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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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2
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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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3
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Conlan B, Messinger J. Thomas John Wydrzynski (8 July 1947-16 March 2018). PHOTOSYNTHESIS RESEARCH 2019; 140:253-261. [PMID: 30478710 PMCID: PMC6509086 DOI: 10.1007/s11120-018-0606-9] [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: 10/22/2018] [Accepted: 11/12/2018] [Indexed: 06/09/2023]
Abstract
With this Tribute, we remember and honor Thomas John (Tom) Wydrzynski. Tom was a highly innovative, independent and committed researcher, who had, early in his career, defined his life-long research goal. He was committed to understand how Photosystem II produces molecular oxygen from water, using the energy of sunlight, and to apply this knowledge towards making artificial systems. In this tribute, we summarize his research journey, which involved working on 'soft money' in several laboratories around the world for many years, as well as his research achievements. We also reflect upon his approach to life, science and student supervision, as we perceive it. Tom was not only a thoughtful scientist that inspired many to enter this field of research, but also a wonderful supervisor and friend, who is deeply missed (see footnote*).
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Affiliation(s)
- Brendon Conlan
- Research School of Biological Sciences, Australian Capital Territory, Australian National University, Acton, ACT, 0200, Australia
| | - Johannes Messinger
- Department of Chemistry - Ångström, Uppsala University, Lägerhyddsvägen 1, 75120, Uppsala, Sweden.
- Department of Chemistry, Umeå University, Linnaeus väg 6, 90187, Umeå, Sweden.
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4
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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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5
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Guerra F, Siemers M, Mielack C, Bondar AN. Dynamics of Long-Distance Hydrogen-Bond Networks in Photosystem II. J Phys Chem B 2018; 122:4625-4641. [PMID: 29589763 DOI: 10.1021/acs.jpcb.8b00649] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Photosystem II uses the energy of absorbed light to split water molecules, generating molecular oxygen, electrons, and protons. The four protons generated during each reaction cycle are released to the lumen via mechanisms that are poorly understood. Given the complexity of photosystem II, which consists of multiple protein subunits and cofactor molecules and hosts numerous waters, a fundamental issue is finding transient networks of hydrogen bonds that bridge potential proton donor and acceptor groups. Here, we address this issue by performing all-atom molecular dynamics simulations of wild-type and mutant photosystem II monomers, which we analyze using a new protocol designed to facilitate efficient analysis of hydrogen-bond networks. Our computations reveal that local protein/water hydrogen-bond networks can assemble transiently in photosystem II such that the reaction center connects to the lumen. The dynamics of the hydrogen-bond networks couple to the protonation state of specific carboxylate groups and are altered in a mutant with defective proton transfer. Simulations on photosystem II without its extrinsic PsbO subunit provide a molecular interpretation of the elusive functional role of this subunit.
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Affiliation(s)
- Federico Guerra
- Freie Universität Berlin, Department of Physics , Theoretical Molecular Biophysics Group , Arnimallee 14 , D-14195 Berlin , Germany
| | - Malte Siemers
- Freie Universität Berlin, Department of Physics , Theoretical Molecular Biophysics Group , Arnimallee 14 , D-14195 Berlin , Germany
| | - Christopher Mielack
- Freie Universität Berlin, Department of Physics , Theoretical Molecular Biophysics Group , Arnimallee 14 , D-14195 Berlin , Germany
| | - Ana-Nicoleta Bondar
- Freie Universität Berlin, Department of Physics , Theoretical Molecular Biophysics Group , Arnimallee 14 , D-14195 Berlin , Germany
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6
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Lorch S, Capponi S, Pieront F, Bondar AN. Dynamic Carboxylate/Water Networks on the Surface of the PsbO Subunit of Photosystem II. J Phys Chem B 2015; 119:12172-81. [DOI: 10.1021/acs.jpcb.5b06594] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sebastian Lorch
- Theoretical
Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
| | - Sara Capponi
- Department
of Physiology and Biophysics, University of California at Irvine, Medical Sciences I, Irvine, California 92697, United States
| | - Florian Pieront
- Theoretical
Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
| | - Ana-Nicoleta Bondar
- Theoretical
Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
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7
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Pigolev AV, Klimov VV. The green alga Chlamydomonas reinhardtii as a tool for in vivo study of site-directed mutations in PsbO protein of photosystem II. BIOCHEMISTRY (MOSCOW) 2015; 80:662-73. [DOI: 10.1134/s0006297915060036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Messinger J, Debus R, Dismukes GC. Warwick Hillier: a tribute. PHOTOSYNTHESIS RESEARCH 2014; 122:1-11. [PMID: 25038923 DOI: 10.1007/s11120-014-0025-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 06/30/2014] [Indexed: 06/03/2023]
Abstract
Warwick Hillier (October 18, 1967-January 10, 2014) made seminal contributions to our understanding of photosynthetic water oxidation employing membrane inlet mass spectrometry and FTIR spectroscopy. This article offers a collection of historical perspectives on the scientific impact of Warwick Hillier's work and tributes to the personal impact his life and ideas had on his collaborators and colleagues.
