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Liu J, Yang KR, Long Z, Armstrong WH, Brudvig GW, Batista VS. Water Ligands Regulate the Redox Leveling Mechanism of the Oxygen-Evolving Complex of the Photosystem II. J Am Chem Soc 2024; 146:15986-15999. [PMID: 38833517 DOI: 10.1021/jacs.4c02926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
Understanding how water ligands regulate the conformational changes and functionality of the oxygen-evolving complex (OEC) in photosystem II (PSII) throughout the catalytic cycle of oxygen evolution remains a highly intriguing and unresolved challenge. In this study, we investigate the effect of water insertion (WI) on the redox state of the OEC by using the molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) hybrid methods. We find that water binding significantly reduces the free energy change for proton-coupled electron transfer (PCET) from Mn to YZ•, underscoring the important regulatory role of water binding, which is essential for enabling the OEC redox-leveling mechanism along the catalytic cycle. We propose a water binding mechanism in which WI is thermodynamically favored by the closed-cubane form of the OEC, with water delivery mediated by Ca2+ ligand exchange. Isomerization from the closed- to open-cubane conformation at three post-WI states highlights the importance of the location of the MnIII center in the OEC and the orientation of its Jahn-Teller axis to conformational changes of the OEC, which might be critical for the formation of the O-O bond. These findings reveal a complex interplay between conformational changes in the OEC and the ligand environment during the activation of the OEC by YZ•. Analogous regulatory effects due to water ligand binding are expected to be important for a wide range of catalysts activated by redox state transitions in aqueous environments.
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Affiliation(s)
- Jinchan Liu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Ke R Yang
- Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry, Nankai University, Tianjin 300071, China
| | - Zhuoran Long
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - William H Armstrong
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Gary W Brudvig
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Victor S Batista
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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2
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Koník P, Skotnicová P, Gupta S, Tichý M, Sharma S, Komenda J, Sobotka R, Krynická V. The cyanobacterial FtsH4 protease controls accumulation of protein factors involved in the biogenesis of photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2024; 1865:149017. [PMID: 37827327 DOI: 10.1016/j.bbabio.2023.149017] [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: 05/30/2023] [Revised: 09/18/2023] [Accepted: 10/04/2023] [Indexed: 10/14/2023]
Abstract
Membrane-bound FtsH proteases are universally present in prokaryotes and in mitochondria and chloroplasts of eukaryotic cells. These metalloproteases are often critical for viability and play both protease and chaperone roles to maintain cellular homeostasis. In contrast to most bacteria bearing a single ftsH gene, cyanobacteria typically possess four FtsH proteases (FtsH1-4) forming heteromeric (FtsH1/3 and FtsH2/3) and homomeric (FtsH4) complexes. The functions and substrate repertoire of each complex are however poorly understood. To identify substrates of the FtsH4 protease complex we established a trapping assay in the cyanobacterium Synechocystis PCC 6803 utilizing a proteolytically inactivated trapFtsH4-His. Around 40 proteins were specifically enriched in trapFtsH4 pulldown when compared with the active FtsH4. As the list of putative FtsH4 substrates contained Ycf4 and Ycf37 assembly factors of Photosystem I (PSI), its core PsaB subunit and the IsiA chlorophyll-binding protein that associates with PSI during iron stress, we focused on these PSI-related proteins. Therefore, we analysed their degradation by FtsH4 in vivo in Synechocystis mutants and in vitro using purified substrates. The data confirmed that FtsH4 degrades Ycf4, Ycf37, IsiA, and also the individual PsaA and PsaB subunits in the unassembled state but not when assembled within the PSI complexes. A possible role of FtsH4 in the PSI life-cycle is discussed.
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Affiliation(s)
- Peter Koník
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Třeboň 379 01, Czech Republic; Faculty of Science, University of South Bohemia, České Budějovice 370 05, Czech Republic
| | - Petra Skotnicová
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Třeboň 379 01, Czech Republic
| | - Sadanand Gupta
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Třeboň 379 01, Czech Republic; Faculty of Science, University of South Bohemia, České Budějovice 370 05, Czech Republic
| | - Martin Tichý
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Třeboň 379 01, Czech Republic
| | - Surbhi Sharma
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Třeboň 379 01, Czech Republic; Faculty of Science, University of South Bohemia, České Budějovice 370 05, Czech Republic
| | - Josef Komenda
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Třeboň 379 01, Czech Republic
| | - Roman Sobotka
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Třeboň 379 01, Czech Republic; Faculty of Science, University of South Bohemia, České Budějovice 370 05, Czech Republic
| | - Vendula Krynická
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Třeboň 379 01, Czech Republic.
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3
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Dumont R, Dowdell J, Song J, Li J, Wang S, Kang W, Li B. Control of charge transport in electronically active systems towards integrated biomolecular circuits (IbC). J Mater Chem B 2023; 11:8302-8314. [PMID: 37464922 DOI: 10.1039/d3tb00701d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
The miniaturization of traditional silicon-based electronics will soon reach its limitation as quantum tunneling and heat become serious problems at the several-nanometer scale. Crafting integrated circuits via self-assembly of electronically active molecules using a "bottom-up" paradigm provides a potential solution to these technological challenges. In particular, integrated biomolecular circuits (IbC) offer promising advantages to achieve this goal, as nature offers countless examples of functionalities entailed by self-assembly and examples of controlling charge transport at the molecular level within the self-assembled structures. To this end, the review summarizes the progress in understanding how charge transport is regulated in biosystems and the key redox-active amino acids that enable the charge transport. In addition, charge transport mechanisms at different length scales are also reviewed, offering key insights for controlling charge transport in IbC in the future.
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Affiliation(s)
- Ryan Dumont
- Department of Mechanical Engineering, Kennesaw State University, Marietta, GA, USA.
| | - Juwaan Dowdell
- Department of Mechanical Engineering, Kennesaw State University, Marietta, GA, USA.
| | - Jisoo Song
- Department of Mechanical Engineering, Kennesaw State University, Marietta, GA, USA.
| | - Jiani Li
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials Oriented Chemical Engineering, School of Bioengineering, Dalian University of Technology, Dalian, China.
| | - Suwan Wang
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials Oriented Chemical Engineering, School of Bioengineering, Dalian University of Technology, Dalian, China.
| | - Wei Kang
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials Oriented Chemical Engineering, School of Bioengineering, Dalian University of Technology, Dalian, China.
- Ningbo Institute of Dalian University of Technology, Ningbo, China
| | - Bo Li
- Department of Mechanical Engineering, Kennesaw State University, Marietta, GA, USA.
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4
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Lambertz J, Meier-Credo J, Kucher S, Bordignon E, Langer JD, Nowaczyk MM. Isolation of a novel heterodimeric PSII complex via strep-tagged PsbO. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148953. [PMID: 36572329 DOI: 10.1016/j.bbabio.2022.148953] [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: 06/15/2022] [Revised: 11/28/2022] [Accepted: 12/14/2022] [Indexed: 12/24/2022]
Abstract
The multi-subunit membrane protein complex photosystem II (PSII) catalyzes the light-driven oxidation of water and with this the initial step of photosynthetic electron transport in plants, algae, and cyanobacteria. Its biogenesis is coordinated by a network of auxiliary proteins that facilitate the stepwise assembly of individual subunits and cofactors, forming various intermediate complexes until fully functional mature PSII is present at the end of the process. In the current study, we purified PSII complexes from a mutant line of the thermophilic cyanobacterium Thermosynechococcus vestitus BP-1 in which the extrinsic subunit PsbO, characteristic for active PSII, was fused with an N-terminal Twin-Strep-tag. Three distinct PSII complexes were separated by ion-exchange chromatography after the initial affinity purification. Two complexes differ in their oligomeric state (monomeric and dimeric) but share the typical subunit composition of mature PSII. They are characterized by the very high oxygen evolving activity of approx. 6000 μmol O2·(mg Chl·h)-1. Analysis of the third (heterodimeric) PSII complex revealed lower oxygen evolving activity of approx. 3000 μmol O2·(mg Chl·h)-1 and a manganese content of 2.7 (±0.2) per reaction center compared to 3.7 (±0.2) of fully active PSII. Mass spectrometry and time-resolved fluorescence spectroscopy further indicated that PsbO is partially replaced by Psb27 in this PSII fraction, thus implying a role of this complex in PSII repair.
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Affiliation(s)
- Jan Lambertz
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitätsstraße 150, 44801 Bochum, Germany
| | - Jakob Meier-Credo
- Proteomics, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany
| | - Svetlana Kucher
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, 44801 Bochum, Germany
| | - Enrica Bordignon
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, 44801 Bochum, Germany; Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, 1211 Geneva, Switzerland(1)
| | - Julian D Langer
- Proteomics, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany; Proteomics, Max Planck Institute for Brain Research, Max-von-Laue-Str. 4, 60438 Frankfurt am Main, Germany
| | - Marc M Nowaczyk
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitätsstraße 150, 44801 Bochum, Germany; Department of Biochemistry, University of Rostock, Albert-Einstein-Str. 3, 18059 Rostock, Germany(1).
