1
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Zhang L, Yang G, Hasan HA, Fan J, Ji B. Adaptation mechanisms of microalgal-bacterial granular sludge to outdoor light-limited conditions. ENVIRONMENTAL RESEARCH 2023; 239:117244. [PMID: 37783330 DOI: 10.1016/j.envres.2023.117244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 09/21/2023] [Accepted: 09/23/2023] [Indexed: 10/04/2023]
Abstract
Microalgal-bacterial granular sludge (MBGS) has attached attention for sustainable wastewater treatment, but it remains elusive whether it can adapt to outdoor light-limited conditions. This paper investigated the biological adaptation mechanisms of MBGS to outdoor light-limited diel conditions using real municipal wastewater. The results indicated that MBGS still had excellent pollutants removal performance, and that both the extracellular polymeric substances and glycogen content of MBGS increased significantly. The main functional microalgae and bacteria were revealed to be Leptolyngbyaceae and Rhodanobacteria, respectively. Further analyses indicated that the abundance of genes encoding PsbA, PsbD, PsbE, PsbJ, PsbP, Psb27, Psb28-2, PsaC, PsaE, PsaL, PsbX, PetB, PetA, and PetE increased in photosystem. Meanwhile, the abundance of gene encoding Rubisco decreased but the gene abundance regarding to crassulacean acid metabolism cycle increased. These suggested that MBGS could adjust the photosynthetic pathway to ensure the completion of photosynthesis. This study is anticipated to add fundamental insights for the MBGS process operated under outdoor light-limited conditions.
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Affiliation(s)
- Lingyang Zhang
- Department of Water and Wastewater Engineering, School of Urban Construction, Wuhan University of Science and Technology, Wuhan, 430065, China
| | - Genji Yang
- Department of Water and Wastewater Engineering, School of Urban Construction, Wuhan University of Science and Technology, Wuhan, 430065, China
| | - Hassimi Abu Hasan
- Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600, UKM Bangi, Selangor, Malaysia; Research Centre for Sustainable Process Technology (CESPRO), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600, UKM Bangi, Selangor, Malaysia
| | - Jie Fan
- Department of Water and Wastewater Engineering, School of Urban Construction, Wuhan University of Science and Technology, Wuhan, 430065, China; Hubei Provincial Engineering Research Center of Urban Regeneration, Wuhan University of Science and Technology, Wuhan, 430065, China
| | - Bin Ji
- Department of Water and Wastewater Engineering, School of Urban Construction, Wuhan University of Science and Technology, Wuhan, 430065, China; Hubei Provincial Engineering Research Center of Urban Regeneration, Wuhan University of Science and Technology, Wuhan, 430065, China.
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2
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Capone M, Sirohiwal A, Aschi M, Pantazis DA, Daidone I. Alternative Fast and Slow Primary Charge-Separation Pathways in Photosystem II. Angew Chem Int Ed Engl 2023; 62:e202216276. [PMID: 36791234 DOI: 10.1002/anie.202216276] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 01/23/2023] [Accepted: 02/13/2023] [Indexed: 02/17/2023]
Abstract
Photosystem-II (PSII) is a multi-subunit protein complex that harvests sunlight to perform oxygenic photosynthesis. Initial light-activated charge separation takes place at a reaction centre consisting of four chlorophylls and two pheophytins. Understanding the processes following light excitation remains elusive due to spectral congestion, the ultrafast nature, and multi-component behaviour of the charge-separation process. Here, using advanced computational multiscale approaches which take into account the large-scale configurational flexibility of the system, we identify two possible primary pathways to radical-pair formation that differ by three orders of magnitude in their kinetics. The fast (short-range) pathway is dominant, but the existence of an alternative slow (long-range) charge-separation pathway hints at the evolution of redundancy that may serve other purposes, adaptive or protective, related to formation of the unique oxidative species that drives water oxidation in PSII.
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Affiliation(s)
- Matteo Capone
- Department of Physical and Chemical Sciences, University of L'Aquila, via Vetoio (Coppito 1), 67010, L'Aquila, Italy
| | - Abhishek Sirohiwal
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany.,Present Address: Department of Biochemistry and Biophysics, Arrhenius Laboratory, Stockholm University, 10691, Stockholm, Sweden
| | - Massimiliano Aschi
- Department of Physical and Chemical Sciences, University of L'Aquila, via Vetoio (Coppito 1), 67010, L'Aquila, Italy
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Isabella Daidone
- Department of Physical and Chemical Sciences, University of L'Aquila, via Vetoio (Coppito 1), 67010, L'Aquila, Italy
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3
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Nie X, Hu Z, Xiao T, Li L, Jin J, Liu K, Liu Z. Light-Powered Ion Pumping in a Cation-Selective Conducting Polymer Membrane. Angew Chem Int Ed Engl 2022; 61:e202201138. [PMID: 35133687 DOI: 10.1002/anie.202201138] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Indexed: 11/09/2022]
Abstract
The simulation of the ion pumping against a proton gradient energized by light in photosynthesis is of significant importance for the energy conversion in a non-biological environment. Herein, we report light-powered ion pumping in a polystyrene sulfonate anion (PSS) doped polypyrrole (PPy) conducting polymer membrane (PSS-PPy) with a symmetric geometry. This PSS-PPy conducting polymer membrane exhibits a cationic selectivity and a light-responsive surface-charge-governed ion transport attributed to the negatively charged PSS groups. An asymmetric visible irradiation on one side of the PSS-PPy membrane induces a built-in electric field across the membrane due to the intrinsic photoelectronic property of PPy, which drives the cationic transport against the concentration gradient, demonstrating an ion-pumping effect. This work is a prototype that uses a geometry-symmetric conducting polymer membrane as a light-powered artificial ion pump for active ion transport, which exhibits potential applications in nanofluidic energy conversion.
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Affiliation(s)
- Xiaoyan Nie
- School of Chemistry, Beihang University, Beijing, 100191, P. R. China
| | - Ziying Hu
- Querrey Simpson Institute for Bioelectronics, Northwestern University, Evanston, IL 60208, USA
| | - Tianliang Xiao
- School of Energy and Power Engineering, Beihang University, Beijing, 100191, P. R. China
| | - Li Li
- School of Chemistry, Beihang University, Beijing, 100191, P. R. China
| | - Jiao Jin
- School of Chemistry, Beihang University, Beijing, 100191, P. R. China
| | - Kesong Liu
- School of Chemistry, Beihang University, Beijing, 100191, P. R. China
| | - Zhaoyue Liu
- School of Chemistry, Beihang University, Beijing, 100191, P. R. China
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4
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Nie X, Hu Z, Xiao T, Li L, Jin J, Liu K, Liu Z. Light‐Powered Ion Pumping in a Cation‐Selective Conducting Polymer Membrane. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202201138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Xiaoyan Nie
- School of Chemistry Beihang University Beijing 100191 P. R. China
| | - Ziying Hu
- Querrey Simpson Institute for Bioelectronics Northwestern University Evanston IL 60208 USA
| | - Tianliang Xiao
- School of Energy and Power Engineering Beihang University Beijing 100191 P. R. China
| | - Li Li
- School of Chemistry Beihang University Beijing 100191 P. R. China
| | - Jiao Jin
- School of Chemistry Beihang University Beijing 100191 P. R. China
| | - Kesong Liu
- School of Chemistry Beihang University Beijing 100191 P. R. China
| | - Zhaoyue Liu
- School of Chemistry Beihang University Beijing 100191 P. R. China
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5
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Wang Z, Sun X, Ru S, Wang J, Xiong J, Yang L, Hao L, Zhang J, Zhang X. Effects of co-exposure of the triazine herbicides atrazine, prometryn and terbutryn on Phaeodactylum tricornutum photosynthesis and nutritional value. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 807:150609. [PMID: 34619212 DOI: 10.1016/j.scitotenv.2021.150609] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 09/04/2021] [Accepted: 09/22/2021] [Indexed: 06/13/2023]
Abstract
Triazine herbicides are widely used in agricultural production, and large amounts of herbicide residue enter the ocean through surface runoff. In this study, the toxicities of the triazine herbicides atrazine, prometryn and terbutryn (separately and mixed) to Phaeodactylum tricornutum were investigated. The EC50 values of atrazine, prometryn and terbutryn were 28.38 μg L-1, 8.86 μg L-1, and 1.38 μg L-1, respectively. The EC50 of an equitoxic mixture of the three herbicides was 0.78 TU, indicating that they had synergistic effects. The equitoxic mixture accumulated in P. tricornutum, which damaged chloroplast and mitochondria structures and significantly decrease the biomass, levels of key cellular components (such as chlorophyll a (chl a), carbon (C) and nitrogen (N) content, fatty acid content) and the effective photochemical quantum yield of photosystem II (PSII, ∆Fv/Fm). The mixture also downregulated key genes in the light response (PsbD, PetF), dark response (PGK, PRK), tricarboxylic acid (TCA) cycle (CS, ID, OGD, and MS) and fatty acid synthesis (FABB, SCD, and PTD9). P. tricornutum partially alleviates the effects of the mixture on photosynthesis and fatty acid synthesis by upregulating PetD, PsaB, RbcL and FabI expression. The triazine herbicide mixture reduced the biomass and nutritional value of marine phytoplankton by inhibiting photosynthesis and energy metabolism.
