1
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Watanabe S, Noguchi T. Intermediate Formation via Proton Release during the Photoassembly of the Water-Oxidizing Mn 4CaO 5 Cluster in Photosystem II. J Phys Chem B 2024; 128:8145-8161. [PMID: 39148348 DOI: 10.1021/acs.jpcb.4c03768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
The early stages of the photoassembly of the water-oxidizing Mn4CaO5 cluster in spinach photosystem II (PSII) were monitored using rapid-scan time-resolved Fourier transform infrared (FTIR) spectroscopy. Carboxylate stretching and the amide I bands, which appeared upon the flash-induced oxidation of a Mn2+ ion, changed their features during the subsequent dark rearrangement process, indicating the relocation of the Mn3+ ion concomitant with protein conformational changes. Monitoring the isotope-edited FTIR signals of a Mes buffer estimated that nearly two protons are released upon the Mn2+ oxidation. Quantum chemical calculations for models of the Mn binding site suggested that the proton of a water ligand is transferred to D1-H332 through a hydrogen bond upon the Mn3+ formation and then released to the bulk as the Mn3+ shifts to bind to this histidine. Another Mn2+ ion may be inserted to form a binuclear Mn3+Mn2+ complex, whose structure was calculated to be stabilized by a μ-hydroxo bridge hydrogen-bonded with deprotonated D1-H337. Nearly one additional proton can thus be released from this histidine, assuming that it is mostly protonated before illumination. Alternatively, a proton could be released by further insertion of Ca2+, forming a Mn3+Mn2+Ca2+ complex with another hydroxo ligand connecting Ca2+ to the Mn3+Mn2+ complex.
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Affiliation(s)
- Shunya Watanabe
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takumi Noguchi
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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2
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Haider S, Bibi K, Munyaneza V, Zhang H, Zhang W, Ali A, Ahmad IA, Muhammad M, Xu F, Yang C, Yang J, Ding G. Drought-induced adaptive and ameliorative strategies in plants. CHEMOSPHERE 2024:143134. [PMID: 39168385 DOI: 10.1016/j.chemosphere.2024.143134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 05/01/2024] [Accepted: 08/18/2024] [Indexed: 08/23/2024]
Affiliation(s)
- Sharjeel Haider
- College of Resources and Environment/Microelement Research Center/Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, 430070, Wuhan
| | - Khadija Bibi
- Department of Botany, Faculty of Sciences, Ghazi University, Dera Ghazi Khan, Pakistan
| | - Venuste Munyaneza
- College of Resources and Environment/Microelement Research Center/Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, 430070, Wuhan
| | - Hao Zhang
- College of Resources and Environment/Microelement Research Center/Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, 430070, Wuhan
| | - Wen Zhang
- College of Resources and Environment/Microelement Research Center/Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, 430070, Wuhan
| | - Ayaz Ali
- College of Resources and Environment/Microelement Research Center/Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, 430070, Wuhan
| | - Iftikhar Ali Ahmad
- Key Laboratory of Soil Health Diagnostic and Green Remediation, Ministry of Ecology and Environment, College of Resource and Environment, Huazhong Agricultural University, China
| | - Mehran Muhammad
- College of Resources and Environment/Microelement Research Center/Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, 430070, Wuhan
| | - Fangsen Xu
- College of Resources and Environment/Microelement Research Center/Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, 430070, Wuhan
| | - Chunlei Yang
- Hubei Academy of Tobacco Science, Wuhan 430030, China.
| | - Jinpeng Yang
- Hubei Academy of Tobacco Science, Wuhan 430030, China
| | - Guangda Ding
- College of Resources and Environment/Microelement Research Center/Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, 430070, Wuhan.
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3
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Matsubara T, Shimada Y, Kitajima-Ihara T, Nagao R, Noguchi T. Rapid-Scan Fourier Transform Infrared Monitoring of the Photoactivation Process in Cyanobacterial Photosystem II. J Phys Chem B 2023; 127:8150-8161. [PMID: 37718495 DOI: 10.1021/acs.jpcb.3c04325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
The catalytic site of photosynthetic water oxidation, the Mn4CaO5 cluster, in photosystem II (PSII) is known to be formed by a light-induced process called photoactivation. However, details of its molecular mechanism remain unresolved. In this study, we monitored the photoactivation process in cyanobacterial PSII using rapid-scan, time-resolved Fourier transform infrared (FTIR) spectroscopy. The Mn3+/Mn2+ FTIR difference spectra of PSII, in which D1-D170 was specifically 13C labeled, and PSII from the D1-D170A, D1-E189A, and D1-D342A mutants provide strong evidence that the initial Mn2+ is coordinated by D1-D170 and D1-E189. Protein conformational changes and relocation of photo-oxidized Mn3+ in the dark rearrangement process were detected as slow-phase signals in the amide I and carboxylate regions, whereas similar signals were not observed in D1-E189A PSII. It is thus proposed that relocation of Mn3+ via D1-E189 induces the conformational changes of the proteins to form proper Mn binding sites in the mature protein conformation.
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Affiliation(s)
- Takumi Matsubara
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Yuichiro Shimada
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Tomomi Kitajima-Ihara
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Ryo Nagao
- Faculty of Agriculture, Shizuoka University, Shizuoka 422-8529, Japan
| | - Takumi Noguchi
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
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4
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Lovyagina ER, Luneva OG, Loktyushkin AV, Semin BK. Effect of lanthanides on oxidation of Mn 2+ cations via a high-affinity Mn-binding site in photosystem II membranes. J Inorg Biochem 2023; 244:112237. [PMID: 37105009 DOI: 10.1016/j.jinorgbio.2023.112237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Revised: 04/04/2023] [Accepted: 04/19/2023] [Indexed: 04/29/2023]
Abstract
Lanthanide cations (La3+ and Tb3+) bind to the Ca-binding site of the oxygen-evolving complex in Ca-depleted PSII membranes and irreversibly inhibit the oxygen evolution. Оn the other hand, EPR measurement of Mn2+ concentration in buffer revealed that lanthanide cations inhibit the light-dependent oxidation of Mn2+ cations via the high-affinity Mn-binding site in Mn-depleted PSII membranes, which suggests that they bind to and inhibit the high-affinity Mn-binding site of the oxygen-evolving complex. The inhibition is irreversible, bound Ln3+ cation could not be washed out from the sample. Calcium ion inhibits oxidation of Mn2+ (5 μM) at very high concentration (tens mM) and the inhibition is reversible. In this work we measured the reduction rate of exogenic electron acceptor 2,6-dichlorophenolindophenol during the oxidation of Mn2+ cations in the Ca-depleted PSII and in the Ca-depleted PSII treated with lanthanides after extraction of Mn cluster from these preparations. We found that irreversible binding of the lanthanide cation to the Ca-binding site in the Ca-depleted PSII membranes leads to a partial inhibition of the high-affinity Mn-binding site.
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Affiliation(s)
- E R Lovyagina
- Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, Moscow 119234, Russia
| | - O G Luneva
- Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, Moscow 119234, Russia
| | - A V Loktyushkin
- Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, Moscow 119234, Russia
| | - B K Semin
- Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, Moscow 119234, Russia.