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5
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Krynická V, Skotnicová P, Jackson PJ, Barnett S, Yu J, Wysocka A, Kaňa R, Dickman MJ, Nixon PJ, Hunter CN, Komenda J. FtsH4 protease controls biogenesis of the PSII complex by dual regulation of high light-inducible proteins. PLANT COMMUNICATIONS 2023; 4:100502. [PMID: 36463410 PMCID: PMC9860182 DOI: 10.1016/j.xplc.2022.100502] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 11/11/2022] [Accepted: 11/29/2022] [Indexed: 06/17/2023]
Abstract
FtsH proteases are membrane-embedded proteolytic complexes important for protein quality control and regulation of various physiological processes in bacteria, mitochondria, and chloroplasts. Like most cyanobacteria, the model species Synechocystis sp. PCC 6803 contains four FtsH homologs, FtsH1-FtsH4. FtsH1-FtsH3 form two hetero-oligomeric complexes, FtsH1/3 and FtsH2/3, which play a pivotal role in acclimation to nutrient deficiency and photosystem II quality control, respectively. FtsH4 differs from the other three homologs by the formation of a homo-oligomeric complex, and together with Arabidopsis thaliana AtFtsH7/9 orthologs, it has been assigned to another phylogenetic group of unknown function. Our results exclude the possibility that Synechocystis FtsH4 structurally or functionally substitutes for the missing or non-functional FtsH2 subunit in the FtsH2/3 complex. Instead, we demonstrate that FtsH4 is involved in the biogenesis of photosystem II by dual regulation of high light-inducible proteins (Hlips). FtsH4 positively regulates expression of Hlips shortly after high light exposure but is also responsible for Hlip removal under conditions when their elevated levels are no longer needed. We provide experimental support for Hlips as proteolytic substrates of FtsH4. Fluorescent labeling of FtsH4 enabled us to assess its localization using advanced microscopic techniques. Results show that FtsH4 complexes are concentrated in well-defined membrane regions at the inner and outer periphery of the thylakoid system. Based on the identification of proteins that co-purified with the tagged FtsH4, we speculate that FtsH4 concentrates in special compartments in which the biogenesis of photosynthetic complexes takes place.
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Affiliation(s)
- Vendula Krynická
- The Czech Academy of Sciences, Institute of Microbiology, Centre Algatech, Novohradská 237, 379 01 Třeboň, Czech Republic.
| | - Petra Skotnicová
- The Czech Academy of Sciences, Institute of Microbiology, Centre Algatech, Novohradská 237, 379 01 Třeboň, Czech Republic
| | - Philip J Jackson
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK; Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, UK
| | - Samuel Barnett
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Jianfeng Yu
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, South Kensington Campus, Imperial College London, London SW7 2AZ, UK
| | - Anna Wysocka
- The Czech Academy of Sciences, Institute of Microbiology, Centre Algatech, Novohradská 237, 379 01 Třeboň, Czech Republic; Faculty of Science, University of South Bohemia, 370 05 České Budějovice, Czech Republic
| | - Radek Kaňa
- The Czech Academy of Sciences, Institute of Microbiology, Centre Algatech, Novohradská 237, 379 01 Třeboň, Czech Republic
| | - Mark J Dickman
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, UK
| | - Peter J Nixon
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, South Kensington Campus, Imperial College London, London SW7 2AZ, UK
| | - C Neil Hunter
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Josef Komenda
- The Czech Academy of Sciences, Institute of Microbiology, Centre Algatech, Novohradská 237, 379 01 Třeboň, Czech Republic
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6
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Shimada Y, Sugiyama A, Nagao R, Noguchi T. Role of D1-Glu65 in Proton Transfer during Photosynthetic Water Oxidation in Photosystem II. J Phys Chem B 2022; 126:8202-8213. [PMID: 36199221 DOI: 10.1021/acs.jpcb.2c05869] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Photosynthetic water oxidation takes place at the Mn4CaO5 cluster in photosystem II (PSII) through a light-driven cycle of five intermediates called S states (S0-S4). Although the PSII structures have shown the presence of several channels around the Mn4CaO5 cluster leading to the lumen, the pathways for proton release in the individual S-state transitions remain unidentified. Here, we studied the involvement of the so-called Cl channel in proton transfer during water oxidation by examining the effect of the mutation of D1-Glu65, a key residue in this channel, to Ala using Fourier transform infrared difference and time-resolved infrared spectroscopies together with thermoluminescence and delayed luminescence measurements. It was shown that the structure and the redox property of the catalytic site were little affected by the D1-Glu65Ala mutation. In the S2 → S3 transition, the efficiency was still high and the transition rate was only moderately retarded in the D1-Glu65Ala mutant. In contrast, the S3 → S0 transition was significantly inhibited by this mutation. These results suggest that proton transfer in the S2 → S3 transition occurs through multiple pathways including the Cl channel, whereas this channel likely serves as a single pathway for proton exit in the S3 → S0 transition.
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Affiliation(s)
- Yuichiro Shimada
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
| | - Ayane Sugiyama
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
| | - Ryo Nagao
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan.,Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Okayama700-8530, Japan
| | - Takumi Noguchi
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
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7
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Su Q, Zheng J, Xi J, Yang J, Wang L, Xiong D. Evaluation of the acute toxic response induced by triazophos to the non-target green algae Chlorella pyrenoidosa. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2022; 182:105036. [PMID: 35249646 DOI: 10.1016/j.pestbp.2022.105036] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 12/22/2021] [Accepted: 01/03/2022] [Indexed: 06/14/2023]
Abstract
Residues of triazophos in aquatic ecosystems due to extensive use for controlling pests in agriculture has became worldwide concern, while the toxic response of triazophos on the non-target green algae in aquatic environment is not well studied. Therefore, the acute (96 h) toxic effects of 1 and 10 mg/L triazophos on green algae Chlorella pyrenoidosa were evaluated in present study. The results showed that the growth was notably inhibited when treated with triazophos and the 96 h-EC50 (median inhibition concentration) were 12.79 mg/L. The content of photosynthetic pigments (including chl a, chl b, total-chl and carotinoids) clearly decreased under two treatments after 48 h and 96 h with exception for the values at 48 h exposure in 1 mg/L treatment. In addition, the transcript abundance of photosynthesis-related genes (psbA, psbC and rbcL) showed obvious decrease in above two treatments after exposure 96 h to triazophos. In response to 10 mg/L triazophos treatment, the morphology of thylakoid chloroplast of algal cells were obviously damaged. It was also found that starch granules increased with down-regulation of atpB gene expression in 10 mg/L treatment, which suggests that triazophos may inhibit the energy metabolism of C. pyrenoidosa. Moreover, the algal growth inhibition was along with the increase of intracellular reactive oxygen species (ROS), activity of antioxidant enzymes and malondialdehyde content indicating oxidative damage and lipid peroxidation in the algal cells. Our findings reveal that triazophos has potential toxicity and environmental risks to one of the primary producers green algae.
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Affiliation(s)
- Qi Su
- College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Juan Zheng
- Shaanxi Environmental Investigation and Assessment Center, Xi'an, Shaanxi 710054, China
| | - Jiejun Xi
- College of Grassland Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Jing Yang
- Chinese Sturgeon Research Institute, China Three Gorges Corporation, Yichang, Hubei 443100, China
| | - Lixin Wang
- College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China.
| | - Dongmei Xiong
- College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China.
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8
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Gao L, Cui X, Sewell CD, Li J, Lin Z. Recent advances in activating surface reconstruction for the high-efficiency oxygen evolution reaction. Chem Soc Rev 2021; 50:8428-8469. [PMID: 34259239 DOI: 10.1039/d0cs00962h] [Citation(s) in RCA: 195] [Impact Index Per Article: 65.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A climax in the development of cost-effective and high-efficiency transition metal-based electrocatalysts has been witnessed recently for sustainable energy and related conversion technologies. In this regard, structure-activity relationships based on several descriptors have already been proposed to rationally design electrocatalysts. However, the dynamic reconstruction of the surface structures and compositions of catalysts during electrocatalytic water oxidation, especially during the anodic oxygen evolution reaction (OER), complicate the streamlined prediction of the catalytic activity. With the achievements in operando and in situ techniques, it has been found that electrocatalysts undergo surface reconstruction to form the actual active species in situ accompanied with an increase in their oxidation state during OER in alkaline solution. Accordingly, a thorough understanding of the surface reconstruction process plays a critical role in establishing unambiguous structure-composition-property relationships in pursuit of high-efficiency electrocatalysts. However, several issues still need to be explored before high electrocatalytic activities can be realized, as follows: (1) the identification of initiators and pathways for surface reconstruction, (2) establishing the relationships between structure, composition, and electrocatalytic activity, and (3) the rational manipulation of in situ catalyst surface reconstruction. In this review, the recent progress in the surface reconstruction of transition metal-based OER catalysts including oxides, non-oxides, hydroxides and alloys is summarized, emphasizing the fundamental understanding of reconstruction behavior from the original precatalysts to the actual catalysts based on operando analysis and theoretical calculations. The state-of-the-art strategies to tailor the surface reconstruction such as substituting/doping with metals, introducing anions, incorporating oxygen vacancies, tuning morphologies and exploiting plasmonic/thermal/photothermal effects are then introduced. Notably, comprehensive operando/in situ characterization together with computational calculations are responsible for unveiling the improvement mechanism for OER. By delivering the progress, strategies, insights, techniques, and perspectives, this review will provide a comprehensive understanding of the surface reconstruction in transition metal-based OER catalysts and future guidelines for their rational development.
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Affiliation(s)
- Likun Gao
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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Baituti B, Odisitse S. A Computational Study of the S 2 State in the Oxygen-Evolving Complex of Photosystem II by Electron Paramagnetic Resonance Spectroscopy. Molecules 2021; 26:2699. [PMID: 34064533 PMCID: PMC8125536 DOI: 10.3390/molecules26092699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/22/2021] [Accepted: 04/24/2021] [Indexed: 11/16/2022] Open
Abstract
The S2 state produces two basic electron paramagnetic resonance signal types due to the manganese cluster in oxygen-evolving complex, which are influenced by the solvents, and cryoprotectant added to the photosystem II samples. It is presumed that a single manganese center oxidation occurs on S1 → S2 state transition. The S2 state has readily visible multiline and g4.1 electron paramagnetic resonance signals and hence it has been the most studied of all the Kok cycle intermediates due to the ease of experimental preparation and stability. The S2 state was studied using electron paramagnetic resonance spectroscopy at X-band frequencies. The aim of this study was to determine the spin states of the g4.1 signal. The multiline signal was observed to arise from a ground state spin ½ centre while the g4.1 signal generated at ≈140 K NIR illumination was proposed to arise from a spin 52 center with rhombic distortion. The 'ground' state g4.1 signal was generated solely or by conversion from the multiline. The data analysis methods used involved numerical simulations of the experimental spectra on relevant models of the oxygen-evolving complex cluster. A strong focus in this paper was on the 'ground' state g4.1 signal, whether it is a rhombic 52 spin state signal or an axial 32 spin state signal. The data supported an X-band CW-EPR-generated g4.1 signal as originating from a near rhombic spin 5/2 of the S2 state of the PSII manganese cluster.
