; 1862:148424. [PMID: 33785317 DOI: 10.1016/j.bbabio.2021.148424] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 02/28/2021] [Accepted: 03/24/2021] [Indexed: 12/17/2022]
Abstract
Recent studies on Photosystem I (PS I) have shown that the six core chlorophyll a molecules are highly coupled, allowing for efficient creation and stabilization of the charge-separated state. One area of particular interest is the identity and function of the primary acceptor, A0, as the factors that influence its ultrafast processes and redox properties are not yet fully elucidated. It was recently shown that A0 exists as a dimer of the closely-spaced Chl2/Chl3 molecules wherein the reduced A0- state has an asymmetric distribution of electron spin density that favors Chl3. Previous experimental work in which this ligand was changed to a hard base (histidine, M688HPsaA) revealed severely impacted electron transfer processes at both the A0 and A1 acceptors; molecular dynamics simulations further suggested two distinct conformations of PS I in which the His residue coordinates and forms a hydrogen bond to the A0 and A1 cofactors, respectively. In this study, we have applied 2D HYSCORE spectroscopy in conjunction with molecular dynamics simulations and density functional theory calculations to the study of the M688HPsaA variant. Analysis of the hyperfine parameters demonstrates that the His imidazole serves as the axial ligand to the central Mg2+ ion in Chl3A in the M688HPsaA variant. Although the change in ligand identity does not alter delocalization of electron density over the Chl2/Chl3 dimer, a small shift in the asymmetry of delocalization, coupled with the electron withdrawing properties of the ligand, most likely accounts for the inhibition of forward electron transfer in the His-ligated conformation.
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Affiliation(s)
- Michael Gorka
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, State College, PA 16802, USA
| | - Elijah Gruszecki
- Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Philip Charles
- Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Vidmantas Kalendra
- Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - K V Lakshmi
- Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
| | - John H Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, State College, PA 16802, USA; Department of Chemistry, The Pennsylvania State University, State College, PA 16802, USA.
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4
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Charles P, Kalendra V, He Z, Khatami MH, Golbeck JH, van der Est A, Lakshmi KV, Bryant DA. Two-dimensional 67Zn HYSCORE spectroscopy reveals that a Zn-bacteriochlorophyll aP′ dimer is the primary donor (P840) in the type-1 reaction centers of Chloracidobacterium thermophilum. Phys Chem Chem Phys 2020; 22:6457-6467. [DOI: 10.1039/c9cp06556c] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Using pulsed EPR spectroscopy and isotopic labeling we demonstrate that reaction centers of Chloracidobacterium thermophilum have an unusual primary donor that is a dimer of Zn-bacteriochlorophyll aP′ molecules.
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Affiliation(s)
- Philip Charles
- Departments of Chemistry and Physics and The Baruch ’60 Center for Biochemical Solar Energy Research
- Rensselaer Polytechnic Institute
- Troy
- USA
| | - Vidmantas Kalendra
- Departments of Chemistry and Physics and The Baruch ’60 Center for Biochemical Solar Energy Research
- Rensselaer Polytechnic Institute
- Troy
- USA
| | - Zhihui He
- Department of Biochemistry and Molecular Biology
- The Pennsylvania State University
- State College
- USA
| | | | - John H. Golbeck
- Department of Biochemistry and Molecular Biology
- The Pennsylvania State University
- State College
- USA
- Department of Chemistry
| | | | - K. V. Lakshmi
- Departments of Chemistry and Physics and The Baruch ’60 Center for Biochemical Solar Energy Research
- Rensselaer Polytechnic Institute
- Troy
- USA
| | - Donald A. Bryant
- Department of Biochemistry and Molecular Biology
- The Pennsylvania State University
- State College
- USA
- Department of Chemistry and Biochemistry
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Santabarbara S, Casazza AP. Kinetics and Energetics of Phylloquinone Reduction in Photosystem I: Insight From Modeling of the Site Directed Mutants. FRONTIERS IN PLANT SCIENCE 2019; 10:852. [PMID: 31312208 PMCID: PMC6614487 DOI: 10.3389/fpls.2019.00852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 06/13/2019] [Indexed: 06/10/2023]
Abstract
Two phylloquinone molecules (A 1), one being predominantly coordinated by PsaA subunit residues (A 1A) the other by those of PsaB (A 1B), act as intermediates in the two parallel electron transfer chains of Photosystem I. The oxidation kinetics of the two phyllosemiquinones by the iron-sulfur cluster FX differ by approximately one order of magnitude, with A 1 A - being oxidized in about 200 ns and A 1 B - in about 20 ns. These differences are generally explained in terms of asymmetries in the driving force for FX reduction on the two electron transfer chains. Site directed mutations of conserved amino acids composing the A 1 binding site have been engineered on both reaction center subunits, and proved to affect selectively the oxidation lifetime of either A 1 A - , for PsaA mutants, or A 1 B - , for PsaB mutants. The mutation effects are here critically reviewed, also by novel modeling simulations employing the tunneling formalism to estimate the electron transfer rates. Three main classes of mutation effects are in particular addressed: (i) those leading to an acceleration, (ii) those leading to a moderated slowing (~5-folds), and (iii) those leading to a severe slowing (>20-folds) of the kinetics. The effect of specific amino acid perturbations contributing to the poising of the phylloquinones redox potential and, in turn, to PSI functionality, is discussed.