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5
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Application of Exogenous Silicon for Alleviating Photosynthetic Inhibition in Tomato Seedlings under Low−Calcium Stress. Int J Mol Sci 2022; 23:ijms232113526. [DOI: 10.3390/ijms232113526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 10/28/2022] [Accepted: 11/02/2022] [Indexed: 11/06/2022] Open
Abstract
To address the low Ca−induced growth inhibition of tomato plants, the mitigation effect of exogenous Si on tomato seedlings under low−Ca stress was investigated using different application methods. We specifically analyzed the effects of root application or foliar spraying of 1 mM Si on growth conditions, leaf photosynthetic properties, stomatal status, chlorophyll content, chlorophyll fluorescence, ATP activity and content, Calvin cycle−related enzymatic activity, and gene expression in tomato seedlings under low vs. adequate calcium conditions. We found that the low−Ca environment significantly affected (reduced) these parameters, resulting in growth limitation. Surprisingly, the application of 1 mM Si significantly increased plant height, stem diameter, and biomass accumulation, protected photosynthetic pigments, improved gas exchange, promoted ATP production, enhanced the activity of Calvin cycle key enzymes and expression of related genes, and ensured efficient photosynthesis to occur in plants under low−Ca conditions. Interestingly, when the same amount of Si was applied, the beneficial effects of Si were more pronounced under low−Ca conditions that under adequate Ca. We speculate that Si might promote the absorption and transport of calcium in plants. The effects of Si also differed depending on the application method; foliar spraying was better in alleviating photosynthetic inhibition in plants under low−Ca stress, whereas root application of Si significantly promoted root growth and development. Enhancing the photosynthetic capacity by foliar Si application is an effective strategy for ameliorating the growth inhibition of plants under low−Ca stress.
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6
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Russell BP, Vinyard DJ. Chloride facilitates Mn(III) formation during photoassembly of the Photosystem II oxygen-evolving complex. PHOTOSYNTHESIS RESEARCH 2022; 152:283-288. [PMID: 34817779 DOI: 10.1007/s11120-021-00886-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 11/12/2021] [Indexed: 06/13/2023]
Abstract
The Mn4Ca oxygen-evolving complex (OEC) in Photosystem II (PSII) is assembled in situ from free Mn2+, Ca2+, and water. In an early light-driven step, Mn2+ in a protein high-affinity site is oxidized to Mn3+. Using dual-mode electron paramagnetic resonance spectroscopy, we observed that Mn3+ accumulation increases as chloride concentration increases in spinach PSII membranes depleted of all extrinsic subunits. At physiologically relevant pH values, this effect requires the presence of calcium. When combined with pH studies, we conclude that the first Mn2+ oxidation event in OEC assembly requires a deprotonation that is facilitated by chloride.
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Affiliation(s)
- Brandon P Russell
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - David J Vinyard
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA.
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7
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Oliver N, Avramov AP, Nürnberg DJ, Dau H, Burnap RL. From manganese oxidation to water oxidation: assembly and evolution of the water-splitting complex in photosystem II. PHOTOSYNTHESIS RESEARCH 2022; 152:107-133. [PMID: 35397059 DOI: 10.1007/s11120-022-00912-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/03/2022] [Indexed: 06/14/2023]
Abstract
The manganese cluster of photosystem II has been the focus of intense research aiming to understand the mechanism of H2O-oxidation. Great effort has also been applied to investigating its oxidative photoassembly process, termed photoactivation that involves the light-driven incorporation of metal ions into the active Mn4CaO5 cluster. The knowledge gained on these topics has fundamental scientific significance, but may also provide the blueprints for the development of biomimetic devices capable of splitting water for solar energy applications. Accordingly, synthetic chemical approaches inspired by the native Mn cluster are actively being explored, for which the native catalyst is a useful benchmark. For both the natural and artificial catalysts, the assembly process of incorporating Mn ions into catalytically active Mn oxide complexes is an oxidative process. In both cases this process appears to share certain chemical features, such as producing an optimal fraction of open coordination sites on the metals to facilitate the binding of substrate water, as well as the involvement of alkali metals (e.g., Ca2+) to facilitate assembly and activate water-splitting catalysis. This review discusses the structure and formation of the metal cluster of the PSII H2O-oxidizing complex in the context of what is known about the formation and chemical properties of different Mn oxides. Additionally, the evolutionary origin of the Mn4CaO5 is considered in light of hypotheses that soluble Mn2+ was an ancient source of reductant for some early photosynthetic reaction centers ('photomanganotrophy'), and recent evidence that PSII can form Mn oxides with structural resemblance to the geologically abundant birnessite class of minerals. A new functional role for Ca2+ to facilitate sustained Mn2+ oxidation during photomanganotrophy is proposed, which may explain proposed physiological intermediates during the likely evolutionary transition from anoxygenic to oxygenic photosynthesis.
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Affiliation(s)
- Nicholas Oliver
- Physics Department, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Anton P Avramov
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Dennis J Nürnberg
- Physics Department, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Holger Dau
- Physics Department, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Robert L Burnap
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, 74078, USA.
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8
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Gates C, Ananyev G, Roy-Chowdhury S, Cullinane B, Miller M, Fromme P, Dismukes GC. Why Did Nature Choose Manganese over Cobalt to Make Oxygen Photosynthetically on the Earth? J Phys Chem B 2022; 126:3257-3268. [PMID: 35446582 DOI: 10.1021/acs.jpcb.2c00749] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
All contemporary oxygenic phototrophs─from primitive cyanobacteria to complex multicellular plants─split water using a single invariant cluster comprising Mn4CaO5 (the water oxidation catalyst) as the catalyst within photosystem II, the universal oxygenic reaction center of natural photosynthesis. This cluster is unstable outside of PSII and can be reconstituted, both in vivo and in vitro, using elemental aqueous ions and light, via photoassembly. Here, we demonstrate the first functional substitution of manganese in any oxygenic reaction center by in vitro photoassembly. Following complete removal of inorganic cofactors from cyanobacterial photosystem II microcrystal (PSIIX), photoassembly with free cobalt (Co2+), calcium (Ca2+), and water (OH-) restores O2 evolution activity. Photoassembly occurs at least threefold faster using Co2+ versus Mn2+ due to a higher quantum yield for PSIIX-mediated charge separation (P*): Co2+ → P* → Co3+QA-. However, this kinetic preference for Co2+ over native Mn2+ during photoassembly is offset by significantly poorer catalytic activity (∼25% of the activity with Mn2+) and ∼3- to 30-fold faster photoinactivation rate. The resulting reconstituted Co-PSIIX oxidizes water by the standard four-flash photocycle, although they produce 4-fold less O2 per PSII, suggested to arise from faster charge recombination (Co3+QA ← Co4+QA-) in the catalytic cycle. The faster photoinactivation of reconstituted Co-PSIIX occurs under anaerobic conditions during the catalytic cycle, suggesting direct photodamage without the involvement of O2. Manganese offers two advantages for oxygenic phototrophs, which may explain its exclusive retention throughout Darwinian evolution: significantly slower charge recombination (Mn3+QA ← Mn4+QA-) permits more water oxidation at low and fluctuating solar irradiation (greater net energy conversion) and much greater tolerance to photodamage at high light intensities (Mn4+ is less oxidizing than Co4+). Future work to identify the chemical nature of the intermediates will be needed for further interpretation.