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Affiliation(s)
- Bernard Baituti
- Department of Chemical and Forensic Science, Faculty of Science, Botswana International University of Science and Technology, Private Bag 16, Palapye, Botswana;
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10
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Li Y, Liu X, Zheng X, Yang M, Gao X, Huang J, Zhang L, Fan Z. Toxic effects and mechanisms of PFOA and its substitute GenX on the photosynthesis of Chlorella pyrenoidosa. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 765:144431. [PMID: 33387923 DOI: 10.1016/j.scitotenv.2020.144431] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 12/07/2020] [Accepted: 12/08/2020] [Indexed: 06/12/2023]
Abstract
Perfluorooctanoic acid (PFOA) and its substitute GenX are toxic chemicals that are widespread in the aquatic environment. However, there is little information about their toxicity mechanisms to aquatic organisms. In this study, Chlorella pyrenoidosa (C. pyrenoidosa) was treated with two concentrations (100 ng L-1 and 100 μg L-1) of PFOA or GenX for 12 days. The results showed that these two concentrations of PFOA and GenX began to inhibit the growth of algae after 6 days of treatment, and the Chlorophyll content and photosynthetic activity of C. pyrenoidosa were also negatively affected by these two chemicals. The transcriptomic results indicated that most of the genes related to the photosynthetic metabolism of C. pyrenoidosa were down-regulated (in 100 ng L-1 treatment groups) on the 12th day. Besides, GenX and PFOA showed similar effects on algae photosynthesis including physical damage and metabolic disorders. According to this study, GenX might not be an ideal substitute for PFOA, and more attention should be paid on the management of emerging perfluoroalkyl substances.
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Affiliation(s)
- Yanyao Li
- Department of Environmental Science & Engineering, Fudan University, Shanghai 200438. China
| | - Xianglin Liu
- Department of Environmental Science & Engineering, Fudan University, Shanghai 200438. China
| | - Xiaowei Zheng
- Department of Environmental Science & Engineering, Fudan University, Shanghai 200438. China
| | - Meng Yang
- Department of Environmental Science & Engineering, Fudan University, Shanghai 200438. China
| | - Xutao Gao
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Jingling Huang
- Department of Environmental Science & Engineering, Fudan University, Shanghai 200438. China
| | - Liangliang Zhang
- Department of Environmental Science & Engineering, Fudan University, Shanghai 200438. China
| | - Zhengqiu Fan
- Department of Environmental Science & Engineering, Fudan University, Shanghai 200438. China.
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11
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Mamedov MD, Milanovsky GE, Malferrari M, Vitukhnovskaya LA, Francia F, Semenov AY, Venturoli G. Trehalose matrix effects on electron transfer in Mn-depleted protein-pigment complexes of Photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2021; 1862:148413. [PMID: 33716033 DOI: 10.1016/j.bbabio.2021.148413] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 02/15/2021] [Accepted: 03/07/2021] [Indexed: 11/18/2022]
Abstract
The kinetics of flash-induced re-reduction of the Photosystem II (PS II) primary electron donor P680 was studied in solution and in trehalose glassy matrices at different relative humidity. In solution, and in the re-dissolved glass, kinetics were dominated by two fast components with lifetimes in the range of 2-7 μs, which accounted for >85% of the decay. These components were ascribed to the direct electron transfer from the redox-active tyrosine YZ to P680+. The minor slower components were due to charge recombination between the primary plastoquinone acceptor QA- and P680+. Incorporation of the PS II complex into the trehalose glassy matrix and its successive dehydration caused a progressive increase in the lifetime of all kinetic phases, accompanied by an increase of the amplitudes of the slower phases at the expense of the faster phases. At 63% relative humidity the fast components contribution dropped to ~50%. A further dehydration of the trehalose glass did not change the lifetimes and contribution of the kinetic components. This effect was ascribed to the decrease of conformational mobility of the protein domain between YZ and P680, which resulted in the inhibition of YZ → P680+ electron transfer in about half of the PS II population, wherein the recombination between QA- and P680+ occurred. The data indicate that PS II binds a larger number of water molecules as compared to PS I complexes. We conclude that our data disprove the "water replacement" hypothesis of trehalose matrix biopreservation.
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Affiliation(s)
- Mahir D Mamedov
- A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Leninskye gory, 1, b.40, Russia
| | - Georgy E Milanovsky
- A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Leninskye gory, 1, b.40, Russia
| | - Marco Malferrari
- Laboratory of Biochemistry and Molecular Biophysics, Department of Pharmacy and Biotechnology, FaBiT, University of Bologna, Bologna, Via Irnerio, 42, Italy
| | - Liya A Vitukhnovskaya
- A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Leninskye gory, 1, b.40, Russia; N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Moscow, 119991, Kosygina Street, 4, b.1, Russia
| | - Francesco Francia
- Laboratory of Biochemistry and Molecular Biophysics, Department of Pharmacy and Biotechnology, FaBiT, University of Bologna, Bologna, Via Irnerio, 42, Italy
| | - Alexey Yu Semenov
- A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Leninskye gory, 1, b.40, Russia; N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Moscow, 119991, Kosygina Street, 4, b.1, Russia.
| | - Giovanni Venturoli
- Laboratory of Biochemistry and Molecular Biophysics, Department of Pharmacy and Biotechnology, FaBiT, University of Bologna, Bologna, Via Irnerio, 42, Italy; Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, CNISM, c/o Department of Physics and Astronomy "Augusto Righi", DIFA, University of Bologna, Bologna, Via Irnerio, 46, Italy.
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12
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Nakamura S, Capone M, Mattioli G, Guidoni L. Early-stage formation of (hydr)oxo bridges in transition-metal catalysts for photosynthetic processes. Catal Sci Technol 2021. [DOI: 10.1039/d0cy02227f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ab initio simulations have been used to assess reaction pathways for the formation of M–(hydr)oxo–M (M = Co, Mn, Ni) bridges from M(ii) aqueous solutions, as early-stage building blocks of transition-metal catalysts for oxygen evolution.
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Affiliation(s)
- Shin Nakamura
- Department of Biochemical Sciences “A. Rossi Fanelli”
- Sapienza University of Rome
- Rome
- Italy
| | - Matteo Capone
- Department of physical and chemical science
- Università dell'Aquila
- L'Aquila
- Italy
| | - Giuseppe Mattioli
- Istituto di Struttura della Materia del CNR (ISM-CNR)
- I-00015 Monterotondo Scalo
- Italy
| | - Leonardo Guidoni
- Department of physical and chemical science
- Università dell'Aquila
- L'Aquila
- Italy
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13
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Ghosh I, Banerjee G, Reiss K, Kim CJ, Debus RJ, Batista VS, Brudvig GW. D1-S169A substitution of photosystem II reveals a novel S 2-state structure. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148301. [PMID: 32860756 DOI: 10.1016/j.bbabio.2020.148301] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 08/18/2020] [Accepted: 08/22/2020] [Indexed: 10/23/2022]
Abstract
In photosystem II (PSII), photosynthetic water oxidation occurs at the O2-evolving complex (OEC), a tetramanganese-calcium cluster that cycles through light-induced redox intermediates (S0-S4) to produce oxygen from two substrate water molecules. The OEC is surrounded by a hydrogen-bonded network of amino-acid residues that plays a crucial role in proton transfer and substrate water delivery. Previously, we found that D1-S169 was crucial for water oxidation and its mutation to alanine perturbed the hydrogen-bonding network. In this study, we demonstrate that the activation energy for the S2 to S1 transition of D1-S169A PSII is higher than wild-type PSII with a ~1.7-2.7× slower rate of charge recombination with QA- relative to wild-type PSII. Arrhenius analysis of the decay kinetics shows an Ea of 5.87 ± 1.15 kcal mol-1 for decay back to the S1 state, compared to 0.80 ± 0.13 kcal mol-1 for the wild-type S2 state. In addition, we find that ammonia does not affect the S2-state EPR signal, indicating that ammonia does not bind to the Mn cluster in D1-S169A PSII. Finally, a QM/MM analysis indicates that an additional water molecule binds to the Mn4 ion in place of an oxo ligand O5 in the S2 state of D1-S169A PSII. The altered S2 state of D1-S169A PSII provides insight into the S2➔S3 state transition.
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Affiliation(s)
- Ipsita Ghosh
- Department of Chemistry, Yale University, New Haven, CT 06520-8107, USA
| | - Gourab Banerjee
- Department of Chemistry, Yale University, New Haven, CT 06520-8107, USA
| | - Krystle Reiss
- Department of Chemistry, Yale University, New Haven, CT 06520-8107, USA
| | - Christopher J Kim
- Department of Biochemistry, University of California, Riverside, CA 92521, USA
| | - Richard J Debus
- Department of Biochemistry, University of California, Riverside, CA 92521, USA.
| | - Victor S Batista
- Department of Chemistry, Yale University, New Haven, CT 06520-8107, USA
| | - Gary W Brudvig
- Department of Chemistry, Yale University, New Haven, CT 06520-8107, USA.