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Affiliation(s)
- Johannes Messinger
- Department of Chemistry, Chemical Biological Centre (KBC), Umeå University, Linnaeus väg 6, 90187, Umeå, Sweden
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9
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Cationic screening of charged surface groups (carboxylates) affects electron transfer steps in photosystem-II water oxidation and quinone reduction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1625-34. [DOI: 10.1016/j.bbabio.2014.07.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 07/14/2014] [Accepted: 07/16/2014] [Indexed: 11/23/2022]
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10
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Substrate water exchange in photosystem II core complexes of the extremophilic red alga Cyanidioschyzon merolae. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1257-62. [DOI: 10.1016/j.bbabio.2014.04.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 03/31/2014] [Accepted: 04/01/2014] [Indexed: 10/25/2022]
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11
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Cox N, Messinger J. Reflections on substrate water and dioxygen formation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:1020-30. [PMID: 23380392 DOI: 10.1016/j.bbabio.2013.01.013] [Citation(s) in RCA: 204] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 01/23/2013] [Accepted: 01/25/2013] [Indexed: 11/30/2022]
Abstract
This brief article aims at presenting a concise summary of all experimental findings regarding substrate water-binding to the Mn4CaO5 cluster in photosystem II. Mass spectrometric and spectroscopic results are interpreted in light of recent structural information of the water oxidizing complex obtained by X-ray crystallography, spectroscopy and theoretical modeling. Within this framework current proposals for the mechanism of photosynthetic water-oxidation are evaluated. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
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Affiliation(s)
- Nicholas Cox
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, Mülheim an der Ruhr, Germany
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12
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Grundmeier A, Dau H. Structural models of the manganese complex of photosystem II and mechanistic implications. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:88-105. [PMID: 21787743 DOI: 10.1016/j.bbabio.2011.07.004] [Citation(s) in RCA: 191] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Revised: 07/06/2011] [Accepted: 07/08/2011] [Indexed: 11/29/2022]
Abstract
Photosynthetic water oxidation and O₂ formation are catalyzed by a Mn₄Ca complex bound to the proteins of photosystem II (PSII). The catalytic site, including the inorganic Mn₄CaO(n)H(x) core and its protein environment, is denoted as oxygen-evolving complex (OEC). Earlier and recent progress in the endeavor to elucidate the structure of the OEC is reviewed, with focus on recent results obtained by (i) X−ray spectroscopy (specifically by EXAFS analyses), and (ii) X-ray diffraction (XRD, protein crystallography). Very recently, an impressive resolution of 1.9Å has been achieved by XRD. Most likely however, all XRD data on the Mn₄CaO(n)H(x) core of the OEC are affected by X-ray induced modifications (radiation damage). Therefore and to address (important) details of the geometric and electronic structure of the OEC, a combined analysis of XRD and XAS data has been approached by several research groups. These efforts are reviewed and extended using an especially comprehensive approach. Taking into account XRD results on the protein environment of the inorganic core of the Mn complex, 12 alternative OEC models are considered and evaluated by quantitative comparison to (i) extended-range EXAFS data, (ii) polarized EXAFS of partially oriented PSII membrane particles, and (iii) polarized EXAFS of PSII crystals. We conclude that there is a class of OEC models that is in good agreement with both the recent crystallographic models and the XAS data. On these grounds, mechanistic implications for the O−O bond formation chemistry are discussed. This article is part of a Special Issue entitled: Photosystem II.
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13
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Williamson A, Conlan B, Hillier W, Wydrzynski T. The evolution of Photosystem II: insights into the past and future. PHOTOSYNTHESIS RESEARCH 2011; 107:71-86. [PMID: 20512415 DOI: 10.1007/s11120-010-9559-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 05/07/2010] [Indexed: 05/29/2023]
Abstract
This article attempts to address the molecular origin of Photosystem II (PSII), the central component in oxygenic photosynthesis. It discusses the possible evolution of the relevant cofactors needed for splitting water into molecular O2 with respect to the following functional domains in PSII: the reaction center (RC), the oxygen evolving complex (OEC), and the manganese stabilizing protein (MSP). Possible ancestral sources of the relevant cofactors are considered, as are scenarios of how these components may have been brought together to produce the intermediate steps in the evolution of PSII. Most importantly, the driving forces that maintained these intermediates for continued adaptation are considered. We then apply our understanding of the evolution of PSII to the bioengineering of a water oxidizing catalyst for utilization of solar energy.
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Affiliation(s)
- Adele Williamson
- Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra, ACT, 0200, Australia
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Service RJ, Yano J, McConnell I, Hwang HJ, Niks D, Hille R, Wydrzynski T, Burnap RL, Hillier W, Debus RJ. Participation of glutamate-354 of the CP43 polypeptide in the ligation of manganese and the binding of substrate water in photosystem II. Biochemistry 2010; 50:63-81. [PMID: 21114287 DOI: 10.1021/bi1015937] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the current X-ray crystallographic structural models of photosystem II, Glu354 of the CP43 polypeptide is the only amino acid ligand of the oxygen-evolving Mn(4)Ca cluster that is not provided by the D1 polypeptide. To further explore the influence of this structurally unique residue on the properties of the Mn(4)Ca cluster, the CP43-E354Q mutant of the cyanobacterium Synechocystis sp. PCC 6803 was characterized with a variety of biophysical and spectroscopic methods, including polarography, EPR, X-ray absorption, FTIR, and mass spectrometry. The kinetics of oxygen release in the mutant were essentially unchanged from those in wild type. In addition, the oxygen flash yields exhibited normal period four oscillations having normal S state parameters, although the yields were lower, correlating with the mutant's lower steady-state rate (approximately 20% compared to wild type). Experiments conducted with H(2)(18)O showed that the fast and slow phases of substrate water exchange in CP43-E354Q thylakoid membranes were accelerated 8.5- and 1.8-fold, respectively, in the S(3) state compared to wild type. Purified oxygen-evolving CP43-E354Q PSII core complexes exhibited a slightly altered S(1) state Mn-EXAFS spectrum, a slightly altered S(2) state multiline EPR signal, a substantially altered S(2)-minus-S(1) FTIR difference spectrum, and an unusually long lifetime for the S(2) state (>10 h) in a substantial fraction of reaction centers. In contrast, the S(2) state Mn-EXAFS spectrum was nearly indistinguishable from that of wild type. The S(2)-minus-S(1) FTIR difference spectrum showed alterations throughout the amide and carboxylate stretching regions. Global labeling with (15)N and specific labeling with l-[1-(13)C]alanine revealed that the mutation perturbs both amide II and carboxylate stretching modes and shifts the symmetric carboxylate stretching modes of the α-COO(-) group of D1-Ala344 (the C-terminus of the D1 polypeptide) to higher frequencies by 3-4 cm(-1) in both the S(1) and S(2) states. The EPR and FTIR data implied that 76-82% of CP43-E354Q PSII centers can achieve the S(2) state and that most of these can achieve the S(3) state, but no evidence for advancement beyond the S(3) state was observed in the FTIR data, at least not in a majority of PSII centers. Although the X-ray absorption and EPR data showed that the CP43-E354Q mutation only subtly perturbs the structure and spin state of the Mn(4)Ca cluster in the S(2) state, the FTIR and H(2)(18)O exchange data show that the mutation strongly influences other properties of the Mn(4)Ca cluster, altering the response of numerous carboxylate and amide groups to the increased positive charge that develops on the cluster during the S(1) to S(2) transition and weakening the binding of both substrate water molecules (or water-derived ligands), especially the one that exchanges rapidly in the S(3) state. The FTIR data provide evidence that CP43-Glu354 coordinates to the Mn(4)Ca cluster in the S(1) state as a bridging ligand between two metal ions but provide no compelling evidence that this residue changes its coordination mode during the S(1) to S(2) transition. The H(2)(18)O exchange data provide evidence that CP43-Glu354 interacts with the Mn ion that ligates the substrate water molecule (or water-derived ligand) that is in rapid exchange in the S(3) state.