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Affiliation(s)
- Zengyuan Wang
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Xiaojie Sun
- Key Laboratory of Testing and Evaluation for Aquatic Product Safety and Quality, Ministry of Agriculture and Rural Affairs; Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, PR China.
| | - Shaoguo Ru
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Jun Wang
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Jiuqiang Xiong
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Liqiang Yang
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Liping Hao
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Jie Zhang
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China
| | - Xiaona Zhang
- College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China.
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6
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Zarrabi N, Bayard BJ, Seetharaman S, Holzer N, Karr P, Ciuti S, Barbon A, Di Valentin M, van der Est A, D'Souza F, Poddutoori PK. A charge transfer state induced by strong exciton coupling in a cofacial μ-oxo-bridged porphyrin heterodimer. Phys Chem Chem Phys 2021; 23:960-970. [PMID: 33367389 DOI: 10.1039/d0cp05783e] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photosensitizers with high energy, long lasting charge-transfer states are important components in systems designed for solar energy conversion by multistep electron transfer. Here, we show that in a push-pull type, μ-oxo-bridged porphyrin heterodimer composed of octaethylporphyrinatoaluminum(iii) and octaethylporphyrinatophosphorus(v), the strong excitonic coupling between the porphyrins and the different electron withdrawing abilities of Al(iii) and P(v) promote the formation of a high energy CT state. Using, an array of optical and magnetic resonance spectroscopic methods along with theoretical calculations, we demonstrate photodynamics of the heterodimer that involves the initial formation of a singlet CT which relaxes to a triplet CT state with a lifetime of ∼130 ps. The high-energy triplet CT state (3CT = 1.68 eV) lasts for nearly 105 μs prior to relaxing to the ground state.
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Affiliation(s)
- Niloofar Zarrabi
- Department of Chemistry & Biochemistry, University of Minnesota Duluth, 1039 University Drive, Duluth, Minnesota 55812, USA.
| | - Brandon J Bayard
- Department of Chemistry & Biochemistry, University of Minnesota Duluth, 1039 University Drive, Duluth, Minnesota 55812, USA.
| | - Sairaman Seetharaman
- Department of Chemistry, University of North Texas, 1155 Union Circle, # 305070, Denton, Texas 76203-5017, USA.
| | - Noah Holzer
- Department of Chemistry & Biochemistry, University of Minnesota Duluth, 1039 University Drive, Duluth, Minnesota 55812, USA.
| | - Paul Karr
- Department of Physical Sciences and Mathematics, Wayne State College, 111 Main Street, Wayne, Nebraska 68787, USA
| | - Susanna Ciuti
- Dipartimento di Scienze Chimiche, Università degli studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Antonio Barbon
- Dipartimento di Scienze Chimiche, Università degli studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Marilena Di Valentin
- Dipartimento di Scienze Chimiche, Università degli studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Art van der Est
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON L2S 3A1, Canada.
| | - Francis D'Souza
- Department of Chemistry, University of North Texas, 1155 Union Circle, # 305070, Denton, Texas 76203-5017, USA.
| | - Prashanth K Poddutoori
- Department of Chemistry & Biochemistry, University of Minnesota Duluth, 1039 University Drive, Duluth, Minnesota 55812, USA.
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7
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Clifford ER, Bradley RW, Wey LT, Lawrence JM, Chen X, Howe CJ, Zhang JZ. Phenazines as model low-midpoint potential electron shuttles for photosynthetic bioelectrochemical systems. Chem Sci 2021; 12:3328-3338. [PMID: 34164103 PMCID: PMC8179378 DOI: 10.1039/d0sc05655c] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 01/14/2021] [Indexed: 11/21/2022] Open
Abstract
Bioelectrochemical approaches for energy conversion rely on efficient wiring of natural electron transport chains to electrodes. However, state-of-the-art exogenous electron mediators give rise to significant energy losses and, in the case of living systems, long-term cytotoxicity. Here, we explored new selection criteria for exogenous electron mediation by examining phenazines as novel low-midpoint potential molecules for wiring the photosynthetic electron transport chain of the cyanobacterium Synechocystis sp. PCC 6803 to electrodes. We identified pyocyanin (PYO) as an effective cell-permeable phenazine that can harvest electrons from highly reducing points of photosynthesis. PYO-mediated photocurrents were observed to be 4-fold higher than mediator-free systems with an energetic gain of 200 mV compared to the common high-midpoint potential mediator 2,6-dichloro-1,4-benzoquinone (DCBQ). The low-midpoint potential of PYO led to O2 reduction side-reactions, which competed significantly against photocurrent generation; the tuning of mediator concentration was important for outcompeting the side-reactions whilst avoiding acute cytotoxicity. DCBQ-mediated photocurrents were generally much higher but also decayed rapidly and were non-recoverable with fresh mediator addition. This suggests that the cells can acquire DCBQ-resistance over time. In contrast, PYO gave rise to steadier current enhancement despite the co-generation of undesirable reactive oxygen species, and PYO-exposed cells did not develop acquired resistance. Moreover, we demonstrated that the cyanobacteria can be genetically engineered to produce PYO endogenously to improve long-term prospects. Overall, this study established that energetic gains can be achieved via the use of low-potential phenazines in photosynthetic bioelectrochemical systems, and quantifies the factors and trade-offs that determine efficacious mediation in living bioelectrochemical systems.
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Affiliation(s)
- Eleanor R Clifford
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
| | - Robert W Bradley
- Department of Life Sciences Sir Alexander Fleming Building, Imperial College SW7 2AZ UK
| | - Laura T Wey
- Department of Biochemistry, University of Cambridge Tennis Court Road Cambridge CB2 1QW UK
| | - Joshua M Lawrence
- Department of Biochemistry, University of Cambridge Tennis Court Road Cambridge CB2 1QW UK
| | - Xiaolong Chen
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
| | - Christopher J Howe
- Department of Biochemistry, University of Cambridge Tennis Court Road Cambridge CB2 1QW UK
| | - Jenny Z Zhang
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
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8
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Zhen S, Bugbee B. Steady-state stomatal responses of C 3 and C 4 species to blue light fraction: Interactions with CO 2 concentration. PLANT, CELL & ENVIRONMENT 2020; 43:1259-1272. [PMID: 32929764 DOI: 10.1111/pce.13730] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 01/21/2020] [Accepted: 01/22/2020] [Indexed: 05/22/2023]
Abstract
Blue light induced stomatal opening has been studied by applying a short pulse (~5 to 60 s) of blue light to a background of saturating photosynthetic red photons, but little is known about steady-state stomatal responses. Here we report stomatal responses to blue light at high and low CO2 concentrations. Steady-state stomatal conductance (gs ) of C3 plants increased asymptotically with increasing blue light to a maximum at 20% blue (120 μmol m-2 s-1 ). This response was consistent from 200 to 800 μmol mol-1 atmospheric CO2 (Ca ). In contrast, blue light induced only a transient stomatal opening (~5 min) in C4 species above a Ca of 400 μmol mol-1 . Steady-state gs of C4 plants generally decreased with increasing blue intensity. The net photosynthetic rate of all species decreased above 20% blue because blue photons have lower quantum yield (moles carbon fixed per mole photons absorbed) than red photons. Our findings indicate that photosynthesis, rather than a blue light signal, plays a dominant role in stomatal regulation in C4 species. Additionally, we found that blue light affected only stomata on the illuminated side of the leaf. Contrary to widely held belief, the blue light-induced stomatal opening minimally enhanced photosynthesis and consistently decreased water use efficiency.
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Affiliation(s)
- Shuyang Zhen
- Crop Physiology Laboratory, Department of Plants Soils and Climate, Utah State University, Logan, Utah, USA
| | - Bruce Bugbee
- Crop Physiology Laboratory, Department of Plants Soils and Climate, Utah State University, Logan, Utah, USA
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9
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Takano HK, Beffa R, Preston C, Westra P, Dayan FE. A novel insight into the mode of action of glufosinate: how reactive oxygen species are formed. PHOTOSYNTHESIS RESEARCH 2020; 144:361-372. [PMID: 32372199 DOI: 10.1007/s11120-020-00749-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 04/08/2020] [Indexed: 05/26/2023]
Abstract
Glufosinate targets glutamine synthetase (GS), but its fast herbicidal action is triggered by reactive oxygen species (ROS). The relationship between GS inhibition and ROS accumulation was investigated in Amaranthus palmeri. Glufosinate's fast action is light-dependent with no visual symptoms or ROS formation in the dark. Inhibition of GS leads to accumulation of ammonia and metabolites of the photorespiration pathway, such as glycolate and glyoxylate, as well as depletion of other intermediates such as glycine, serine, hydroxypyruvate, and glycerate. Exogenous supply of glycolate to glufosinate-treated plants enhanced herbicidal activity and dramatically increased hydrogen peroxide accumulation (possibly from peroxisomal glycolate oxidase activity). Glufosinate affected the balance between ROS generation and scavenging. The activity of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase increased after glufosinate treatment in an attempt to quench the nascent ROS burst. Low doses of atrazine and dinoseb were used to investigate the sources of ROS by manipulating photosynthetic electron transport and oxygen (O2) evolution. ROS formation depended on electron flow and O2 evolution in photosystem II (PSII). Inhibition of GS disrupted photorespiration, carbon assimilation, and linear electron flow in the light reactions. Consequently, the antioxidant machinery and the water-water cycle are overwhelmed in the presence of light and glufosinate. The O2 generated by the splitting of water in PSII becomes the acceptor of electrons, generating ROS. The cascade of events leads to lipid peroxidation and forms the basis for the fast action of glufosinate.