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Affiliation(s)
- Colin Gates
- Waksman Institute of Microbiology, Rutgers University, Piscataway, New Jersey 08854, United States.,Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States.,Department of Computational Biology & Molecular Biophysics, Rutgers University, Piscataway, New Jersey 08854, United States.,Department of Chemistry & Biochemistry, Loyola University Chicago, Chicago, Illinois 60660, United States
| | - Gennady Ananyev
- Waksman Institute of Microbiology, Rutgers University, Piscataway, New Jersey 08854, United States.,Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Shatabdi Roy-Chowdhury
- Biodesign Center for Applied Structural Discovery and School of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, United States
| | - Brendan Cullinane
- Waksman Institute of Microbiology, Rutgers University, Piscataway, New Jersey 08854, United States.,Department of Molecular Biology & Biochemistry, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Mathias Miller
- Waksman Institute of Microbiology, Rutgers University, Piscataway, New Jersey 08854, United States.,Department of Molecular Biology & Biochemistry, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Petra Fromme
- Biodesign Center for Applied Structural Discovery and School of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, United States
| | - G Charles Dismukes
- Waksman Institute of Microbiology, Rutgers University, Piscataway, New Jersey 08854, United States.,Department of Chemistry & Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States
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9
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Sato A, Nakano Y, Nakamura S, Noguchi T. Rapid-Scan Time-Resolved ATR-FTIR Study on the Photoassembly of the Water-Oxidizing Mn4CaO5 Cluster in Photosystem II. J Phys Chem B 2021; 125:4031-4045. [DOI: 10.1021/acs.jpcb.1c01624] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Akihiko Sato
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Yuki Nakano
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Shin Nakamura
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takumi Noguchi
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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10
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Zabret J, Bohn S, Schuller SK, Arnolds O, Möller M, Meier-Credo J, Liauw P, Chan A, Tajkhorshid E, Langer JD, Stoll R, Krieger-Liszkay A, Engel BD, Rudack T, Schuller JM, Nowaczyk MM. Structural insights into photosystem II assembly. NATURE PLANTS 2021; 7:524-538. [PMID: 33846594 PMCID: PMC8094115 DOI: 10.1038/s41477-021-00895-0] [Citation(s) in RCA: 84] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 03/04/2021] [Indexed: 05/07/2023]
Abstract
Biogenesis of photosystem II (PSII), nature's water-splitting catalyst, is assisted by auxiliary proteins that form transient complexes with PSII components to facilitate stepwise assembly events. Using cryo-electron microscopy, we solved the structure of such a PSII assembly intermediate from Thermosynechococcus elongatus at 2.94 Å resolution. It contains three assembly factors (Psb27, Psb28 and Psb34) and provides detailed insights into their molecular function. Binding of Psb28 induces large conformational changes at the PSII acceptor side, which distort the binding pocket of the mobile quinone (QB) and replace the bicarbonate ligand of non-haem iron with glutamate, a structural motif found in reaction centres of non-oxygenic photosynthetic bacteria. These results reveal mechanisms that protect PSII from damage during biogenesis until water splitting is activated. Our structure further demonstrates how the PSII active site is prepared for the incorporation of the Mn4CaO5 cluster, which performs the unique water-splitting reaction.
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Affiliation(s)
- Jure Zabret
- Department of Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Stefan Bohn
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Sandra K Schuller
- Department of Structural Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
- CryoEM of Molecular Machines, SYNMIKRO Research Center and Department of Chemistry, Philipps University of Marburg, Marburg, Germany
| | - Oliver Arnolds
- Biomolecular Spectroscopy and RUBiospek|NMR, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Madeline Möller
- Department of Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | | | - Pasqual Liauw
- Department of Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Aaron Chan
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Julian D Langer
- Proteomics, Max Planck Institute of Biophysics, Frankfurt, Germany
- Proteomics, Max Planck Institute for Brain Research, Frankfurt, Germany
| | - Raphael Stoll
- Biomolecular Spectroscopy and RUBiospek|NMR, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Anja Krieger-Liszkay
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, Gif-sur-Yvette, France
| | - Benjamin D Engel
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
- Helmholtz Pioneer Campus, Helmholtz Zentrum München, Neuherberg, Germany
- Department of Chemistry, Technical University of Munich, Garching, Germany
| | - Till Rudack
- Biospectroscopy, Center for Protein Diagnostics (ProDi), Ruhr University Bochum, Bochum, Germany.
- Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany.
| | - Jan M Schuller
- Department of Structural Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany.
- CryoEM of Molecular Machines, SYNMIKRO Research Center and Department of Chemistry, Philipps University of Marburg, Marburg, Germany.
| | - Marc M Nowaczyk
- Department of Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany.
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11
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The role of Ca 2+ and protein scaffolding in the formation of nature's water oxidizing complex. Proc Natl Acad Sci U S A 2020; 117:28036-28045. [PMID: 33106422 PMCID: PMC7668025 DOI: 10.1073/pnas.2011315117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Photosynthetic O2 evolution is catalyzed by the Mn4CaO5 cluster of the water oxidation complex of the photosystem II (PSII) complex. The photooxidative self-assembly of the Mn4CaO5 cluster, termed photoactivation, utilizes the same highly oxidizing species that drive the water oxidation in order to drive the incorporation of Mn2+ into the high-valence Mn4CaO5 cluster. This multistep process proceeds with low quantum efficiency, involves a molecular rearrangement between light-activated steps, and is prone to photoinactivation and misassembly. A sensitive polarographic technique was used to track the assembly process under flash illumination as a function of the constituent Mn2+ and Ca2+ ions in genetically engineered membranes of the cyanobacterium Synechocystis sp. PCC6803 to elucidate the action of Ca2+ and peripheral proteins. We show that the protein scaffolding organizing this process is allosterically modulated by the assembly protein Psb27, which together with Ca2+ stabilizes the intermediates of photoactivation, a feature especially evident at long intervals between photoactivating flashes. The results indicate three critical metal-binding sites: two Mn and one Ca, with occupation of the Ca site by Ca2+ critical for the suppression of photoinactivation. The long-observed competition between Mn2+ and Ca2+ occurs at the second Mn site, and its occupation by competing Ca2+ slows the rearrangement. The relatively low overall quantum efficiency of photoactivation is explained by the requirement of correct occupancy of these metal-binding sites coupled to a slow restructuring of the protein ligation environment, which are jointly necessary for the photooxidative trapping of the first stable assembly intermediate.
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12
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Photosystem II oxygen-evolving complex photoassembly displays an inverse H/D solvent isotope effect under chloride-limiting conditions. Proc Natl Acad Sci U S A 2019; 116:18917-18922. [PMID: 31484762 PMCID: PMC6754581 DOI: 10.1073/pnas.1910231116] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Metal clusters play important roles in a wide variety of proteins. In cyanobacteria, algae, and plants, photosystem II uses light energy to oxidize water and release O2 at an active site that contains 1 calcium and 4 manganese atoms. This cluster must be built within the protein environment through a process known as photoassembly. Through experiments and simulations, we found that the efficiency of photoassembly was highly dependent on protons and chloride. Surprisingly, when the solvent was switched from H2O to deuterated water, D2O, the yield of photoassembly was higher. These results provide insights into the stepwise mechanism of photoassembly that can inform synthesis and repair strategies being developed for artificial photosynthesis technologies. Photosystem II (PSII) performs the solar-driven oxidation of water used to fuel oxygenic photosynthesis. The active site of water oxidation is the oxygen-evolving complex (OEC), a Mn4CaO5 cluster. PSII requires degradation of key subunits and reassembly of the OEC as frequently as every 20 to 40 min. The metals for the OEC are assembled within the PSII protein environment via a series of binding events and photochemically induced oxidation events, but the full mechanism is unknown. A role of proton release in this mechanism is suggested here by the observation that the yield of in vitro OEC photoassembly is higher in deuterated water, D2O, compared with H2O when chloride is limiting. In kinetic studies, OEC photoassembly shows a significant lag phase in H2O at limiting chloride concentrations with an apparent H/D solvent isotope effect of 0.14 ± 0.05. The growth phase of OEC photoassembly shows an H/D solvent isotope effect of 1.5 ± 0.2. We analyzed the protonation states of the OEC protein environment using classical Multiconformer Continuum Electrostatics. Combining experiments and simulations leads to a model in which protons are lost from amino acid that will serve as OEC ligands as metals are bound. Chloride and D2O increase the proton affinities of key amino acid residues. These residues tune the binding affinity of Mn2+/3+ and facilitate the deprotonation of water to form a proposed μ-hydroxo bridged Mn2+Mn3+ intermediate.
