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Maroudas-Sklare N, Goren N, Yochelis S, Jung G, Keren N, Paltiel Y. Probing the design principles of photosynthetic systems through fluorescence noise measurement. Sci Rep 2024; 14:13877. [PMID: 38880795 DOI: 10.1038/s41598-024-64068-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Accepted: 06/05/2024] [Indexed: 06/18/2024] Open
Abstract
Elucidating the energetic processes which govern photosynthesis, the engine of life on earth, are an essential goal both for fundamental research and for cutting-edge biotechnological applications. Fluorescent signal of photosynthetic markers has long been utilised in this endeavour. In this research we demonstrate the use of fluorescent noise analysis to reveal further layers of intricacy in photosynthetic energy transfer. While noise is a common tool analysing dynamics in physics and engineering, its application in biology has thus far been limited. Here, a distinct behaviour in photosynthetic pigments across various chemical and biological environments is measured. These changes seem to elucidate quantum effects governing the generation of oxidative radicals. Although our method offers insights, it is important to note that the interpretation should be further validated expertly to support as conclusive theory. This innovative method is simple, non-invasive, and immediate, making it a promising tool to uncover further, more complex energetic events in photosynthesis, with potential uses in environmental monitoring, agriculture, and food-tech.
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Affiliation(s)
- Naama Maroudas-Sklare
- Department of Applied Physics, Hebrew University of Jerusalem, 91904, Jerusalem, Israel
- Department of Plant & Environmental Sciences, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Naama Goren
- Department of Applied Physics, Hebrew University of Jerusalem, 91904, Jerusalem, Israel
| | - Shira Yochelis
- Department of Applied Physics, Hebrew University of Jerusalem, 91904, Jerusalem, Israel
| | - Grzegorz Jung
- Department of Physics, Ben Gurion University of the Negev, 84105, Beer Sheva, Israel
- Instytut Fizyki PAN, 02668, Warszawa, Poland
| | - Nir Keren
- Department of Plant & Environmental Sciences, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yossi Paltiel
- Department of Applied Physics, Hebrew University of Jerusalem, 91904, Jerusalem, Israel.
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2
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Chernev P, Aydin AO, Messinger J. On the simulation and interpretation of substrate-water exchange experiments in photosynthetic water oxidation. PHOTOSYNTHESIS RESEARCH 2024:10.1007/s11120-024-01084-8. [PMID: 38512410 DOI: 10.1007/s11120-024-01084-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 02/01/2024] [Indexed: 03/23/2024]
Abstract
Water oxidation by photosystem II (PSII) sustains most life on Earth, but the molecular mechanism of this unique process remains controversial. The ongoing identification of the binding sites and modes of the two water-derived substrate oxygens ('substrate waters') in the various intermediates (Si states, i = 0, 1, 2, 3, 4) that the water-splitting tetra-manganese calcium penta-oxygen (Mn4CaO5) cluster attains during the reaction cycle provides central information towards resolving the unique chemistry of biological water oxidation. Mass spectrometric measurements of single- and double-labeled dioxygen species after various incubation times of PSII with H218O provide insight into the substrate binding modes and sites via determination of exchange rates. Such experiments have revealed that the two substrate waters exchange with different rates that vary independently with the Si state and are hence referred to as the fast (Wf) and the slow (WS) substrate waters. New insight for the molecular interpretation of these rates arises from our recent finding that in the S2 state, under special experimental conditions, two different rates of WS exchange are observed that appear to correlate with the high spin and low spin conformations of the Mn4CaO5 cluster. Here, we reexamine and unite various proposed methods for extracting and assigning rate constants from this recent data set. The analysis results in a molecular model for substrate-water binding and exchange that reconciles the expected non-exchangeability of the central oxo bridge O5 when located between two Mn(IV) ions with the experimental and theoretical assignment of O5 as WS in all S states. The analysis also excludes other published proposals for explaining the water exchange kinetics.
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Affiliation(s)
- Petko Chernev
- Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, 75120, Uppsala, Sweden
| | - A Orkun Aydin
- Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, 75120, Uppsala, Sweden
| | - Johannes Messinger
- Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, 75120, Uppsala, Sweden.
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3
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Müh F, Bothe A, Zouni A. Towards understanding the crystallization of photosystem II: influence of poly(ethylene glycol) of various molecular sizes on the micelle formation of alkyl maltosides. PHOTOSYNTHESIS RESEARCH 2024:10.1007/s11120-024-01079-5. [PMID: 38488943 DOI: 10.1007/s11120-024-01079-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 01/24/2024] [Indexed: 03/17/2024]
Abstract
The influence of poly(ethylene glycol) (PEG) polymers H-(O-CH2-CH2)p-OH with different average molecular sizes p on the micelle formation of n-alkyl-β-D-maltoside detergents with the number of carbon atoms in the alkyl chain ranging from 10 to 12 is investigated with the aim to learn more about the detergent behavior under conditions suitable for the crystallization of the photosynthetic pigment-protein complex photosystem II. PEG is shown to increase the critical micelle concentration (CMC) of all three detergents in the crystallization buffer in a way that the free energy of micelle formation increases linearly with the concentration of oxyethylene units (O-CH2-CH2) irrespective of the actual molecular weight of the polymer. The CMC shift is modeled by assuming for simplicity that it is dominated by the interaction between PEG and detergent monomers and is interpreted in terms of an increase of the transfer free energy of a methylene group of the alkyl chain by 0.2 kJ mol-1 per 1 mol L-1 increase of the concentration of oxyethylene units at 298 K. Implications of this effect for the solubilization and crystallization of protein-detergent complexes as well as detergent extraction from crystals are discussed.
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Affiliation(s)
- Frank Müh
- Institut für Theoretische Physik, Johannes Kepler Universität Linz, Altenberger Strasse 69, 4040, Linz, Austria.
| | - Adrian Bothe
- Institut für Molekularbiologie und Biophysik, ETH Zürich, HPK, Otto-Stern-Weg 5, CH-8093, Zurich, Switzerland
| | - Athina Zouni
- Institut für Biologie, Humboldt Universität zu Berlin, Leonor-Michaelis-Haus, Philippstrasse 13, 10095, Berlin, Germany
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4
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Singh A, Roy L. Evolution in the Design of Water Oxidation Catalysts with Transition-Metals: A Perspective on Biological, Molecular, Supramolecular, and Hybrid Approaches. ACS OMEGA 2024; 9:9886-9920. [PMID: 38463281 PMCID: PMC10918817 DOI: 10.1021/acsomega.3c07847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 03/12/2024]
Abstract
Increased demand for a carbon-neutral sustainable energy scheme augmented by climatic threats motivates the design and exploration of novel approaches that reserve intermittent solar energy in the form of chemical bonds in molecules and materials. In this context, inspired by biological processes, artificial photosynthesis has garnered significant attention as a promising solution to convert solar power into chemical fuels from abundantly found H2O. Among the two redox half-reactions in artificial photosynthesis, the four-electron oxidation of water according to 2H2O → O2 + 4H+ + 4e- comprises the major bottleneck and is a severe impediment toward sustainable energy production. As such, devising new catalytic platforms, with traditional concepts of molecular, materials and biological catalysis and capable of integrating the functional architectures of the natural oxygen-evolving complex in photosystem II would certainly be a value-addition toward this objective. In this review, we discuss the progress in construction of ideal water oxidation catalysts (WOCs), starting with the ingenuity of the biological design with earth-abundant transition metal ions, which then diverges into molecular, supramolecular and hybrid approaches, blurring any existing chemical or conceptual boundaries. We focus on the geometric, electronic, and mechanistic understanding of state-of-the-art homogeneous transition-metal containing molecular WOCs and summarize the limiting factors such as choice of ligands and predominance of environmentally unrewarding and expensive noble-metals, necessity of high-valency on metal, thermodynamic instability of intermediates, and reversibility of reactions that create challenges in construction of robust and efficient water oxidation catalyst. We highlight how judicious heterogenization of atom-efficient molecular WOCs in supramolecular and hybrid approaches put forth promising avenues to alleviate the existing problems in molecular catalysis, albeit retaining their fascinating intrinsic reactivities. Taken together, our overview is expected to provide guiding principles on opportunities, challenges, and crucial factors for designing novel water oxidation catalysts based on a synergy between conventional and contemporary methodologies that will incite the expansion of the domain of artificial photosynthesis.
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Affiliation(s)
- Ajeet
Kumar Singh
- Institute of Chemical Technology
Mumbai−IOC Odisha Campus Bhubaneswar, IIT Kharagpur Extension
Centre, Bhubaneswar − 751013 India
| | - Lisa Roy
- Institute of Chemical Technology
Mumbai−IOC Odisha Campus Bhubaneswar, IIT Kharagpur Extension
Centre, Bhubaneswar − 751013 India
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5
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Dekmak MY, Mäusle SM, Brandhorst J, Simon PS, Dau H. Tracking the first electron transfer step at the donor side of oxygen-evolving photosystem II by time-resolved infrared spectroscopy. PHOTOSYNTHESIS RESEARCH 2023:10.1007/s11120-023-01057-3. [PMID: 37995064 DOI: 10.1007/s11120-023-01057-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 10/24/2023] [Indexed: 11/24/2023]
Abstract
In oxygen-evolving photosystem II (PSII), the multi-phasic electron transfer from a redox-active tyrosine residue (TyrZ) to a chlorophyll cation radical (P680+) precedes the water-oxidation chemistry of the S-state cycle of the Mn4Ca cluster. Here we investigate these early events, observable within about 10 ns to 10 ms after laser-flash excitation, by time-resolved single-frequency infrared (IR) spectroscopy in the spectral range of 1310-1890 cm-1 for oxygen-evolving PSII membrane particles from spinach. Comparing the IR difference spectra at 80 ns, 500 ns, and 10 µs allowed for the identification of quinone, P680 and TyrZ contributions. A broad electronic absorption band assignable P680+ was used to trace largely specifically the P680+ reduction kinetics. The experimental time resolution was taken into account in least-square fits of P680+ transients with a sum of four exponentials, revealing two nanosecond phases (30-46 ns and 690-1110 ns) and two microsecond phases (4.5-8.3 µs and 42 µs), which mostly exhibit a clear S-state dependence, in agreement with results obtained by other methods. Our investigation paves the road for further insight in the early events associated with TyrZ oxidation and their role in the preparing the PSII donor side for the subsequent water oxidation chemistry.