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14
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Kim CJ, Debus RJ. Roles of D1-Glu189 and D1-Glu329 in O2 Formation by the Water-Splitting Mn4Ca Cluster in Photosystem II. Biochemistry 2020; 59:3902-3917. [DOI: 10.1021/acs.biochem.0c00541] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Christopher J. Kim
- Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Richard J. Debus
- Department of Biochemistry, University of California, Riverside, California 92521, United States
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15
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Recent advances in heterogeneous Mn-based electrocatalysts toward biological photosynthetic Mn4Ca cluster. Catal Today 2020. [DOI: 10.1016/j.cattod.2016.12.041] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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16
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Transcriptomic analysis of hydrogen photoproduction in Chlorella pyrenoidosa under nitrogen deprivation. ALGAL RES 2020. [DOI: 10.1016/j.algal.2020.101827] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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17
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Schenck CA, Westphal J, Jayaraman D, Garcia K, Wen J, Mysore KS, Ané J, Sumner LW, Maeda HA. Role of cytosolic, tyrosine-insensitive prephenate dehydrogenase in Medicago truncatula. PLANT DIRECT 2020; 4:e00218. [PMID: 32368714 PMCID: PMC7196213 DOI: 10.1002/pld3.218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 03/21/2020] [Accepted: 03/25/2020] [Indexed: 05/26/2023]
Abstract
l-Tyrosine (Tyr) is an aromatic amino acid synthesized de novo in plants and microbes downstream of the shikimate pathway. In plants, Tyr and a Tyr pathway intermediate, 4-hydroxyphenylpyruvate (HPP), are precursors to numerous specialized metabolites, which are crucial for plant and human health. Tyr is synthesized in the plastids by a TyrA family enzyme, arogenate dehydrogenase (ADH/TyrAa), which is feedback inhibited by Tyr. Additionally, many legumes possess prephenate dehydrogenases (PDH/TyrAp), which are insensitive to Tyr and localized to the cytosol. Yet the role of PDH enzymes in legumes is currently unknown. This study isolated and characterized Tnt1-transposon mutants of MtPDH1 (pdh1) in Medicago truncatula to investigate PDH function. The pdh1 mutants lacked PDH transcript and PDH activity, and displayed little aberrant morphological phenotypes under standard growth conditions, providing genetic evidence that MtPDH1 is responsible for the PDH activity detected in M. truncatula. Though plant PDH enzymes and activity have been specifically found in legumes, nodule number and nitrogenase activity of pdh1 mutants were not significantly reduced compared with wild-type (Wt) during symbiosis with nitrogen-fixing bacteria. Although Tyr levels were not significantly different between Wt and mutants under standard conditions, when carbon flux was increased by shikimate precursor feeding, mutants accumulated significantly less Tyr than Wt. These data suggest that MtPDH1 is involved in Tyr biosynthesis when the shikimate pathway is stimulated and possibly linked to unidentified legume-specific specialized metabolism.
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Affiliation(s)
- Craig A. Schenck
- Department of BotanyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Present address:
Department of Biochemistry and Molecular BiologyMichigan State UniversityEast LansingMIUSA
| | - Josh Westphal
- Department of BotanyUniversity of Wisconsin‐MadisonMadisonWIUSA
| | | | - Kevin Garcia
- Department of BacteriologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of Crop and Soil SciencesNorth Carolina State UniversityRaleighNCUSA
| | | | | | - Jean‐Michel Ané
- Department of BacteriologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of AgronomyUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Lloyd W. Sumner
- Department of BiochemistryUniversity of MissouriColumbiaMOUSA
- Metabolomics and Bond Life Sciences CentersUniversity of MissouriColumbiaMOUSA
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18
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Schenck CA, Maeda HA. Tyrosine biosynthesis, metabolism, and catabolism in plants. PHYTOCHEMISTRY 2018; 149:82-102. [PMID: 29477627 DOI: 10.1016/j.phytochem.2018.02.003] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 01/26/2018] [Accepted: 02/02/2018] [Indexed: 05/22/2023]
Abstract
L-Tyrosine (Tyr) is an aromatic amino acid (AAA) required for protein synthesis in all organisms, but synthesized de novo only in plants and microorganisms. In plants, Tyr also serves as a precursor of numerous specialized metabolites that have diverse physiological roles as electron carriers, antioxidants, attractants, and defense compounds. Some of these Tyr-derived plant natural products are also used in human medicine and nutrition (e.g. morphine and vitamin E). While the Tyr biosynthesis and catabolic pathways have been extensively studied in microbes and animals, respectively, those of plants have received much less attention until recently. Accumulating evidence suggest that the Tyr biosynthetic pathways differ between microbes and plants and even within the plant kingdom, likely to support the production of lineage-specific plant specialized metabolites derived from Tyr. The interspecies variations of plant Tyr pathway enzymes can now be used to enhance the production of Tyr and Tyr-derived compounds in plants and other synthetic biology platforms.
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Affiliation(s)
- Craig A Schenck
- Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Hiroshi A Maeda
- Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA.
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19
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Liu S, Lei YJ, Xin ZJ, Lu YB, Wang HY. Water splitting based on homogeneous copper molecular catalysts. J Photochem Photobiol A Chem 2018. [DOI: 10.1016/j.jphotochem.2017.09.060] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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20
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Li YF, Liu ZP. Active Site Revealed for Water Oxidation on Electrochemically Induced δ-MnO2: Role of Spinel-to-Layer Phase Transition. J Am Chem Soc 2018; 140:1783-1792. [DOI: 10.1021/jacs.7b11393] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ye-Fei Li
- Collaborative Innovation Center of
Chemistry for Energy Material, Key Laboratory of Computational Physical
Science (Ministry of Education), Shanghai Key Laboratory of Molecular
Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai 200433, China
| | - Zhi-Pan Liu
- Collaborative Innovation Center of
Chemistry for Energy Material, Key Laboratory of Computational Physical
Science (Ministry of Education), Shanghai Key Laboratory of Molecular
Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai 200433, China
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21
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Nakamura S, Noguchi T. Infrared Determination of the Protonation State of a Key Histidine Residue in the Photosynthetic Water Oxidizing Center. J Am Chem Soc 2017. [DOI: 10.1021/jacs.7b04924] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- 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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22
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Nagao R, Yamaguchi M, Nakamura S, Ueoka-Nakanishi H, Noguchi T. Genetically introduced hydrogen bond interactions reveal an asymmetric charge distribution on the radical cation of the special-pair chlorophyll P680. J Biol Chem 2017; 292:7474-7486. [PMID: 28302724 DOI: 10.1074/jbc.m117.781062] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2017] [Revised: 03/08/2017] [Indexed: 11/06/2022] Open
Abstract
The special-pair chlorophyll (Chl) P680 in photosystem II has an extremely high redox potential (Em ) to enable water oxidation in photosynthesis. Significant positive-charge localization on one of the Chl constituents, PD1 or PD2, in P680+ has been proposed to contribute to this high Em To identify the Chl molecule on which the charge is mainly localized, we genetically introduced a hydrogen bond to the 131-keto C=O group of PD1 and PD2 by changing the nearby D1-Val-157 and D2-Val-156 residues to His, respectively. Successful hydrogen bond formation at PD1 and PD2 in the obtained D1-V157H and D2-V156H mutants, respectively, was monitored by detecting 131-keto C=O vibrations in Fourier transfer infrared (FTIR) difference spectra upon oxidation of P680 and the symmetrically located redox-active tyrosines YZ and YD, and they were simulated by quantum-chemical calculations. Analysis of the P680+/P680 FTIR difference spectra of D1-V157H and D2-V156H showed that upon P680+ formation, the 131-keto C=O frequency upshifts by a much larger extent in PD1 (23 cm-1) than in PD2 (<9 cm-1). In addition, thermoluminescence measurements revealed that the D1-V157H mutation increased the Em of P680 to a larger extent than did the D2-V156H mutation. These results, together with the previous results for the mutants of the His ligands of PD1 and PD2, lead to a definite conclusion that a charge is mainly localized to PD1 in P680<sup/>.
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Affiliation(s)
- Ryo Nagao
- From the Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Motoki Yamaguchi
- From the Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Shin Nakamura
- From the Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Hanayo Ueoka-Nakanishi
- From the Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takumi Noguchi
- From the Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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23
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Najafpour MM, Heidari S, Balaghi SE, Hołyńska M, Sadr MH, Soltani B, Khatamian M, Larkum AW, Allakhverdiev SI. Proposed mechanisms for water oxidation by Photosystem II and nanosized manganese oxides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:156-174. [DOI: 10.1016/j.bbabio.2016.11.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 11/05/2016] [Accepted: 11/08/2016] [Indexed: 12/18/2022]
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24
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Yamamoto M, Tanaka K. Artificial Molecular Photosynthetic Systems: Towards Efficient Photoelectrochemical Water Oxidation. Chempluschem 2016; 81:1028-1044. [DOI: 10.1002/cplu.201600236] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Masanori Yamamoto
- Department of Molecular Engineering; Graduate School of Engineering; Kyoto University; Nishikyo-ku Kyoto 615-8510 Japan
| | - Koji Tanaka
- Advanced Chemical Technology Center in Kyoto; Institute for Integrated Cell-Material Sciences; Kyoto University; Jibucho 105, Fushimi-ku Kyoto 612-8374 Japan
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25
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Najafpour MM, Renger G, Hołyńska M, Moghaddam AN, Aro EM, Carpentier R, Nishihara H, Eaton-Rye JJ, Shen JR, Allakhverdiev SI. Manganese Compounds as Water-Oxidizing Catalysts: From the Natural Water-Oxidizing Complex to Nanosized Manganese Oxide Structures. Chem Rev 2016; 116:2886-936. [PMID: 26812090 DOI: 10.1021/acs.chemrev.5b00340] [Citation(s) in RCA: 332] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
All cyanobacteria, algae, and plants use a similar water-oxidizing catalyst for water oxidation. This catalyst is housed in Photosystem II, a membrane-protein complex that functions as a light-driven water oxidase in oxygenic photosynthesis. Water oxidation is also an important reaction in artificial photosynthesis because it has the potential to provide cheap electrons from water for hydrogen production or for the reduction of carbon dioxide on an industrial scale. The water-oxidizing complex of Photosystem II is a Mn-Ca cluster that oxidizes water with a low overpotential and high turnover frequency number of up to 25-90 molecules of O2 released per second. In this Review, we discuss the atomic structure of the Mn-Ca cluster of the Photosystem II water-oxidizing complex from the viewpoint that the underlying mechanism can be informative when designing artificial water-oxidizing catalysts. This is followed by consideration of functional Mn-based model complexes for water oxidation and the issue of Mn complexes decomposing to Mn oxide. We then provide a detailed assessment of the chemistry of Mn oxides by considering how their bulk and nanoscale properties contribute to their effectiveness as water-oxidizing catalysts.