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Affiliation(s)
- Stefano Santabarbara
- Centre for Fundamental Research in Photosynthesis, Vergiate, Italy
- Photosynthesis Research Unit, Centro Studi sulla Biologia Cellulare e Molecolare delle Piante, Milan, Italy
| | - Anna Paola Casazza
- Istituto di Biologia e Biotecnologia Agraria, Consiglio Nazionale delle Ricerche, Milan, Italy
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6
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Makita H, Hastings G. Photosystem I with benzoquinone analogues incorporated into the A 1 binding site. PHOTOSYNTHESIS RESEARCH 2018; 137:85-93. [PMID: 29332243 DOI: 10.1007/s11120-018-0480-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 01/02/2018] [Indexed: 06/07/2023]
Abstract
Time-resolved FTIR difference spectroscopy has been used to study photosystem I (PSI) particles with three different benzoquinones [plastoquinone-9 (PQ), 2,6-dimethyl-1,4-benzoquinone (DMBQ), 2,3,5,6-tetrachloro-1,4-benzoquinone (Cl4BQ)] incorporated into the A1 binding site. If PSI samples are cooled in the dark to 77 K, the incorporated benzoquinones are shown to be functional, allowing the production of time-resolved (P700+A1--P700A1) FTIR difference spectra. If samples are subjected to repetitive flash illumination at room temperature prior to cooling, however, the time-resolved FTIR difference spectra at 77 K display contributions typical of the P700 triplet state (3P700), indicating a loss of functionality of the incorporated benzoquinones, that occurs because of double protonation of the incorporated benzoquinones. The benzoquinone protonation mechanism likely involves nearby water molecules but does not involve the terminal iron-sulfur clusters FA and FB. These results and conclusions resolve discrepancies between results from previous low-temperature FTIR and EPR studies on similar PSI samples with PQ incorporated.
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Affiliation(s)
- Hiroki Makita
- Department of Physics and Astronomy, Georgia State University, 25 Park Place, Suite 605, Atlanta, GA, 30303, USA
| | - Gary Hastings
- Department of Physics and Astronomy, Georgia State University, 25 Park Place, Suite 605, Atlanta, GA, 30303, USA.
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7
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Mutations in algal and cyanobacterial Photosystem I that independently affect the yield of initial charge separation in the two electron transfer cofactor branches. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:42-55. [DOI: 10.1016/j.bbabio.2017.10.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 10/16/2017] [Accepted: 10/17/2017] [Indexed: 01/02/2023]
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8
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Santabarbara S, Bullock B, Rappaport F, Redding KE. Controlling electron transfer between the two cofactor chains of photosystem I by the redox state of one of their components. Biophys J 2016; 108:1537-1547. [PMID: 25809266 DOI: 10.1016/j.bpj.2015.01.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 12/29/2014] [Accepted: 01/07/2015] [Indexed: 10/23/2022] Open
Abstract
Two functional electron transfer (ET) chains, related by a pseudo-C2 symmetry, are present in the reaction center of photosystem I (PSI). Due to slight differences in the environment around the cofactors of the two branches, there are differences in both the kinetics of ET and the proportion of ET that occurs on the two branches. The strongest evidence that this is indeed the case relied on the observation that the oxidation rates of the reduced phylloquinone (PhQ) cofactor differ by an order of magnitude. Site-directed mutagenesis of residues involved in the respective PhQ-binding sites resulted in a specific alteration of the rates of semiquinone oxidation. Here, we show that the PsaA-F689N mutation results in an ∼100-fold decrease in the observed rate of PhQA(-) oxidation. This is the largest change of PhQA(-) oxidation kinetics observed so far for a single-point mutation, resulting in a lifetime that exceeds that of the terminal electron donor, P700(+). This situation allows a second photochemical charge separation event to be initiated before PhQA(-) has decayed, thereby mimicking in PSI a situation that occurs in type II reaction centers. The results indicate that the presence of PhQA(-) does not impact the overall quantum yield and leads to an almost complete redistribution of the fractional utilization of the two functional ET chains, in favor of the one that does not bear the charged species. The evolutionary implications of these results are also briefly discussed.