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13
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Electrochemical Conversion of the Lignin Model Veratryl Alcohol to Veratryl Aldehyde Using Manganese(III)-Schiff Base Homogeneous Catalysts. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9163430] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Lignin and other colored structures need to be bleached after the Kraft process in the pulp industry. Development of environmentally-safe bleaching catalysts or electrocatalysts constitutes an attractive strategy for selective removal of lignin. Seven manganese(III)-complexes with Schiff base ligands 1–7 were synthetized and characterized by different analytical and spectroscopic techniques. The tetragonally elongated octahedral geometry for the manganese coordination sphere and the global µ-aquo dimeric structure were revealed by X-ray diffraction (XRD) studies for 1, Mn2L12(H2O)2(N(CN)2)2 (N(CN)2 = dicyanamide). Complexes 1–4 behave as more efficient peroxidase mimics as compared to 5–7. Electrochemical oxidation of the lignin model veratrylalcohol (VA) to veratrylaldehyde (VAH) is efficiently catalyzed by a type of dimanganese(III) complexes in a chlorine-free medium. The electrocatalytic reaction proceeds through the oxidation of chloride into hypochlorite at alkaline pH along with the formation of hydrogen from water as a subproduct.
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14
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Nakamura S, Noguchi T. Initial Mn2+ binding site in photoassembly of the water-oxidizing Mn4CaO5 cluster in photosystem II as studied by quantum mechanics/molecular mechanics calculations. Chem Phys Lett 2019. [DOI: 10.1016/j.cplett.2019.02.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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15
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The Significance of Calcium in Photosynthesis. Int J Mol Sci 2019; 20:ijms20061353. [PMID: 30889814 PMCID: PMC6471148 DOI: 10.3390/ijms20061353] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/23/2019] [Accepted: 03/01/2019] [Indexed: 01/12/2023] Open
Abstract
As a secondary messenger, calcium participates in various physiological and biochemical reactions in plants. Photosynthesis is the most extensive biosynthesis process on Earth. To date, researchers have found that some chloroplast proteins have Ca2+-binding sites, and the structure and function of some of these proteins have been discussed in detail. Although the roles of Ca2+ signal transduction related to photosynthesis have been discussed, the relationship between calcium and photosynthesis is seldom systematically summarized. In this review, we provide an overview of current knowledge of calcium’s role in photosynthesis.
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16
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Soldatova AV, Romano CA, Tao L, Stich TA, Casey WH, Britt RD, Tebo BM, Spiro TG. Mn(II) Oxidation by the Multicopper Oxidase Complex Mnx: A Coordinated Two-Stage Mn(II)/(III) and Mn(III)/(IV) Mechanism. J Am Chem Soc 2017; 139:11381-11391. [PMID: 28712303 DOI: 10.1021/jacs.7b02772] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The bacterial manganese oxidase MnxG of the Mnx protein complex is unique among multicopper oxidases (MCOs) in carrying out a two-electron metal oxidation, converting Mn(II) to MnO2 nanoparticles. The reaction occurs in two stages: Mn(II) → Mn(III) and Mn(III) → MnO2. In a companion study , we show that the electron transfer from Mn(II) to the low-potential type 1 Cu of MnxG requires an activation step, likely forming a hydroxide bridge at a dinuclear Mn(II) site. Here we study the second oxidation step, using pyrophosphate (PP) as a Mn(III) trap. PP chelates Mn(III) produced by the enzyme and subsequently allows it to become a substrate for the second stage of the reaction. EPR spectroscopy confirms the presence of Mn(III) bound to the enzyme. The Mn(III) oxidation step does not involve direct electron transfer to the enzyme from Mn(III), which is shown by kinetic measurements to be excluded from the Mn(II) binding site. Instead, Mn(III) is proposed to disproportionate at an adjacent polynuclear site, thereby allowing indirect oxidation to Mn(IV) and recycling of Mn(II). PP plays a multifaceted role, slowing the reaction by complexing both Mn(II) and Mn(III) in solution, and also inhibiting catalysis, likely through binding at or near the active site. An overall mechanism for Mnx-catalyzed MnO2 production from Mn(II) is presented.
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Affiliation(s)
- Alexandra V Soldatova
- Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195, United States
| | - Christine A Romano
- Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University , Portland, Oregon 97239, United States
| | | | | | | | | | - Bradley M Tebo
- Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University , Portland, Oregon 97239, United States
| | - Thomas G Spiro
- Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195, United States
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17
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Bao H, Burnap RL. Photoactivation: The Light-Driven Assembly of the Water Oxidation Complex of Photosystem II. FRONTIERS IN PLANT SCIENCE 2016; 7:578. [PMID: 27200051 PMCID: PMC4853684 DOI: 10.3389/fpls.2016.00578] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 04/14/2016] [Indexed: 05/10/2023]
Abstract
Photosynthetic water oxidation is catalyzed by the Mn4CaO5 cluster of photosystem II. The assembly of the Mn4O5Ca requires light and involves a sequential process called photoactivation. This process harnesses the charge-separation of the photochemical reaction center and the coordination environment provided by the amino acid side chains of the protein to oxidize and organize the incoming manganese ions to form the oxo-bridged metal cluster capable of H2O-oxidation. Although most aspects of this assembly process remain poorly understood, recent advances in the elucidation of the crystal structure of the fully assembled cyanobacterial PSII complex help in the interpretation of the rich history of experiments designed to understand this process. Moreover, recent insights on the structure and stability of the constituent ions of the Mn4CaO5 cluster may guide future experiments. Here we consider the literature and suggest possible models of assembly including one involving single Mn(2+) oxidation site for all Mn but requiring ion relocation.
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Affiliation(s)
| | - Robert L. Burnap
- Department of Microbiology and Molecular Genetics, Oklahoma State UniversityStillwater, OK, USA
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18
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Cardona T. Reconstructing the Origin of Oxygenic Photosynthesis: Do Assembly and Photoactivation Recapitulate Evolution? FRONTIERS IN PLANT SCIENCE 2016; 7:257. [PMID: 26973693 PMCID: PMC4773611 DOI: 10.3389/fpls.2016.00257] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 02/16/2016] [Indexed: 05/21/2023]
Abstract
Due to the great abundance of genomes and protein structures that today span a broad diversity of organisms, now more than ever before, it is possible to reconstruct the molecular evolution of protein complexes at an incredible level of detail. Here, I recount the story of oxygenic photosynthesis or how an ancestral reaction center was transformed into a sophisticated photochemical machine capable of water oxidation. First, I review the evolution of all reaction center proteins in order to highlight that Photosystem II and Photosystem I, today only found in the phylum Cyanobacteria, branched out very early in the history of photosynthesis. Therefore, it is very unlikely that they were acquired via horizontal gene transfer from any of the described phyla of anoxygenic phototrophic bacteria. Second, I present a new evolutionary scenario for the origin of the CP43 and CP47 antenna of Photosystem II. I suggest that the antenna proteins originated from the remodeling of an entire Type I reaction center protein and not from the partial gene duplication of a Type I reaction center gene. Third, I highlight how Photosystem II and Photosystem I reaction center proteins interact with small peripheral subunits in remarkably similar patterns and hypothesize that some of this complexity may be traced back to the most ancestral reaction center. Fourth, I outline the sequence of events that led to the origin of the Mn4CaO5 cluster and show that the most ancestral Type II reaction center had some of the basic structural components that would become essential in the coordination of the water-oxidizing complex. Finally, I collect all these ideas, starting at the origin of the first reaction center proteins and ending with the emergence of the water-oxidizing cluster, to hypothesize that the complex and well-organized process of assembly and photoactivation of Photosystem II recapitulate evolutionary transitions in the path to oxygenic photosynthesis.