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Affiliation(s)
- Hudson K Takano
- Agricultural Biology Department, Colorado State University, Fort Collins, CO, 80523, USA
| | - Roland Beffa
- Weed Resistance Competence Centre, Bayer AG, Industriepark Hoechst, Frankfurt, Germany
| | - Christopher Preston
- School of Agriculture, Food and Wine, University of Adelaide, Adelaide, SA, Australia
| | - Philip Westra
- Agricultural Biology Department, Colorado State University, Fort Collins, CO, 80523, USA
| | - Franck E Dayan
- Agricultural Biology Department, Colorado State University, Fort Collins, CO, 80523, USA.
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10
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From photosynthesis to photocatalysis: Dual catalytic oxidation/reduction in one system. Proc Natl Acad Sci U S A 2020; 117:8672-8673. [PMID: 32277026 DOI: 10.1073/pnas.2003512117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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11
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Müh F, Zouni A. Structural basis of light-harvesting in the photosystem II core complex. Protein Sci 2020; 29:1090-1119. [PMID: 32067287 PMCID: PMC7184784 DOI: 10.1002/pro.3841] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 02/06/2020] [Accepted: 02/06/2020] [Indexed: 12/20/2022]
Abstract
Photosystem II (PSII) is a membrane-spanning, multi-subunit pigment-protein complex responsible for the oxidation of water and the reduction of plastoquinone in oxygenic photosynthesis. In the present review, the recent explosive increase in available structural information about the PSII core complex based on X-ray crystallography and cryo-electron microscopy is described at a level of detail that is suitable for a future structure-based analysis of light-harvesting processes. This description includes a proposal for a consistent numbering scheme of protein-bound pigment cofactors across species. The structural survey is complemented by an overview of the state of affairs in structure-based modeling of excitation energy transfer in the PSII core complex with emphasis on electrostatic computations, optical properties of the reaction center, the assignment of long-wavelength chlorophylls, and energy trapping mechanisms.
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Affiliation(s)
- Frank Müh
- Department of Theoretical Biophysics, Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Athina Zouni
- Humboldt-Universität zu Berlin, Institute for Biology, Biophysics of Photosynthesis, Berlin, Germany
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12
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Sipka G, Müller P, Brettel K, Magyar M, Kovács L, Zhu Q, Xiao Y, Han G, Lambrev PH, Shen JR, Garab G. Redox transients of P680 associated with the incremental chlorophyll-a fluorescence yield rises elicited by a series of saturating flashes in diuron-treated photosystem II core complex of Thermosynechococcus vulcanus. PHYSIOLOGIA PLANTARUM 2019; 166:22-32. [PMID: 30790299 DOI: 10.1111/ppl.12945] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 02/14/2019] [Accepted: 02/18/2019] [Indexed: 06/09/2023]
Abstract
Recent chlorophyll-a fluorescence yield measurements, using single-turnover saturating flashes (STSFs), have revealed the involvement of a rate-limiting step in the reactions following the charge separation induced by the first flash. As also shown here, in diuron-inhibited PSII core complexes isolated from Thermosynechococcus vulcanus the fluorescence maximum could only be reached by a train of STSFs. In order to elucidate the origin of the fluorescence yield increments in STSF series, we performed transient absorption measurements at 819 nm, reflecting the photooxidation and re-reduction kinetics of the primary electron donor P680. Upon single flash excitation of the dark-adapted sample, the decay kinetics could be described with lifetimes of 17 ns (∼50%) and 167 ns (∼30%), and a longer-lived component (∼20%). This kinetics are attributed to re-reduction of P680•+ by the donor side of PSII. In contrast, upon second-flash (with Δt between 5 μs and 100 ms) or repetitive excitation, the 819 nm absorption changes decayed with lifetimes of about 2 ns (∼60%) and 10 ns (∼30%), attributed to recombination of the primary radical pair P680•+ Pheo•- , and a small longer-lived component (∼10%). These data confirm that only the first STSF is capable of generating stable charge separation - leading to the reduction of QA ; and thus, the fluorescence yield increments elicited by the consecutive flashes must have a different physical origin. Our double-flash experiments indicate that the rate-limiting steps, detected by chlorophyll-a fluorescence, are not correlated with the turnover of P680.
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Affiliation(s)
- Gábor Sipka
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Pavel Müller
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Klaus Brettel
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Melinda Magyar
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Kovács
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Qingjun Zhu
- Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Yanan Xiao
- Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Guangye Han
- Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Petar H Lambrev
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jian-Ren Shen
- Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- Photosynthesis Research Center, Okayama University, Okayama, Japan
| | - Győző Garab
- Institute of Plant Biology, Laboratory of Photosynthetic Membranes, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
- Faculty of Science, University of Ostrava, Ostrava, Czech Republic
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13
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Lämmermann N, Schmid-Michels F, Weißmann A, Wobbe L, Hütten A, Kruse O. Extremely robust photocurrent generation of titanium dioxide photoanodes bio-sensitized with recombinant microalgal light-harvesting proteins. Sci Rep 2019; 9:2109. [PMID: 30765846 PMCID: PMC6376048 DOI: 10.1038/s41598-019-39344-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 12/11/2018] [Indexed: 01/19/2023] Open
Abstract
Bio-dyes for light harvesting in dye-sensitized solar cells (DSSC) have the advantage of being environmentally-friendly, non-toxic alternatives, which can be produced in a sustainable fashion. Free photosynthetic pigments are unstable in the presence of light and oxygen, a situation which can hardly be avoided during the operation of DSSCs, especially in large-scale applications. We therefore investigated the recombinant light-harvesting protein LHCBM6, which naturally occurs in the photosynthetic apparatus of the green microalga Chlamydomonas reinhardtii as a bio-dye in DSSCs. Photocurrent densities of up to 0.87 and 0.94 mA·cm-2 were determined for the DSSCs and solar energy to electricity conversion efficiencies (η) reached about 0.3% (100 mW·cm-2; AM 1.5 G filter applied). Importantly, we observed an unprecedented stability of LHCII-based DSSCs within long DSSC operation times of at least 7 days in continuous light and show that operation times are restricted by electrolyte decomposition rather than reduced dye performance, as could be demonstrated by DSSC reactivation following re-supplementation with fresh electrolyte. To the best of our knowledge, this is the first study analysing bio-dye sensitized DSSCs over such long periods, which revealed that during illumination an activation of the DSSCs occurs.
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Affiliation(s)
- Nina Lämmermann
- Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse 27, 33615, Bielefeld, Germany
| | - Fabian Schmid-Michels
- Bielefeld University, Department of Physics, Center for Spinelectronic Materials and Devices, Universitätsstrasse 25, 33615, Bielefeld, Germany
| | - Aike Weißmann
- Bielefeld University, Department of Physics, Center for Spinelectronic Materials and Devices, Universitätsstrasse 25, 33615, Bielefeld, Germany
| | - Lutz Wobbe
- Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse 27, 33615, Bielefeld, Germany
| | - Andreas Hütten
- Bielefeld University, Department of Physics, Center for Spinelectronic Materials and Devices, Universitätsstrasse 25, 33615, Bielefeld, Germany.
| | - Olaf Kruse
- Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse 27, 33615, Bielefeld, Germany.
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14
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Du B, Zhang Z, Liu W, Ye Y, Lu T, Zhou Z, Li Y, Fu Z, Qian H. Acute toxicity of the fungicide azoxystrobin on the diatom Phaeodactylum tricornutum. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 168:72-79. [PMID: 30384169 DOI: 10.1016/j.ecoenv.2018.10.074] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/18/2018] [Accepted: 10/20/2018] [Indexed: 06/08/2023]
Abstract
Azoxystrobin (AZ) is an effective broad-spectrum fungicide. Due to its extensive application, AZ is detectable in aquatic ecosystems and thus influences aquatic organisms. In this study, the acute toxicity (96 h) of AZ at concentrations of 1.0 mg/L and 5.0 mg/L on the diatom Phaeodactylum tricornutum were examined. At the tested concentrations, AZ significantly inhibited P. tricornutum growth and destroyed its cellular structure. Furthermore, the mechanisms of AZ-induced toxicity on P. tricornutum changed as the exposure time extended. Forty-eight hours after exposure, AZ inhibited P. tricornutum growth primarily via inducing oxidative stress, which increased the activity of two main antioxidant enzymes, superoxide dismutase and peroxidase, and inhibited energy metabolism. However, after 96 h of treatment, the decline in the photosynthetic capacity of P. tricornutum demonstrated that the photosystem was the main AZ target. The pigment content and expression levels of genes related to photosynthetic electron transfer reactions were also significantly decreased. The present study describes AZ toxicity in P. tricornutum and is very valuable for assessing the environmental risk of AZ.
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Affiliation(s)
- Benben Du
- College of Environment, Zhejiang University of Technology, Hangzhou 310032, PR China
| | - Zhenyan Zhang
- College of Environment, Zhejiang University of Technology, Hangzhou 310032, PR China
| | - Wanyue Liu
- Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Chinese Academy of Sciences, Urumqi 830011, PR China
| | - Yizhi Ye
- College of Environment, Zhejiang University of Technology, Hangzhou 310032, PR China
| | - Tao Lu
- College of Environment, Zhejiang University of Technology, Hangzhou 310032, PR China
| | - Zhigao Zhou
- College of Environment, Zhejiang University of Technology, Hangzhou 310032, PR China
| | - Yan Li
- College of Environment, Zhejiang University of Technology, Hangzhou 310032, PR China
| | - Zhanyu Fu
- College of Environment, Zhejiang University of Technology, Hangzhou 310032, PR China
| | - Haifeng Qian
- College of Environment, Zhejiang University of Technology, Hangzhou 310032, PR China; Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Chinese Academy of Sciences, Urumqi 830011, PR China.