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Affiliation(s)
- Rachel J Service
- Department of Biochemistry, University of California, Riverside, California 92521, United States
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15
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Lieb D, Zahl A, Shubina TE, Ivanović-Burmazović I. Water exchange on manganese(III) porphyrins. Mechanistic insights relevant for oxygen evolving complex and superoxide dismutation catalysis. J Am Chem Soc 2010; 132:7282-4. [PMID: 20462177 DOI: 10.1021/ja1014585] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this work the rate constants (k(ex)) and the activation parameters (DeltaH(double dagger), DeltaS(double dagger), and DeltaV(double dagger)) for the water exchange process on Mn(III) centers have experimentally been determined using temperature and pressure dependent (17)O NMR techniques. For the investigations the Mn(III) porphyrin complexes [Mn(III)(TPPS)S(2)](n-) and [Mn(III)(TMpyP)S(2)](n+) (S = H(2)O and/or OH(-)) have been selected due to their high solution stability in a wide pH range, enabling the measurements of water exchange in the case of both diaqua and aqua-hydroxo complexes. We have experimentally demonstrated that the water exchange on Mn(III) porphyrins is a fast process (k(ex) approximately = 10(7) s(-1)) of an I(d) to I mechanism, strongly influenced by a Jahn-Teller effect and as such almost independent of a porphyrin charge and a trans ligand. This is also supported by our DFT calculations which show only a slight difference in an average Mn(III)-OH(2) bond found for a positively charged model porphyrin with protonated pyridine groups (2.446 A) and for a simple model without any substituents on the porphyrin ring (2.437 A). The calculated effective charge on the Mn center, which is significantly lower than its formal +3 charge (ca. +1.5 for diaqua; +1.4 for aqua-hydroxo), also contributes to its substitution lability. The herein presented results are discussed in connection to a possible fast exchanging substrate binding site in photosystem II and corresponding inorganic model complexes, as well as in the context of a possible inner-sphere catalytic pathway for superoxide dismutation on Mn centers.
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Affiliation(s)
- Dominik Lieb
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Department Chemie und Pharmazie, Egerlandstr. 1, 91058 Erlangen, Germany
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16
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Nikitina J, Shutova T, Melnik B, Chernyshov S, Marchenkov V, Semisotnov G, Klimov V, Samuelsson G. Importance of a single disulfide bond for the PsbO protein of photosystem II: protein structure stability and soluble overexpression in Escherichia coli. PHOTOSYNTHESIS RESEARCH 2008; 98:391-403. [PMID: 18709441 DOI: 10.1007/s11120-008-9327-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2008] [Accepted: 07/01/2008] [Indexed: 05/09/2023]
Abstract
PsbO protein is an important constituent of the water-oxidizing complex, located on the lumenal side of photosystem II. We report here the efficient expression of the spinach PsbO in E. coli where the solubility depends entirely on the formation of the disulfide bond. The PsbO protein purified from a pET32 system that includes thioredoxin fusion is properly folded and functionally active. Urea unfolding experiments imply that the reduction of the single disulfide bridge decreases stability of the protein. Analysis of inter-residue contact density through the PsbO molecule shows that Cys51 is located in a cluster with high contact density. Reduction of the Cys28-Cys51 bond is proposed to perturb the packing interactions in this cluster and destabilize the protein as a whole. Taken together, our results give evidence that PsbO exists in solution as a compact highly ordered structure, provided that the disulfide bridge is not reduced.
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Affiliation(s)
- Julia Nikitina
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 901 87 Umea, Sweden
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Williamson AK. Structural and functional aspects of the MSP (PsbO) and study of its differences in thermophilic versus mesophilic organisms. PHOTOSYNTHESIS RESEARCH 2008; 98:365-89. [PMID: 18780158 DOI: 10.1007/s11120-008-9353-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Accepted: 08/06/2008] [Indexed: 05/16/2023]
Abstract
The Manganese Stabilizing Protein (MSP) of Photosystem II (PSII) is a so-called extrinsic subunit, which reversibly associates with the other membrane-bound PSII subunits. The MSP is essential for maximum rates of O(2) production under physiological conditions as stabilizes the catalytic [Mn(4)Ca] cluster, which is the site of water oxidation. The function of the MSP subunit in the PSII complex has been extensively studied in higher plants, and the structure of non-PSII associated MSP has been studied by low-resolution biophysical techniques. Recently, crystal structures of PSII from the thermophilic cyanobacterium Thermosynechococcus elongatus have resolved the MSP subunit in its PSII-associated state. However, neither any crystal structure is available yet for MSP from mesophilic organisms, higher plants or algae nor has the non-PSII associated form of MSP been crystallized. This article reviews the current understanding of the structure, dynamics, and function of MSP, with a particular focus on properties of the MSP from T. elongatus that may be attributable to the thermophilic ecology of this organism rather than being general features of MSP.