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Affiliation(s)
| | - Gernot Renger
- Institute of Chemistry, Max-Volmer-Laboratory of Biophysical Chemistry, Technical University Berlin , Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Małgorzata Hołyńska
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften (WZMW), Philipps-Universität Marburg , Hans-Meerwein-Straße, D-35032 Marburg, Germany
| | | | - Eva-Mari Aro
- Department of Biochemistry and Food Chemistry, University of Turku , 20014 Turku, Finland
| | - Robert Carpentier
- Groupe de Recherche en Biologie Végétale (GRBV), Université du Québec à Trois-Rivières , C.P. 500, Trois-Rivières, Québec G9A 5H7, Canada
| | - Hiroshi Nishihara
- Department of Chemistry, School of Science, The University of Tokyo , 7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-0033, Japan
| | - Julian J Eaton-Rye
- Department of Biochemistry, University of Otago , P.O. Box 56, Dunedin 9054, New Zealand
| | - Jian-Ren Shen
- Photosynthesis Research Center, Graduate School of Natural Science and Technology, Faculty of Science, Okayama University , Okayama 700-8530, Japan.,Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences , Beijing 100093, China
| | - Suleyman I Allakhverdiev
- Controlled Photobiosynthesis Laboratory, Institute of Plant Physiology, Russian Academy of Sciences , Botanicheskaya Street 35, Moscow 127276, Russia.,Institute of Basic Biological Problems, Russian Academy of Sciences , Pushchino, Moscow Region 142290, Russia.,Department of Plant Physiology, Faculty of Biology, M.V. Lomonosov Moscow State University , Leninskie Gory 1-12, Moscow 119991, Russia
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26
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27
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Nakamura S, Noguchi T. Infrared Detection of a Proton Released from Tyrosine YD to the Bulk upon Its Photo-oxidation in Photosystem II. Biochemistry 2015; 54:5045-53. [PMID: 26241205 DOI: 10.1021/acs.biochem.5b00568] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photosystem II (PSII) has two symmetrically located, redox-active tyrosine residues, YZ and YD. Whereas YZ mediates the electron transfer from the water-oxidizing center to P680 in the main electron transfer pathway, YD functions as a peripheral electron donor to P680. To understand the mechanism of this functional difference between YZ and YD, it is essential to know where the proton is transferred upon its oxidation in the proton-coupled electron transfer process. In this study, we used Fourier transform infrared (FTIR) spectroscopy to examine whether the proton from YD is released from the protein into the bulk. The proton detection method previously used for water oxidation in PSII [Suzuki et al. (2009) J. Am. Chem. Soc. 131, 7849-7857] was applied to YD; a proton released into the bulk upon YD oxidation was trapped by a high-concentration Mes buffer, and the protonation reaction of Mes was monitored by FTIR difference spectroscopy. It was shown that 0.84 ± 0.10 protons are released into the bulk by oxidation of YD in one PSII center. This result indicates that the proton of YD is not transferred to the neighboring D2-His198 but is released from the protein; this is in sharp contrast to the YZ reaction, in which a proton is transferred to D1-His190 through a strong hydrogen bond. This functional difference is caused by differences in the hydrogen-bonded structures of YD and YZ, which are determined by the hydrogen bond partners at the Nπ sites of these His residues, i.e., D2-Arg294 and D1-Asn298, which function as a hydrogen bond donor and acceptor, respectively. This FTIR spectroscopy result supports the recent theoretical prediction [Saito et al. (2013) Proc. Natl. Acad. Sci. U.S.A. 110, 7690-7695] based on the X-ray crystallographic structure of PSII and explains the different rates of the redox reactions of YD and YZ.
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Affiliation(s)
- 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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28
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Du Q, Huang Z, Wu Z, Meng X, Yin G, Gao F, Wang L. Facile preparation and bifunctional imaging of Eu-doped GdPO4 nanorods with MRI and cellular luminescence. Dalton Trans 2015; 44:3934-40. [PMID: 25630852 DOI: 10.1039/c4dt03444a] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Eu-doped GdPO4 NRs coated by silk fibroin have been prepared in a template of silk fibroin (SF) peptides via a mineralization process. A growth mechanism of SF-NRs is proposed to explain their stronger luminescence, better cyto-compatibility and higher longitudinal relaxivity r1.
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Affiliation(s)
- Qijun Du
- College of Materials Science and Engineering
- Sichuan University
- Chengdu
- People's Republic of China
| | - Zhongbing Huang
- College of Materials Science and Engineering
- Sichuan University
- Chengdu
- People's Republic of China
| | - Zhi Wu
- College of Materials Science and Engineering
- Sichuan University
- Chengdu
- People's Republic of China
| | - Xianwei Meng
- Laboratory of Controllable Preparation and Application of Nanomaterials
- Research Center for Micro & Nano Materials and Technology
- Technical Institute of Physics and Chemistry
- Chinese Academy of Sciences
- Beijing 100190
| | - Guangfu Yin
- College of Materials Science and Engineering
- Sichuan University
- Chengdu
- People's Republic of China
| | - Fabao Gao
- Molecular Imaging Center
- Department of Radiology
- West China Hospital of Sichuan University
- Chengdu
- China
| | - Lei Wang
- Molecular Imaging Center
- Department of Radiology
- West China Hospital of Sichuan University
- Chengdu
- China
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29
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Yamaguchi A, Inuzuka R, Takashima T, Hayashi T, Hashimoto K, Nakamura R. Regulating proton-coupled electron transfer for efficient water splitting by manganese oxides at neutral pH. Nat Commun 2014; 5:4256. [PMID: 24977746 PMCID: PMC4083427 DOI: 10.1038/ncomms5256] [Citation(s) in RCA: 135] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 05/30/2014] [Indexed: 12/24/2022] Open
Abstract
Manganese oxides have been extensively investigated as model systems for the oxygen-evolving complex of photosystem II. However, most bioinspired catalysts are inefficient at neutral pH and functional similarity to the oxygen-evolving complex has been rarely achieved with manganese. Here we report the regulation of proton-coupled electron transfer involved in water oxidation by manganese oxides. Pyridine and its derivatives, which have pKa values intermediate to the water ligand bound to manganese(II) and manganese(III), are used as proton-coupled electron transfer induction reagents. The induction of concerted proton-coupled electron transfer is demonstrated by the detection of deuterium kinetic isotope effects and compliance of the reactions with the libido rule. Although proton-coupled electron transfer regulation is essential for the facial redox change of manganese in photosystem II, most manganese oxides impair these regulatory mechanisms. Thus, the present findings may provide a new design rationale for functional analogues of the oxygen-evolving complex for efficient water splitting at neutral pH. Manganese oxides are extensively investigated as analogues of nature's oxygen-evolving complex, but they rarely function at neutral pH. Here, the authors investigate the induction and regulation of the proton-coupled electron-transfer mechanism involved in water oxidation by manganese oxides.
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Affiliation(s)
- Akira Yamaguchi
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Riko Inuzuka
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Toshihiro Takashima
- Clean Energy Research Center, University of Yamanashi, Kofu, Yamanashi 400-8511, Japan
| | - Toru Hayashi
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Kazuhito Hashimoto
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Ryuhei Nakamura
- Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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Nakamura S, Nagao R, Takahashi R, Noguchi T. Fourier transform infrared detection of a polarizable proton trapped between photooxidized tyrosine YZ and a coupled histidine in photosystem II: relevance to the proton transfer mechanism of water oxidation. Biochemistry 2014; 53:3131-44. [PMID: 24786306 DOI: 10.1021/bi500237y] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The redox-active tyrosine YZ (D1-Tyr161) in photosystem II (PSII) functions as an immediate electron acceptor of the Mn4Ca cluster, which is the catalytic center of photosynthetic water oxidation. YZ is also located in the hydrogen bond network that connects the Mn4Ca cluster to the lumen and hence is possibly related to the proton transfer process during water oxidation. To understand the role of YZ in the water oxidation mechanism, we have studied the hydrogen bonding interactions of YZ and its photooxidized neutral radical YZ(•) together with the interaction of the coupled His residue, D1-His190, using light-induced Fourier transform infrared (FTIR) difference spectroscopy. The YZ(•)-minus-YZ FTIR difference spectrum of Mn-depleted PSII core complexes exhibited a broad positive feature around 2800 cm(-1), which was absent in the corresponding spectrum of another redox-active tyrosine YD (D2-Tyr160). Analyses by (15)N and H/D substitutions, examination of the pH dependence, and density functional theory and quantum mechanics/molecular mechanics (QM/MM) calculations showed that this band arises from the N-H stretching vibration of the protonated cation of D1-His190 forming a charge-assisted strong hydrogen bond with YZ(•). This result provides strong evidence that the proton released from YZ upon its oxidation is trapped in D1-His190 and a positive charge remains on this His. The broad feature of the ~2800 cm(-1) band reflects a large proton polarizability in the hydrogen bond between YZ(•) and HisH(+). QM/MM calculations further showed that upon YZ oxidation the hydrogen bond network is rearranged and one water molecule moves toward D1-His190. From these data, a novel proton transfer mechanism via YZ(•)-HisH(+) is proposed, in which hopping of the polarizable proton of HisH(+) to this water triggers the transfer of the proton from substrate water to the luminal side. This proton transfer mechanism could be functional in the S2 → S3 transition, which requires proton release before electron transfer because of an excess positive charge on the Mn4Ca cluster.