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15
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'Photosystem II: the water splitting enzyme of photosynthesis and the origin of oxygen in our atmosphere'. Q Rev Biophys 2016; 49:e14. [PMID: 27659174 DOI: 10.1017/s0033583516000093] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
About 3 billion years ago an enzyme emerged which would dramatically change the chemical composition of our planet and set in motion an unprecedented explosion in biological activity. This enzyme used solar energy to power the thermodynamically and chemically demanding reaction of water splitting. In so doing it provided biology with an unlimited supply of reducing equivalents needed to convert carbon dioxide into the organic molecules of life while at the same time produced oxygen to transform our planetary atmosphere from an anaerobic to an aerobic state. The enzyme which facilitates this reaction and therefore underpins virtually all life on our planet is known as Photosystem II (PSII). It is a pigment-binding, multisubunit protein complex embedded in the lipid environment of the thylakoid membranes of plants, algae and cyanobacteria. Today we have detailed understanding of the structure and functioning of this key and unique enzyme. The journey to this level of knowledge can be traced back to the discovery of oxygen itself in the 18th-century. Since then there has been a sequence of mile stone discoveries which makes a fascinating story, stretching over 200 years. But it is the last few years that have provided the level of detail necessary to reveal the chemistry of water oxidation and O-O bond formation. In particular, the crystal structure of the isolated PSII enzyme has been reported with ever increasing improvement in resolution. Thus the organisational and structural details of its many subunits and cofactors are now well understood. The water splitting site was revealed as a cluster of four Mn ions and a Ca ion surrounded by amino-acid side chains, of which seven provide direct ligands to the metals. The metal cluster is organised as a cubane structure composed of three Mn ions and a Ca2+ linked by oxo-bonds with the fourth Mn ion attached to the cubane. This structure has now been synthesised in a non-protein environment suggesting that it is a totally inorganic precursor for the evolution of the photosynthetic oxygen-evolving complex. In summary, the overall structure of the catalytic site has given a framework on which to build a mechanistic scheme for photosynthetic dioxygen generation and at the same time provide a blue-print and incentive to develop catalysts for artificial photo-electrochemical systems to split water and generate renewable solar fuels.
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16
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Mutlu BR, Sakkos JK, Yeom S, Wackett LP, Aksan A. Silica ecosystem for synergistic biotransformation. Sci Rep 2016; 6:27404. [PMID: 27264916 PMCID: PMC4893658 DOI: 10.1038/srep27404] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 05/18/2016] [Indexed: 01/07/2023] Open
Abstract
Synergistical bacterial species can perform more varied and complex transformations of chemical substances than either species alone, but this is rarely used commercially because of technical difficulties in maintaining mixed cultures. Typical problems with mixed cultures on scale are unrestrained growth of one bacterium, which leads to suboptimal population ratios, and lack of control over bacterial spatial distribution, which leads to inefficient substrate transport. To address these issues, we designed and produced a synthetic ecosystem by co-encapsulation in a silica gel matrix, which enabled precise control of the microbial populations and their microenvironment. As a case study, two greatly different microorganisms: Pseudomonas sp. NCIB 9816 and Synechococcus elongatus PCC 7942 were encapsulated. NCIB 9816 can aerobically biotransform over 100 aromatic hydrocarbons, a feat useful for synthesis of higher value commodity chemicals or environmental remediation. In our system, NCIB 9816 was used for biotransformation of naphthalene (a model substrate) into CO2 and the cyanobacterium PCC 7942 was used to provide the necessary oxygen for the biotransformation reactions via photosynthesis. A mathematical model was constructed to determine the critical cell density parameter to maximize oxygen production, and was then used to maximize the biotransformation rate of the system.
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Affiliation(s)
- Baris R Mutlu
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jonathan K Sakkos
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Sujin Yeom
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Lawrence P Wackett
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.,BioTechnology Institute, University of Minnesota, St Paul, MN 55108, USA
| | - Alptekin Aksan
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA.,BioTechnology Institute, University of Minnesota, St Paul, MN 55108, USA
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17
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Chuah WY, Stranger R, Pace RJ, Krausz E, Frankcombe TJ. Deprotonation of Water/Hydroxo Ligands in Clusters Mimicking the Water Oxidizing Complex of PSII and Its Effect on the Vibrational Frequencies of Ligated Carboxylate Groups. J Phys Chem B 2016; 120:377-85. [PMID: 26727127 DOI: 10.1021/acs.jpcb.5b09987] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The IR absorptions of several first-shell carboxylate ligands of the water oxidizing complex (WOC) have been experimentally shown to be unaffected by oxidation state changes in the WOC during its catalytic cycle. Several model clusters that mimic the Mn4O5Ca core of the WOC in the S1 state, with electronic configurations that correspond to both the so-called "high" and "low" oxidation paradigms, were investigated. Deprotonation at W2, W1, or O3 sites was found to strongly reduce carboxylate ligand frequency shifts on oxidation of the metal cluster. The frequency shifts were smallest in neutrally charged clusters where the initial mean Mn oxidation state was +3, with W2 as an hydroxide and O5 a water. Deprotonation also reduced and balanced the oxidation energy of all clusters in successive oxidations.
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Affiliation(s)
- Wooi Yee Chuah
- Research School of Chemistry, Australian National University , Canberra, Australian Capital Territory 2601, Australia
| | - Rob Stranger
- Research School of Chemistry, Australian National University , Canberra, Australian Capital Territory 2601, Australia
| | - Ron J Pace
- Research School of Chemistry, Australian National University , Canberra, Australian Capital Territory 2601, Australia
| | - Elmars Krausz
- Research School of Chemistry, Australian National University , Canberra, Australian Capital Territory 2601, Australia
| | - Terry J Frankcombe
- Research School of Chemistry, Australian National University , Canberra, Australian Capital Territory 2601, Australia.,School of Physical, Environmental and Mathematical Sciences, University of New South Wales , Canberra, Australian Capital Territory 2600, Australia
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18
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Improving the sunlight-to-biomass conversion efficiency in microalgal biofactories. J Biotechnol 2014; 201:28-42. [PMID: 25160918 DOI: 10.1016/j.jbiotec.2014.08.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 07/31/2014] [Accepted: 08/18/2014] [Indexed: 12/31/2022]
Abstract
Microalgae represent promising organisms for the sustainable production of commodities, chemicals or fuels. Future use of such systems, however, requires increased productivity of microalgal mass cultures in order to reach an economic viability for microalgae-based production schemes. The efficiency of sunlight-to-biomass conversion that can be observed in bulk cultures is generally far lower (35-80%) than the theoretical maximum, because energy losses occur at multiple steps during the light-driven conversion of carbon dioxide to organic carbon. The light-harvesting system is a major source of energy losses and thus a prime target for strain engineering. Truncation of the light-harvesting antenna in the algal model organism Chlamydomonas reinhardtii was shown to be an effective way of increasing culture productivity at least under saturating light conditions. Furthermore engineering of the Calvin-Benson cycle or the creation of photorespiratory bypasses in A. thaliana proved to be successful in terms of achieving higher biomass productivities. An efficient generation of novel microalgal strains with improved sunlight conversion efficiencies by targeted engineering in the future will require an expanded molecular toolkit. In the meantime random mutagenesis coupled to high-throughput screening for desired phenotypes can be used to provide engineered microalgae.
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19
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Telfer A. Singlet oxygen production by PSII under light stress: mechanism, detection and the protective role of β-carotene. PLANT & CELL PHYSIOLOGY 2014; 55:1216-23. [PMID: 24566536 PMCID: PMC4080269 DOI: 10.1093/pcp/pcu040] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 02/14/2014] [Indexed: 05/18/2023]
Abstract
In this review, I outline the indirect evidence for the formation of singlet oxygen ((1)O(2)) obtained from experiments with the isolated PSII reaction center complex. I also review the methods we used to measure singlet oxygen directly, including luminescence at 1,270 nm, both steady state and time resolved. Other methods we used were histidine-catalyzed molecular oxygen uptake (enabling (1)O(2) yield measurements), and dye bleaching and difference absorption spectroscopy to identify where quenchers of (1)O(2) can access this toxic species. We also demonstrated the protective behavior of carotenoids bound within Chl-protein complexes which bring about a substantial amount of (1)O(2) quenching within the reaction center complex. Finally, I describe how these techniques have been used and expanded in research on photoinhibition and on the role of (1)O(2) as a signaling molecule in instigating cellular responses to various stress factors. I also discuss the current views on the role of (1)O(2) as a signaling molecule and the distance it might be able to travel within cells.