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Affiliation(s)
- Stefano Santabarbara
- Department of Chemistry & Biochemistry, Arizona State University, Tempe, Arizona; Institut de Biologie Physico-Chimique, UMR7141 CNRS-UPMC, Paris, France; Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Milano, Italy
| | - Bradford Bullock
- Department of Chemistry, University of Alabama, Tuscaloosa, Alabama
| | - Fabrice Rappaport
- Institut de Biologie Physico-Chimique, UMR7141 CNRS-UPMC, Paris, France.
| | - Kevin E Redding
- Department of Chemistry & Biochemistry, Arizona State University, Tempe, Arizona.
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9
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Caffarri S, Tibiletti T, Jennings RC, Santabarbara S. A comparison between plant photosystem I and photosystem II architecture and functioning. Curr Protein Pept Sci 2015; 15:296-331. [PMID: 24678674 PMCID: PMC4030627 DOI: 10.2174/1389203715666140327102218] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 11/22/2013] [Accepted: 03/16/2014] [Indexed: 01/31/2023]
Abstract
Oxygenic photosynthesis is indispensable both for the development and maintenance of life on earth by converting
light energy into chemical energy and by producing molecular oxygen and consuming carbon dioxide. This latter
process has been responsible for reducing the CO2 from its very high levels in the primitive atmosphere to the present low
levels and thus reducing global temperatures to levels conducive to the development of life. Photosystem I and photosystem
II are the two multi-protein complexes that contain the pigments necessary to harvest photons and use light energy to
catalyse the primary photosynthetic endergonic reactions producing high energy compounds. Both photosystems are
highly organised membrane supercomplexes composed of a core complex, containing the reaction centre where electron
transport is initiated, and of a peripheral antenna system, which is important for light harvesting and photosynthetic activity
regulation. If on the one hand both the chemical reactions catalysed by the two photosystems and their detailed structure
are different, on the other hand they share many similarities. In this review we discuss and compare various aspects of
the organisation, functioning and regulation of plant photosystems by comparing them for similarities and differences as
obtained by structural, biochemical and spectroscopic investigations.
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Affiliation(s)
| | | | | | - Stefano Santabarbara
- Laboratoire de Génétique et de Biophysique des Plantes (LGBP), Aix-Marseille Université, Faculté des Sciences de Luminy, 163 Avenue de Luminy, 13009, Marseille, France.
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10
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Santabarbara S, Casazza AP, Ali K, Economou CK, Wannathong T, Zito F, Redding KE, Rappaport F, Purton S. The requirement for carotenoids in the assembly and function of the photosynthetic complexes in Chlamydomonas reinhardtii. PLANT PHYSIOLOGY 2013; 161:535-46. [PMID: 23161889 PMCID: PMC3532283 DOI: 10.1104/pp.112.205260] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We have investigated the importance of carotenoids on the accumulation and function of the photosynthetic apparatus using a mutant of the green alga Chlamydomonas reinhardtii lacking carotenoids. The FN68 mutant is deficient in phytoene synthase, the first enzyme of the carotenoid biosynthesis pathway, and therefore is unable to synthesize any carotenes and xanthophylls. We find that FN68 is unable to accumulate the light-harvesting complexes associated with both photosystems as well as the RC subunits of photosystem II. The accumulation of the cytochrome b₆f complex is also strongly reduced to a level approximately 10% that of the wild type. However, the residual fraction of assembled cytochrome b₆f complexes exhibits single-turnover electron transfer kinetics comparable to those observed in the wild-type strain. Surprisingly, photosystem I is assembled to significant levels in the absence of carotenoids in FN68 and possesses functional properties that are very similar to those of the wild-type complex.
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Affiliation(s)
- Stefano Santabarbara
- Institute of Structural and Molecular Biology, University College London, London WC1E 6BT, United Kingdom.