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Affiliation(s)
- Shin Nakamura
- Division of Material Science, Graduate School of Science, Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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Shinopoulos KE, Yu J, Nixon PJ, Brudvig GW. Using site-directed mutagenesis to probe the role of the D2 carotenoid in the secondary electron-transfer pathway of photosystem II. PHOTOSYNTHESIS RESEARCH 2014; 120:141-52. [PMID: 23334888 PMCID: PMC3961632 DOI: 10.1007/s11120-013-9793-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Accepted: 01/02/2013] [Indexed: 05/07/2023]
Abstract
Secondary electron transfer in photosystem II (PSII), which occurs when water oxidation is inhibited, involves redox-active carotenoids (Car), as well as chlorophylls (Chl), and cytochrome b 559 (Cyt b 559), and is believed to play a role in photoprotection. CarD2 may be the initial point of secondary electron transfer because it is the closest cofactor to both P680, the initial oxidant, and to Cyt b 559, the terminal secondary electron donor within PSII. In order to characterize the role of CarD2 and to determine the effects of perturbing CarD2 on both the electron-transfer events and on the identity of the redox-active cofactors, it is necessary to vary the properties of CarD2 selectively without affecting the ten other Car per PSII. To this end, site-directed mutations around the binding pocket of CarD2 (D2-G47W, D2-G47F, and D2-T50F) have been generated in Synechocystis sp. PCC 6803. Characterization by near-IR and EPR spectroscopy provides the first experimental evidence that CarD2 is one of the redox-active carotenoids in PSII. There is a specific perturbation of the Car(∙+) near-IR spectrum in all three mutated PSII samples, allowing the assignment of the spectral signature of Car D2 (∙+) ; Car D2 (∙+) exhibits a near-IR peak at 980 nm and is the predominant secondary donor oxidized in a charge separation at low temperature in ferricyanide-treated wild-type PSII. The yield of secondary donor radicals is substantially decreased in PSII complexes isolated from each mutant. In addition, the kinetics of radical formation are altered in the mutated PSII samples. These results are consistent with oxidation of CarD2 being the initial step in secondary electron transfer. Furthermore, normal light levels during mutant cell growth perturb the shape of the Chl(∙+) near-IR absorption peak and generate a dark-stable radical observable in the EPR spectra, indicating a higher susceptibility to photodamage further linking the secondary electron-transfer pathway to photoprotection.
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Affiliation(s)
| | - Jianfeng Yu
- Division of Molecular Biosciences, Sir Ernst Chain Building – Wolfson Laboratories, Imperial College London, S. Kensington campus, London, SW7 2AY UK
| | - Peter J. Nixon
- Division of Molecular Biosciences, Sir Ernst Chain Building – Wolfson Laboratories, Imperial College London, S. Kensington campus, London, SW7 2AY UK
| | - Gary W. Brudvig
- Department of Chemistry, Yale University, New Haven, CT 06520-8107 USA
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Keough JM, Zuniga AN, Jenson DL, Barry BA. Redox control and hydrogen bonding networks: proton-coupled electron transfer reactions and tyrosine Z in the photosynthetic oxygen-evolving complex. J Phys Chem B 2013; 117:1296-307. [PMID: 23346921 DOI: 10.1021/jp3118314] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In photosynthetic oxygen evolution, redox active tyrosine Z (YZ) plays an essential role in proton-coupled electron transfer (PCET) reactions. Four sequential photooxidation reactions are necessary to produce oxygen at a Mn(4)CaO(5) cluster. The sequentially oxidized states of this oxygen-evolving cluster (OEC) are called the S(n) states, where n refers to the number of oxidizing equivalents stored. The neutral radical, YZ•, is generated and then acts as an electron transfer intermediate during each S state transition. In the X-ray structure, YZ, Tyr161 of the D1 subunit, is involved in an extensive hydrogen bonding network, which includes calcium-bound water. In electron paramagnetic resonance experiments, we measured the YZ• recombination rate, in the presence of an intact Mn(4)CaO(5) cluster. We compared the S(0) and S(2) states, which differ in Mn oxidation state, and found a significant difference in the YZ• decay rate (t(1/2) = 3.3 ± 0.3 s in S(0); t(1/2) = 2.1 ± 0.3 s in S(2)) and in the solvent isotope effect (SIE) on the reaction (1.3 ± 0.3 in S(0); 2.1 ± 0.3 in S(2)). Although the YZ site is known to be solvent accessible, the recombination rate and SIE were pH independent in both S states. To define the origin of these effects, we measured the YZ• recombination rate in the presence of ammonia, which inhibits oxygen evolution and disrupts the hydrogen bond network. We report that ammonia dramatically slowed the YZ• recombination rate in the S(2) state but had a smaller effect in the S(0) state. In contrast, ammonia had no significant effect on YD•, the stable tyrosyl radical. Therefore, the alterations in YZ• decay, observed with S state advancement, are attributed to alterations in OEC hydrogen bonding and consequent differences in the YZ midpoint potential/pK(a). These changes may be caused by activation of metal-bound water molecules, which hydrogen bond to YZ. These observations document the importance of redox control in proton-coupled electron transfer reactions.
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Affiliation(s)
- James M Keough
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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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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Barry BA, Chen J, Keough J, Jenson D, Offenbacher A, Pagba C. Proton Coupled Electron Transfer and Redox Active Tyrosines: Structure and Function of the Tyrosyl Radicals in Ribonucleotide Reductase and Photosystem II. J Phys Chem Lett 2012; 3:543-554. [PMID: 22662289 PMCID: PMC3362996 DOI: 10.1021/jz2014117] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Proton coupled electron transfer (PCET) reactions are important in many biological processes. Tyrosine oxidation/reduction can play a critical role in facilitating these reactions. Two examples are photosystem II (PSII) and ribonucleotide reductase (RNR). RNR is essential in DNA synthesis in all organisms. In E. coli RNR, a tyrosyl radical, Y122(•), is required as a radical initiator. Photosystem II (PSII) generates molecular oxygen from water. In PSII, an essential tyrosyl radical, YZ(•), oxidizes the oxygen evolving center. However, the mechanisms, by which the extraordinary oxidizing power of the tyrosyl radical is controlled, are not well understood. This is due to the difficulty in acquiring high-resolution structural information about the radical state. Spectroscopic approaches, such as EPR and UV resonance Raman (UVRR), can give new information. Here, we discuss EPR studies of PCET and the PSII YZ radical. We also present UVRR results, which support the conclusion that Y122 undergoes an alteration in ring and backbone dihedral angle when it is oxidized. This conformational change results in a loss of hydrogen bonding to the phenolic oxygen. Our analysis suggests that access of water is an important factor in determining tyrosyl radical lifetime and function. TOC graphic.
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Renger G. Mechanism of light induced water splitting in Photosystem II of oxygen evolving photosynthetic organisms. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1164-76. [PMID: 22353626 DOI: 10.1016/j.bbabio.2012.02.005] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 01/27/2012] [Accepted: 02/05/2012] [Indexed: 11/24/2022]
Abstract
The reactions of light induced oxidative water splitting were analyzed within the framework of the empirical rate constant-distance relationship of non-adiabatic electron transfer in biological systems (C. C. Page, C. C. Moser, X. Chen , P. L. Dutton, Nature 402 (1999) 47-52) on the basis of structure information on Photosystem II (PS II) (A. Guskov, A. Gabdulkhakov, M. Broser, C. Glöckner, J. Hellmich, J. Kern, J. Frank, W. Saenger, A. Zouni, Chem. Phys. Chem. 11 (2010) 1160-1171, Y. Umena, K. Kawakami, J-R Shen, N. Kamiya, Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9Å. Nature 47 (2011) 55-60). Comparison of these results with experimental data leads to the following conclusions: 1) The oxidation of tyrosine Y(z) by the cation radical P680(+·) in systems with an intact water oxidizing complex (WOC) is kinetically limited by the non-adiabatic electron transfer step and the extent of this reaction is thermodynamically determined by relaxation processes in the environment including rearrangements of hydrogen bond network(s). In marked contrast, all Y(z)(ox) induced oxidation steps in the WOC up to redox state S(3) are kinetically limited by trigger reactions which are slower by orders of magnitude than the rates calculated for non-adiabatic electron transfer. 3) The overall rate of the triggered reaction sequence of Y(z)(ox) reduction by the WOC in redox state S(3) eventually leading to formation and release of O(2) is kinetically limited by an uphill electron transfer step. Alternative models are discussed for this reaction. The protein matrix of the WOC and bound water molecules provide an optimized dynamic landscape of hydrogen bonded protons for catalyzing oxidative water splitting energetically driven by light induced formation of the cation radical P680(+·). In this way the PS II core acts as a molecular machine formed during a long evolutionary process. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.
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Takashima T, Hashimoto K, Nakamura R. Mechanisms of pH-dependent activity for water oxidation to molecular oxygen by MnO2 electrocatalysts. J Am Chem Soc 2012; 134:1519-27. [PMID: 22206433 DOI: 10.1021/ja206511w] [Citation(s) in RCA: 257] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Manganese oxides function as efficient electrocatalysts for water oxidation to molecular oxygen in strongly alkaline conditions, but are inefficient at neutral pH. To provide new insight into the mechanism underlying the pH-dependent activity of the electrooxidation reaction, we performed UV-vis spectroelectrochemical detection of the intermediate species for water oxidation by a manganese oxide electrode. Layered manganese oxide nanoparticles, δ-MnO(2) (K(0.17)[Mn(4+)(0.90)Mn(3+)(0.07)□(0.03)]O(2)·0.53H(2)O) deposited on fluorine-doped tin oxide electrodes were shown to catalyze water oxidation at pH from 4 to 13. At this pH range, a sharp rise in absorption at 510 nm was observed with a concomitant increase of anodic current for O(2) evolution. Using pyrophosphate as a probe molecule, the 510 nm absorption was attributable to Mn(3+) on the surface of δ-MnO(2). The onset potential of the water oxidation current was constant at approximately 1.5 V vs SHE from pH 4 to pH 8, but sharply shifted to negative at pH > 8. Strikingly, this behavior was well reproduced by the pH dependence of the onset of 510 nm absorption, indicating that Mn(3+) acts as the precursor of water oxidation. Mn(3+) is unstable at pH < 9 due to the disproportionation reaction resulting in the formation of Mn(2+) and Mn(4+), whereas it is effectively stabilized by the comproportionation of Mn(2+) and Mn(4+) in alkaline conditions. Thus, the low activity of manganese oxides for water oxidation under neutral conditions is most likely due to the inherent instability of Mn(3+), whose accumulation at the surface of catalysts requires the electrochemical oxidation of Mn(2+) at a potential of approximately 1.4 V. This new model suggests that the control of the disproportionation and comproportionation efficiencies of Mn(3+) is essential for the development of Mn catalysts that afford water oxidation with a small overpotential at neutral pH.