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Affiliation(s)
| | - Sarah M Mäusle
- Department of Physics, Freie Universität Berlin, Berlin, Germany.
| | | | - Philipp S Simon
- Department of Physics, Freie Universität Berlin, Berlin, Germany
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Holger Dau
- Department of Physics, Freie Universität Berlin, Berlin, Germany.
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6
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Mishima K, Kano N. Contribution Factors of the First Kind Calculated for the Marcus Electron-Transfer Rate and Their Applications. J Phys Chem B 2023; 127:8509-8524. [PMID: 37782079 DOI: 10.1021/acs.jpcb.3c03420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
In this study, we applied the concept of the "contribution factor of the first kind (CFFK)" to the original electron-transfer (ET) rate theory proposed by Marcus. Mathematical derivations provided simple and convenient formulas for estimating the relative contributions of ten physical and chemical parameters involved in the Marcus ET rate formula: (1) the maximum strength of the electronic coupling energy between two molecules, (2) the exponential decay rate of the electronic coupling energy versus the distance between both molecules, (3) the distance between both molecules, (4) the equilibrium distance between both molecules, (5) the Gibbs free energy, (6) reorganization free energy in the prefactor of the Marcus ET rate equation, (7) reorganization free energy in the denominator of the exponential term, (8) reorganization free energy in the argument of the exponential term, (9) Boltzmann constant times absolute temperature in the prefactor of the rate equation, and (10) Boltzmann constant times absolute temperature in the denominator of the exponential term. We applied our theories to (i) ET reactions at bacterial photosynthesis reaction centers, PSI and PSII, and soluble ferredoxins (Fd); (ii) intraprotein ET reactions for designed azurin mutants; and (iii) ET reactions in flavodoxin (Fld). The formulas and calculations suggest that the theory behind the CFFK is useful for quantitatively identifying major and minor physical and chemical factors and corresponding trade-offs, all of which affect the magnitude of the Marcus ET rate.
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Affiliation(s)
- Kenji Mishima
- Independent Researcher, Bunkyo-ku, Tokyo 113-0024, Japan
| | - Naoki Kano
- Department of Chemistry and Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181, Japan
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7
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Chen M, Sawicki A, Wang F. Modeling the Characteristic Residues of Chlorophyll f Synthase (ChlF) from Halomicronema hongdechloris to Determine Its Reaction Mechanism. Microorganisms 2023; 11:2305. [PMID: 37764149 PMCID: PMC10535343 DOI: 10.3390/microorganisms11092305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 09/07/2023] [Accepted: 09/07/2023] [Indexed: 09/29/2023] Open
Abstract
Photosystem II (PSII) is a quinone-utilizing photosynthetic system that converts light energy into chemical energy and catalyzes water splitting. PsbA (D1) and PsbD (D2) are the core subunits of the reaction center that provide most of the ligands to redox-active cofactors and exhibit photooxidoreductase activities that convert quinone and water into quinol and dioxygen. The performed analysis explored the putative uncoupled electron transfer pathways surrounding P680+ induced by far-red light (FRL) based on photosystem II (PSII) complexes containing substituted D1 subunits in Halomicronema hongdechloris. Chlorophyll f-synthase (ChlF) is a D1 protein paralog. Modeling PSII-ChlF complexes determined several key protein motifs of ChlF. The PSII complexes included a dysfunctional Mn4CaO5 cluster where ChlF replaced the D1 protein. We propose the mechanism of chlorophyll f synthesis from chlorophyll a via free radical chemistry in an oxygenated environment created by over-excited pheophytin a and an inactive water splitting reaction owing to an uncoupled Mn4CaO5 cluster in PSII-ChlF complexes. The role of ChlF in the formation of an inactive PSII reaction center is under debate, and putative mechanisms of chlorophyll f biosynthesis are discussed.
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Affiliation(s)
- Min Chen
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia
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8
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Shevela D, Kern JF, Govindjee G, Messinger J. Solar energy conversion by photosystem II: principles and structures. PHOTOSYNTHESIS RESEARCH 2023; 156:279-307. [PMID: 36826741 PMCID: PMC10203033 DOI: 10.1007/s11120-022-00991-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 12/01/2022] [Indexed: 05/23/2023]
Abstract
Photosynthetic water oxidation by Photosystem II (PSII) is a fascinating process because it sustains life on Earth and serves as a blue print for scalable synthetic catalysts required for renewable energy applications. The biophysical, computational, and structural description of this process, which started more than 50 years ago, has made tremendous progress over the past two decades, with its high-resolution crystal structures being available not only of the dark-stable state of PSII, but of all the semi-stable reaction intermediates and even some transient states. Here, we summarize the current knowledge on PSII with emphasis on the basic principles that govern the conversion of light energy to chemical energy in PSII, as well as on the illustration of the molecular structures that enable these reactions. The important remaining questions regarding the mechanism of biological water oxidation are highlighted, and one possible pathway for this fundamental reaction is described at a molecular level.
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Affiliation(s)
- Dmitry Shevela
- Department of Chemistry, Chemical Biological Centre, Umeå University, 90187, Umeå, Sweden.
| | - Jan F Kern
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Govindjee Govindjee
- Department of Plant Biology, Department of Biochemistry and Center of Biophysics & Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Johannes Messinger
- Department of Chemistry, Chemical Biological Centre, Umeå University, 90187, Umeå, Sweden.
- Molecular Biomimetics, Department of Chemistry - Ångström, Uppsala University, 75120, Uppsala, Sweden.
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9
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Greife P, Schönborn M, Capone M, Assunção R, Narzi D, Guidoni L, Dau H. The electron-proton bottleneck of photosynthetic oxygen evolution. Nature 2023; 617:623-628. [PMID: 37138082 PMCID: PMC10191853 DOI: 10.1038/s41586-023-06008-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 03/23/2023] [Indexed: 05/05/2023]
Abstract
Photosynthesis fuels life on Earth by storing solar energy in chemical form. Today's oxygen-rich atmosphere has resulted from the splitting of water at the protein-bound manganese cluster of photosystem II during photosynthesis. Formation of molecular oxygen starts from a state with four accumulated electron holes, the S4 state-which was postulated half a century ago1 and remains largely uncharacterized. Here we resolve this key stage of photosynthetic O2 formation and its crucial mechanistic role. We tracked 230,000 excitation cycles of dark-adapted photosystems with microsecond infrared spectroscopy. Combining these results with computational chemistry reveals that a crucial proton vacancy is initally created through gated sidechain deprotonation. Subsequently, a reactive oxygen radical is formed in a single-electron, multi-proton transfer event. This is the slowest step in photosynthetic O2 formation, with a moderate energetic barrier and marked entropic slowdown. We identify the S4 state as the oxygen-radical state; its formation is followed by fast O-O bonding and O2 release. In conjunction with previous breakthroughs in experimental and computational investigations, a compelling atomistic picture of photosynthetic O2 formation emerges. Our results provide insights into a biological process that is likely to have occurred unchanged for the past three billion years, which we expect to support the knowledge-based design of artificial water-splitting systems.
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Affiliation(s)
- Paul Greife
- Department of Physics, Freie Universität, Berlin, Germany
| | | | - Matteo Capone
- Department of Information Engineering, Computer Science and Mathematics, University of L'Aquila, L'Aquila, Italy
- Department of Physical and Chemical Sciences, University of L'Aquila, L'Aquila, Italy
| | | | - Daniele Narzi
- Department of Physical and Chemical Sciences, University of L'Aquila, L'Aquila, Italy
| | - Leonardo Guidoni
- Department of Physical and Chemical Sciences, University of L'Aquila, L'Aquila, Italy.
| | - Holger Dau
- Department of Physics, Freie Universität, Berlin, Germany.
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10
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Lubitz W, Pantazis DA, Cox N. Water oxidation in oxygenic photosynthesis studied by magnetic resonance techniques. FEBS Lett 2023; 597:6-29. [PMID: 36409002 DOI: 10.1002/1873-3468.14543] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 11/23/2022]
Abstract
The understanding of light-induced biological water oxidation in oxygenic photosynthesis is of great importance both for biology and (bio)technological applications. The chemically difficult multistep reaction takes place at a unique protein-bound tetra-manganese/calcium cluster in photosystem II whose structure has been elucidated by X-ray crystallography (Umena et al. Nature 2011, 473, 55). The cluster moves through several intermediate states in the catalytic cycle. A detailed understanding of these intermediates requires information about the spatial and electronic structure of the Mn4 Ca complex; the latter is only available from spectroscopic techniques. Here, the important role of Electron Paramagnetic Resonance (EPR) and related double resonance techniques (ENDOR, EDNMR), complemented by quantum chemical calculations, is described. This has led to the elucidation of the cluster's redox and protonation states, the valence and spin states of the manganese ions and the interactions between them, and contributed substantially to the understanding of the role of the protein surrounding, as well as the binding and processing of the substrate water molecules, the O-O bond formation and dioxygen release. Based on these data, models for the water oxidation cycle are developed.
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Affiliation(s)
- Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion, Mülheim/Ruhr, Germany
| | | | - Nicholas Cox
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia
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11
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Q-lipid-containing membranes show high in-plane conductivity using a membrane-on-a-chip setup. iScience 2022; 26:105918. [PMID: 36711244 PMCID: PMC9874011 DOI: 10.1016/j.isci.2022.105918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 10/05/2022] [Accepted: 12/28/2022] [Indexed: 12/31/2022] Open
Abstract
The light-driven reactions of photosynthesis as well as the mitochondrial power supply are located in specialized membranes containing a high fraction of redox-active lipids. In-plane charge transfer along such cell membranes is currently thought to be facilitated by the diffusion of redox lipids and proteins. Using a membrane on-a-chip setup, we show here that redox-active model membranes can sustain surprisingly high currents (mA) in-plane at distances of 25 μm. We also show the same phenomenon in free-standing monolayers at the air-water interface once the film is compressed such that the distance between redox centers is below 1 nm. Our data suggest that charge transfer within cell walls hosting electron transfer chains could be enabled by the coupling of redox-lipids via simultaneous electron and proton in-plane hopping, similar to conductive polymers. This has major implications for our understanding of the role of lipid membranes, suggesting that Q-lipid-containing membranes may be essential for evolving the complex redox machineries of life.