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19
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Asada M, Mino H. Location of the High-Affinity Mn(2+) Site in Photosystem II Detected by PELDOR. J Phys Chem B 2015. [PMID: 26203770 DOI: 10.1021/acs.jpcb.5b03994] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The location of the high-affinity Mn(2+) site in apo-photosystem (PS) II was investigated by pulsed EPR. The electron-electron magnetic dipole interaction of 1.7 MHz between the YD(•) radical and Mn(2+) ion was observed using the pulsed electron-electron double resonance (PELDOR) technique, and the Mn(2+) ion was bound to one apo-PS II in the absence and presence of Ca(2+). PELDOR signals were calculated using the previously determined spin distribution on the YD(•) radical and its known position in the crystal structure, assuming that the specific Mn(2+) site was located in the oxygen evolving complex. The results show that the high-affinity Mn(2+) site is located at the position denoted by Mn4(A) in the native crystal structure. The Mn(2+) is coordinated with axial ligands Asp170 and Glu333 in the D1 polypeptide.
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Affiliation(s)
- Mizue Asada
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, 464-8602, Japan
| | - Hiroyuki Mino
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, 464-8602, Japan
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20
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Kanady J, Lin PH, Carsch KM, Nielsen RJ, Takase M, Goddard WA, Agapie T. Toward models for the full oxygen-evolving complex of photosystem II by ligand coordination to lower the symmetry of the Mn3CaO4 cubane: demonstration that electronic effects facilitate binding of a fifth metal. J Am Chem Soc 2014; 136:14373-6. [PMID: 25241826 PMCID: PMC4210109 DOI: 10.1021/ja508160x] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Indexed: 12/25/2022]
Abstract
Synthetic model compounds have been targeted to benchmark and better understand the electronic structure, geometry, spectroscopy, and reactivity of the oxygen-evolving complex (OEC) of photosystem II, a low-symmetry Mn4CaOn cluster. Herein, low-symmetry Mn(IV)3GdO4 and Mn(IV)3CaO4 cubanes are synthesized in a rational, stepwise fashion through desymmetrization by ligand substitution, causing significant cubane distortions. As a result of increased electron richness and desymmetrization, a specific μ3-oxo moiety of the Mn3CaO4 unit becomes more basic allowing for selective protonation. Coordination of a fifth metal ion, Ag(+), to the same site gives a Mn3CaAgO4 cluster that models the topology of the OEC by displaying both a cubane motif and a "dangler" transition metal. The present synthetic strategy provides a rational roadmap for accessing more accurate models of the biological catalyst.
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Affiliation(s)
- Jacob
S. Kanady
- Divison of Chemistry and
Chemical Engineering, California Institute
of Technology, Pasadena, California 91125, United States
| | - Po-Heng Lin
- Divison of Chemistry and
Chemical Engineering, California Institute
of Technology, Pasadena, California 91125, United States
| | - Kurtis M. Carsch
- Divison of Chemistry and
Chemical Engineering, California Institute
of Technology, Pasadena, California 91125, United States
| | - Robert J. Nielsen
- Divison of Chemistry and
Chemical Engineering, California Institute
of Technology, Pasadena, California 91125, United States
| | - Michael
K. Takase
- Divison of Chemistry and
Chemical Engineering, California Institute
of Technology, Pasadena, California 91125, United States
| | - William A. Goddard
- Divison of Chemistry and
Chemical Engineering, California Institute
of Technology, Pasadena, California 91125, United States
| | - Theodor Agapie
- Divison of Chemistry and
Chemical Engineering, California Institute
of Technology, Pasadena, California 91125, United States
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21
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Yanykin DV, Khorobrykh AA, Khorobrykh SA, Pshybytko NL, Klimov VV. Flash-induced consumption of molecular oxygen on the donor side of photosystem II in Mn-depleted subchloroplast membrane fragments: specific effects of manganese and calcium ions. PHOTOSYNTHESIS RESEARCH 2013; 117:367-374. [PMID: 23756831 DOI: 10.1007/s11120-013-9868-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 05/30/2013] [Indexed: 06/02/2023]
Abstract
It has been shown that removal of manganese from the water-oxidizing complex (WOC) of photosystem II (PSII) leads to flash-induced oxygen consumption (FIOC) which is activated by low concentration of Mn(2+) (Yanykin et al., Biochim Biophys Acta 1797:516-523, 2010). In the present work, we examined the effect of transition and non-transition divalent metal ions on FIOC in Mn-depleted PSII (apo-WOC-PSII) preparations. It was shown that only Mn(2+) ions are able to activate FIOC while other transition metal ions (Fe(2+), V(2+) and Cr(2+)) capable of electron donation to the apo-WOC-PSII suppressed the photoconsumption of O2. Co(2+) ions with a high redox potential (E (0) for Co(2+)/Co(3+) is 1.8 V) showed no effect. Non-transition metal ions Ca(2+) by Mg(2+) did not stimulate FIOC. However, Ca(2+) (in contrast to Mg(2+)) showed an additional activation effect in the presence of exogenic Mn(2+). The Ca(2+) effect depended on the concentration of both Mn(2+) and Ca(2+). The Ca effect was only observed when: (1) the activation of FIOC induced by Mn(2+) did not reach its maximum, (2) the concentration of Ca(2+) did not exceed 40 μM; at higher concentrations Ca(2+) inhibited the Mn(2+)-activated O2 photoconsumption. Replacement of Ca(2+) by Mg(2+) led to a suppression of Mn(2+)-activated O2 photoconsumption; while, addition of Ca(2+) resulted in elimination of the Mg(2+) inhibitory effect and activation of FIOC. Thus, only Mn(2+) and Ca(2+) (which are constituents of the WOC) have specific effects of activation of FIOC in apo-WOC-PSII preparations. Possible reactions involving Mn(2+) and Ca(2+) which could lead to the activation of FIOC in the apo-WOC-PSII are discussed.