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Affiliation(s)
- Adele K Williamson
- Research School of Biological Sciences, the Australian National University, Canberra 0200, Australia.
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18
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McConnell IL. Substrate water binding and oxidation in photosystem II. PHOTOSYNTHESIS RESEARCH 2008; 98:261-276. [PMID: 18766463 DOI: 10.1007/s11120-008-9337-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Accepted: 07/19/2008] [Indexed: 05/26/2023]
Abstract
This mini review presents a general introduction to photosystem II with an emphasis on the oxygen evolving complex. An attempt is made to summarise what is currently known about substrate interaction in the oxygen evolving complex of photosystem II in terms of the nature of the substrate, the timing and the location of its binding. As the nature of substrate water binding has a direct bearing on the mechanism of O-O bond formation in PSII, a discussion of O-O bond formation follows the summary of current opinion in substrate interaction.
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Affiliation(s)
- Iain L McConnell
- Research School of Biological Sciences, The Australian National University, 0200 Canberra, ACT, Australia.
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19
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Govindjee. Recollections of Thomas John Wydrzynski. PHOTOSYNTHESIS RESEARCH 2008; 98:13-31. [PMID: 18770010 DOI: 10.1007/s11120-008-9341-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Accepted: 07/23/2008] [Indexed: 05/26/2023]
Abstract
In appreciation of his contribution to the Photosystsem II research and commemoration of the book Photosystem II: The Light-Driven Water-Plastoquinone Oxido-Reductase, co-edited with Kimiyuki Satoh, I present here some of my recollections of Thomas John Wydrzynski and by several others with whom he has associated over the years at Urbana (Illinois), Berkeley (California), Standard Oil Company-Indiana (Illinois), Berlin (Germany), Gothenburg (Sweden), and Canberra (Australia). We not only recognize him for his unique career path in Photosystem II research, but also for his qualities as a collaborative scientist working on the only system on Earth that has the ability to oxidize water to molecular oxygen using the energy of sunlight.
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20
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Ho FM. Uncovering channels in photosystem II by computer modelling: current progress, future prospects, and lessons from analogous systems. PHOTOSYNTHESIS RESEARCH 2008; 98:503-522. [PMID: 18798008 DOI: 10.1007/s11120-008-9358-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Accepted: 08/18/2008] [Indexed: 05/26/2023]
Abstract
Even prior to the publication of the crystal structures for photosystem II (PSII), it had already been suggested that water, O(2) and H(+) channels exist in PSII to achieve directed transport of these molecules, and to avoid undesirable side reactions. Computational efforts to uncover these channels and investigate their properties are still at early stages, and have so far only been based on the static PSII structure. The rationale behind the proposals for such channels and the computer modelling studies thus far are reviewed here. The need to take the dynamic protein into account is then highlighted with reference to the specific issues and techniques applicable to the simulation of each of the three channels. In particular, lessons are drawn from simulation studies on other protein systems containing similar channels.
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Affiliation(s)
- Felix M Ho
- Department of Photochemistry and Molecular Science, The Angström Laboratory, Uppsala University, Uppsala, Sweden.
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21
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Meelich K, Zaleski CM, Pecoraro VL. Using small molecule complexes to elucidate features of photosynthetic water oxidation. Philos Trans R Soc Lond B Biol Sci 2008; 363:1271-9; discussion 1279-81. [PMID: 17954438 DOI: 10.1098/rstb.2007.2224] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The molecular oxygen produced in photosynthesis is generated via water oxidation at a manganese-calcium cluster called the oxygen-evolving complex (OEC). While studies in biophysics, biochemistry, and structural and molecular biology are well known to provide deeper insight into the structure and workings of this system, it is often less appreciated that biomimetic modelling provides the foundation for interpreting photosynthetic reactions. The synthesis and characterization of small model complexes, which either mimic structural features of the OEC or are capable of providing insight into the mechanism of O2 evolution, have become a vital contributor to this scientific field. Our group has contributed to these findings in recent years through synthesis of model complexes, spectroscopic characterization of these systems and probing the reactivity in the context of water oxidation. In this article we describe how models have made significant contributions ranging from understanding the structure of the water-oxidation centre (e.g. contributions to defining a tetrameric Mn3Ca-cluster with a dangler Mn) to the ability to discriminate between different mechanistic proposals (e.g. showing that the Babcock scheme for water oxidation is unlikely).
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Affiliation(s)
- Kristof Meelich
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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22
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Singh S, Debus RJ, Wydrzynski T, Hillier W. Investigation of substrate water interactions at the high-affinity Mn site in the photosystem II oxygen-evolving complex. Philos Trans R Soc Lond B Biol Sci 2008; 363:1229-34; discussion 1234-5. [PMID: 17954434 DOI: 10.1098/rstb.2007.2219] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
18 O isotope exchange measurements of photosystem II (PSII) in thylakoids from wild-type and mutant Synechocystis have been performed to investigate binding of substrate water to the high-affinity Mn4 site in the oxygen-evolving complex (OEC). The mutants investigated were D1-D170H, a mutation of a direct ligand to the Mn4 ion, and D1-D61N, a mutation in the second coordination sphere. The substrate water 18 O exchange rates for D61N were found to be 0.16+/-0.02 s(-1) and 3.03+/-0.32 s(-1) for the slow and fast phases of exchange, respectively, compared with 0.47+/-0.04 s(-1) and 19.7+/-1.3 s(-1) for the wild-type. The D1-D170H rates were found to be 0.70+/-0.16 s(-1) and 24.4+/-4.6 s(-1) and thus are almost within the error limits for the wild-type rates. The results from the D1-D170H mutant indicate that the high-affinity Mn4 site does not directly bind to the substrate water molecule in slow exchange, but the binding of non-substrate water to this Mn ion cannot be excluded. The results from the D61N mutation show an interaction with both substrate water molecules, which could be an indication that D61 is involved in a hydrogen bonding network with the substrate water. Our results provide limitations as to where the two substrate water molecules bind in the OEC of PSII.
