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Fadeeva M, Klaiman D, Caspy I, Nelson N. Structure of Chlorella ohadii Photosystem II Reveals Protective Mechanisms against Environmental Stress. Cells 2023; 12:1971. [PMID: 37566050 PMCID: PMC10416949 DOI: 10.3390/cells12151971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 07/23/2023] [Accepted: 07/29/2023] [Indexed: 08/12/2023] Open
Abstract
Green alga Chlorella ohadii is known for its ability to carry out photosynthesis under harsh conditions. Using cryogenic electron microscopy (cryoEM), we obtained a high-resolution structure of PSII at 2.72 Å. This structure revealed 64 subunits, which encompassed 386 chlorophylls, 86 carotenoids, four plastoquinones, and several structural lipids. At the luminal side of PSII, a unique subunit arrangement was observed to protect the oxygen-evolving complex. This arrangement involved PsbO (OEE1), PsbP (OEE2), PsbB, and PsbU (a homolog of plant OEE3). PsbU interacted with PsbO, PsbC, and PsbP, thereby stabilizing the shield of the oxygen-evolving complex. Significant changes were also observed at the stromal electron acceptor side. PsbY, identified as a transmembrane helix, was situated alongside PsbF and PsbE, which enclosed cytochrome b559. Supported by the adjacent C-terminal helix of Psb10, these four transmembrane helices formed a bundle that shielded cytochrome b559 from the surrounding solvent. Moreover, the bulk of Psb10 formed a protective cap, which safeguarded the quinone site and likely contributed to the stacking of PSII complexes. Based on our findings, we propose a protective mechanism that prevents QB (plastoquinone B) from becoming fully reduced. This mechanism offers insights into the regulation of electron transfer within PSII.
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Affiliation(s)
| | | | | | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel; (M.F.); (D.K.); (I.C.)
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Fadeeva M, Klaiman D, Caspy I, Nelson N. CryoEM PSII structure reveals adaptation mechanisms to environmental stress in Chlorella ohadii. bioRxiv 2023:2023.05.04.539358. [PMID: 37205566 PMCID: PMC10187303 DOI: 10.1101/2023.05.04.539358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Performing photosynthesis in the desert is a challenging task since it requires a fast adaptation to extreme illumination and temperature changes. To understand adaptive mechanisms, we purified Photosystem II (PSII) from Chlorella ohadii , a green alga from the desert soil surface, and identified structural elements that might enable the photosystem functioning under harsh conditions. The 2.72 Å cryogenic electron-microscopy (cryoEM) structure of PSII exhibited 64 subunits, encompassing 386 chlorophylls, 86 carotenoids, four plastoquinones, and several structural lipids. At the luminal side of PSII, the oxygen evolving complex was protected by a unique subunit arrangement - PsbO (OEE1), PsbP (OEE2), CP47, and PsbU (plant OEE3 homolog). PsbU interacted with PsbO, CP43, and PsbP, thus stabilising the oxygen evolving shield. Substantial changes were observed on the stromal electron acceptor side - PsbY was identified as a transmembrane helix situated alongside PsbF and PsbE enclosing cytochrome b559, supported by the adjacent C-terminal helix of Psb10. These four transmembrane helices bundled jointly, shielding cytochrome b559 from the solvent. The bulk of Psb10 formed a cap protecting the quinone site and probably contributed to the PSII stacking. So far, the C. ohadii PSII structure is the most complete description of the complex, suggesting numerous future experiments. A protective mechanism that prevented Q B from rendering itself fully reduced is proposed.
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Affiliation(s)
| | | | - Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
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Caspy I, Fadeeva M, Mazor Y, Nelson N. Structure of Dunaliella photosystem II reveals conformational flexibility of stacked and unstacked supercomplexes. eLife 2023; 12:e81150. [PMID: 36799903 PMCID: PMC9949808 DOI: 10.7554/elife.81150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 02/16/2023] [Indexed: 02/18/2023] Open
Abstract
Photosystem II (PSII) generates an oxidant whose redox potential is high enough to enable water oxidation , a substrate so abundant that it assures a practically unlimited electron source for life on earth . Our knowledge on the mechanism of water photooxidation was greatly advanced by high-resolution structures of prokaryotic PSII . Here, we show high-resolution cryogenic electron microscopy (cryo-EM) structures of eukaryotic PSII from the green alga Dunaliella salina at two distinct conformations. The conformers are also present in stacked PSII, exhibiting flexibility that may be relevant to the grana formation in chloroplasts of the green lineage. CP29, one of PSII associated light-harvesting antennae, plays a major role in distinguishing the two conformations of the supercomplex. We also show that the stacked PSII dimer, a form suggested to support the organisation of thylakoid membranes , can appear in many different orientations providing a flexible stacking mechanism for the arrangement of grana stacks in thylakoids. Our findings provide a structural basis for the heterogenous nature of the eukaryotic PSII on multiple levels.