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12
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Sirohiwal A, Pantazis DA. Functional Water Networks in Fully Hydrated Photosystem II. J Am Chem Soc 2022; 144:22035-22050. [PMID: 36413491 PMCID: PMC9732884 DOI: 10.1021/jacs.2c09121] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Water channels and networks within photosystem II (PSII) of oxygenic photosynthesis are critical for enzyme structure and function. They control substrate delivery to the oxygen-evolving center and mediate proton transfer at both the oxidative and reductive endpoints. Current views on PSII hydration are derived from protein crystallography, but structural information may be compromised by sample dehydration and technical limitations. Here, we simulate the physiological hydration structure of a cyanobacterial PSII model following a thorough hydration procedure and large-scale unconstrained all-atom molecular dynamics enabled by massively parallel simulations. We show that crystallographic models of PSII are moderately to severely dehydrated and that this problem is particularly acute for models derived from X-ray free electron laser (XFEL) serial femtosecond crystallography. We present a fully hydrated representation of cyanobacterial PSII and map all water channels, both static and dynamic, associated with the electron donor and acceptor sides. Among them, we describe a series of transient channels and the attendant conformational gating role of protein components. On the acceptor side, we characterize a channel system that is absent from existing crystallographic models but is likely functionally important for the reduction of the terminal electron acceptor plastoquinone QB. The results of the present work build a foundation for properly (re)evaluating crystallographic models and for eliciting new insights into PSII structure and function.
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13
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Gololobova MA, Belyakova GA. Position of Algae on the Tree of Life. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2022; 507:312-326. [PMID: 36781528 DOI: 10.1134/s0012496622060035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 07/27/2022] [Accepted: 07/27/2022] [Indexed: 02/15/2023]
Abstract
Issues related to evolution of algal chloroplasts are considered. The position of algae on the Tree of Life is discussed. Algae are now included in five of the monophyletic eukaryotic supergroups: Archaeplastida (Glaucocystophyta, Rhodophyta, Prasinodermophyta, Chlorophyta, and Charophyta), TSAR (Ochrophyta; Dinophyta; Chlorarachniophyta; and photosynthetic species of the genera Chromera, Vetrella, and Paulinella), Haptista (Prymnesiophyta and Rappemonads), Cryptista (Cryptophyta), and Discoba (Euglenophyta). The algal divisions and the respective supergroups are characterized in brief.
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Affiliation(s)
- M A Gololobova
- Biological Faculty, Moscow State University, Moscow, Russia.
| | - G A Belyakova
- Biological Faculty, Moscow State University, Moscow, Russia
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14
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Nixon PJ, Telfer A. Remembering James Barber (1940-2020). PHOTOSYNTHESIS RESEARCH 2022; 153:1-20. [PMID: 35534741 PMCID: PMC9522743 DOI: 10.1007/s11120-022-00919-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 03/31/2022] [Indexed: 06/14/2023]
Abstract
James Barber, known to colleagues and friends as Jim, passed away in January 2020 after a long battle against cancer. During his long and distinguished career in photosynthesis research, Jim made many outstanding contributions with the pinnacle achieving his dream of determining the first detailed structure of the Mn cluster involved in photosynthetic water oxidation. Here, colleagues and friends remember Jim and reflect upon his scientific career and the impact he had on their lives and the scientific community.
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Affiliation(s)
- Peter J Nixon
- Sir Ernst Chain Building - Wolfson Laboratories, Department of Life Sciences, Imperial College London, S. Kensington Campus, London, SW7 2AZ, UK.
| | - Alison Telfer
- Sir Ernst Chain Building - Wolfson Laboratories, Department of Life Sciences, Imperial College London, S. Kensington Campus, London, SW7 2AZ, UK.
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15
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Chen Y, Xu B, Yao R, Chen C, Zhang C. Mimicking the Oxygen-Evolving Center in Photosynthesis. FRONTIERS IN PLANT SCIENCE 2022; 13:929532. [PMID: 35874004 PMCID: PMC9302449 DOI: 10.3389/fpls.2022.929532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 06/20/2022] [Indexed: 06/15/2023]
Abstract
The oxygen-evolving center (OEC) in photosystem II (PSII) of oxygenic photosynthetic organisms is a unique heterometallic-oxide Mn4CaO5-cluster that catalyzes water splitting into electrons, protons, and molecular oxygen through a five-state cycle (Sn, n = 0 ~ 4). It serves as the blueprint for the developing of the man-made water-splitting catalysts to generate solar fuel in artificial photosynthesis. Understanding the structure-function relationship of this natural catalyst is a great challenge and a long-standing issue, which is severely restricted by the lack of a precise chemical model for this heterometallic-oxide cluster. However, it is a great challenge for chemists to precisely mimic the OEC in a laboratory. Recently, significant advances have been achieved and a series of artificial Mn4XO4-clusters (X = Ca/Y/Gd) have been reported, which closely mimic both the geometric structure and the electronic structure, as well as the redox property of the OEC. These new advances provide a structurally well-defined molecular platform to study the structure-function relationship of the OEC and shed new light on the design of efficient catalysts for the water-splitting reaction in artificial photosynthesis.
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Affiliation(s)
- Yang Chen
- Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Boran Xu
- Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Ruoqing Yao
- Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Changhui Chen
- Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Chunxi Zhang
- Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
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16
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Competitive interaction of Mn(II) and Fe(II) cations with the high-affinity Mn-binding site of the photosystem II: evolutionary aspect. ORIGINS LIFE EVOL B 2022; 52:113-128. [PMID: 35796895 DOI: 10.1007/s11084-022-09625-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Accepted: 06/16/2022] [Indexed: 10/17/2022]
Abstract
The evolutionary origin of the oxygen-evolving complex (OEC) in the photosystem II (PSII) is still unclear, as is the nature of electron source for the photosystem before the OEC had appeared. Johnson et al. (in PNAS 110:11238, 2013) speculated that Mn(II) cations were the source of electrons for transitional photosystems. However, Archean oceans also contained Fe(II) cations at concentrations comparable or higher than that of Mn(II). Fe(II) cations can bind to the high-affinity (НА) Mn-binding site in the OEC (Semin et al. in Biochemistry 41:5854, 2002). Now we have investigated the competitive interaction of Mn(II) and Fe(II) cations with the HA site in the Mn-depleted PSII membranes (PSII[-Mn]). Fe cations, oxidized under illumination, bind strongly to the HA site and, thus, prevent the interaction of Mn(II) with this site. If the Mn(II) and Fe(II) cations, at relatively equal concentration, are simultaneously present in the buffer, together with PSII(-Mn) membranes, there is competition between these two cations for the binding site, which manifests itself in partial inhibition of the Mn(II) oxidation and the blocking of the HA site by Fe(II) cations. If the concentration of Fe(II) cations is several times higher than the concentration of Mn(II), the HA site is completely blocked and the oxidation of Mn(II) cations is inhibited; under saturating light, the effectiveness of this inhibitory effect increases. This may be due to the generation of H2O2 on the acceptor side of the photosystem, which significantly accelerates the rate of the turnover reaction of Mn(II) on the HA site.
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17
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Guo Y, Messinger J, Kloo L, Sun L. Reversible Structural Isomerization of Nature's Water Oxidation Catalyst Prior to O-O Bond Formation. J Am Chem Soc 2022; 144:11736-11747. [PMID: 35748306 PMCID: PMC9264352 DOI: 10.1021/jacs.2c03528] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
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Photosynthetic water
oxidation is catalyzed by a manganese–calcium
oxide cluster, which experiences five “S-states” during
a light-driven reaction cycle. The unique “distorted chair”-like
geometry of the Mn4CaO5(6) cluster shows structural
flexibility that has been frequently proposed to involve “open”
and “closed”-cubane forms from the S1 to
S3 states. The isomers are interconvertible in the S1 and S2 states, while in the S3 state,
the open-cubane structure is observed to dominate inThermosynechococcus elongatus (cyanobacteria) samples.
In this work, using density functional theory calculations, we go
beyond the S3+Yz state to the S3nYz• → S4+Yz step, and report for the first time
that the reversible isomerism, which is suppressed in the S3+Yz state, is fully recovered
in the ensuing S3nYz• state due to the proton release
from a manganese-bound water ligand. The altered coordination strength
of the manganese–ligand facilitates formation of the closed-cubane
form, in a dynamic equilibrium with the open-cubane form. This tautomerism
immediately preceding dioxygen formation may constitute the rate limiting
step for O2 formation, and exert a significant influence
on the water oxidation mechanism in photosystem II.
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Affiliation(s)
- Yu Guo
- Center of Artificial Photosynthesis for Solar Fuels and Department of Chemistry, School of Science, Westlake University, Hangzhou 310024, China.,Institute of Natural Sciences, Westlake Institute for Advanced Study, Hangzhou 310024, China
| | - Johannes Messinger
- Department of Chemistry, Umeå University, Linnaeus väg 6 (KBC huset), SE-90187 Umeå, Sweden.,Molecular Biomimetics, Department of Chemistry─Ångström Laboratory, Uppsala University, SE-75120 Uppsala, Sweden
| | - Lars Kloo
- Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Licheng Sun
- Center of Artificial Photosynthesis for Solar Fuels and Department of Chemistry, School of Science, Westlake University, Hangzhou 310024, China.,Institute of Natural Sciences, Westlake Institute for Advanced Study, Hangzhou 310024, China
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18
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Opel F, Siebert NA, Klatt S, Tüllinghoff A, Hantke JG, Toepel J, Bühler B, Nürnberg DJ, Klähn S. Generation of Synthetic Shuttle Vectors Enabling Modular Genetic Engineering of Cyanobacteria. ACS Synth Biol 2022; 11:1758-1771. [PMID: 35405070 DOI: 10.1021/acssynbio.1c00605] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cyanobacteria have raised great interest in biotechnology due to their potential for a sustainable, photosynthesis-driven production of fuels and value-added chemicals. This has led to a concomitant development of molecular tools to engineer the metabolism of those organisms. In this regard, however, even cyanobacterial model strains lag behind compared to their heterotrophic counterparts. For instance, replicative shuttle vectors that allow gene transfer independent of recombination into host DNA are still scarce. Here, we introduce the pSOMA shuttle vector series comprising 10 synthetic plasmids for comprehensive genetic engineering of Synechocystis sp. PCC 6803. The series is based on the small endogenous plasmids pCA2.4 and pCB2.4, each combined with a replicon from Escherichia coli, different selection markers as well as features facilitating molecular cloning and the insulated introduction of gene expression cassettes. We made use of genes encoding green fluorescent protein (GFP) and a Baeyer-Villiger monooxygenase (BVMO) to demonstrate functional gene expression from the pSOMA plasmids in vivo. Moreover, we demonstrate the expression of distinct heterologous genes from individual plasmids maintained in the same strain and thereby confirmed compatibility between the two pSOMA subseries as well as with derivatives of the broad-host-range plasmid RSF1010. We also show that gene transfer into the filamentous model strain Anabaena sp. PCC 7120 is generally possible, which is encouraging to further explore the range of cyanobacterial host species that could be engineered via pSOMA plasmids. Altogether, the pSOMA shuttle vector series displays an attractive alternative to existing plasmid series and thus meets the current demand for the introduction of complex genetic setups and to perform extensive metabolic engineering of cyanobacteria.