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Affiliation(s)
- Sonita Singh
- Photobioenergetics Group, Research School of Biological Sciences, The Australian National University, Canberra, Australian Capital Territory 0200, Australia
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23
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Williamson AK, Liggins JR, Hillier W, Wydrzynski T. The importance of protein-protein interactions for optimising oxygen activity in photosystem II: reconstitution with a recombinant thioredoxin--manganese stabilising protein. PHOTOSYNTHESIS RESEARCH 2007; 92:305-14. [PMID: 17484036 DOI: 10.1007/s11120-007-9165-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Accepted: 03/29/2007] [Indexed: 05/15/2023]
Abstract
In this paper we describe how photosystem II (PSII) from higher plants, which have been depleted, of the extrinsic proteins can be reconstituted with a chimeric fusion protein comprising thioredoxin from Escherichia coli and the manganese stabilising protein from Thermosynechococcus elongatus. Surprisingly, even though E. coli thioredoxin is completely unrelated to PSII, the fusion protein restores higher rates of activity upon rebinding to PSII than either the native spinach MSP, or T. elongatus MSP. PSII reconstituted with the fusion protein also has a lower requirement for calcium than PSII with the small extrinsic proteins removed, or PSII reconstituted with spinach or T. elongatus MSP. The MSP portion of the fusion protein is less thermally stable compared to isolated MSP from T. elongatus, which could be the key to its superior activation capability through greater flexibility. This work reveals the importance of protein-protein interactions in the water splitting activity of PSII and suggests that conformational configurations, which increase flexibility in MSP, are essential to its function, even when these are induced by an unrelated protein.
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Affiliation(s)
- A K Williamson
- Research School of Biological Sciences, The Australian National University, Canberra 0200, Australia.
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McConnell IL, Badger MR, Wydrzynski T, Hillier W. A quantitative assessment of the carbonic anhydrase activity in photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:639-47. [PMID: 17467655 DOI: 10.1016/j.bbabio.2007.01.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Revised: 01/25/2007] [Accepted: 01/26/2007] [Indexed: 11/15/2022]
Abstract
Using a carbonic anhydrase assay based on membrane inlet mass spectrometry (MIMS), we have extended our earlier investigations of Photosystem II (PSII)-associated carbonic anhydrase activity in spinach PSII preparations (W. Hillier, I. McConnell, M. R. Badger, A. Boussac, V.V. Klimov G. C. Dismukes, T. Wydrzynski Biochemistry 2006, 45:2094). The relationship between the carbonic anhydrase activity and O(2) evolution has been evaluated in terms of the effects of metal ion addition, preparation type, light, and response to specific inhibitors. The results indicate that the PSII-associated carbonic anhydrase activity is variable and appears not to be associated specifically with the oxygen evolving activity nor the 33 kDa extrinsic manganese stabilising protein.
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Affiliation(s)
- I L McConnell
- Research School of Biological Sciences, The Australian National University, Canberra, ACT 0200, Australia.
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Arsköld SP, Smith PJ, Shen JR, Pace RJ, Krausz E. Key cofactors of photosystem II cores from four organisms identified by 1.7-K absorption, CD and MCD. PHOTOSYNTHESIS RESEARCH 2005; 84:309-16. [PMID: 16049791 DOI: 10.1007/s11120-005-2135-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2004] [Accepted: 02/10/2005] [Indexed: 05/03/2023]
Abstract
Active Photosystem II (PS II) cores were prepared from spinach, pea, Synechocystis PCC 6803, and Thermosynechococcus vulcanus, the latter of which has been structurally determined [Kamiya and Shen (2003) Proc Natl Acad Sci USA 100: 98-103]. Electrochromic shifts resulting from QA reduction by 1.7-K illumination were recorded, and the Qx and Qy absorption bands of the redox-active pheophytin a thus identified in the different organisms. The Qx transition is approximately 3 nm (100 cm-1) to higher energy in cyanobacteria than in the plants. The predominant Qy shift appears in the range 683-686 nm depending on species, and does not appear to have a systematic shift. Low-temperature absorption, circular dichroism (CD) and magnetic circular dichroism (MCD) spectra of the chlorophyll Qy region are very similar in spinach and pea, but vary in cyanobacteria. We assigned CP43 and CP47 trap-chlorophyll absorption features in all species, as well as a P680 transition. Each absorption identified has an area of one chlorophyll a. The MCD deficit, introduced previously for spinach as an indicator of P680 activity, occurs in the same spectral region and has the same area in all species, pointing to a robustness of this as a signature for P680. MCD and CD characteristics point towards a significant variance in P680 structure between cyanobacteria, thermophilic cyanobacteria, and higher plants.
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Affiliation(s)
- Sindra Peterson Arsköld
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia.