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Affiliation(s)
- D V Yanykin
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
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22
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Khorobrykh A, Dasgupta J, Kolling DRJ, Terentyev V, Klimov VV, Dismukes GC. Evolutionary origins of the photosynthetic water oxidation cluster: bicarbonate permits Mn(2+) photo-oxidation by anoxygenic bacterial reaction centers. Chembiochem 2013; 14:1725-31. [PMID: 24006214 DOI: 10.1002/cbic.201300355] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Indexed: 12/15/2022]
Abstract
The enzyme that catalyzes water oxidation in oxygenic photosynthesis contains an inorganic cluster (Mn4 CaO5 ) that is universally conserved in all photosystem II (PSII) protein complexes. Its hypothesized precursor is an anoxygenic photobacterium containing a type 2 reaction center as photo-oxidant (bRC2, iron-quinone type). Here we provide the first experimental evidence that a native bRC2 complex can catalyze the photo-oxidation of Mn(2+) to Mn(3+) , but only in the presence of bicarbonate concentrations that allows the formation of (bRC2)Mn(2+) (bicarbonate)1-2 complexes. Parallel-mode EPR spectroscopy was used to characterize the photoproduct, (bRC2)Mn(3+) (CO3 (2-) ), based on the g tensor and (55) Mn hyperfine splitting. (Bi)carbonate coordination extends the lifetime of the Mn(3+) photoproduct by slowing charge recombination. Prior electrochemical measurements show that carbonate complexation thermodynamically stabilizes the Mn(3+) product by 0.9-1 V relative to water ligands. A model for the origin of the water oxidation catalyst is presented that proposes chemically feasible steps in the evolution of oxygenic PSIIs, and is supported by literature results on the photoassembly of contemporary PSIIs.
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Affiliation(s)
- Andrei Khorobrykh
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, 142290 (Russia)
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23
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Vinyard DJ, Ananyev GM, Charles Dismukes G. Photosystem II: The Reaction Center of Oxygenic Photosynthesis. Annu Rev Biochem 2013; 82:577-606. [DOI: 10.1146/annurev-biochem-070511-100425] [Citation(s) in RCA: 279] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- David J. Vinyard
- Department of Chemistry and Chemical Biology and the Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854; ,
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540;
| | - Gennady M. Ananyev
- Department of Chemistry and Chemical Biology and the Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854; ,
| | - G. Charles Dismukes
- Department of Chemistry and Chemical Biology and the Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854; ,
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24
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Kanady JS, Mendoza-Cortes JL, Tsui EY, Nielsen RJ, Goddard WA, Agapie T. Oxygen Atom Transfer and Oxidative Water Incorporation in Cuboidal Mn3MOn Complexes Based on Synthetic, Isotopic Labeling, and Computational Studies. J Am Chem Soc 2013; 135:1073-82. [DOI: 10.1021/ja310022p] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jacob S. Kanady
- Division of Chemistry and Chemical
Engineering , California Institute of Technology, Pasadena, California 91125, United States
| | - Jose L. Mendoza-Cortes
- Materials and Process Simulation
Center, California Institute of Technology, Pasadena, California 91125, United States
| | - Emily Y. Tsui
- Division of Chemistry and Chemical
Engineering , California Institute of Technology, Pasadena, California 91125, United States
| | - Robert J. Nielsen
- Materials and Process Simulation
Center, California Institute of Technology, Pasadena, California 91125, United States
| | - William A. Goddard
- Materials and Process Simulation
Center, California Institute of Technology, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and Chemical
Engineering , California Institute of Technology, Pasadena, California 91125, United States
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25
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Kanady JS, Tran R, Stull JA, Lu L, Stich TA, Day MW, Yano J, Britt RD, Agapie T. Role of Oxido Incorporation and Ligand Lability in Expanding Redox Accessibility of Structurally Related Mn 4 Clusters. Chem Sci 2013; 4:3986-3996. [PMID: 24163730 DOI: 10.1039/c3sc51406d] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Photosystem II supports four manganese centers through nine oxidation states from manganese(II) during assembly through to the most oxidized state before O2 formation and release. The protein-based carboxylate and imidazole ligands allow for significant changes of the coordination environment during the incorporation of hydroxido and oxido ligands upon oxidation of the metal centers. We report the synthesis and characterization of a series of tetramanganese complexes in four of the six oxidation states from MnII3MnIII to MnIII2 MnIV2 with the same ligand framework (L) by incorporating four oxido ligands. A 1,3,5-triarylbenzene framework appended with six pyridyl and three alkoxy groups was utilized along with three acetate anions to access tetramanganese complexes, Mn4O x , with x = 1, 2, 3, and 4. Alongside two previously reported complexes, four new clusters in various states were isolated and characterized by crystallography, and four were observed electrochemically, thus accessing the eight oxidation states from MnII4 to MnIIIMnIV3. This structurally related series of compounds was characterized by EXAFS, XANES, EPR, magnetism, and cyclic voltammetry. Similar to the ligands in the active site of the protein, the ancillary ligand (L) is preserved throughout the series and changes its binding mode between the low and high oxido-content clusters. Implications for the rational assembly and properties of high oxidation state metal-oxido clusters are presented.
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Affiliation(s)
- Jacob S Kanady
- Department of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd MC 127-72, Pasadena CA 91125, USA
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26
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What are the oxidation states of manganese required to catalyze photosynthetic water oxidation? Biophys J 2012; 103:313-22. [PMID: 22853909 DOI: 10.1016/j.bpj.2012.05.031] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 05/04/2012] [Accepted: 05/08/2012] [Indexed: 11/22/2022] Open
Abstract
Photosynthetic O(2) production from water is catalyzed by a cluster of four manganese ions and a tyrosine residue that comprise the redox-active components of the water-oxidizing complex (WOC) of photosystem II (PSII) in all known oxygenic phototrophs. Knowledge of the oxidation states is indispensable for understanding the fundamental principles of catalysis by PSII and the catalytic mechanism of the WOC. Previous spectroscopic studies and redox titrations predicted the net oxidation state of the S(0) state to be (Mn(III))(3)Mn(IV). We have refined a previously developed photoassembly procedure that directly determines the number of oxidizing equivalents needed to assemble the Mn(4)Ca core of WOC during photoassembly, starting from free Mn(II) and the Mn-depleted apo-WOC complex. This experiment entails counting the number of light flashes required to produce the first O(2) molecules during photoassembly. Unlike spectroscopic methods, this process does not require reference to synthetic model complexes. We find the number of photoassembly intermediates required to reach the lowest oxidation state of the WOC, S(0), to be three, indicating a net oxidation state three equivalents above four Mn(II), formally (Mn(III))(3)Mn(II), whereas the O(2) releasing state, S(4), corresponds formally to (Mn(IV))(3)Mn(III). The results from this study have major implications for proposed mechanisms of photosynthetic water oxidation.