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Affiliation(s)
- Franz Opel
- Department of Solar Materials (SOMA), Helmholtz Centre for Environmental Research─UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Nina A. Siebert
- Department of Solar Materials (SOMA), Helmholtz Centre for Environmental Research─UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Sabine Klatt
- Department of Solar Materials (SOMA), Helmholtz Centre for Environmental Research─UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Adrian Tüllinghoff
- Department of Solar Materials (SOMA), Helmholtz Centre for Environmental Research─UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Janis G. Hantke
- Institute of Experimental Physics, Biochemistry and Biophysics of Photosynthetic Organisms, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Jörg Toepel
- Department of Solar Materials (SOMA), Helmholtz Centre for Environmental Research─UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Bruno Bühler
- Department of Solar Materials (SOMA), Helmholtz Centre for Environmental Research─UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Dennis J. Nürnberg
- Institute of Experimental Physics, Biochemistry and Biophysics of Photosynthetic Organisms, Free University Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Stephan Klähn
- Department of Solar Materials (SOMA), Helmholtz Centre for Environmental Research─UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
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Yocum CF. Photosystem 2 and the oxygen evolving complex: a brief overview. PHOTOSYNTHESIS RESEARCH 2022; 152:97-105. [PMID: 35294671 DOI: 10.1007/s11120-022-00910-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 02/28/2022] [Indexed: 06/14/2023]
Abstract
These special issues of photosynthesis research present papers documenting progress in revealing the many aspects of photosystem 2, a unique, one-of-a-kind complex system that can reduce a plastoquinone to a plastoquinol on every second flash of light and oxidize 2 H2O to an O2 on every fourth flash. This overview is a brief personal assessment of the progress observed by the author over a four-decade research career, including a discussion of some remaining unsolved issues. It will come as no surprise to readers that there are remaining questions given the complexity of PS2, and the efforts that have been needed so far to uncover its secrets. In fact, most readers will have their own lists of outstanding questions.
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Affiliation(s)
- Charles F Yocum
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA.
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20
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Lysenko V, Varduny T. High levels of anoxygenic photosynthesis revealed by dual-frequency Fourier photoacoustics in Ailanthus altissima leaves. FUNCTIONAL PLANT BIOLOGY : FPB 2022; 49:573-586. [PMID: 35413232 DOI: 10.1071/fp21093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 03/02/2022] [Indexed: 06/14/2023]
Abstract
In contrast to oxygenic photosynthesis, true anoxygenic photosynthesis is not associated with O2 evolution originated from water photolysis but still converts light energy to that of the phosphoanhydride bonds of ATP. In a narrow sense, anoxygenic photosynthesis is mainly known as to be related to the purple and green sulfur bacteria, but in a broad sense, it also occurs in the vascular plants. The portion of photosynthetic water photolysis that is compensated by the processes of O2 uptake (respiration, photorespiration, Mehler cycle, etc.) may be referred to as 'quasi' anoxygenic photosynthesis. Photoacoustic method allows for the separate detection of photolytic O2 at frequencies of measuring light about 20-40Hz, whereas at 250-400Hz, it detects the photochemical energy storage. We have developed a fast-Fourier transform photoacoustic method enabling measurements of both these signals simultaneously in one sample. This method allows to calculate oxygenic coefficients, which reflect the part of photochemically stored light energy that is used for the water photolysis. We show that the true anoxygenic photosynthesis in Ailanthus altissima Mill. leaves reached very high levels under low light, under moderate light at the beginning of the 1-h period, and at the end of the 40-min period under saturating light.
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Affiliation(s)
- Vladimir Lysenko
- Academy of Biology and Biotechnology, Southern Federal University, Botanichesky spusk 7, 344041 Rostov-on-Don, Russia
| | - Tatyana Varduny
- Academy of Biology and Biotechnology, Southern Federal University, Botanichesky spusk 7, 344041 Rostov-on-Don, Russia
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21
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Inagaki N. Processing of D1 Protein: A Mysterious Process Carried Out in Thylakoid Lumen. Int J Mol Sci 2022; 23:2520. [PMID: 35269663 PMCID: PMC8909930 DOI: 10.3390/ijms23052520] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 02/16/2022] [Accepted: 02/21/2022] [Indexed: 11/16/2022] Open
Abstract
In oxygenic photosynthetic organisms, D1 protein, a core subunit of photosystem II (PSII), displays a rapid turnover in the light, in which D1 proteins are distinctively damaged and immediately removed from the PSII. In parallel, as a repair process, D1 proteins are synthesized and simultaneously assembled into the PSII. On this flow, the D1 protein is synthesized as a precursor with a carboxyl-terminal extension, and the D1 processing is defined as a step for proteolytic removal of the extension by a specific protease, CtpA. The D1 processing plays a crucial role in appearance of water-oxidizing capacity of PSII, because the main chain carboxyl group at carboxyl-terminus of the D1 protein, exposed by the D1 processing, ligates a manganese and a calcium atom in the Mn4CaO5-cluster, a special equipment for water-oxidizing chemistry of PSII. This review focuses on the D1 processing and discusses it from four angles: (i) Discovery of the D1 processing and recognition of its importance: (ii) Enzyme involved in the D1 processing: (iii) Efforts for understanding significance of the D1 processing: (iv) Remaining mysteries in the D1 processing. Through the review, I summarize the current status of our knowledge on and around the D1 processing.
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Affiliation(s)
- Noritoshi Inagaki
- Research Center for Advanced Analysis, National Agriculture and Food Research Organization (NARO), Tsukuba 305-8518, Japan
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22
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Schmidt-Rohr K. O 2 and Other High-Energy Molecules in Photosynthesis: Why Plants Need Two Photosystems. Life (Basel) 2021; 11:life11111191. [PMID: 34833066 PMCID: PMC8621363 DOI: 10.3390/life11111191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Revised: 10/24/2021] [Accepted: 10/29/2021] [Indexed: 11/16/2022] Open
Abstract
The energetics of photosynthesis in plants have been re-analyzed in a framework that represents the relatively high energy of O2 correctly. Starting with the photon energy exciting P680 and "loosening an electron", the energy transfer and electron transport are represented in a comprehensive, self-explanatory sequence of redox energy transfer and release diagrams. The resulting expanded Z-scheme explicitly shows charge separation as well as important high-energy species such as O2, TyrZ˙, and P680+˙, whose energies are not apparent in the classical Z-scheme of photosynthesis. Crucially, the energetics of the three important forms of P680 and of P700 are clarified. The relative free energies of oxidized and reduced species are shown explicitly in kJ/mol, not encrypted in volts. Of the chemical energy produced in photosynthesis, more is stored in O2 than in glucose. The expanded Z-scheme introduced here provides explanatory power lacking in the classical scheme. It shows that P680* is energetically boosted to P680+˙ by the favorable electron affinity of pheophytin and that Photosystem I (PSI) has insufficient energy to split H2O and produce O2 because P700* is too easily ionized. It also avoids the Z-scheme's bewildering implication, according to the "electron waterfall" concept, that H2O gives off electrons that spontaneously flow to chlorophyll while releasing energy. The new analysis explains convincingly why plants need two different photosystems in tandem: (i) PSII mostly extracts hydrogen from H2O, producing PQH2 (plastoquinol), and generates the energetically expensive product O2; this step provides little energy directly to the plant; (ii) PSI produces chemical energy for the organism, by pumping protons against a concentration gradient and producing less reluctant hydrogen donors. It also documents that electron transport and energy transfer occur in opposite directions and do not involve redox voltages. The analysis makes it clear that the high-energy species in photosynthesis are unstable, electron-deficient species such as P680+˙ and TyrZ˙, not putative high-energy electrons.
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23
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de Lichtenberg C, Kim CJ, Chernev P, Debus RJ, Messinger J. The exchange of the fast substrate water in the S 2 state of photosystem II is limited by diffusion of bulk water through channels - implications for the water oxidation mechanism. Chem Sci 2021; 12:12763-12775. [PMID: 34703563 PMCID: PMC8494045 DOI: 10.1039/d1sc02265b] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/31/2021] [Indexed: 12/02/2022] Open
Abstract
The molecular oxygen we breathe is produced from water-derived oxygen species bound to the Mn4CaO5 cluster in photosystem II (PSII). Present research points to the central oxo-bridge O5 as the 'slow exchanging substrate water (Ws)', while, in the S2 state, the terminal water ligands W2 and W3 are both discussed as the 'fast exchanging substrate water (Wf)'. A critical point for the assignment of Wf is whether or not its exchange with bulk water is limited by barriers in the channels leading to the Mn4CaO5 cluster. In this study, we measured the rates of H2 16O/H2 18O substrate water exchange in the S2 and S3 states of PSII core complexes from wild-type (WT) Synechocystis sp. PCC 6803, and from two mutants, D1-D61A and D1-E189Q, that are expected to alter water access via the Cl1/O4 channels and the O1 channel, respectively. We found that the exchange rates of Wf and Ws were unaffected by the E189Q mutation (O1 channel), but strongly perturbed by the D61A mutation (Cl1/O4 channel). It is concluded that all channels have restrictions limiting the isotopic equilibration of the inner water pool near the Mn4CaO5 cluster, and that D61 participates in one such barrier. In the D61A mutant this barrier is lowered so that Wf exchange occurs more rapidly. This finding removes the main argument against Ca-bound W3 as fast substrate water in the S2 state, namely the indifference of the rate of Wf exchange towards Ca/Sr substitution.