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26
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Clausen J, Debus RJ, Junge W. Time-resolved oxygen production by PSII: chasing chemical intermediates. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1655:184-94. [PMID: 15100031 DOI: 10.1016/j.bbabio.2003.06.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2003] [Revised: 06/25/2003] [Accepted: 06/25/2003] [Indexed: 11/21/2022]
Abstract
Photosystem II (PSII) produces dioxygen from water in a four-stepped process, which is driven by four quanta of light and catalysed by a Mn-cluster and tyrosine Z. Oxygen is liberated during one step, coined S(3)=>S(0). Chemical intermediates on the way from reversibly bound water to dioxygen have not yet been tracked, however, a break in the Arrhenius plot of the oxygen-evolving step has been taken as evidence for its existence. We scrutinised the temperature dependence of (i) UV-absorption transients attributable to the reduction of the Mn-cluster and tyrosine Z by water, and (ii) polarographic transients attributable to the release of dioxygen. Using a centrifugatable and kinetically competent Pt-electrode, we observed no deviation from a linear Arrhenius plot of oxygen release in the temperature range from -2 to 32 degrees C, and hence no evidence, by this approach, for a sufficiently long-lived chemical intermediate. The half-rise times of oxygen release differed between Synechocystis WT* (at 20 degrees C: 1.35 ms) and a point mutant (D1-D61N: 13.1 ms), and the activation energies differed between species (Spinacia oleracea, 30 kJ/mol versus Synechocystis, 41 kJ/mol) and preparations (PSII membranes, 41 kJ/mol versus core complexes, 33 kJ/mol, Synechocystis). Correction for polarographic artefacts revealed, for the first time, a temperature-dependent lag-phase of the polarographic transient (duration at 20 degrees C: 0.45 ms, activation energy: 31 kJ/mol), which was indicative of a short-lived intermediate. It was, however, not apparent in the UV-transients. Thus the "intermediate" was probably newly formed and transiently bound oxygen.
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Affiliation(s)
- Jürgen Clausen
- Abteilung Biophysik, Fachbereich Biologie/Chemie, Barbarastr. 11, Universität Osnabrück, D-49069 Osnabrück, Germany
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27
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Arsköld SP, Masters VM, Prince BJ, Smith PJ, Pace RJ, Krausz E. Optical spectra of synechocystis and spinach photosystem II preparations at 1.7 K: identification of the D1-pheophytin energies and stark shifts. J Am Chem Soc 2004; 125:13063-74. [PMID: 14570479 DOI: 10.1021/ja034548s] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report and compare highly resolved, simultaneously recorded absorption and CD spectra of active Photosystem II (PSII) samples in the range 440-750 nm. From an appropriately scaled comparison of spinach membrane fragment (BBY) and PSII core spectra, we show that key features of the core spectrum are quantitatively represented in the BBY data. PSII from the cyanobacterium Synechocystis 6803 display spectral features in the Qy region of comparable width (50-70 cm(-1) fwhm) to those seen in plant PSII but the energies of the resolved features are distinctly different. A comparison of spectra taken of PSII poised in the S1QA and S2QA(-) redox states reveals electrochromic shifts largely attributable to the influence of QA(-) on Pheo(D1). This allows accurate determinations of the Pheo(D1) Qy absorption positions to be at 685.0 nm for spinach cores, 685.8 nm for BBY particles, and 683.0 nm for Synechocystis. These are discussed in terms of earlier reports of the Pheo(D1) energies in PSII. The Qx transition of Pheo(D1) undergoes a blue shift upon Q(A) reduction, and we place a lower limit of 80 cm(-1) on this shift in plant material. By comparing the magnitude of the Stark shifts of the Qx and Qy bands of Pheo(D1), the directions of the transition-induced dipole moment changes, Deltamu(x) and Deltamu(y), for this functionally important pigment could be determined, assuming normal magnitudes of the Deltamu's. Consequently, Deltamu(x) and Deltamu(y) are determined to be approximately orthogonal to the directions expected for these transitions. Low-fluence illumination experiments at 1.7 K resulted in very efficient formation of QA(-). This was accompanied by cyt b(559) oxidation in BBYs and carotenoid oxidation in cores. No chlorophyll oxidation was observed. Our data allow us to estimate the quantum efficiency of PSII at this temperature to be of the order 0.1-1. No Stark shift associated with the S1-to-S2 transition of the Mn cluster is evident in our samples. The similarity of Stark data in plants and Synechocystis points to minimal interactions of Pheo(D1) with nearby chloropyll pigments in active PSII preparations. This appears to be at variance with interpretations of experiments performed with inactive solubilized reaction-center preparations.
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Affiliation(s)
- Sindra Peterson Arsköld
- Research School of Chemistry and Department of Chemistry, Faculties of Science, Australian National University, Canberra ACT 0200, Australia.
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28
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Hillier W, Wydrzynski T. Substrate water interactions within the Photosystem II oxygen evolving complex. Phys Chem Chem Phys 2004. [DOI: 10.1039/b407269c] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Balsera M, Arellano JB, Pazos F, Devos D, Valencia A, De Las Rivas J. The single tryptophan of the PsbQ protein of photosystem II is at the end of a 4-α-helical bundle domain. ACTA ACUST UNITED AC 2003; 270:3916-27. [PMID: 14511373 DOI: 10.1046/j.1432-1033.2003.03774.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We examined the microenvironment of the single tryptophan and the tyrosine residues of PsbQ, one of the three main extrinsic proteins of green algal and higher plant photosystem II. On the basis of this information and the previous data on secondary structure [Balsera, M., Arellano, J.B., Gutiérrez, J.R., Heredia, P., Revuelta, J.L. & De Las Rivas, J. (2003) Biochemistry42, 1000-1007], we screened structural models derived by combining various threading approaches. Experimental results showed that the tryptophan residue is partially buried in the core of the protein but still in a polar environment, according to the intrinsic fluorescence emission of PsbQ and the fact that fluorescence quenching by iodide was weaker than that by acrylamide. Furthermore, quenching by cesium suggested that a positively charged barrier shields the tryptophan microenvironment. Comparison of the absorption spectra in native and denaturing conditions indicated that one or two out of six tyrosines of PsbQ are buried in the core of the structure. Using threading methods, a 3D structural model was built for the C-terminal domain of the PsbQ protein family (residues 46-149), while the N-terminal domain is predicted to have a flexible structure. The model for the C-terminal domain is based on the 3D structure of cytochrome b562, a mainly alpha-protein with a helical up/down bundle folding. Despite the large sequence differences between the template and PsbQ, the structural and energetic parameters for the explicit model are acceptable, as judged by the corresponding tools. This 3D model is compatible with the experimentally determined environment of the tryptophan residue and with published structural information. The future experimental determination of the 3D structure of the protein will offer a good validation point for our model and the technology used. Until then, the model can provide a starting point for further studies on the function of PsbQ.