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27
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Gao Y, Crabtree RH, Brudvig GW. Water Oxidation Catalyzed by the Tetranuclear Mn Complex [MnIV4O5(terpy)4(H2O)2](ClO4)6. Inorg Chem 2012; 51:4043-50. [DOI: 10.1021/ic2021897] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yunlong Gao
- Department of Chemistry, Yale University, New Haven, Connecticut
06520-8107, United States
| | - Robert H. Crabtree
- Department of Chemistry, Yale University, New Haven, Connecticut
06520-8107, United States
| | - Gary W. Brudvig
- Department of Chemistry, Yale University, New Haven, Connecticut
06520-8107, United States
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28
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Kanady JS, Tsui EY, Day MW, Agapie T. A Synthetic Model of the Mn3Ca Subsite of the Oxygen-Evolving Complex in Photosystem II. Science 2011; 333:733-6. [DOI: 10.1126/science.1206036] [Citation(s) in RCA: 455] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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29
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Assembly of the water-oxidizing complex in photosystem II. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:204-11. [DOI: 10.1016/j.jphotobiol.2011.02.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 01/27/2011] [Accepted: 02/03/2011] [Indexed: 11/21/2022]
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30
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Dismukes GC, Brimblecombe R, Felton GAN, Pryadun RS, Sheats JE, Spiccia L, Swiegers GF. Development of bioinspired Mn4O4-cubane water oxidation catalysts: lessons from photosynthesis. Acc Chem Res 2009; 42:1935-43. [PMID: 19908827 DOI: 10.1021/ar900249x] [Citation(s) in RCA: 478] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydrogen is the most promising fuel of the future owing to its carbon-free, high-energy content and potential to be efficiently converted into either electrical or thermal energy. The greatest technical barrier to accessing this renewable resource remains the inability to create inexpensive catalysts for the solar-driven oxidation of water. To date, the most efficient system that uses solar energy to oxidize water is the photosystem II water-oxidizing complex (PSII-WOC), which is found within naturally occurring photosynthetic organisms. The catalytic core of this enzyme is a CaMn(4)O(x) cluster, which is present in all known species of oxygenic phototrophs and has been conserved since the emergence of this type of photosynthesis about 2.5 billion years ago. The key features that facilitate the catalytic success of the PSII-WOC offer important lessons for the design of abiological water oxidation catalysts. In this Account, we examine the chemical principles that may govern the PSII-WOC by comparing the water oxidation capabilities of structurally related synthetic manganese-oxo complexes, particularly those with a cubical Mn(4)O(4) core ("cubanes"). We summarize this research, from the self-assembly of the first such clusters, through the elucidation of their mechanism of photoinduced rearrangement to release O(2), to recent advances highlighting their capability to catalyze sustained light-activated electrolysis of water. The [Mn(4)O(4)](6+) cubane core assembles spontaneously in solution from monomeric precursors or from [Mn(2)O(2)](3+) core complexes in the presence of metrically appropriate bidentate chelates, for example, diarylphosphinates (ligands of Ph(2)PO(2)(-) and 4-phenyl-substituted derivatives), which bridge pairs of Mn atoms on each cube face (Mn(4)O(4)L(6)). The [Mn(4)O(4)](6+) core is enlarged relative to the [Mn(2)O(2)](3+) core, resulting in considerably weaker Mn-O bonds. Cubanes are ferocious oxidizing agents, stronger than analogous complexes with the [Mn(2)O(2)](3+) core, as demonstrated both by the range of substrates they dehydrogenate or oxygenate (unactivated alkanes, for example) and the 25% larger O-H bond enthalpy of the resulting mu(3)-OH bridge. The cubane core topology is structurally suited to releasing O(2), and it does so in high yield upon removal of one phosphinate by photoexcitation in the gas phase or thermal excitation in the solid state. This is quite unlike other Mn-oxo complexes and can be attributed to the elongated Mn-O bond lengths and low-energy transition state to the mu-peroxo precursor. The photoproduct, [Mn(4)O(2)L(5)](+), an intact nonplanar butterfly core complex, is poised for oxidative regeneration of the cubane core upon binding of two water molecules and coupling to an anode. Catalytic evolution of O(2) and protons from water exceeding 1000 turnovers can be readily achieved by suspending the oxidized cubane, [Mn(4)O(4)L(6)](+), into a proton-conducting membrane (Nafion) preadsorbed onto a conducting electrode and electroxidizing the photoreduced butterfly complexes by the application of an external bias. Catalytic water oxidation can be achieved using sunlight as the only source of energy by replacing the external electrical bias with redox coupling to a photoanode incorporating a Ru(bipyridyl) dye.
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Affiliation(s)
- G. Charles Dismukes
- Department of Chemistry & Chemical Biology, Waksman Institute, Rutgers University, Piscataway, New Jersey 08854
| | - Robin Brimblecombe
- School of Chemistry, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540
| | - Greg A. N. Felton
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540
| | - Ruslan S. Pryadun
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540
| | - John E. Sheats
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540
| | - Leone Spiccia
- School of Chemistry, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - Gerhard F. Swiegers
- Intelligent Polymer Research Institute, University of Wollongong, Wollongong, New South Wales 2522, Australia
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Conlan B, Cox N, Su JH, Hillier W, Messinger J, Lubitz W, Dutton PL, Wydrzynski T. Photo-catalytic oxidation of a di-nuclear manganese centre in an engineered bacterioferritin ‘reaction centre’. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1112-21. [DOI: 10.1016/j.bbabio.2009.04.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 04/16/2009] [Accepted: 04/21/2009] [Indexed: 11/15/2022]
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Miqyass M, Marosvölgyi MA, Nagel Z, Yocum CF, van Gorkom HJ. S-State Dependence of the Calcium Requirement and Binding Characteristics in the Oxygen-Evolving Complex of Photosystem II. Biochemistry 2008; 47:7915-24. [DOI: 10.1021/bi8006059] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mohamed Miqyass
- Department of Biophysics, Huygens Laboratory, Leiden University, P.O. Box 9504, NL-2300 RA Leiden, The Netherlands, and Departments of MCD Biology and Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1048
| | - Marcell A. Marosvölgyi
- Department of Biophysics, Huygens Laboratory, Leiden University, P.O. Box 9504, NL-2300 RA Leiden, The Netherlands, and Departments of MCD Biology and Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1048
| | - Zachary Nagel
- Department of Biophysics, Huygens Laboratory, Leiden University, P.O. Box 9504, NL-2300 RA Leiden, The Netherlands, and Departments of MCD Biology and Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1048
| | - Charles F. Yocum
- Department of Biophysics, Huygens Laboratory, Leiden University, P.O. Box 9504, NL-2300 RA Leiden, The Netherlands, and Departments of MCD Biology and Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1048
| | - Hans J. van Gorkom
- Department of Biophysics, Huygens Laboratory, Leiden University, P.O. Box 9504, NL-2300 RA Leiden, The Netherlands, and Departments of MCD Biology and Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1048
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Pecoraro VL, Hsieh WY. In search of elusive high-valent manganese species that evaluate mechanisms of photosynthetic water oxidation. Inorg Chem 2008; 47:1765-78. [PMID: 18330968 DOI: 10.1021/ic7017488] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Significant progress in the understanding of biological water oxidation has occurred during the past 25 years. Today we have a somewhat clearer description of the structure of the Mn4Ca cluster and an idea of the appropriate oxidation states for the enzyme during catalysis. At issue is the mechanism of water oxidation. Depending on one's belief of the manganese ion oxidation levels at the catalytically active S4 configuration, one can invoke a variety of different processes that could lead to water oxidation. We have suggested that the most likely process is the nucleophilic attack of a water bound to calcium (or manganese) onto a highly electrophilic Mn(V)=O center. In this Article, we explore the difficulties of preparing Mn(V) in dimeric systems and the even more arduous task of definitively assigning oxidation states to such highly reactive species.
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Affiliation(s)
- Vincent L Pecoraro
- Department of Chemistry and Biophysics, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA.