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12
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Mula S, McConnell MD, Ching A, Zhao N, Gordon HL, Hastings G, Redding KE, van der Est A. Introduction of a Hydrogen Bond between Phylloquinone PhQA and a Threonine Side-Chain OH Group in Photosystem I. J Phys Chem B 2012; 116:14008-16. [DOI: 10.1021/jp309410w] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sam Mula
- Department of Chemistry, Brock University, St. Catharines, Ontario,
Canada
| | - Michael D. McConnell
- Department
of Chemistry
and Biochemistry, Arizona State University, Tempe, Arizona, United States
| | - Amy Ching
- Department of Chemistry, Brock University, St. Catharines, Ontario,
Canada
| | - Nan Zhao
- Department of Physics
and Astronomy, Georgia State University, Atlanta, Georgia, United States
| | - Heather L. Gordon
- Department of Chemistry, Brock University, St. Catharines, Ontario,
Canada
| | - Gary Hastings
- Department of Physics
and Astronomy, Georgia State University, Atlanta, Georgia, United States
| | - Kevin E. Redding
- Department
of Chemistry
and Biochemistry, Arizona State University, Tempe, Arizona, United States
| | - Art van der Est
- Department of Chemistry, Brock University, St. Catharines, Ontario,
Canada
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13
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Renaud N, Powell D, Zarea M, Movaghar B, Wasielewski MR, Ratner MA. Quantum Interferences and Electron Transfer in Photosystem I. J Phys Chem A 2012; 117:5899-908. [DOI: 10.1021/jp308216y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Nicolas Renaud
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston,
Illinois 60208-3113, United States
| | - Daniel Powell
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston,
Illinois 60208-3113, United States
| | - Mahdi Zarea
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston,
Illinois 60208-3113, United States
| | - Bijan Movaghar
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston,
Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston,
Illinois 60208-3113, United States
| | - Mark A. Ratner
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston,
Illinois 60208-3113, United States
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14
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Berthold T, Donner von Gromoff E, Santabarbara S, Stehle P, Link G, Poluektov OG, Heathcote P, Beck CF, Thurnauer MC, Kothe G. Exploring the Electron Transfer Pathways in Photosystem I by High-Time-Resolution Electron Paramagnetic Resonance: Observation of the B-Side Radical Pair P700+A1B– in Whole Cells of the Deuterated Green Alga Chlamydomonas reinhardtii at Cryogenic Temperatures. J Am Chem Soc 2012; 134:5563-76. [DOI: 10.1021/ja208806g] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Thomas Berthold
- Department
of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg,
Germany
| | | | - Stefano Santabarbara
- School of Biological
and Chemical
Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Patricia Stehle
- Department
of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg,
Germany
| | - Gerhard Link
- Department
of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg,
Germany
| | - Oleg G. Poluektov
- Chemical Sciences and Engineering
Division, Argonne National Laboratory,
9700 South Cass Avenue, Argonne, Illinois 60439, United States
| | - Peter Heathcote
- School of Biological
and Chemical
Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Christoph F. Beck
- Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg,
Germany
| | - Marion C. Thurnauer
- Chemical Sciences and Engineering
Division, Argonne National Laboratory,
9700 South Cass Avenue, Argonne, Illinois 60439, United States
| | - Gerd Kothe
- Department
of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg,
Germany
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15
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Santabarbara S, Bailleul B, Redding K, Barber J, Rappaport F, Telfer A. Kinetics of phyllosemiquinone oxidation in the Photosystem I reaction centre of Acaryochloris marina. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:328-35. [DOI: 10.1016/j.bbabio.2011.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 10/10/2011] [Accepted: 10/11/2011] [Indexed: 11/28/2022]
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16
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Mula S, Savitsky A, Möbius K, Lubitz W, Golbeck JH, Mamedov MD, Semenov AY, van der Est A. Incorporation of a high potential quinone reveals that electron transfer in Photosystem I becomes highly asymmetric at low temperature. Photochem Photobiol Sci 2012; 11:946-56. [PMID: 22246442 DOI: 10.1039/c2pp05340c] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photosystem I (PS I) has two nearly identical branches of electron-transfer co-factors. Based on point mutation studies, there is general agreement that both branches are active at ambient temperature but that the majority of electron-transfer events occur in the A-branch. At low temperature, reversible electron transfer between P(700) and A(1A) occurs in the A-branch. However, it has been postulated that irreversible electron transfer from P(700) through A(1B) to the terminal iron-sulfur clusters F(A) and F(B) occurs via the B-branch. Thus, to study the directionality of electron transfer at low temperature, electron transfer to the iron-sulfur clusters must be blocked. Because the geometries of the donor-acceptor radical pairs formed by electron transfer in the A- and B-branch differ, they have different spin-polarized EPR spectra and echo-modulation decay curves. Hence, time-resolved, multiple-frequency EPR spectroscopy, both in the direct-detection and pulse mode, can be used to probe the use of the two branches if electron transfer to the iron-sulfur clusters is blocked. Here, we use the PS I variant from the menB deletion mutant strain of Synechocyctis sp. PCC 6803, which is unable to synthesize phylloquinone, to incorporate 2,3-dichloro-1,4-naphthoquinone (Cl(2)NQ) into the A(1A) and A(1B) binding sites. The reduction midpoint potential of Cl(2)NQ is approximately 400 mV more positive than that of phylloquinone and is unable to transfer electrons to the iron-sulfur clusters. In contrast to previous studies, in which the iron-sulfur clusters were chemically reduced and/or point mutations were used to prevent electron transfer past the quinones, we find no evidence for radical-pair formation in the B-branch. The implications of this result for the directionality of electron transfer in PS I are discussed.