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Affiliation(s)
- Mónica Balsera
- Instituto de Recursos Naturales y Agrobiología (CSIC), Cordel de Merinas, Salamanca, Spain
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Shutova T, Villarejo A, Zietz B, Klimov V, Gillbro T, Samuelsson G, Renger G. Comparative studies on the properties of the extrinsic manganese-stabilizing protein from higher plants and of a synthetic peptide of its C-terminus. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1604:95-104. [PMID: 12765766 DOI: 10.1016/s0005-2728(03)00025-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The present study describes a comparative analysis on the fluorescence properties of the manganese-stabilizing protein (MSP), a synthetic peptide corresponding to its C terminus and a 7:1 (molar ratio) mixture of N-acetyl-tyrosine and N-acetyl-tryptophan, respectively, together with reconstitution experiments of oxygen evolution in MSP-depleted photosystem II (PS II) membrane fragments. It is found: (i) at neutral pH, the fluorescence from Trp(241) is strongly diminished in MSP solutions, whereas it highly dominates the overall emission from the C-terminus peptide; (ii) at alkaline pH, the emission of Tyr and Trp is quenched in both, MSP and C-terminus peptide, with increasing pH but the decline curve is shifted by about two pH units towards the alkaline region in MSP; (iii) a drastically different pattern emerges in the 7:1 mixture where the Trp emission even slightly increases at high pH; (iv) the anisotropy of the fluorescence emission is wavelength-independent (310-395 nm) and indicative of one emitter type (Trp) in the C-terminus peptide and of two emitter types (Tyr, Trp) in MSP; and (v) in MSP-depleted PS II membrane fragments the oxygen evolution is restored (up to 85% of untreated control) by rebinding of MSP but not by the C-terminus peptide, however, the presence of the latter diminishes the restoration effect of MSP. A quenching mechanism of Trp fluorescence by a next neighbored tyrosinate in the peptide chain is proposed and the relevance of the C terminus of MSP briefly discussed.
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Affiliation(s)
- T Shutova
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Sweden
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31
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Styring S, Feyziyev Y, Mamedov F, Hillier W, Babcock GT. pH dependence of the donor side reactions in Ca2+-depleted photosystem II. Biochemistry 2003; 42:6185-92. [PMID: 12755621 DOI: 10.1021/bi027035r] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have studied how low pH affects the water-oxidizing complex in Photosystem II when depleted of the essential Ca(2+) ion cofactor. For these samples, it was found that the EPR signal from the Y(Z)(*) radical decays faster at low pH than at high pH. At 20 degrees C, Y(Z)(*) decays with biphasic kinetics. At pH 6.5, the fast phase encompasses about 65% of the amplitude and has a lifetime of approximately 0.8 s, while the slow phase has a lifetime of approximately 22 s. At pH 3.9, the kinetics become totally dominated by the fast phase, with more than 90% of the signal intensity operating with a lifetime of approximately 0.3 s. The kinetic changes occurred with an approximate pK(a) of 4.5. Low pH also affected the induction of the so-called split radical EPR signal from the S(2)Y(Z)(*) state that is induced in Ca(2+)-depleted PSII membranes because of an inability of Y(Z)(*) to oxidize the S(2) state. At pH 4.5, about 50% of the split signal was induced, as compared to the amplitude of the signal that was induced at pH 6.5-7, using similar illumination conditions. Thus, the split-signal induction decreased with an apparent pK(a) of 4.5. In the same samples, the stable multiline signal from the S(2) state, which is modified by the removal of Ca(2+), was decreased by the illumination to the same extent at all pHs. It is proposed that decreased induction of the S(2)Y(Z)(*) state at lower pH was not due to inability to oxidize the modified S(2) state induced by the Ca(2+) depletion. Instead, we propose that the low pH makes Y(Z)(*) able to oxidize the S(2) state, making the S(2) --> S(3) transition available in Ca(2+)-depleted PSII. Implications of these results for the catalytic role of Ca(2+) and the role of proton transfer between the Mn cluster and Y(Z) during oxygen evolution is discussed.
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Affiliation(s)
- Stenbjörn Styring
- Department of Biochemistry, Centre for Chemistry and Chemical Engineering P.O. Box 124, Lund University, Sweden
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32
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Hendry G, Wydrzynski T. (18)O isotope exchange measurements reveal that calcium is involved in the binding of one substrate-water molecule to the oxygen-evolving complex in photosystem II. Biochemistry 2003; 42:6209-17. [PMID: 12755624 DOI: 10.1021/bi034279i] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Direct evidence is presented to show that calcium is inherently involved in the binding of one of the two substrate-water molecules to the oxygen-evolving complex in photosystem II. Previous rapid (millisecond range) (18)O isotope exchange measurements between added H(2)(18)O and the photogenerated O(2) have shown that the two substrate-water molecules bind to separate sites throughout the S-state cycle, as revealed by their kinetically distinct rates of (18)O exchange [Hillier, W., and Wydrzynski, T. (2000) Biochemistry 39, 4399-4405]. Upon extraction of the functionally bound calcium using a either a low-pH/citrate treatment or a NaCl/A23187/EGTA treatment and subsequent reconstitution of activity with strontium, we show for the first time a specific increase in the slow rate of (18)O exchange by a factor of 3-4. This increase in the slow rate of exchange is consistently observed across the S(1), S(2), and S(3) states. In contrast, the fast phase of (18)O exchange in the S(3) state appears to be affected little upon strontium reconstitution, while the fast phases of exchange in the S(1) and S(2) states remain largely unresolvable, at the detectable limits of the current techniques. The results are discussed in terms of a possible substrate bridging structure between the functional calcium and a catalytic manganese ion that gives rise to the slowly exchanging component.