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Affiliation(s)
- Casper de Lichtenberg
- Department of Chemistry, Umeå University Linnaeus väg 6 (KBC huset), SE-901 87 Umeå Sweden
- Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, Uppsala University POB 523 SE-75120 Uppsala Sweden
| | - Christopher J Kim
- Department of Biochemistry, University of California Riverside California 92521 USA
| | - Petko Chernev
- Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, Uppsala University POB 523 SE-75120 Uppsala Sweden
| | - Richard J Debus
- Department of Biochemistry, University of California Riverside California 92521 USA
| | - Johannes Messinger
- Department of Chemistry, Umeå University Linnaeus väg 6 (KBC huset), SE-901 87 Umeå Sweden
- Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, Uppsala University POB 523 SE-75120 Uppsala Sweden
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24
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Drosou M, Pantazis DA. Redox Isomerism in the S 3 State of the Oxygen-Evolving Complex Resolved by Coupled Cluster Theory. Chemistry 2021; 27:12815-12825. [PMID: 34288176 PMCID: PMC8518824 DOI: 10.1002/chem.202101567] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Indexed: 01/19/2023]
Abstract
The electronic and geometric structures of the water-oxidizing complex of photosystem II in the steps of the catalytic cycle that precede dioxygen evolution remain hotly debated. Recent structural and spectroscopic investigations support contradictory redox formulations for the active-site Mn4 CaOx cofactor in the final metastable S3 state. These range from the widely accepted MnIV 4 oxo-hydroxo model, which presumes that O-O bond formation occurs in the ultimate transient intermediate (S4 ) of the catalytic cycle, to a MnIII 2 MnIV 2 peroxo model representative of the contrasting "early-onset" O-O bond formation hypothesis. Density functional theory energetics of suggested S3 redox isomers are inconclusive because of extreme functional dependence. Here, we use the power of the domain-based local pair natural orbital approach to coupled cluster theory, DLPNO-CCSD(T), to present the first correlated wave function theory calculations of relative stabilities for distinct redox-isomeric forms of the S3 state. Our results enabled us to evaluate conflicting models for the S3 state of the oxygen-evolving complex (OEC) and to quantify the accuracy of lower-level theoretical approaches. Our assessment of the relevance of distinct redox-isomeric forms for the mechanism of biological water oxidation strongly disfavors the scenario of early-onset O-O formation advanced by literal interpretations of certain crystallographic models. This work serves as a case study in the application of modern coupled cluster implementations to redox isomerism problems in oligonuclear transition metal systems.
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Affiliation(s)
- Maria Drosou
- Inorganic Chemistry LaboratoryNational and Kapodistrian University of AthensPanepistimiopolisZografou15771Greece
| | - Dimitrios A. Pantazis
- Max-Planck-Institut für KohlenforschungKaiser-Wilhelm-Platz 145470Mülheim an derRuhrGermany
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25
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Bio-Inspired Molecular Catalysts for Water Oxidation. Catalysts 2021. [DOI: 10.3390/catal11091068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The catalytic tetranuclear manganese-calcium-oxo cluster in the photosynthetic reaction center, photosystem II, provides an excellent blueprint for light-driven water oxidation in nature. The water oxidation reaction has attracted intense interest due to its potential as a renewable, clean, and environmentally benign source of energy production. Inspired by the oxygen-evolving complex of photosystem II, a large of number of highly innovative synthetic bio-inspired molecular catalysts are being developed that incorporate relatively cheap and abundant metals such as Mn, Fe, Co, Ni, and Cu, as well as Ru and Ir, in their design. In this review, we briefly discuss the historic milestones that have been achieved in the development of transition metal catalysts and focus on a detailed description of recent progress in the field.
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26
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Tanvir RU, Zhang J, Canter T, Chen D, Lu J, Hu Z. Harnessing Solar Energy using Phototrophic Microorganisms: A Sustainable Pathway to Bioenergy, Biomaterials, and Environmental Solutions. RENEWABLE & SUSTAINABLE ENERGY REVIEWS 2021; 146:1-111181. [PMID: 34526853 PMCID: PMC8437043 DOI: 10.1016/j.rser.2021.111181] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Phototrophic microorganisms (microbial phototrophs) use light as an energy source to carry out various metabolic processes producing biomaterials and bioenergy and supporting their own growth. Among them, microalgae and cyanobacteria have been utilized extensively for bioenergy, biomaterials, and environmental applications. Their superior photosynthetic efficiency, lipid content, and shorter cultivation time compared to terrestrial biomass make them more suitable for efficient production of bioenergy and biomaterials. Other phototrophic microorganisms, especially anoxygenic phototrophs, demonstrated the ability to survive and flourish while producing renewable energy and high-value products under harsh environmental conditions. This review presents a comprehensive overview of microbial phototrophs on their (i) production of bioenergy and biomaterials, (ii) emerging and innovative applications for environmental conservation, mitigation, and remediation, and (iii) physical, genetic, and metabolic pathways to improve light harvesting and biomass/biofuel/biomaterial production. Both physical (e.g., incremental irradiation) and genetic approaches (e.g., truncated antenna) are implemented to increase the light-harvesting efficiency. Increases in biomass yield and metabolic products are possible through the manipulation of metabolic pathways and selection of a proper strain under optimal cultivation conditions and downstream processing, including harvesting, extraction, and purification. Finally, the current barriers in harnessing solar energy using phototrophic microorganisms are presented, and future research perspectives are discussed, such as integrating phototrophic microorganisms with emerging technologies.
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Affiliation(s)
- Rahamat Ullah Tanvir
- Department of Civil and Environmental Engineering, University of Missouri, Columbia, Missouri, 65211, USA
| | - Jianying Zhang
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Timothy Canter
- Department of Civil and Environmental Engineering, University of Missouri, Columbia, Missouri, 65211, USA
| | - Dick Chen
- Dual Enrollment Program, University of Missouri, Columbia, Missouri, 65211, USA
| | - Jingrang Lu
- Office of Research and Development, United States Environmental Protection Agency (EPA), Cincinnati, Ohio, 45268, USA
| | - Zhiqiang Hu
- Department of Civil and Environmental Engineering, University of Missouri, Columbia, Missouri, 65211, USA
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27
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Pastore AJ, Teo RD, Montoya A, Burg MJ, Twahir UT, Bruner SD, Beratan DN, Angerhofer A. Oxalate decarboxylase uses electron hole hopping for catalysis. J Biol Chem 2021; 297:100857. [PMID: 34097877 PMCID: PMC8254039 DOI: 10.1016/j.jbc.2021.100857] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 05/28/2021] [Accepted: 06/03/2021] [Indexed: 01/16/2023] Open
Abstract
The hexameric low-pH stress response enzyme oxalate decarboxylase catalyzes the decarboxylation of the oxalate mono-anion in the soil bacterium Bacillus subtilis. A single protein subunit contains two Mn-binding cupin domains, and catalysis depends on Mn(III) at the N-terminal site. The present study suggests a mechanistic function for the C-terminal Mn as an electron hole donor for the N-terminal Mn. The resulting spatial separation of the radical intermediates directs the chemistry toward decarboxylation of the substrate. A π-stacked tryptophan pair (W96/W274) links two neighboring protein subunits together, thus reducing the Mn-to-Mn distance from 25.9 Å (intrasubunit) to 21.5 Å (intersubunit). Here, we used theoretical analysis of electron hole-hopping paths through redox-active sites in the enzyme combined with site-directed mutagenesis and X-ray crystallography to demonstrate that this tryptophan pair supports effective electron hole hopping between the C-terminal Mn of one subunit and the N-terminal Mn of the other subunit through two short hops of ∼8.5 Å. Replacement of W96, W274, or both with phenylalanine led to a large reduction in catalytic efficiency, whereas replacement with tyrosine led to recovery of most of this activity. W96F and W96Y mutants share the wildtype tertiary structure. Two additional hole-hopping networks were identified leading from the Mn ions to the protein surface, potentially protecting the enzyme from high Mn oxidation states during turnover. Our findings strongly suggest that multistep hole-hopping transport between the two Mn ions is required for enzymatic function, adding to the growing examples of proteins that employ aromatic residues as hopping stations.
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Affiliation(s)
- Anthony J Pastore
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
| | - Ruijie D Teo
- Department of Chemistry, Duke University, Durham, North Carolina, USA
| | - Alvaro Montoya
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
| | - Matthew J Burg
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
| | - Umar T Twahir
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
| | - Steven D Bruner
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
| | - David N Beratan
- Department of Chemistry, Duke University, Durham, North Carolina, USA.
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28
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Cruz JA, Avenson TJ. Photosynthesis: a multiscopic view. JOURNAL OF PLANT RESEARCH 2021; 134:665-682. [PMID: 34170422 DOI: 10.1007/s10265-021-01321-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 06/11/2021] [Indexed: 06/13/2023]
Abstract
A recurring analogy for photosynthesis research is the fable of the blind men and the elephant. Photosynthesis has many complex working parts, which has driven the need to study each of them individually, with an inherent understanding that a more complete picture will require systematic integration of these views. However, unlike the blind men, who are limited to using their hands, researchers have developed over the past decades a repertoire of methods for studying these components, many of which capitalize on unique features intrinsic to each. More recent concerns about food security and clean, renewable energy have increased support for applied photosynthesis research, with the idea of either improving photosynthetic performance as a desired trait in select species or using photosynthetic measurements as a phenotyping tool in breeding efforts or for high precision crop management. In this review, we spotlight the migration of approaches for studying photosynthesis from the laboratory into field environments, highlight some recent advances and speculate on areas where further development would be fruitful, with an eye towards how applied photosynthesis research can have impacts at local and global scales.
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Affiliation(s)
- Jeffrey A Cruz
- Plant Research Laboratories, Michigan State University, 612 Wilson Road, MI, S-206, Lansing, USA.
- Department of Biochemistry and Molecular Biology, Michigan State University, Lansing, MI, USA.
| | - Thomas J Avenson
- Department of Plant Sciences, University of Cambridge, CB2 9EW, Cambridge, UK
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29
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Kell DB. A protet-based, protonic charge transfer model of energy coupling in oxidative and photosynthetic phosphorylation. Adv Microb Physiol 2021; 78:1-177. [PMID: 34147184 DOI: 10.1016/bs.ampbs.2021.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170mV; to achieve in vivo rates the imposed pmf must reach 200mV. The key question then is 'does the pmf generated by electron transport exceed 200mV, or even 170mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined.