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Affiliation(s)
- Alison Telfer
- Department of Life Sciences, Sir Ernst Chain Building, Imperial College London, London SW7 2AZ, UK
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20
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Mokvist F, Sjöholm J, Mamedov F, Styring S. The Photochemistry in Photosystem II at 5 K Is Different in Visible and Far-Red Light. Biochemistry 2014; 53:4228-38. [DOI: 10.1021/bi5006392] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Fredrik Mokvist
- Molecular Biomimetics, Department
of Chemistry-Ångström, Uppsala University, Ångström Laboratory, P.O. Box 523, S-751 20 Uppsala, Sweden
| | - Johannes Sjöholm
- Molecular Biomimetics, Department
of Chemistry-Ångström, Uppsala University, Ångström Laboratory, P.O. Box 523, S-751 20 Uppsala, Sweden
| | - Fikret Mamedov
- Molecular Biomimetics, Department
of Chemistry-Ångström, Uppsala University, Ångström Laboratory, P.O. Box 523, S-751 20 Uppsala, Sweden
| | - Stenbjörn Styring
- Molecular Biomimetics, Department
of Chemistry-Ångström, Uppsala University, Ångström Laboratory, P.O. Box 523, S-751 20 Uppsala, Sweden
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21
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Grewe S, Ballottari M, Alcocer M, D'Andrea C, Blifernez-Klassen O, Hankamer B, Mussgnug JH, Bassi R, Kruse O. Light-Harvesting Complex Protein LHCBM9 Is Critical for Photosystem II Activity and Hydrogen Production in Chlamydomonas reinhardtii. THE PLANT CELL 2014; 26:1598-1611. [PMID: 24706511 PMCID: PMC4036574 DOI: 10.1105/tpc.114.124198] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Photosynthetic organisms developed multiple strategies for balancing light-harvesting versus intracellular energy utilization to survive ever-changing environmental conditions. The light-harvesting complex (LHC) protein family is of paramount importance for this function and can form light-harvesting pigment protein complexes. In this work, we describe detailed analyses of the photosystem II (PSII) LHC protein LHCBM9 of the microalga Chlamydomonas reinhardtii in terms of expression kinetics, localization, and function. In contrast to most LHC members described before, LHCBM9 expression was determined to be very low during standard cell cultivation but strongly increased as a response to specific stress conditions, e.g., when nutrient availability was limited. LHCBM9 was localized as part of PSII supercomplexes but was not found in association with photosystem I complexes. Knockdown cell lines with 50 to 70% reduced amounts of LHCBM9 showed reduced photosynthetic activity upon illumination and severe perturbation of hydrogen production activity. Functional analysis, performed on isolated PSII supercomplexes and recombinant LHCBM9 proteins, demonstrated that presence of LHCBM9 resulted in faster chlorophyll fluorescence decay and reduced production of singlet oxygen, indicating upgraded photoprotection. We conclude that LHCBM9 has a special role within the family of LHCII proteins and serves an important protective function during stress conditions by promoting efficient light energy dissipation and stabilizing PSII supercomplexes.
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Affiliation(s)
- Sabrina Grewe
- Algae Biotechnology and Bioenergy Group, Department of Biology, Center for Biotechnology, Bielefeld University, D-33615 Bielefeld, Germany
| | - Matteo Ballottari
- Dipartimento di Biotecnologie, Università di Verona, I-37134 Verona, Italy
| | - Marcelo Alcocer
- INF-CNR, Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, 20133 Milan, Italy
| | - Cosimo D'Andrea
- INF-CNR, Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, 20133 Milan, Italy
| | - Olga Blifernez-Klassen
- Algae Biotechnology and Bioenergy Group, Department of Biology, Center for Biotechnology, Bielefeld University, D-33615 Bielefeld, Germany
| | - Ben Hankamer
- Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Jan H Mussgnug
- Algae Biotechnology and Bioenergy Group, Department of Biology, Center for Biotechnology, Bielefeld University, D-33615 Bielefeld, Germany
| | - Roberto Bassi
- Dipartimento di Biotecnologie, Università di Verona, I-37134 Verona, Italy
| | - Olaf Kruse
- Algae Biotechnology and Bioenergy Group, Department of Biology, Center for Biotechnology, Bielefeld University, D-33615 Bielefeld, Germany
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22
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Barber J. Photosystem II: Its function, structure, and implications for artificial photosynthesis. BIOCHEMISTRY (MOSCOW) 2014; 79:185-96. [DOI: 10.1134/s0006297914030031] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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23
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Murray NS, Rudd JA, Chamayou AC, Constable EC, Housecroft CE, Neuburger M, Zampese JA. Assembling model tris(bipyridine)ruthenium(ii) photosensitizers into ordered monolayers in the presence of the polyoxometallate anion [Co4(H2O)2(α-PW9O34)2]10−. RSC Adv 2014. [DOI: 10.1039/c4ra00085d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Model ruthenium(ii) photosensitizers with long alkyl chains are assembled into ordered monolayers on water with or without an anionic polyoxometallate. LB films on mica substrates are visualized using AFM.
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Affiliation(s)
- Niamh S. Murray
- Department of Chemistry
- University of Basel
- CH-4056 Basel, Switzerland
| | - Jennifer A. Rudd
- Department of Chemistry
- University of Basel
- CH-4056 Basel, Switzerland
| | | | | | | | - Markus Neuburger
- Department of Chemistry
- University of Basel
- CH-4056 Basel, Switzerland
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24
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Razeghifard R. Algal biofuels. PHOTOSYNTHESIS RESEARCH 2013; 117:207-19. [PMID: 23605290 DOI: 10.1007/s11120-013-9828-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 04/10/2013] [Indexed: 05/12/2023]
Abstract
The world is facing energy crisis and environmental issues due to the depletion of fossil fuels and increasing CO2 concentration in the atmosphere. Growing microalgae can contribute to practical solutions for these global problems because they can harvest solar energy and capture CO2 by converting it into biofuel using photosynthesis. Microalgae are robust organisms capable of rapid growth under a variety of conditions including in open ponds or closed photobioreactors. Their reduced biomass compounds can be used as the feedstock for mass production of a variety of biofuels. As another advantage, their ability to accumulate or secrete biofuels can be controlled by changing their growth conditions or metabolic engineering. This review is aimed to highlight different forms of biofuels produced by microalgae and the approaches taken to improve their biofuel productivity. The costs for industrial-scale production of algal biofuels in open ponds or closed photobioreactors are analyzed. Different strategies for photoproduction of hydrogen by the hydrogenase enzyme of green algae are discussed. Algae are also good sources of biodiesel since some species can make large quantities of lipids as their biomass. The lipid contents for some of the best oil-producing strains of algae in optimized growth conditions are reviewed. The potential of microalgae for producing petroleum related chemicals or ready-make fuels such as bioethanol, triterpenic hydrocarbons, isobutyraldehyde, isobutanol, and isoprene from their biomass are also presented.
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Affiliation(s)
- Reza Razeghifard
- Division of Math Science & Technology, Farquhar College of Arts & Science, Nova Southeastern University, Fort Lauderdale, FL, 33314, USA,
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25
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Razeghifard R. Artificial photoactive proteins. PHOTOSYNTHESIS RESEARCH 2008; 98:677-685. [PMID: 18830805 DOI: 10.1007/s11120-008-9367-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2008] [Accepted: 09/09/2008] [Indexed: 05/26/2023]
Abstract
Solar power is the most abundant source of renewable energy. In this respect, the goal of making photoactive proteins is to utilize this energy to generate an electron flow. Photosystems have provided the blueprint for making such systems, since they are capable of converting the energy of light into an electron flow using a series of redox cofactors. Protein tunes the redox potential of the cofactors and arranges them such that their distance and orientation are optimal for the creation of a stable charge separation. The aim of this review is to present an overview of the literature with regard to some elegant functional structures that protein designers have created by introducing cofactors and photoactivity into synthetic proteins.
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Affiliation(s)
- Reza Razeghifard
- Division of Math, Science, and Technology, Farquhar College of Arts & Science, Nova Southeastern University, Fort Lauderdale, FL 33314, USA.
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26
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Noy D. Natural photosystems from an engineer's perspective: length, time, and energy scales of charge and energy transfer. PHOTOSYNTHESIS RESEARCH 2008; 95:23-35. [PMID: 17968671 DOI: 10.1007/s11120-007-9269-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Accepted: 10/03/2007] [Indexed: 05/25/2023]
Abstract
The vast structural and functional information database of photosynthetic enzymes includes, in addition to detailed kinetic records from decades of research on physical processes and chemical reaction-pathways, a variety of high and medium resolution crystal structures of key photosynthetic enzymes. Here, it is examined from an engineer's point of view with the long-term goal of reproducing the key features of natural photosystems in novel biological and non-biological solar-energy conversion systems. This survey reveals that the basic physics of the transfer processes, namely, the time constraints imposed by the rates of incoming photon flux and the various decay processes allow for a large degree of tolerance in the engineering parameters. Furthermore, the requirements to guarantee energy and electron transfer rates that yield high efficiency in natural photosystems are largely met by control of distance between chromophores and redox cofactors. This underlines a critical challenge for projected de novo designed constructions, that is, the control of spatial organization of cofactor molecules within dense array of different cofactors, some well within 1 nm from each other.
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Affiliation(s)
- Dror Noy
- Plant Sciences Department, Weizmann Institute of Science, Rehovot, 76100, Israel.
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27
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Abstract
Photosystem II (PSII) is a multisubunit enzyme embedded in the lipid environment of the thylakoid membranes of plants, algae and cyanobacteria. Powered by light, this enzyme catalyses the chemically and thermodynamically demanding reaction of water splitting. In so doing, it releases dioxygen into the atmosphere and provides the reducing equivalents required for the conversion of CO2 into the organic molecules of life. Recently, a fully refined structure of a 700 kDa cyanobacterial dimeric PSII complex was elucidated by X-ray crystallography which gave organizational and structural details of the 19 subunits (16 intrinsic and three extrinsic) which make up each monomer and provided information about the position and protein environments of 57 different cofactors. The water-splitting site was revealed as a cluster of four Mn ions and a Ca2+ ion surrounded by amino acid side chains, of which six or seven form direct ligands to the metals. The metal cluster was modelled as a cubane-like structure composed of three Mn ions and the Ca2+ linked by oxo-bonds with the fourth Mn attached to the cubane via one of its oxygens. The overall structure of the catalytic site is providing a framework to develop a mechanistic scheme for the water-splitting process, knowledge which could have significant implications for mimicking the reaction in an artificial chemical system.