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Bartlett JE, Baranov SV, Ananyev GM, Dismukes GC. Calcium controls the assembly of the photosynthetic water-oxidizing complex: a cadmium(II) inorganic mutant of the Mn4Ca core. Philos Trans R Soc Lond B Biol Sci 2008; 363:1253-61. [PMID: 17954439 DOI: 10.1098/rstb.2007.2222] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Perturbation of the catalytic inorganic core (Mn4Ca1OxCly) of the photosystem II-water-oxidizing complex (PSII-WOC) isolated from spinach is examined by substitution of Ca2+ with cadmium(II) during core assembly. Cd2+ inhibits the yield of reconstitution of O2-evolution activity, called photoactivation, starting from the free inorganic cofactors and the cofactor-depleted apo-WOC-PSII complex. Ca2+ affinity increases following photooxidation of the first Mn2+ to Mn3+ bound to the 'high-affinity' site. Ca2+ binding occurs in the dark and is the slowest overall step of photoactivation (IM1-->IM1* step). Cd2+ competitively blocks the binding of Ca2+ to its functional site with 10- to 30-fold higher affinity, but does not influence the binding of Mn2+ to its high-affinity site. By contrast, even 10-fold higher concentrations of Cd2+ have no effect on O2-evolution activity in intact PSII-WOC. Paradoxically, Cd2+ both inhibits photoactivation yield, while accelerating the rate of photoassembly of active centres 10-fold relative to Ca2+. Cd2+ increases the kinetic stability of the photooxidized Mn3+ assembly intermediate(s) by twofold (mean lifetime for dark decay). The rate data provide evidence that Cd2+ binding following photooxidation of the first Mn3+, IM1-->IM1*, causes three outcomes: (i) a longer intermediate lifetime that slows IM1 decay to IM0 by charge recombination, (ii) 10-fold higher probability of attaining the degrees of freedom (either or both cofactor and protein d.f.) needed to bind and photooxidize the remaining 3 Mn2+ that form the functional cluster, and (iii) increased lability of Cd2+ following Mn4 cluster assembly results in (re)exchange of Cd2+ by Ca2+ which restores active O2-evolving centres. Prior EPR spectroscopic data provide evidence for an oxo-bridged assembly intermediate, Mn3+(mu-O2(-))Ca2+, for IM1*. We postulate an analogous inhibited intermediate with Cd2+ replacing Ca2+.
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Affiliation(s)
- John E Bartlett
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
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35
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Geletii Y, Botar B, Kögerler P, Hillesheim D, Musaev D, Hill C. An All-Inorganic, Stable, and Highly Active Tetraruthenium Homogeneous Catalyst for Water Oxidation. Angew Chem Int Ed Engl 2008; 47:3896-9. [DOI: 10.1002/anie.200705652] [Citation(s) in RCA: 530] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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36
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Geletii Y, Botar B, Kögerler P, Hillesheim D, Musaev D, Hill C. An All-Inorganic, Stable, and Highly Active Tetraruthenium Homogeneous Catalyst for Water Oxidation. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200705652] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Dasgupta J, Ananyev GM, Dismukes GC. Photoassembly of the Water-Oxidizing Complex in Photosystem II. Coord Chem Rev 2008; 252:347-360. [PMID: 19190725 DOI: 10.1016/j.ccr.2007.08.022] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The light-driven steps in the biogenesis and repair of the inorganic core comprising the O(2)-evolving center of oxygenic photosynthesis (photosystem II water-oxidation complex, PSII-WOC) are reviewed. These steps, known collectively as photoactivation, involve the photoassembly of the free inorganic cofactors to the cofactor-depleted PSII-(apo-WOC) driven by light and produce the active O(2)-evolving core comprised of Mn(4)CaO(x)Cl(y). We focus on the functional role of the inorganic components as seen through the competition with non-native cofactors ("inorganic mutants") on water oxidation activity, the rate of the photoassembly reaction, and on structural insights gained from EPR spectroscopy of trapped intermediates formed in the initial steps of the assembly reaction. A chemical mechanism for the initial steps in photoactivation is given that is based on these data. Photoactivation experiments offer the powerful insights gained from replacement of the native cofactors, which together with the recent X-ray structural data for the resting holoenzyme provide a deeper understanding of the chemistry of water oxidation. We also review some new directions in research that photoactivation studies have inspired that look at the evolutionary history of this remarkable catalyst.
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Affiliation(s)
- Jyotishman Dasgupta
- 306 Lewis Hall, Department of Chemistry, University of California, Berkeley, CA 94709, USA
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Dasgupta J, Tyryshkin A, Dismukes G. ESEEM Spectroscopy Reveals Carbonate and an N-Donor Protein-Ligand Binding to Mn2+ in the Photoassembly Reaction of the Mn4Ca Cluster in Photosystem II. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200702347] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Dasgupta J, Tyryshkin AM, Dismukes GC. ESEEM Spectroscopy Reveals Carbonate and an N-Donor Protein-Ligand Binding to Mn2+ in the Photoassembly Reaction of the Mn4Ca Cluster in Photosystem II. Angew Chem Int Ed Engl 2007; 46:8028-31. [PMID: 17847136 DOI: 10.1002/anie.200702347] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Jyotishman Dasgupta
- 7 Hoyt Laboratory, Chemistry Department, Princeton University, Princeton, NJ 08544, USA
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Russell MJ. The alkaline solution to the emergence of life: energy, entropy and early evolution. Acta Biotheor 2007; 55:133-79. [PMID: 17704896 DOI: 10.1007/s10441-007-9018-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Accepted: 05/07/2007] [Indexed: 11/27/2022]
Abstract
The Earth agglomerates and heats. Convection cells within the planetary interior expedite the cooling process. Volcanoes evolve steam, carbon dioxide, sulfur dioxide and pyrophosphate. An acidulous Hadean ocean condenses from the carbon dioxide atmosphere. Dusts and stratospheric sulfurous smogs absorb a proportion of the Sun's rays. The cooled ocean leaks into the stressed crust and also convects. High temperature acid springs, coupled to magmatic plumes and spreading centers, emit iron, manganese, zinc, cobalt and nickel ions to the ocean. Away from the spreading centers cooler alkaline spring waters emanate from the ocean floor. These bear hydrogen, formate, ammonia, hydrosulfide and minor methane thiol. The thermal potential begins to be dissipated but the chemical potential is dammed. The exhaling alkaline solutions are frustrated in their further attempt to mix thoroughly with their oceanic source by the spontaneous precipitation of biomorphic barriers of colloidal iron compounds and other minerals. It is here we surmise that organic molecules are synthesized, filtered, concentrated and adsorbed, while acetate and methane--separate products of the precursor to the reductive acetyl-coenzyme-A pathway-are exhaled as waste. Reactions in mineral compartments produce acetate, amino acids, and the components of nucleosides. Short peptides, condensed from the simple amino acids, sequester 'ready-made' iron sulfide clusters to form protoferredoxins, and also bind phosphates. Nucleotides are assembled from amino acids, simple phosphates carbon dioxide and ribose phosphate upon nanocrystalline mineral surfaces. The side chains of particular amino acids register to fitting nucleotide triplet clefts. Keyed in, the amino acids are polymerized, through acid-base catalysis, to alpha chains. Peptides, the tenuous outer-most filaments of the nanocrysts, continually peel away from bound RNA. The polymers are concentrated at cooler regions of the mineral compartments through thermophoresis. RNA is reproduced through a convective polymerase chain reaction operating between 40 and 100 degrees C. The coded peptides produce true ferredoxins, the ubiquitous proteins with the longest evolutionary pedigree. They take over the role of catalyst and electron transfer agent from the iron sulfides. Other iron-nickel sulfide clusters, sequestered now by cysteine residues as CO-dehydrogenase and acetyl-coenzyme-A synthase, promote further chemosynthesis and support the hatchery--the electrochemical reactor--from which they sprang. Reactions and interactions fall into step as further pathways are negotiated. This hydrothermal circuitry offers a continuous supply of material and chemical energy, as well as electricity and proticity at a potential appropriate for the onset of life in the dark, a rapidly emerging kinetic structure born to persist, evolve and generate entropy while the sun shines.
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Affiliation(s)
- Michael J Russell
- Planetary Science and Life Detection Section 3220, MS:183-601, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109-8099, USA.
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