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Affiliation(s)
- Douglas B Kell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative, Biology, University of Liverpool, Liverpool, United Kingdom; The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
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Sirohiwal A, Neese F, Pantazis DA. How Can We Predict Accurate Electrochromic Shifts for Biochromophores? A Case Study on the Photosynthetic Reaction Center. J Chem Theory Comput 2021; 17:1858-1873. [PMID: 33566610 PMCID: PMC8023663 DOI: 10.1021/acs.jctc.0c01152] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Indexed: 01/28/2023]
Abstract
Protein-embedded chromophores are responsible for light harvesting, excitation energy transfer, and charge separation in photosynthesis. A critical part of the photosynthetic apparatus are reaction centers (RCs), which comprise groups of (bacterio)chlorophyll and (bacterio)pheophytin molecules that transform the excitation energy derived from light absorption into charge separation. The lowest excitation energies of individual pigments (site energies) are key for understanding photosynthetic systems, and form a prime target for quantum chemistry. A major theoretical challenge is to accurately describe the electrochromic (Stark) shifts in site energies produced by the inhomogeneous electric field of the protein matrix. Here, we present large-scale quantum mechanics/molecular mechanics calculations of electrochromic shifts for the RC chromophores of photosystem II (PSII) using various quantum chemical methods evaluated against the domain-based local pair natural orbital (DLPNO) implementation of the similarity-transformed equation of motion coupled cluster theory with single and double excitations (STEOM-CCSD). We show that certain range-separated density functionals (ωΒ97, ωΒ97X-V, ωΒ2PLYP, and LC-BLYP) correctly reproduce RC site energy shifts with time-dependent density functional theory (TD-DFT). The popular CAM-B3LYP functional underestimates the shifts and is not recommended. Global hybrid functionals are too insensitive to the environment and should be avoided, while nonhybrid functionals are strictly nonapplicable. Among the applicable approximate coupled cluster methods, the canonical versions of CC2 and ADC(2) were found to deviate significantly from the reference results both for the description of the lowest excited state and for the electrochromic shifts. By contrast, their spin-component-scaled (SCS) and particularly the scale-opposite-spin (SOS) variants compare well with the reference DLPNO-STEOM-CCSD and the best range-separated DFT methods. The emergence of RC excitation asymmetry is discussed in terms of intrinsic and protein electrostatic potentials. In addition, we evaluate a minimal structural scaffold of PSII, the D1-D2-CytB559 RC complex often employed in experimental studies, and show that it would have the same site energy distribution of RC chromophores as the full PSII supercomplex, but only under the unlikely conditions that the core protein organization and cofactor arrangement remain identical to those of the intact enzyme.
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Affiliation(s)
- Abhishek Sirohiwal
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
- Fakultät
für Chemie und Biochemie, Ruhr-Universität
Bochum, 44780 Bochum, Germany
| | - Frank Neese
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Dimitrios A. Pantazis
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
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31
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Mäusle SM, Abzaliyeva A, Greife P, Simon PS, Perez R, Zilliges Y, Dau H. Activation energies for two steps in the S 2→ S 3 transition of photosynthetic water oxidation from time-resolved single-frequency infrared spectroscopy. J Chem Phys 2020; 153:215101. [PMID: 33291916 DOI: 10.1063/5.0027995] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The mechanism of water oxidation by the Photosystem II (PSII) protein-cofactor complex is of high interest, but specifically, the crucial coupling of protonation dynamics to electron transfer (ET) and dioxygen chemistry remains insufficiently understood. We drove spinach-PSII membranes by nanosecond-laser flashes synchronously through the water-oxidation cycle and traced the PSII processes by time-resolved single-frequency infrared (IR) spectroscopy in the spectral range of symmetric carboxylate vibrations of protein side chains. After the collection of IR-transients from 100 ns to 1 s, we analyzed the proton-removal step in the S2 ⇒ S3 transition, which precedes the ET that oxidizes the Mn4CaOx-cluster. Around 1400 cm-1, pronounced changes in the IR-transients reflect this pre-ET process (∼40 µs at 20 °C) and the ET step (∼300 µs at 20 °C). For transients collected at various temperatures, unconstrained multi-exponential simulations did not provide a coherent set of time constants, but constraining the ET time constants to previously determined values solved the parameter correlation problem and resulted in an exceptionally high activation energy of 540 ± 30 meV for the pre-ET step. We assign the pre-ET step to deprotonation of a group that is re-protonated by accepting a proton from the substrate-water, which binds concurrently with the ET step. The analyzed IR-transients disfavor carboxylic-acid deprotonation in the pre-ET step. Temperature-dependent amplitudes suggest thermal equilibria that determine how strongly the proton-removal step is reflected in the IR-transients. Unexpectedly, the proton-removal step is only weakly reflected in the 1400 cm-1 transients of PSII core complexes of a thermophilic cyanobacterium (T. elongatus).
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Affiliation(s)
- Sarah M Mäusle
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Aiganym Abzaliyeva
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Paul Greife
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Philipp S Simon
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Rebeca Perez
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Yvonne Zilliges
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Holger Dau
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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Marzolf DR, McKenzie AM, O’Malley MC, Ponomarenko NS, Swaim CM, Brittain TJ, Simmons NL, Pokkuluri PR, Mulfort KL, Tiede DM, Kokhan O. Mimicking Natural Photosynthesis: Designing Ultrafast Photosensitized Electron Transfer into Multiheme Cytochrome Protein Nanowires. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E2143. [PMID: 33126541 PMCID: PMC7693585 DOI: 10.3390/nano10112143] [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: 09/30/2020] [Revised: 10/23/2020] [Accepted: 10/26/2020] [Indexed: 05/02/2023]
Abstract
Efficient nanomaterials for artificial photosynthesis require fast and robust unidirectional electron transfer (ET) from photosensitizers through charge-separation and accumulation units to redox-active catalytic sites. We explored the ultrafast time-scale limits of photo-induced charge transfer between a Ru(II)tris(bipyridine) derivative photosensitizer and PpcA, a 3-heme c-type cytochrome serving as a nanoscale biological wire. Four covalent attachment sites (K28C, K29C, K52C, and G53C) were engineered in PpcA enabling site-specific covalent labeling with expected donor-acceptor (DA) distances of 4-8 Å. X-ray scattering results demonstrated that mutations and chemical labeling did not disrupt the structure of the proteins. Time-resolved spectroscopy revealed three orders of magnitude difference in charge transfer rates for the systems with otherwise similar DA distances and the same number of covalent bonds separating donors and acceptors. All-atom molecular dynamics simulations provided additional insight into the structure-function requirements for ultrafast charge transfer and the requirement of van der Waals contact between aromatic atoms of photosensitizers and hemes in order to observe sub-nanosecond ET. This work demonstrates opportunities to utilize multi-heme c-cytochromes as frameworks for designing ultrafast light-driven ET into charge-accumulating biohybrid model systems, and ultimately for mimicking the photosynthetic paradigm of efficiently coupling ultrafast, light-driven electron transfer chemistry to multi-step catalysis within small, experimentally versatile photosynthetic biohybrid assemblies.
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Affiliation(s)
- Daniel R. Marzolf
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Aidan M. McKenzie
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Matthew C. O’Malley
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Nina S. Ponomarenko
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, USA; (N.S.P.); (K.L.M.); (D.M.T.)
| | - Coleman M. Swaim
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Tyler J. Brittain
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
| | - Natalie L. Simmons
- Department of Biology, James Madison University, Harrisonburg, VA 22807, USA;
| | | | - Karen L. Mulfort
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, USA; (N.S.P.); (K.L.M.); (D.M.T.)
| | - David M. Tiede
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, USA; (N.S.P.); (K.L.M.); (D.M.T.)
| | - Oleksandr Kokhan
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA; (D.R.M.); (A.M.M.); (C.M.S.); (T.J.B.)
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33
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de Lichtenberg C, Avramov AP, Zhang M, Mamedov F, Burnap RL, Messinger J. The D1-V185N mutation alters substrate water exchange by stabilizing alternative structures of the Mn 4Ca-cluster in photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148319. [PMID: 32979346 DOI: 10.1016/j.bbabio.2020.148319] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 09/15/2020] [Accepted: 09/19/2020] [Indexed: 11/30/2022]
Abstract
In photosynthesis, the oxygen-evolving complex (OEC) of the pigment-protein complex photosystem II (PSII) orchestrates the oxidation of water. Introduction of the V185N mutation into the D1 protein was previously reported to drastically slow O2-release and strongly perturb the water network surrounding the Mn4Ca cluster. Employing time-resolved membrane inlet mass spectrometry, we measured here the H218O/H216O-exchange kinetics of the fast (Wf) and slow (Ws) exchanging substrate waters bound in the S1, S2 and S3 states to the Mn4Ca cluster of PSII core complexes isolated from wild type and D1-V185N strains of Synechocystis sp. PCC 6803. We found that the rate of exchange for Ws was increased in the S1 and S2 states, while both Wf and Ws exchange rates were decreased in the S3 state. Additionally, we used EPR spectroscopy to characterize the Mn4Ca cluster and its interaction with the redox active D1-Tyr161 (YZ). In the S2 state, we observed a greatly diminished multiline signal in the V185N-PSII that could be recovered by addition of ammonia. The split signal in the S1 state was not affected, while the split signal in the S3 state was absent in the D1-V185N mutant. These findings are rationalized by the proposal that the N185 residue stabilizes the binding of an additional water-derived ligand at the Mn1 site of the Mn4Ca cluster via hydrogen bonding. Implications for the sites of substrate water binding are discussed.
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Affiliation(s)
- Casper de Lichtenberg
- Department of Chemistry, Umeå University, Linnaeus väg 6 (KBC huset), SE-901 87 Umeå, Sweden; Molecular Biomimetics, Department of Chemistry - Ångström, Uppsala University, POB 523, SE-75120 Uppsala, Sweden
| | - Anton P Avramov
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078, United States
| | - Minquan Zhang
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078, United States
| | - Fikret Mamedov
- Molecular Biomimetics, Department of Chemistry - Ångström, Uppsala University, POB 523, SE-75120 Uppsala, Sweden
| | - Robert L Burnap
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078, United States
| | - Johannes Messinger
- Department of Chemistry, Umeå University, Linnaeus väg 6 (KBC huset), SE-901 87 Umeå, Sweden; Molecular Biomimetics, Department of Chemistry - Ångström, Uppsala University, POB 523, SE-75120 Uppsala, Sweden.