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Affiliation(s)
- Toshihiro Takashima
- Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-8656, Japan
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Kargul J, Barber J. Structure and Function of Photosynthetic Reaction Centres. MOLECULAR SOLAR FUELS 2011. [DOI: 10.1039/9781849733038-00107] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Extensive biochemical, biophysical, molecular biological and structural studies on a wide range of prokaryotic and eukaryotic photosynthetic organisms has revealed common features of their reaction centres where light induced charge separation and stabilization occurs. There is little doubt that all reaction centres have evolved from a common ancestor and have been optimized to maximum efficiency. As such they provide principles that can be used as a blueprint for developing artificial photo-electrochemical catalytic systems to generate solar fuels. This chapter summarises the common features of the organization of cofactors, electron transfer pathways and protein environments of reaction centres of anoxygenic and oxygenic phototrophs. In particular, the latest molecular details derived from X-ray crystallography are discussed in context of the specific catalytic functions of the Type I and Type II reaction centres.
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Affiliation(s)
- Joanna Kargul
- Division of Molecular Biosciences, Faculty of Natural Sciences Imperial College London, London, SW7 2AZ UK
| | - James Barber
- Division of Molecular Biosciences, Faculty of Natural Sciences Imperial College London, London, SW7 2AZ UK
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Shinopoulos KE, Brudvig GW. Cytochrome b₅₅₉ and cyclic electron transfer within photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:66-75. [PMID: 21864501 DOI: 10.1016/j.bbabio.2011.08.002] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 08/06/2011] [Accepted: 08/08/2011] [Indexed: 11/18/2022]
Abstract
Cytochrome b₅₅₉ (Cyt b₅₅₉), β-carotene (Car), and chlorophyll (Chl) cofactors participate in the secondary electron-transfer pathways in photosystem II (PSII), which are believed to protect PSII from photodamage under conditions in which the primary electron-donation pathway leading to water oxidation is inhibited. Among these cofactors, Cyt b₅₅₉ is preferentially photooxidized under conditions in which the primary electron-donation pathway is blocked. When Cyt b₅₅₉ is preoxidized, the photooxidation of several of the 11 Car and 35 Chl molecules present per PSII is observed. In this review, the discovery of the secondary electron donors, their structures and electron-transfer properties, and progress in the characterization of the secondary electron-transfer pathways are discussed. This article is part of a Special Issue entitled: Photosystem II.
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Keough JM, Jenson DL, Zuniga AN, Barry BA. Proton coupled electron transfer and redox-active tyrosine Z in the photosynthetic oxygen-evolving complex. J Am Chem Soc 2011; 133:11084-7. [PMID: 21714528 PMCID: PMC3246746 DOI: 10.1021/ja2041139] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proton coupled electron transfer (PCET) reactions play an essential role in many enzymatic processes. In PCET, redox-active tyrosines may be involved as intermediates when the oxidized phenolic side chain deprotonates. Photosystem II (PSII) is an excellent framework for studying PCET reactions, because it contains two redox-active tyrosines, YD and YZ, with different roles in catalysis. One of the redox-active tyrosines, YZ, is essential for oxygen evolution and is rapidly reduced by the manganese-catalytic site. In this report, we investigate the mechanism of YZ PCET in oxygen-evolving PSII. To isolate YZ(•) reactions, but retain the manganese-calcium cluster, low temperatures were used to block the oxidation of the metal cluster, high microwave powers were used to saturate the YD(•) EPR signal, and YZ(•) decay kinetics were measured with EPR spectroscopy. Analysis of the pH and solvent isotope dependence was performed. The rate of YZ(•) decay exhibited a significant solvent isotope effect, and the rate of recombination and the solvent isotope effect were pH independent from pH 5.0 to 7.5. These results are consistent with a rate-limiting, coupled proton electron transfer (CPET) reaction and are contrasted to results obtained for YD(•) decay kinetics at low pH. This effect may be mediated by an extensive hydrogen-bond network around YZ. These experiments imply that PCET reactions distinguish the two PSII redox-active tyrosines.
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Affiliation(s)
- James M. Keough
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - David L. Jenson
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Ashley N. Zuniga
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Bridgette A. Barry
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
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Najafpour MM. Calcium-manganese oxides as structural and functional models for active site in oxygen evolving complex in photosystem II: Lessons from simple models. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:111-7. [DOI: 10.1016/j.jphotobiol.2010.12.009] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 12/10/2010] [Accepted: 12/13/2010] [Indexed: 01/12/2023]
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Listening to PS II: Enthalpy, entropy, and volume changes. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:357-65. [DOI: 10.1016/j.jphotobiol.2011.03.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Revised: 03/05/2011] [Accepted: 03/08/2011] [Indexed: 11/17/2022]
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Barry BA. Proton coupled electron transfer and redox active tyrosines in Photosystem II. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2011; 104:60-71. [PMID: 21419640 PMCID: PMC3164834 DOI: 10.1016/j.jphotobiol.2011.01.026] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 01/25/2011] [Accepted: 01/31/2011] [Indexed: 11/30/2022]
Abstract
In this article, progress in understanding proton coupled electron transfer (PCET) in Photosystem II is reviewed. Changes in acidity/basicity may accompany oxidation/reduction reactions in biological catalysis. Alterations in the proton transfer pathway can then be used to alter the rates of the electron transfer reactions. Studies of the bioenergetic complexes have played a central role in advancing our understanding of PCET. Because oxidation of the tyrosine results in deprotonation of the phenolic oxygen, redox active tyrosines are involved in PCET reactions in several enzymes. This review focuses on PCET involving the redox active tyrosines in Photosystem II. Photosystem II catalyzes the light-driven oxidation of water and reduction of plastoquinone. Photosystem II provides a paradigm for the study of redox active tyrosines, because this photosynthetic reaction center contains two tyrosines with different roles in catalysis. The tyrosines, YZ and YD, exhibit differences in kinetics and midpoint potentials, and these differences may be due to noncovalent interactions with the protein environment. Here, studies of YD and YZ and relevant model compounds are described.
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Affiliation(s)
- Bridgette A Barry
- School of Chemistry and Biochemistry and The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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Styring S, Sjöholm J, Mamedov F. Two tyrosines that changed the world: Interfacing the oxidizing power of photochemistry to water splitting in photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:76-87. [PMID: 21557928 DOI: 10.1016/j.bbabio.2011.03.016] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 03/10/2011] [Accepted: 03/29/2011] [Indexed: 11/16/2022]
Abstract
Photosystem II (PSII), the thylakoid membrane enzyme which uses sunlight to oxidize water to molecular oxygen, holds many organic and inorganic redox cofactors participating in the electron transfer reactions. Among them, two tyrosine residues, Tyr-Z and Tyr-D are found on the oxidizing side of PSII. Both tyrosines demonstrate similar spectroscopic features while their kinetic characteristics are quite different. Tyr-Z, which is bound to the D1 core protein, acts as an intermediate in electron transfer between the primary donor, P(680) and the CaMn₄ cluster. In contrast, Tyr-D, which is bound to the D2 core protein, does not participate in linear electron transfer in PSII and stays fully oxidized during PSII function. The phenolic oxygens on both tyrosines form well-defined hydrogen bonds to nearby histidine residues, His(Z) and His(D) respectively. These hydrogen bonds allow swift and almost activation less movement of the proton between respective tyrosine and histidine. This proton movement is critical and the phenolic proton from the tyrosine is thought to toggle between the tyrosine and the histidine in the hydrogen bond. It is found towards the tyrosine when this is reduced and towards the histidine when the tyrosine is oxidized. The proton movement occurs at both room temperature and ultra low temperature and is sensitive to the pH. Essentially it has been found that when the pH is below the pK(a) for respective histidine the function of the tyrosine is slowed down or, at ultra low temperature, halted. This has important consequences for the function also of the CaMn₄ complex and the protonation reactions as the critical Tyr-His hydrogen bond also steer a multitude of reactions at the CaMn₄ cluster. This review deals with the discovery and functional assignments of the two tyrosines. The pH dependent phenomena involved in oxidation and reduction of respective tyrosine is covered in detail. This article is part of a Special Issue entitled: Photosystem II.
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Affiliation(s)
- Stenbjörn Styring
- Molecular Biomimetics, Department for Photochemistry and Molecular Science, Angström Laboratory, Uppsala University, Sweden.
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Nagarajan A, Winter R, Eaton-Rye J, Burnap R. A synthetic DNA and fusion PCR approach to the ectopic expression of high levels of the D1 protein of photosystem II in Synechocystis sp. PCC 6803. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:212-9. [PMID: 21377372 DOI: 10.1016/j.jphotobiol.2011.02.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2010] [Revised: 02/04/2011] [Accepted: 02/07/2011] [Indexed: 11/24/2022]
Abstract
A hybrid approach involving synthetic DNA, fusion PCR, and ectopic expression has been used to genetically manipulate the expression of the D1 protein of photosystem II (PSII) in the model cyanobacterium Synechocystis sp. PCC6803. Due to the toxicity of the full-length psbA gene in E. coli, a chimeric psbA2 gene locus was commercially synthesised and cloned in two halves. High-fidelity fusion PCR utilizing sequence overlap between the two synthetic gene halves allowed the production of a DNA fragment that was able to recombine the full-length psbA2 gene into the Synechocystis chromosome at an ectopic (non-native) location. This was accomplished by designing the synthetic DNA/fusion PCR product to have the psbA2 gene, with control sequences, interposed between chimeric sequences corresponding to an ectopic target chromosomal location. Additionally, a recipient strain of Synechocystis lacking all three psbA genes was produced by a combination of traditional marker replacement and markerless replacement techniques. Transformation of this multiple deletion strain by the synthetic DNA/fusion PCR product faithfully restored D1 expression in terms of its expression and PSII repair capacity. The advantages and potential issues for using this approach to rapidly introduce chimeric sequence characteristics as a general tool to produce novel genetic constructs are discussed.