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Affiliation(s)
- Garth Hendry
- Photobioenergetics, Research School of Biological Sciences, The Australian National University, Canberra ACT 0200, Australia
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33
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Hendry G, Wydrzynski T. The two substrate-water molecules are already bound to the oxygen-evolving complex in the S2 state of photosystem II. Biochemistry 2002; 41:13328-34. [PMID: 12403635 DOI: 10.1021/bi026246t] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The first direct evidence which shows that both substrate-water molecules are bound to the O(2)-evolving catalytic site in the S(2) state of photosystem II (PSII) is presented. Rapid (18)O isotope exchange measurements between H(2)(18)O incubated in the S(2) state of PSII-enriched membrane samples and the photogenerated O(2) reveal a fast and a slow phase of exchange at m/e 34 (which measures the level of the (16)O(18)O product). The rate constant for the slow phase of exchange ((34)k(1)) equals 1.9 +/- 0.3 s(-1) at 10 degrees C, while the fast phase of exchange is unresolved by our current experimental setup ((34)k(2) >or= 175 s(-1)). The unresolvable fast phase has left open the possibility that the second substrate-water molecule binds to the catalytic site only after the formation of the S(3) state [Hillier, W., and Wydrzynski, T. (2000) Biochemistry 39, 4399-4405]. However, for PSII samples depleted of the 17 and 23 kDa extrinsic proteins (Ex-depleted PSII), two completely resolvable phases of (18)O exchange are observed in the S(2) state of the residual activity, with the following rate constants: (34)k(1) = 2.6 +/- 0.3 s(-1) and (34)k(2) = 120 +/- 14 s(-1) at 10 degrees C. Upon addition of 15 mM CaCl(2) to Ex-depleted PSII, the O(2) evolution activity increases to approximately 80% of the control level, while the two resolvable phases of exchange remain the same. In measurements of Ex-depleted PSII at m/e 36 (which measures the level of the (18)O(18)O product), only a single phase of exchange is observed in the S(2) state, with a rate constant ((36)k(1) = 2.5 +/- 0.2 s(-1)) that is identical to the slow rate of exchange in the m/e 34 data. Taken together, these results show that the fast phase of (18)O exchange is specifically slowed by the removal of the 17 and 23 kDa extrinsic proteins and that the two substrate-water molecules must be bound to independent sites already in the S(2) state. In contrast, the (18)O exchange behavior in the S(1) state of Ex-depleted PSII is no different from what is observed for the control, with or without the addition of CaCl(2). Since the fast phase of exchange in the S(1) state is unresolved (i.e., (34)k(2) > 100 s(-1)), the possibility remains that the second substrate-water molecule binds to the catalytic site only after the formation of the S(2) state. The role of the 17 and 23 kDa extrinsic proteins in establishing an asymmetric dielectric environment around the substrate binding sites is discussed.
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Affiliation(s)
- Garth Hendry
- Photobioenergetics, Research School of Biological Sciences, The Australian National University, Canberra ACT 0200, Australia
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Anderson JM, Chow WS. Structural and functional dynamics of plant photosystem II. Philos Trans R Soc Lond B Biol Sci 2002; 357:1421-30; discussion 1469-70. [PMID: 12437881 PMCID: PMC1693045 DOI: 10.1098/rstb.2002.1138] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Given the unique problem of the extremely high potential of the oxidant P(+)(680) that is required to oxidize water to oxygen, the photoinactivation of photosystem II in vivo is inevitable, despite many photoprotective strategies. There is, however, a robustness of photosystem II, which depends partly on the highly dynamic compositional and structural heterogeneity of the cycle between functional and non-functional photosystem II complexes in response to light level. This coordinated regulation involves photon usage (energy utilization in photochemistry) and excess energy dissipation as heat, photoprotection by many molecular strategies, photoinactivation followed by photon damage and ultimately the D1 protein dynamics involved in the photosystem II repair cycle. Compelling, though indirect evidence suggests that the radical pair P(+)(680)Pheo(-) in functional PSII should be protected from oxygen. By analogy to the tentative oxygen channel of cytochrome c oxidase, oxygen may be liberated from the two water molecules bound to the catalytic site of the Mn cluster, via a specific pathway to the membrane surface. The function of the proposed oxygen pathway is to prevent O(2) from having direct access to P(+)(680)Pheo(-) and prevent the generation of singlet oxygen via the triplet-P(680) state in functional photosytem IIs. Only when the, as yet unidentified, potential trigger with a fateful first oxidative step destroys oxygen evolution, will the ensuing cascade of structural perturbations of photosystem II destroy the proposed oxygen, water and proton pathways. Then oxygen has direct access to P(+)(680)Pheo(-), singlet oxygen will be produced and may successively oxidize specific amino acids of the phosphorylated D1 protein of photosystem II dimers that are confined to appressed granal domains, thereby targeting D1 protein for eventual degradation and replacement in non-appressed thylakoid domains.
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Affiliation(s)
- Jan M Anderson
- Photobioenergetics, Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra ACT 2601, Australia.
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