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34
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Shevela D, Do HN, Fantuzzi A, Rutherford AW, Messinger J. Bicarbonate-Mediated CO 2 Formation on Both Sides of Photosystem II. Biochemistry 2020; 59:2442-2449. [PMID: 32574489 PMCID: PMC7467574 DOI: 10.1021/acs.biochem.0c00208] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 06/10/2020] [Indexed: 01/25/2023]
Abstract
The effect of bicarbonate (HCO3-) on photosystem II (PSII) activity was discovered in the 1950s, but only recently have its molecular mechanisms begun to be clarified. Two chemical mechanisms have been proposed. One is for the electron-donor side, in which mobile HCO3- enhances and possibly regulates water oxidation by acting as proton acceptor, after which it dissociates into CO2 and H2O. The other is for the electron-acceptor side, in which (i) reduction of the QA quinone leads to the release of HCO3- from its binding site on the non-heme iron and (ii) the Em potential of the QA/QA•- couple increases when HCO3- dissociates. This suggested a protective/regulatory role of HCO3- as it is known that increasing the Em of QA decreases the extent of back-reaction-associated photodamage. Here we demonstrate, using plant thylakoids, that time-resolved membrane-inlet mass spectrometry together with 13C isotope labeling of HCO3- allows donor- and acceptor-side formation of CO2 by PSII to be demonstrated and distinguished, which opens the door for future studies of the importance of both mechanisms under in vivo conditions.
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Affiliation(s)
- Dmitry Shevela
- Department
of Chemistry, Chemical Biological Centre, Umeå University, 90187 Umeå, Sweden
| | - Hoang-Nguyen Do
- Department
of Chemistry, Chemical Biological Centre, Umeå University, 90187 Umeå, Sweden
| | - Andrea Fantuzzi
- Department
of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - A. William Rutherford
- Department
of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Johannes Messinger
- Department
of Chemistry, Chemical Biological Centre, Umeå University, 90187 Umeå, Sweden
- Molecular
Biomimetics, Department of Chemistry-Ångström Laboratory, Uppsala University, 75120 Uppsala, Sweden
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35
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Cox N, Pantazis DA, Lubitz W. Current Understanding of the Mechanism of Water Oxidation in Photosystem II and Its Relation to XFEL Data. Annu Rev Biochem 2020; 89:795-820. [DOI: 10.1146/annurev-biochem-011520-104801] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The investigation of water oxidation in photosynthesis has remained a central topic in biochemical research for the last few decades due to the importance of this catalytic process for technological applications. Significant progress has been made following the 2011 report of a high-resolution X-ray crystallographic structure resolving the site of catalysis, a protein-bound Mn4CaOxcomplex, which passes through ≥5 intermediate states in the water-splitting cycle. Spectroscopic techniques complemented by quantum chemical calculations aided in understanding the electronic structure of the cofactor in all (detectable) states of the enzymatic process. Together with isotope labeling, these techniques also revealed the binding of the two substrate water molecules to the cluster. These results are described in the context of recent progress using X-ray crystallography with free-electron lasers on these intermediates. The data are instrumental for developing a model for the biological water oxidation cycle.
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Affiliation(s)
- Nicholas Cox
- Research School of Chemistry, The Australian National University, Canberra ACT 2601, Australia
| | | | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion, 45470 Mülheim an der Ruhr, Germany
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36
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Jiang Y, Liu Y, Zhang J. Antibiotic contaminants reduced the treatment efficiency of UV-C on Microcystis aeruginosa through hormesis. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 261:114193. [PMID: 32088440 DOI: 10.1016/j.envpol.2020.114193] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 02/12/2020] [Accepted: 02/13/2020] [Indexed: 06/10/2023]
Abstract
Antibiotic contaminants exert stimulatory hormetic effects in cyanobacteria at low (ng L-1) concentrations, which may interfere with the control of cyanobacterial bloom in aquatic environments exhibiting combined pollution. This study investigated the influence of a mixture of four popular antibiotics (sulfamethoxazole, amoxicillin, ciprofloxacin, and tetracycline) during the application of UV-C irradiation for controlling the bloom of Microcystis aeruginosa. In the absence of antibiotics, 100-500 mJ cm-2 UV-C irradiation reduced cell density, growth rate, chlorophyll a content, Fv/Fm value and microcystin concentration in M. aeruginosa in a dose-dependent manner through the downregulation of proteins related to cell division, chlorophyll synthesis, photosynthesis and microcystin synthesis. UV-C irradiation stimulated microcystin release through the upregulation of the microcystin release regulatory protein (mcyH). The presence of 40 ng L-1 antibiotic mixture during UV-C treatment significantly reduced (p < 0.05) the treatment efficiency of 100-300 mJ cm-2 UV-C on microcystin concentration, while 80 and 160 ng L-1 antibiotic mixture significantly reduced (p < 0.05) the treatment efficiency of 100-500 mJ cm-2 UV-C on cell density and microcystin concentration. The antibiotic mixture alleviated the toxicity of UV-C on M. aeruginosa through a significant stimulation of photosynthetic activity (p < 0.05) and the upregulation of proteins involved in photosynthesis, biosynthesis, protein expression, and DNA repair. Microcystin release in UV-C-treated cyanobacterial cells was further stimulated by the antibiotic mixture through the upregulation of mcyH and four ATP-binding cassette transport proteins. The interference effects of antibiotic contaminants should be fully considered when UV-C is applied to control cyanobacterial bloom in antibiotic-polluted environments. In order to eliminate the interference effects of antibiotics, the concentration of each target antibiotic is suggested to be controlled below 5 ng L-1 before the application of UV-C irradiation.
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Affiliation(s)
- Yunhan Jiang
- School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, People's Republic of China
| | - Ying Liu
- School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, People's Republic of China.
| | - Jian Zhang
- School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, People's Republic of China
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37
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Müh F, Zouni A. Structural basis of light-harvesting in the photosystem II core complex. Protein Sci 2020; 29:1090-1119. [PMID: 32067287 PMCID: PMC7184784 DOI: 10.1002/pro.3841] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 02/06/2020] [Accepted: 02/06/2020] [Indexed: 12/20/2022]
Abstract
Photosystem II (PSII) is a membrane-spanning, multi-subunit pigment-protein complex responsible for the oxidation of water and the reduction of plastoquinone in oxygenic photosynthesis. In the present review, the recent explosive increase in available structural information about the PSII core complex based on X-ray crystallography and cryo-electron microscopy is described at a level of detail that is suitable for a future structure-based analysis of light-harvesting processes. This description includes a proposal for a consistent numbering scheme of protein-bound pigment cofactors across species. The structural survey is complemented by an overview of the state of affairs in structure-based modeling of excitation energy transfer in the PSII core complex with emphasis on electrostatic computations, optical properties of the reaction center, the assignment of long-wavelength chlorophylls, and energy trapping mechanisms.
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Affiliation(s)
- Frank Müh
- Department of Theoretical Biophysics, Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Athina Zouni
- Humboldt-Universität zu Berlin, Institute for Biology, Biophysics of Photosynthesis, Berlin, Germany
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38
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Abstract
The oxygen-evolving center (OEC) in photosystem II (PSII) of plants, algae and cyanobacteria is a unique natural catalyst that splits water into electrons, protons and dioxygen. The crystallographic studies of PSII have revealed that the OEC is an asymmetric Mn4CaO5-cluster. The understanding of the structure-function relationship of this natural Mn4CaO5-cluster is impeded mainly due to the complexity of the protein environment and lack of a rational chemical model as a reference. Although it has been a great challenge for chemists to synthesize the OEC in the laboratory, significant advances have been achieved recently. Different artificial complexes have been reported, especially a series of artificial Mn4CaO4-clusters that closely mimic both the geometric and electronic structures of the OEC in PSII, which provides a structurally well-defined chemical model to investigate the structure-function relationship of the natural Mn4CaO5-cluster. The deep investigations on this artificial Mn4CaO4-cluster could provide new insights into the mechanism of the water-splitting reaction in natural photosynthesis and may help the development of efficient catalysts for the water-splitting reaction in artificial photosynthesis.
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39
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Espiritu E, Chamberlain KD, Williams JC, Allen JP. Bound manganese oxides capable of reducing the bacteriochlorophyll dimer of modified reaction centers from Rhodobacter sphaeroides. PHOTOSYNTHESIS RESEARCH 2020; 143:129-141. [PMID: 31641987 DOI: 10.1007/s11120-019-00680-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 10/09/2019] [Indexed: 06/10/2023]
Abstract
A biohybrid model system is described that interfaces synthetic Mn-oxides with bacterial reaction centers to gain knowledge concerning redox reactions by metal clusters in proteins, in particular the Mn4CaO5 cluster of photosystem II. The ability of Mn-oxides to bind to modified bacterial reaction centers and transfer an electron to the light-induced oxidized bacteriochlorophyll dimer, P+, was characterized using optical spectroscopy. The environment of P was altered to obtain a high P/P+ midpoint potential. In addition, different metal-binding sites were introduced by substitution of amino acid residues as well as extension of the C-terminus of the M subunit with the C-terminal region of the D1 subunit of photosystem II. The Mn-compounds MnO2, αMn2O3, Mn3O4, CaMn2O4, and Mn3(PO4)2 were tested and compared to MnCl2. In general, addition of the Mn-compounds resulted in a decrease in the amount of P+ while the reduced quinone was still present, demonstrating that the Mn-compounds can serve as secondary electron donors. The extent of P+ reduction for the Mn-oxides was largest for αMn2O3 and CaMn2O4 and smallest for Mn3O4 and MnO2. The addition of Mn3(PO4)2 resulted in nearly complete P+ reduction, similar to MnCl2. Overall, the activity was correlated with the initial oxidation state of the Mn-compound. Transient optical measurements showed a fast kinetic component, assigned to reduction of P+ by the Mn-oxide, in addition to a slow component due to charge recombination. The results support the conjecture that the incorporation of Mn-oxides by ancient anoxygenic phototrophs was a step in the evolution of oxygenic photosynthesis.
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Affiliation(s)
- Eduardo Espiritu
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287-1604, USA
| | - Kori D Chamberlain
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287-1604, USA
| | - JoAnn C Williams
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287-1604, USA
| | - James P Allen
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287-1604, USA.