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Affiliation(s)
- J Barber
- Division of Molecular Biosciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK.
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28
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Function of two beta-carotenes near the D1 and D2 proteins in photosystem II dimers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1767:79-87. [PMID: 17123463 DOI: 10.1016/j.bbabio.2006.10.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Revised: 10/11/2006] [Accepted: 10/12/2006] [Indexed: 10/24/2022]
Abstract
The antenna proteins in photosystem II (PSII) not only promote energy transfer to the photosynthetic reaction center (RC) but provide also an efficient cation sink to re-reduce chlorophyll a if the electron transfer (ET) from the Mn-cluster is inhibited. Using the newest PSII dimer crystal structure (3.0 A resolution), in which 11 beta-carotene molecules (Car) and 14 lipids are visible in the PSII monomer, we calculated the redox potentials (Em) of one-electron oxidation for all Car (Em(Car)) by solving the Poisson-Boltzmann equation. In each PSII monomer, the D1 protein harbors a previously unlocated Car (CarD1) in van der Waals contact with the chlorin ring of ChlZ(D1). Each CarD1 in the PSII dimer complex is located in the interface between the D1 and CP47 subunits, together with another four Car of the other PSII monomer and several lipid molecules. The proximity of Car bridging between CarD1 and plastoquinone/Q(A) may imply a direct charge recombination of Car+Q(A)-. The calculated Em(CarD1) and Em(ChlZ(D1)) are, respectively, 83 and 126 mV higher than Em(CarD2) and Em(ChlZ(D2)), which could explain why CarD2+ and ChlZ(D2)+ are observed rather than the corresponding CarD1+ and ChlZ(D1)+.
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Saito K, Kikuchi T, Nakayama M, Mukai K, Sumi H. A single chlorophyll in each of the core antennas CP43 and CP47 transferring excitation energies to the reaction center in Photosystem II of photosynthesis. J Photochem Photobiol A Chem 2006. [DOI: 10.1016/j.jphotochem.2005.10.038] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Noy D, Moser CC, Dutton PL. Design and engineering of photosynthetic light-harvesting and electron transfer using length, time, and energy scales. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:90-105. [PMID: 16457774 DOI: 10.1016/j.bbabio.2005.11.010] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2005] [Revised: 11/16/2005] [Accepted: 11/21/2005] [Indexed: 11/20/2022]
Abstract
Decades of research on the physical processes and chemical reaction-pathways in photosynthetic enzymes have resulted in an extensive database of kinetic information. Recently, this database has been augmented by a variety of high and medium resolution crystal structures of key photosynthetic enzymes that now include the two photosystems (PSI and PSII) of oxygenic photosynthetic organisms. Here, we examine the currently available structural and functional information from an engineer's point of view with the long-term goal of reproducing the key features of natural photosystems in de novo designed and custom-built molecular solar energy conversion devices. We find that the basic physics of the transfer processes, namely, the time constraints imposed by the rates of incoming photon flux and the various decay processes allow for a large degree of tolerance in the engineering parameters. Moreover, we find that the requirements to guarantee energy and electron transfer rates that yield high efficiency in natural photosystems are largely met by control of distance between chromophores and redox cofactors. Thus, for projected de novo designed constructions, the control of spatial organization of cofactor molecules within a dense array is initially given priority. Nevertheless, constructions accommodating dense arrays of different cofactors, some well within 1 nm from each other, still presents a significant challenge for protein design.
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Affiliation(s)
- Dror Noy
- Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA
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31
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Abstract
The excited states of a structurally well-determined photosystem II (PSII) reaction center are obtained using an effective Hamiltonian for the interaction between the Q(y) states. The latter are calculated using the time-dependent density functional theory (DFT) method in DFT-optimized geometries, but with conserved side group orientations. Of particular importance is the orientation of the vinyl group of ring I. Couplings are calculated using actual transition charge distributions via the INDO/S model. Good agreement with experimental spectra is obtained. The lowest excited state is mainly located on the inactive B-side, but with a large component on P(A) too, making charge separation to H(A) possible at low temperature. The "trap state" and triplet state are localized on the inactive B-side. Since the spin singlet Q(y) states of the reaction center are all within a rather small energy range, the state with the highest component of B(A)*, on the blue side of the Q(y) absorption, has a rather high Boltzmann population at room temperature. The charge-transfer states, however, have a rather large spread and cannot be calculated accurately at present. The orientation of the phytyl chains is important and has as a consequence that the energy for the charge-separated B(A)+ H(A)- state is significantly lower than the corresponding state on the B-side. It follows that the B(A)* and P(A)* states are both possible origins for a fast charge separation in PSII.
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Affiliation(s)
- Nikolaj Ivashin
- Department of Chemistry, Chalmers University of Technology, S-412 96 Göteborg, Sweden
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Telfer A. Too much light? How beta-carotene protects the photosystem II reaction centre. Photochem Photobiol Sci 2005; 4:950-6. [PMID: 16307107 DOI: 10.1039/b507888c] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photosystem II reaction centre of all oxygenic organisms is subject to photodamage by high light i.e. photoinhibition. In this review I discuss the reasons for the inevitable and unpreventable oxidative damage that occurs in photosystem II and the way in which beta-carotene bound to the reaction centre significantly mitigates this damage. Recent X-ray structures of the photosystem II core complex (reaction centre plus the inner antenna complexes) have revealed the binding sites of some of the carotenoids known to be bound to the complex. In the light of these X-ray structures and their known biophysical properties it is thus possible to identify the two beta-carotenes present in the photosystem II reaction centre. The two carotenes are both bound to the D2 protein and this positioning is discussed in relation to their ability to act as quenchers of singlet oxygen, generated via the triplet state of the primary electron donor. It is proposed that their location on the D2 polypeptide means there is more oxidative damage to the D1 protein and that this underlies the fact that this latter protein is continuously re-synthesised, at a far greater rate than any other protein involved in photosynthesis. The relevance of a cycle of electrons around photosystem II, via cytochrome b(559), in order to re-reduce the beta-carotenes when they are oxidised and hence restore their ability to quench singlet oxygen, is also discussed.
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Affiliation(s)
- Alison Telfer
- Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London, UK SW7 2AZ.
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Poluektov OG, Paschenko SV, Utschig LM, Lakshmi KV, Thurnauer MC. Bidirectional Electron Transfer in Photosystem I: Direct Evidence from High-Frequency Time-Resolved EPR Spectroscopy. J Am Chem Soc 2005; 127:11910-1. [PMID: 16117508 DOI: 10.1021/ja053315t] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Efficient charge separation occurring within membrane-bound reaction center proteins is the most important step of photosynthetic solar energy conversion. All reaction centers are classified into two types, I and II. X-ray crystal structures reveal that both types bind two symmetric membrane-spanning branches of potential electron-transfer cofactors. Determination of the functional roles of these pairs of branches is of fundamental importance. While it is established that in type II reaction centers only one branch functions in electron transfer, we present the first direct spectroscopic evidence that both cofactor branches are active in the type I reaction center, photosystem I.
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Affiliation(s)
- Oleg G Poluektov
- Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
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34
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Ishikita H, Loll B, Biesiadka J, Galstyan A, Saenger W, Knapp EW. Tuning electron transfer by ester-group of chlorophylls in bacterial photosynthetic reaction center. FEBS Lett 2005; 579:712-6. [PMID: 15670833 DOI: 10.1016/j.febslet.2004.12.049] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Revised: 12/20/2004] [Accepted: 12/20/2004] [Indexed: 11/22/2022]
Abstract
Accessory chlorophylls (B(A/B)) in bacterial photosynthetic reaction center play a key role in charge-separation. Although light-exposed and dark-adapted bRC crystal structures are virtually identical, the calculated B(A) redox potentials for one-electron reduction differ. This can be traced back to different orientations of the B(A) ester-group. This tuning ability of chlorophyll redox potentials modulates the electron transfer from SP* to B(A).
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Affiliation(s)
- Hiroshi Ishikita
- Institute of Chemistry, Crystallography, Department of Biology, Chemistry, and Pharmacy, Free University of Berlin, Takustrasse 6, D-14195 Berlin, Germany
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35
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Chen M, Telfer A, Lin S, Pascal A, Larkum AWD, Barber J, Blankenship RE. The nature of the photosystem II reaction centre in the chlorophyll d-containing prokaryote, Acaryochloris marina. Photochem Photobiol Sci 2005; 4:1060-4. [PMID: 16307123 DOI: 10.1039/b507057k] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pigment-protein complexes enriched in photosystem II (PS II) have been isolated from the chlorophyll (Chl) d containing cyanobacterium, Acaryochloris marina. A small PS II-enriched particle, we call 'crude reaction centre', contained 20 Chl d, 0.5 Chl a and 1 redox active cytochrome b-559 per 2 pheophytin a, plus the D1 and D2 proteins. A larger PS II-enriched particle, we call 'core', additionally bound the antenna complexes, CP47 and CP43, and had a higher chlorophyll per pheophytin ratio. Pheophytin a could be photoreduced in the presence of a strong reductant, indicating that it is the primary electron acceptor in photosystem II of A. marina. A substoichiometric amount of Chl a (less than one chlorophyll a per 2 pheophytin a) strongly suggests that Chl a does not have an essential role in the photochemistry of PS II in this organism. We conclude that PS II, in A. marina, utilizes Chl d and not Chl a as primary electron donor and that the primary electron acceptor is one of two molecules of pheophytin a.