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Affiliation(s)
- Sam Mula
- Department of Chemistry, Brock University, St. Catharines, ON, Canada
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McConnell MD, Cowgill JB, Baker PL, Rappaport F, Redding KE. Double reduction of plastoquinone to plastoquinol in photosystem 1. Biochemistry 2011; 50:11034-46. [PMID: 22103567 DOI: 10.1021/bi201131r] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In Photosystem 1 (PS1), phylloquinone (PhQ) acts as a secondary electron acceptor from chlorophyll ec(3) and also as an electron donor to the iron-sulfur cluster F(X). PS1 possesses two virtually equivalent branches of electron transfer (ET) cofactors from P(700) to F(X), and the lifetime of the semiquinone intermediate displays biphasic kinetics, reflecting ET along the two different branches. PhQ in PS1 serves only as an intermediate in ET and is not normally fully reduced to the quinol form. This is in contrast to PS2, in which plastoquinone (PQ) is doubly reduced to plastoquinol (PQH(2)) as the terminal electron acceptor. We purified PS1 particles from the menD1 mutant of Chlamydomonas reinhardtii that cannot synthesize PhQ, resulting in replacement of PhQ by PQ in the quinone-binding pocket. The magnitude of the stable flash-induced P(700)(+) signal of menD1 PS1, but not wild-type PS1, decreased during a train of laser flashes, as it was replaced by a ~30 ns back-reaction from the preceding radical pair (P(700)(+)A(0)(-)). We show that this process of photoinactivation is due to double reduction of PQ in the menD1 PS1 and have characterized the process. It is accelerated at lower pH, consistent with a rate-limiting protonation step. Moreover, a point mutation (PsaA-L722T) in the PhQ(A) site that accelerates ET to F(X) ~2-fold, likely by weakening the sole H-bond to PhQ(A), also accelerates the photoinactivation process. The addition of exogenous PhQ can restore activity to photoinactivated PS1 and confer resistance to further photoinactivation. This process also occurs with PS1 purified from the menB PhQ biosynthesis mutant of Synechocystis PCC 6803, demonstrating that it is a general phenomenon in both prokaryotic and eukaryotic PS1.
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Affiliation(s)
- Michael D McConnell
- Department of Chemistry and Biochemistry and Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, United States.
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Magnuson A, Krassen H, Stensjö K, Ho FM, Styring S. Modeling Photosystem I with the alternative reaction center protein PsaB2 in the nitrogen fixing cyanobacterium Nostoc punctiforme. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1152-61. [PMID: 21605545 DOI: 10.1016/j.bbabio.2011.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 04/21/2011] [Accepted: 05/07/2011] [Indexed: 11/18/2022]
Abstract
Five nitrogen fixing cyanobacterial strains have been found to contain PsaB2, an additional and divergent gene copy for the Photosystem I reaction center protein PsaB. In all five species the divergent gene, psaB2, is located separately from the normal psaAB operon in the genome. The protein, PsaB2, was recently identified in heterocysts of Nostoc punctiforme sp. strain PCC 73102. 12 conserved amino acid replacements and one insertion, were identified by a multiple sequence alignment of several PsaB2 and PsaB1 sequences. Several, including an inserted glutamine, are located close to the iron-sulfur cluster F(X) in the electron transfer chain. By homology modeling, using the Photosystem I crystal structure as template, we have found that the amino acid composition in PsaB2 will introduce changes in critical parts of the Photosystem I protein structure. The changes are close to F(X) and the phylloquinone (PhQ) in the B-branch, indicating that the electron transfer properties most likely will be affected. We suggest that the divergent PsaB2 protein produces an alternative Photosystem I reaction center with different structural and electron transfer properties. Some interesting physiologcial consequences that this can have for the function of Photosystem I in heterocysts, are discussed.
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Affiliation(s)
- Ann Magnuson
- Department of Photochemistryand Molecular Science, Uppsala University, Sweden.
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