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40
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Liu Y, Cui M, Zhang J, Gao B. Impacts of antibiotic contaminants on Microcystis aeruginosa during potassium permanganate treatment. HARMFUL ALGAE 2020; 92:101741. [PMID: 32113608 DOI: 10.1016/j.hal.2020.101741] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Revised: 01/05/2020] [Accepted: 01/10/2020] [Indexed: 06/10/2023]
Abstract
Application of KMnO4 for preventing the formation of cyanobacterial bloom at early growth stage has not been reported. Antibiotics generate hormesis effects in cyanobacteria at currently reported concentrations, which may negatively affect the control of cyanobacterial bloom. This study assessed the treatment performance of KMnO4 in Microcystis aeruginosa with and without the existence of the antibiotic mixture composed of four simultaneously detected antibiotics in aquatic environments (sulfamethoxazole, ciprofloxacin, amoxicillin and tetracycline). KMnO4 downregulated two chlorophyll a synthetases (chlG and chlM), 14 photosynthesis-related proteins and two microcystin synthetases (mcyB and mcyD) in M. aeruginosa, and reduced chlorophyll a content, photosynthetic activity and microcystin concentration in a dose-dependent manner. Inhibition of photosynthesis and biosynthesis resulted in extended lag phase and decreased growth rate in KMnO4-treated Microcystis aeruginosa. In contrast, mixed antibiotics upregulated 6 oxidation-reduction proteins, a cell division regulatory protein (MAE_37210), 14 photosynthesis-related proteins, 14 biosynthesis-related proteins (including microcystin synthetases mcyA and mcyB) and a microcystin transport protein (mcyH), which consequently reduced oxidative stress, shortened lag phase as well as significantly stimulated (p < 0.05) cyanobacterial growth, photosynthetic activity, microcystin synthesis and microcystin release in KMnO4-treated M. aeruginosa. An optimal dose of 3 mg L-1 was suggested for KMnO4 treatment. Mixed antibiotics should be controlled below a no-impact threshold of 20 ng L-1 (5 ng L-1 for each antibiotic) for eliminating their adverse effects during KMnO4 treatment of cyanobacteria in antibiotics polluted environments.
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Affiliation(s)
- Ying Liu
- School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, PR China.
| | - Mengwen Cui
- School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, PR China
| | - Jian Zhang
- School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, PR China
| | - Baoyu Gao
- School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, PR China
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41
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de Lichtenberg C, Messinger J. Substrate water exchange in the S2 state of photosystem II is dependent on the conformation of the Mn4Ca cluster. Phys Chem Chem Phys 2020; 22:12894-12908. [DOI: 10.1039/d0cp01380c] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The structural flexibility of the Mn4Ca cluster in photosystem II supports the exchange of the central O5 bridge.
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Allen JF, Thake B, Martin WF. Nitrogenase Inhibition Limited Oxygenation of Earth's Proterozoic Atmosphere. TRENDS IN PLANT SCIENCE 2019; 24:1022-1031. [PMID: 31447302 DOI: 10.1016/j.tplants.2019.07.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 07/10/2019] [Accepted: 07/10/2019] [Indexed: 05/24/2023]
Abstract
Cyanobacteria produced the oxygen that began to accumulate on Earth 2.5 billion years ago, at the dawn of the Proterozoic Eon. By 2.4 billion years ago, the Great Oxidation Event (GOE) marked the onset of an atmosphere containing oxygen. The oxygen content of the atmosphere then remained low for almost 2 billion years. Why? Nitrogenase, the sole nitrogen-fixing enzyme on Earth, controls the entry of molecular nitrogen into the biosphere. Nitrogenase is inhibited in air containing more than 2% oxygen: the concentration of oxygen in the Proterozoic atmosphere. We propose that oxygen inhibition of nitrogenase limited Proterozoic global primary production. Oxygen levels increased when upright terrestrial plants isolated nitrogen fixation in soil from photosynthetic oxygen production in shoots and leaves.
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Affiliation(s)
- John F Allen
- Research Department of Genetics, Evolution and Environment, Darwin Building, University College London, Gower Street, London WC1E 6BT, UK.
| | - Brenda Thake
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK
| | - William F Martin
- Institute of Molecular Evolution, Heinrich-Heine-Universitaet Duesseldorf, Universitaetsstr. 1, 40225 Duesseldorf, Germany
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Lubitz W, Chrysina M, Cox N. Water oxidation in photosystem II. PHOTOSYNTHESIS RESEARCH 2019; 142:105-125. [PMID: 31187340 PMCID: PMC6763417 DOI: 10.1007/s11120-019-00648-3] [Citation(s) in RCA: 127] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 05/20/2019] [Indexed: 05/18/2023]
Abstract
Biological water oxidation, performed by a single enzyme, photosystem II, is a central research topic not only in understanding the photosynthetic apparatus but also for the development of water splitting catalysts for technological applications. Great progress has been made in this endeavor following the report of a high-resolution X-ray crystallographic structure in 2011 resolving the cofactor site (Umena et al. in Nature 473:55-60, 2011), a tetra-manganese calcium complex. The electronic properties of the protein-bound water oxidizing Mn4OxCa complex are crucial to understand its catalytic activity. These properties include: its redox state(s) which are tuned by the protein matrix, the distribution of the manganese valence and spin states and the complex interactions that exist between the four manganese ions. In this short review we describe how magnetic resonance techniques, particularly EPR, complemented by quantum chemical calculations, have played an important role in understanding the electronic structure of the cofactor. Together with isotope labeling, these techniques have also been instrumental in deciphering the binding of the two substrate water molecules to the cluster. These results are briefly described in the context of the history of biological water oxidation with special emphasis on recent work using time resolved X-ray diffraction with free electron lasers. It is shown that these data are instrumental for developing a model of the biological water oxidation cycle.
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Affiliation(s)
- Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion, Mülheim/Ruhr, Germany
| | - Maria Chrysina
- Max-Planck-Institut für Chemische Energiekonversion, Mülheim/Ruhr, Germany
| | - Nicholas Cox
- Research School of Chemistry, The Australian National University, Canberra, Australia
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Carius AB, Rogne P, Duchoslav M, Wolf-Watz M, Samuelsson G, Shutova T. Dynamic pH-induced conformational changes of the PsbO protein in the fluctuating acidity of the thylakoid lumen. PHYSIOLOGIA PLANTARUM 2019; 166:288-299. [PMID: 30793329 DOI: 10.1111/ppl.12948] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 02/14/2019] [Accepted: 02/19/2019] [Indexed: 06/09/2023]
Abstract
The PsbO protein is an essential extrinsic subunit of photosystem II, the pigment-protein complex responsible for light-driven water splitting. Water oxidation in photosystem II supplies electrons to the photosynthetic electron transfer chain and is accompanied by proton release and oxygen evolution. While the electron transfer steps in this process are well defined and characterized, the driving forces acting on the liberated protons, their dynamics and their destiny are all largely unknown. It was suggested that PsbO undergoes proton-induced conformational changes and forms hydrogen bond networks that ensure prompt proton removal from the catalytic site of water oxidation, i.e. the Mn4 CaO5 cluster. This work reports the purification and characterization of heterologously expressed PsbO from green algae Chlamydomonas reinhardtii and two isoforms from the higher plant Solanum tuberosum (PsbO1 and PsbO2). A comparison to the spinach PsbO reveals striking similarities in intrinsic protein fluorescence and CD spectra, reflecting the near-identical secondary structure of the proteins from algae and higher plants. Titration experiments using the hydrophobic fluorescence probe ANS revealed that eukaryotic PsbO proteins exhibit acid-base hysteresis. This hysteresis is a dynamic effect accompanied by changes in the accessibility of the protein's hydrophobic core and is not due to reversible oligomerization or unfolding of the PsbO protein. These results confirm the hypothesis that pH-dependent dynamic behavior at physiological pH ranges is a common feature of PsbO proteins and causes reversible opening and closing of their β-barrel domain in response to the fluctuating acidity of the thylakoid lumen.
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Affiliation(s)
- Anke B Carius
- Department of Plant Physiology, Umeå University, Umeå, SE-907 36, Sweden
| | - Per Rogne
- Department of Chemistry, Umeå University, Umeå, SE-901 87, Sweden
| | - Miloš Duchoslav
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Magnus Wolf-Watz
- Department of Chemistry, Umeå University, Umeå, SE-901 87, Sweden
| | - Göran Samuelsson
- Department of Plant Physiology, Umeå University, Umeå, SE-907 36, Sweden
| | - Tatyana Shutova
- Department of Plant Physiology, Umeå University, Umeå, SE-907 36, Sweden
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The S3 State of the Oxygen-Evolving Complex: Overview of Spectroscopy and XFEL Crystallography with a Critical Evaluation of Early-Onset Models for O–O Bond Formation. INORGANICS 2019. [DOI: 10.3390/inorganics7040055] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The catalytic cycle of the oxygen-evolving complex (OEC) of photosystem II (PSII) comprises five intermediate states Si (i = 0–4), from the most reduced S0 state to the most oxidized S4, which spontaneously evolves dioxygen. The precise geometric and electronic structure of the Si states, and hence the mechanism of O–O bond formation in the OEC, remain under investigation, particularly for the final steps of the catalytic cycle. Recent advances in protein crystallography based on X-ray free-electron lasers (XFELs) have produced new structural models for the S3 state, which indicate that two of the oxygen atoms of the inorganic Mn4CaO6 core of the OEC are in very close proximity. This has been interpreted as possible evidence for “early-onset” O–O bond formation in the S3 state, as opposed to the more widely accepted view that the O–O bond is formed in the final state of the cycle, S4. Peroxo or superoxo formation in S3 has received partial support from computational studies. Here, a brief overview is provided of spectroscopic information, recent crystallographic results, and computational models for the S3 state. Emphasis is placed on computational S3 models that involve O–O formation, which are discussed with respect to their agreement with structural information, experimental evidence from various spectroscopic studies, and substrate exchange kinetics. Despite seemingly better agreement with some of the available crystallographic interpretations for the S3 state, models that implicate early-onset O–O bond formation are hard to reconcile with the complete line of experimental evidence, especially with X-ray absorption, X-ray emission, and magnetic resonance spectroscopic observations. Specifically with respect to quantum chemical studies, the inconclusive energetics for the possible isoforms of S3 is an acute problem that is probably beyond the capabilities of standard density functional theory.
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