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Affiliation(s)
- Min Chen
- School of Biological Sciences, University of Sydney, NSW 2006, Australia
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36
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Saito K, Mukai K, Sumi H. Excited states of pigments in photosystem II reaction centers of photosynthesis: Characterization into a central dimer and remaining monomers. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2004.11.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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37
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Barber J. Water, water everywhere, and its remarkable chemistry. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1655:123-32. [PMID: 15100024 DOI: 10.1016/j.bbabio.2003.10.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2003] [Revised: 10/30/2003] [Accepted: 10/30/2003] [Indexed: 11/18/2022]
Abstract
Photosystem II (PSII), the multisubunit pigment-protein complex localised in the thylakoid membranes of oxygenic photosynthetic organisms, uses light energy to drive a series of remarkable reactions leading to the oxidation of water. The products of this oxidation are dioxygen, which is released to the atmosphere, and reducing equivalents destined to reduce carbon dioxide to organic molecules. The water oxidation occurs at catalytic sites composed of four manganese atoms (Mn(4)-cluster) and powered by the redox potential of an oxidised chlorophyll a molecule (P680(*+)). Gerald T (Jerry) Babcock and colleagues showed that electron/proton transfer processes from substrate water to P680(*+) involved a tyrosine residue (Y(Z)) and proposed an attractive reaction mechanism for the direct involvement of Y(Z) in the chemistry of water oxidation. The 'hydrogen-atom abstract/metalloradical' mechanism he formulated is an expression of his genius and a highlight of his many other outstanding contributions to photosynthesis research. A structural basis for Jerry's model is now being revealed by X-ray crystallography.
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Affiliation(s)
- Jim Barber
- Department of Biological Sciences, Wolfson Laboratories, Biochemistry Building, South Kensington Campus, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
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Ferreira KN, Iverson TM, Maghlaoui K, Barber J, Iwata S. Architecture of the photosynthetic oxygen-evolving center. Science 2004; 303:1831-8. [PMID: 14764885 DOI: 10.1126/science.1093087] [Citation(s) in RCA: 2335] [Impact Index Per Article: 116.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Photosynthesis uses light energy to drive the oxidation of water at an oxygen-evolving catalytic site within photosystem II (PSII). We report the structure of PSII of the cyanobacterium Thermosynechococcus elongatus at 3.5 angstrom resolution. We have assigned most of the amino acid residues of this 650-kilodalton dimeric multisubunit complex and refined the structure to reveal its molecular architecture. Consequently, we are able to describe details of the binding sites for cofactors and propose a structure of the oxygen-evolving center (OEC). The data strongly suggest that the OEC contains a cubane-like Mn3CaO4 cluster linked to a fourth Mn by a mono-micro-oxo bridge. The details of the surrounding coordination sphere of the metal cluster and the implications for a possible oxygen-evolving mechanism are discussed.
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Affiliation(s)
- Kristina N Ferreira
- Department of Biological Sciences, Imperial College London, London, SW7 2AZ, UK
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39
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Arsköld SP, Masters VM, Prince BJ, Smith PJ, Pace RJ, Krausz E. Optical spectra of synechocystis and spinach photosystem II preparations at 1.7 K: identification of the D1-pheophytin energies and stark shifts. J Am Chem Soc 2004; 125:13063-74. [PMID: 14570479 DOI: 10.1021/ja034548s] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report and compare highly resolved, simultaneously recorded absorption and CD spectra of active Photosystem II (PSII) samples in the range 440-750 nm. From an appropriately scaled comparison of spinach membrane fragment (BBY) and PSII core spectra, we show that key features of the core spectrum are quantitatively represented in the BBY data. PSII from the cyanobacterium Synechocystis 6803 display spectral features in the Qy region of comparable width (50-70 cm(-1) fwhm) to those seen in plant PSII but the energies of the resolved features are distinctly different. A comparison of spectra taken of PSII poised in the S1QA and S2QA(-) redox states reveals electrochromic shifts largely attributable to the influence of QA(-) on Pheo(D1). This allows accurate determinations of the Pheo(D1) Qy absorption positions to be at 685.0 nm for spinach cores, 685.8 nm for BBY particles, and 683.0 nm for Synechocystis. These are discussed in terms of earlier reports of the Pheo(D1) energies in PSII. The Qx transition of Pheo(D1) undergoes a blue shift upon Q(A) reduction, and we place a lower limit of 80 cm(-1) on this shift in plant material. By comparing the magnitude of the Stark shifts of the Qx and Qy bands of Pheo(D1), the directions of the transition-induced dipole moment changes, Deltamu(x) and Deltamu(y), for this functionally important pigment could be determined, assuming normal magnitudes of the Deltamu's. Consequently, Deltamu(x) and Deltamu(y) are determined to be approximately orthogonal to the directions expected for these transitions. Low-fluence illumination experiments at 1.7 K resulted in very efficient formation of QA(-). This was accompanied by cyt b(559) oxidation in BBYs and carotenoid oxidation in cores. No chlorophyll oxidation was observed. Our data allow us to estimate the quantum efficiency of PSII at this temperature to be of the order 0.1-1. No Stark shift associated with the S1-to-S2 transition of the Mn cluster is evident in our samples. The similarity of Stark data in plants and Synechocystis points to minimal interactions of Pheo(D1) with nearby chloropyll pigments in active PSII preparations. This appears to be at variance with interpretations of experiments performed with inactive solubilized reaction-center preparations.
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Affiliation(s)
- Sindra Peterson Arsköld
- Research School of Chemistry and Department of Chemistry, Faculties of Science, Australian National University, Canberra ACT 0200, Australia.
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40
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Biesiadka J, Loll B, Kern J, Irrgang KD, Zouni A. Crystal structure of cyanobacterial photosystem II at 3.2 Å resolution: a closer look at the Mn-cluster. Phys Chem Chem Phys 2004. [DOI: 10.1039/b406989g] [Citation(s) in RCA: 232] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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41
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Moser CC, Page CC, Cogdell RJ, Barber J, Wraight CA, Dutton PL. Length, time, and energy scales of photosystems. ADVANCES IN PROTEIN CHEMISTRY 2003; 63:71-109. [PMID: 12629967 DOI: 10.1016/s0065-3233(03)63004-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The design of photosynthetic systems reflects the length scales of the fundamental physical processes. Energy transfer is rapid at the few angstrom scale and continues to be rapid even at the 50-A scale of the membrane thickness. Electron tunneling is nearly as rapid at the shortest distances, but becomes physiologically too slow well before 20 A. Diffusion, which starts out at a relatively slow nanosecond time scale, has the most modest slowing with distance and is physiologically competent at all biologically relevant distances. Proton transfer always operates on the shortest angstrom scale. The structural consequences of these distance dependencies are that energy transfer networks can extend over large, multisubunit and multicomplex distances and take leaps of 20 A before entering the domain of charge separating centers. Electron transfer systems are effectively limited to individual distances of 15 A or less and span the 50 A dimensions of the bioenergetic membrane by use of redox chains. Diffusion processes are generally used to cover the intercomplex electron transfer distances of 50 A and greater and tend to compensate for the lack of directionality by restricting the diffusional space to the membrane or the membrane surface, and by multiplying the diffusing species through the use of pools. Proton transfer reactions act over distances larger than a few angstroms through the use of clusters or relays, which sometimes rely on water molecules and which may only be dynamically assembled. Proteins appear to place a premium on robustness of design, which is relatively easily achieved in the long-distance physical processes of energy transfer and electron tunneling. By placing cofactors close enough, the physical process is relatively rapid compared to decay processes. Thus suboptimal conditions such as cofactor orientation, energy level, or redox potential level can be tolerated and generally do not have to be finely tuned. The most fragile regions of design tend to come in areas of complex formation and catalysis involving proton management, where relatively small changes in distance or mutations can lead to a dramatic decrease in turnover, which may already be limiting the overall speed of energy conversion in these proteins. Light-activated systems also face a challenge to robust function from the ever-present dangers of high redox potential chemistry. This can turn the protein matrix and wandering oxygen molecules into unintentional redox partners, which in the case of PSII requires the frequent, costly replacement of protein subunits.