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Affiliation(s)
- Aparna Nagarajan
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078, USA
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Sibert RS, Josowicz M, Barry BA. Control of proton and electron transfer in de novo designed, biomimetic β hairpins. ACS Chem Biol 2010; 5:1157-68. [PMID: 20919724 DOI: 10.1021/cb100138m] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tyrosine side chains are involved in proton coupled electron transfer reactions (PCET) in many complex proteins, including photosystem II (PSII) and ribonucleotide reductase. For example, PSII contains two redox-active tyrosines, TyrD (Y160D2) and TyrZ (Y161D1), which have different protein environments, midpoint potentials, and roles in catalysis. TyrD has a midpoint potential lower than that of TyrZ, and its protein environment is distinguished by potential π-cation interactions with arginine residues. Designed biomimetic peptides provide a system that can be used to investigate how the protein matrix controls PCET reactions. As a model for the redox-active tyrosines in PSII, we are employing a designed, 18 amino acid β hairpin peptide in which PCET reactions occur between a tyrosine (Tyr5) and a cross-strand histidine (His14). In this peptide, the single tyrosine is hydrogen-bonded to an arginine residue, Arg16, and a second arginine, Arg12, has a π-cation interaction with Tyr5. In this report, the effect of these hydrogen bonding and electrostatic interactions on the PCET reactions is investigated. Electrochemical titrations show that histidine substitutions change the nature of PCET reactions, and optical titrations show that Arg16 substitution changes the pK of Tyr5. Removal of Arg16 or Arg12 increases the midpoint potential for tyrosine oxidation. The effects of Arg12 substitution are consistent with the midpoint potential difference, which is observed for the PSII redox-active tyrosine residues. Our results demonstrate that a π-cation interaction, hydrogen bonding, and PCET reactions alter redox-active tyrosine function. These interactions can contribute equally to the control of midpoint potential and reaction rate.
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Affiliation(s)
- Robin S. Sibert
- Department of Chemistry and Biochemistry
- Petit Institute for Bioengineering and Bioscience
| | | | - Bridgette A. Barry
- Department of Chemistry and Biochemistry
- Petit Institute for Bioengineering and Bioscience
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Nixon PJ, Michoux F, Yu J, Boehm M, Komenda J. Recent advances in understanding the assembly and repair of photosystem II. ANNALS OF BOTANY 2010; 106:1-16. [PMID: 20338950 PMCID: PMC2889791 DOI: 10.1093/aob/mcq059] [Citation(s) in RCA: 382] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 02/01/2010] [Accepted: 02/09/2010] [Indexed: 05/18/2023]
Abstract
BACKGROUND Photosystem II (PSII) is the light-driven water:plastoquinone oxidoreductase of oxygenic photosynthesis and is found in the thylakoid membrane of chloroplasts and cyanobacteria. Considerable attention is focused on how PSII is assembled in vivo and how it is repaired following irreversible damage by visible light (so-called photoinhibition). Understanding these processes might lead to the development of plants with improved growth characteristics especially under conditions of abiotic stress. SCOPE Here we summarize recent results on the assembly and repair of PSII in cyanobacteria, which are excellent model organisms to study higher plant photosynthesis. CONCLUSIONS Assembly of PSII is highly co-ordinated and proceeds through a number of distinct assembly intermediates. Associated with these assembly complexes are proteins that are not found in the final functional PSII complex. Structural information and possible functions are beginning to emerge for several of these 'assembly' factors, notably Ycf48/Hcf136, Psb27 and Psb28. A number of other auxiliary proteins have been identified that appear to have evolved since the divergence of chloroplasts and cyanobacteria. The repair of PSII involves partial disassembly of the damaged complex, the selective replacement of the damaged sub-unit (predominantly the D1 sub-unit) by a newly synthesized copy, and reassembly. It is likely that chlorophyll released during the repair process is temporarily stored by small CAB-like proteins (SCPs). A model is proposed in which damaged D1 is removed in Synechocystis sp. PCC 6803 by a hetero-oligomeric complex composed of two different types of FtsH sub-unit (FtsH2 and FtsH3), with degradation proceeding from the N-terminus of D1 in a highly processive reaction. It is postulated that a similar mechanism of D1 degradation also operates in chloroplasts. Deg proteases are not required for D1 degradation in Synechocystis 6803 but members of this protease family might play a supplementary role in D1 degradation in chloroplasts under extreme conditions.
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Affiliation(s)
- Peter J Nixon
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK.
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Roelofs TA, Lee CH, Holzwarth AR. Global target analysis of picosecond chlorophyll fluorescence kinetics from pea chloroplasts: A new approach to the characterization of the primary processes in photosystem II alpha- and beta-units. Biophys J 2010; 61:1147-63. [PMID: 19431828 DOI: 10.1016/s0006-3495(92)81924-0] [Citation(s) in RCA: 172] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
In this study, we have used the method of target analysis to analyze the ps fluorescence kinetics of pea chloroplasts with open (F(0)) and closed (F(max)) photosystem II (PS II) centers. Extending the exciton/radical pair equilibrium model (Schatz, G. H., H. Brock, and A. R. Holzwarth. 1988. Biophys. J. 54:397-405) to allow for PS II heterogeneity, we show that two types of PS II (labeled alpha and beta) must be accounted for, each pool being characterized by its own set of molecular rate constants within the model. Simultaneous global target analysis of the data at F(0) and F(max) results in a detailed description of the molecular kinetics and energetics of the primary processes in both types of PS II units. This characterization revealed that the PS IIalpha pool accounts for twice as many Chl molecules as PS IIbeta, which suggests a PSIIalpha/PSIIbeta reaction center stoichiometry of close to unity. By extrapolation it is shown that the primary charge separation in hypothetical "isolated" beta reaction centers is slower than in isolated alpha reaction centers: in open centers by a factor of 4 (1/k(1) (int) = 11 vs 2.9 ps), in closed centers by a factor of 2 (1/k(1) (int) = 34 vs 19 ps). Despite this slower charge separation process in PS IIbeta, the quantum efficiency of the charge separation process is hardly affected: a charge stabilization yield at F(0), (i.e., P(+)IQ(A) (-)) of 86% (as compared to 90% in PS IIalpha). Reduction of Q(A) (closing PS II) has distinctly different effects on the primary kinetics of PS IIbeta, as compared to PS IIalpha. In PS IIalpha the charge separation rate drops by a factor of 6, whereas the charge recombination process is hardly affected. In PS IIbeta the charge separation is slowed down by a factor of 3, whereas the charge recombination rate increases by a factor of 5. In terms of changes in standard free energy, the reduction to Q(A) (-) lifts the free energy of the radical pair P(+)I(-), relative to the excited state (Chl(n)/P)(*), by 47 meV in PS IIalpha and by 67 meV in PS IIbeta. The concomitant increase in fluorescence quantum yield is the same for both types of PS II. These results show that PS IIalpha and PS IIbeta exhibit a different molecular functioning with respect to the primary processes, which might have its origin in a different molecular structure of the reaction centers and/or a different local environment of these centers. Location in different parts of the thylakoid membrane might be involved. We also applied different error analysis procedures to determine the error ranges of the values found for the molecular rate constants. It is shown that the commonly used standard error has very little meaning, as it assumes independence of the fit parameters. Instead, an exhaustive search procedure, accounting for all possible correlations between the fit parameters, gives a more realistic view on the accuracy of the fit parameters.
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Affiliation(s)
- T A Roelofs
- Max-Planck-Institut für Strahlenchemie, Stiftstr. 34-36, D-4330 Mülheim a.d. Ruhr, Germany
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Semin BK, Davletshina LN, Ivanov II, Rubin AB, Seibert M. Decoupling of the processes of molecular oxygen synthesis and electron transport in Ca2+-depleted PSII membranes. PHOTOSYNTHESIS RESEARCH 2008; 98:235-249. [PMID: 18814052 DOI: 10.1007/s11120-008-9347-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Accepted: 07/30/2008] [Indexed: 05/26/2023]
Abstract
Extraction of Ca(2+) from the O(2)-evolving complex (OEC) of photosystem II (PSII) membranes with 2 M NaCl in the light (PSII(-Ca/NaCl)) results in 90% inhibition of the O(2)-evolution reaction. However, electron transfer from the donor to acceptor side of PSII, measured as the reduction of the exogenous acceptor 2,6-dichlorophenolindophenol (DCIP) under continuous light, is inhibited by only 30%. Thus, calcium extraction from the OEC inhibits the synthesis of molecular O(2) but not the oxidation of a substrate we term X, the source of electrons for DCIP reduction. The presence of electron transfer across PSII(-Ca/NaCl) membranes was demonstrated using fluorescence induction kinetics, a method that does not require an artificial acceptor. The calcium chelator, EGTA (5 mM), when added to PSII(-Ca/NaCl) membranes, does not affect the inhibition of O(2) evolution by NaCl but does inhibit DCIP reduction up to 92% (the reason why electron transport in Ca(2+)-depleted materials has not been noticed before). Another chelator, sodium citrate (citrate/low pH method of calcium extraction), also inhibits both O(2) evolution and DCIP reduction. The role of all buffer components (including bicarbonate and sucrose) as possible sources of electrons for PSII(-Ca/NaCl) membranes was investigated, but only the absence of chloride anions strongly inhibited the rate of DCIP reduction. Substitution of other anions for chloride indicates that Cl(-) serves its well-known role as an OEC cofactor, but it is not substrate X. Multiple turnover flash experiments have shown a period of four oscillations of the fluorescence yield (both the maximum level, F(max), and the fluorescence level measured 50 s after an actinic flash in the presence of DCMU) in native PSII membranes, reflecting the normal function of the OEC, but the absence of oscillations in PSII(-Ca/NaCl) samples. Thus, PSII(-Ca/NaCl) samples do not evolve O(2) but do transfer electrons from the donor to acceptor sides and exhibit a disrupted S-state cycle. We explain these results as follows. In Ca(2+)-depleted PSII membranes, obtained without chelators, the oxidation of the OEC stops after the absorption of three quanta of light (from the S1 state), which should convert the native OEC to the S4 state. An one-electron oxidation of the water molecule bound to the Mn cluster then occurs (the second substrate water molecule is absent due to the absence of calcium), and the OEC returns to the S3 state. The appearance of a sub-cycle within the S-state cycle between S3-like and S4-like states supplies electrons (substrate X is postulated to be OH(-)), explains the absence of O(2) production, and results in the absence of a period of four oscillation of the normal functional parameters, such as the fluorescence yield or the EPR signal from S2. Chloride anions probably keep the redox potential of the Mn cluster low enough for its oxidation by Y(Z)(*).
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Affiliation(s)
- Boris K Semin
- Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
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