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Affiliation(s)
- Christopher C Moser
- Johnson Research Foundation, Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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42
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Lakshmi KV, Poluektov OG, Reifler MJ, Wagner AM, Thurnauer MC, Brudvig GW. Pulsed high-frequency EPR study on the location of carotenoid and chlorophyll cation radicals in photosystem II. J Am Chem Soc 2003; 125:5005-14. [PMID: 12708850 DOI: 10.1021/ja0295671] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
When the primary electron-donation pathway from the water-oxidation complex in photosystem II (PS II) is inhibited, chlorophyll (Chl(Z) and Chl(D)), beta-carotene (Car) and cytochrome b(559) are alternate electron donors that are believed to function in a photoprotection mechanism. Previous studies have demonstrated that high-frequency EPR spectroscopy (at 130 GHz), together with deuteration of PS II, yields resolved Car(+) and Chl(+) EPR signals (Lakshmi et al. J. Phys. Chem. B 2000, 104, 10 445-10 448). The present study describes the use of pulsed high-frequency EPR spectroscopy to measure the location of the carotenoid and chlorophyll radicals relative to other paramagnetic cofactors in Synechococcus lividus PS II. The spin-lattice relaxation rates of the Car(+) and Chl(+) radicals are measured in manganese-depleted and manganese-depleted, cyanide-treated PS II; in these samples, the non-heme Fe(II) is high-spin (S = 2) and low-spin (S = 0), respectively. The Car(+) and Chl(+) radicals exhibit dipolar-enhanced relaxation rates in the presence of high-spin (S = 2) Fe(II) that are eliminated when the Fe(II) is low-spin (S = 0). The relaxation enhancements of the Car(+) and Chl(+) by the non-heme Fe(II) are smaller than the relaxation enhancement of Tyr(D)(*) and P(865)(+) by the non-heme Fe(II) in PS II and in the reaction center from Rhodobactersphaeroides, respectively, indicating that the Car(+)-Fe(II) and Chl(+)-Fe(II) distances are greater than the known Tyr(D)(*)-Fe(II) and P(865)(+)-Fe(II) distances. The Car(+) radical exhibits a greater relaxation enhancement by Fe(II) than the Chl(+) radical, consistent with Car being an earlier electron donor to P(680)(+) than Chl. On the basis of the distance estimates obtained in the present study and by analogy to carotenoid-binding sites in other pigment-protein complexes, possible binding sites are discussed for the Car cofactors in PS II. The relative location of Car(+) and Chl(+) radicals determined in this study provides valuable insight into the sequence of electron transfers in the alternate electron-donation pathways of PS II.
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Affiliation(s)
- K V Lakshmi
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA
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Abstract
Based on the current model of its structure and function, photosystem II (PSII) seems to have evolved from an ancestor that was homodimeric in terms of its protein core and contained a special pair of chlorophylls as the photo-oxidizable cofactor. It is proposed that the key event in the evolution of PSII was a mutation that resulted in the separation of the two pigments that made up the special chlorophyll pair, making them into two chlorophylls that were neither special nor paired. These ordinary chlorophylls, along with the two adjacent monomeric chlorophylls, were very oxidizing: a property proposed to be intrinsic to monomeric chlorophylls in the environment provided by reaction centre (RC) proteins. It seems likely that other (mainly electrostatic) changes in the environments of the pigments probably tuned their redox potentials further but these changes would have been minor compared with the redox jump imposed by splitting of the special pair. This sudden increase in redox potential allowed the development of oxygen evolution. The highly oxidizing homodimeric RC would probably have been not only inefficient in terms of photochemistry and charge storage but also wasteful in terms of protein or pigments undergoing damage due to the oxidative chemistry. These problems would have constituted selective pressures in favour of the lop-sided, heterodimeric system that exists as PSII today, in which the highly oxidized species are limited to only one side of the heterodimer: the sacrificial, rapidly turned-over D1 protein. It is also suggested that one reason for maintaining an oxidizable tyrosine, TyrD, on the D2 side of the RC, is that the proton associated with its tyrosyl radical, has an electrostatic role in confining P(+) to the expendable D1 side.
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Affiliation(s)
- A W Rutherford
- Service de Bioénergétique, URA CNRS 2096, Bat 532, CEA Saclay, 91191 Gif-sur-Yvette, France.
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Kamiya N, Shen JR. Crystal structure of oxygen-evolving photosystem II from Thermosynechococcus vulcanus at 3.7-A resolution. Proc Natl Acad Sci U S A 2003; 100:98-103. [PMID: 12518057 PMCID: PMC140893 DOI: 10.1073/pnas.0135651100] [Citation(s) in RCA: 851] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2002] [Indexed: 11/18/2022] Open
Abstract
Photosystem II (PSII) is a multisubunit membrane protein complex performing light-induced electron transfer and water-splitting reactions, leading to the formation of molecular oxygen. The first crystal structure of PSII from a thermophilic cyanobacterium Thermosynechococcus elongatus was reported recently [Zouni, A., Witt, H. T., Kern, J., Fromme, P., Krauss, N., Saenger, W. & Orth, P. (2001) Nature 409, 739-743)] at 3.8-A resolution. To analyze the PSII structure in more detail, we have obtained the crystal structure of PSII from another thermophilic cyanobacterium, Thermosynechococcus vulcanus, at 3.7-A resolution. The present structure was built on the basis of the sequences of PSII large subunits D1, D2, CP47, and CP43; extrinsic 33- and 12-kDa proteins and cytochrome c550; and several low molecular mass subunits, among which the structure of the 12-kDa protein was not reported previously. This yielded much information concerning the molecular interactions within this large protein complex. We also show the arrangement of chlorophylls and cofactors, including two beta-carotenes recently identified in a region close to the reaction center, which provided important clues to the secondary electron transfer pathways around the reaction center. Furthermore, possible ligands for the Mn-cluster were determined. In particular, the C terminus of D1 polypeptide was shown to be connected to the Mn cluster directly. The structural information obtained here provides important insights into the mechanism of PSII reactions.
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Affiliation(s)
- Nobuo Kamiya
- RIKEN Harima InstituteSPring-8, Kouto 1-1-1, Mikazuki-cho, Sayou-gun, Hyogo 679-5148, Japan.
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45
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46
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Barber J, Nield J. Organization of transmembrane helices in photosystem II: comparison of plants and cyanobacteria. Philos Trans R Soc Lond B Biol Sci 2002; 357:1329-35; discussion 1335, 1367. [PMID: 12437871 PMCID: PMC1693040 DOI: 10.1098/rstb.2002.1132] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Electron microscopy and X-ray crystallography are revealing the structure of photosystem II. Electron crystallography has yielded a 3D structure at sufficient resolution to identify subunit positioning and transmembrane organization of the reaction-centre core complex of spinach. Single-particle analyses are providing 3D structures of photosystem II-light-harvesting complex II supercomplexes that can be used to incorporate high-resolution structural data emerging from electron and X-ray crystallography. The positions of the chlorins and metal centres within photosystem II are now available. It can be concluded that photosystem II is a dimeric complex with the transmembrane helices of CP47/D2 proteins related to those of the CP43/D1 proteins by a twofold axis within each monomer. Further, both electron microscopy and X-ray analyses show that P(680) is not a 'special pair' and that cytochrome b559 is located on the D2 side of the reaction centres some distance from P(680). However, although comparison of the electron microscopy and X-ray models for spinach and Synechococcus elongatus show considerable similarities, there seem to be differences in the number and positioning of some small subunits.
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Affiliation(s)
- J Barber
- Department of Biological Sciences, Wolfson Laboratories, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK.
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47
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Goussias C, Boussac A, Rutherford AW. Photosystem II and photosynthetic oxidation of water: an overview. Philos Trans R Soc Lond B Biol Sci 2002; 357:1369-81; discussion 1419-20. [PMID: 12437876 PMCID: PMC1693055 DOI: 10.1098/rstb.2002.1134] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Conceptually, photosystem II, the oxygen-evolving enzyme, can be divided into two parts: the photochemical part and the catalytic part. The photochemical part contains the ultra-fast and ultra-efficient light-induced charge separation and stabilization steps that occur when light is absorbed by chlorophyll. The catalytic part, where water is oxidized, involves a cluster of Mn ions close to a redox-active tyrosine residue. Our current understanding of the catalytic mechanism is mainly based on spectroscopic studies. Here, we present an overview of the current state of knowledge of photosystem II, attempting to delineate the open questions and the directions of current research.
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Affiliation(s)
- Charilaos Goussias
- Service de Bioénergétique, URA CNRS 2096, Bat 532, CEA Saclay, 91191 Gif-sur-Yvette, France
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48
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Zehetner A, Scheer H, Siffel P, Vacha F. Photosystem II reaction center with altered pigment-composition: reconstitution of a complex containing five chlorophyll a per two pheophytin a with modified chlorophylls. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1556:21-8. [PMID: 12351215 DOI: 10.1016/s0005-2728(02)00282-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Pigment-depleted Photosystem II reaction centers (PS II-RCs) from a higher plant (pea) containing five chlorophyll a (Chl) per two pheophytin a (Phe), were treated with Chl and several derivatives under exchange conditions [FEBS Lett. 434 (1998) 88]. The resulting reconstituted complexes were compared to those obtained by pigment exchange of "conventional" PS II-RCs containing six Chl per two Phe. (1) The extraction of one Chl is fully reversible. (2) The site of extraction is the same as the one into which previously extraneous pigments have been exchanged, most likely the peripheral D1-H118. (3) Introducing an efficient quencher (Ni-Chl) into this site results in only 25% reduction of fluorescence, indicating incomplete energy equilibration among the "core" and peripheral chlorophylls.
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Affiliation(s)
- Andrea Zehetner
- Department Biologie I-Botanik, Universität München, Menzinger Str. 67, D-80638, Munich, Germany
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Abstract
A structure of photosystem II recently determined by X-ray crystallography at 3.8 A resolution complements structural studies using high-resolution electron microscopy and represents a major step towards understanding how photosynthetic organisms use light energy to oxidise water.
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Affiliation(s)
- James Barber
- Wolfson Laboratories, Department of Biological Sciences, Imperial College of Science, Technology & Medicine, London SW7 2AY, UK.
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