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Affiliation(s)
- Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv UniversityTel AvivIsrael
| | - Maria Fadeeva
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv UniversityTel AvivIsrael
| | - Yuval Mazor
- School of Molecular Sciences, Arizona State UniversityTempeUnited States
- Biodesign Center for Applied Structural Discovery, Arizona State UniversityTempeUnited States
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv UniversityTel AvivIsrael
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Caspy I, Schwartz T, Bayro-Kaiser V, Fadeeva M, Kessel A, Ben-Tal N, Nelson N. Dimeric and high-resolution structures of Chlamydomonas Photosystem I from a temperature-sensitive Photosystem II mutant. Commun Biol 2021; 4:1380. [PMID: 34887518 PMCID: PMC8660910 DOI: 10.1038/s42003-021-02911-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 11/19/2021] [Indexed: 11/30/2022] Open
Abstract
Water molecules play a pivotal functional role in photosynthesis, primarily as the substrate for Photosystem II (PSII). However, their importance and contribution to Photosystem I (PSI) activity remains obscure. Using a high-resolution cryogenic electron microscopy (cryo-EM) PSI structure from a Chlamydomonas reinhardtii temperature-sensitive photoautotrophic PSII mutant (TSP4), a conserved network of water molecules - dating back to cyanobacteria - was uncovered, mainly in the vicinity of the electron transport chain (ETC). The high-resolution structure illustrated that the water molecules served as a ligand in every chlorophyll that was missing a fifth magnesium coordination in the PSI core and in the light-harvesting complexes (LHC). The asymmetric distribution of the water molecules near the ETC branches modulated their electrostatic landscape, distinctly in the space between the quinones and FX. The data also disclosed the first observation of eukaryotic PSI oligomerisation through a low-resolution PSI dimer that was comprised of PSI-10LHC and PSI-8LHC. Caspy et al. report the structure of PSI from a temperature-sensitive photoautotrophic PSII mutant of Chlamydomonas reinhardtii (TSP4), and report the distribution of conserved water molecules in the structure from cyanobacterial to higher plant PSI. They suggest that the asymmetric distribution of water molecules near the electron transfer chain modulates the electron transfer from quinones to FX.
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Affiliation(s)
- Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Tom Schwartz
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Vinzenz Bayro-Kaiser
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Mariia Fadeeva
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Amit Kessel
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Nir Ben-Tal
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel.
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Akhtar P, Caspy I, Nowakowski PJ, Malavath T, Nelson N, Tan HS, Lambrev PH. Two-Dimensional Electronic Spectroscopy of a Minimal Photosystem I Complex Reveals the Rate of Primary Charge Separation. J Am Chem Soc 2021; 143:14601-14612. [PMID: 34472838 DOI: 10.1021/jacs.1c05010] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photosystem I (PSI), found in all oxygenic photosynthetic organisms, uses solar energy to drive electron transport with nearly 100% quantum efficiency, thanks to fast energy transfer among antenna chlorophylls and charge separation in the reaction center. There is no complete consensus regarding the kinetics of the elementary steps involved in the overall trapping, especially the rate of primary charge separation. In this work, we employed two-dimensional coherent electronic spectroscopy to follow the dynamics of energy and electron transfer in a monomeric PSI complex from Synechocystis PCC 6803, containing only subunits A-E, K, and M, at 77 K. We also determined the structure of the complex to 4.3 Å resolution by cryoelectron microscopy with refinements to 2.5 Å. We applied structure-based modeling using a combined Redfield-Förster theory to compute the excitation dynamics. The absorptive 2D electronic spectra revealed fast excitonic/vibronic relaxation on time scales of 50-100 fs from the high-energy side of the absorption spectrum. Antenna excitations were funneled within 1 ps to a small pool of chlorophylls absorbing around 687 nm, thereafter decaying with 4-20 ps lifetimes, independently of excitation wavelength. Redfield-Förster energy transfer computations showed that the kinetics is limited by transfer from these red-shifted pigments. The rate of primary charge separation, upon direct excitation of the reaction center, was determined to be 1.2-1.5 ps-1. This result implies activationless electron transfer in PSI.
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Affiliation(s)
- Parveen Akhtar
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Nanyang Link 21, 637371 Singapore.,Biological Research Centre, Szeged, Temesvári krt. 62, Szeged 6726, Hungary.,ELI-ALPS, ELI-HU Non-profit Ltd., Wolfgang Sandner u. 3, Szeged 6728, Hungary
| | - Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Paweł J Nowakowski
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Nanyang Link 21, 637371 Singapore
| | - Tirupathi Malavath
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Howe-Siang Tan
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Nanyang Link 21, 637371 Singapore
| | - Petar H Lambrev
- Biological Research Centre, Szeged, Temesvári krt. 62, Szeged 6726, Hungary
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Caspy I, Neumann E, Fadeeva M, Liveanu V, Savitsky A, Frank A, Kalisman YL, Shkolnisky Y, Murik O, Treves H, Hartmann V, Nowaczyk MM, Schuhmann W, Rögner M, Willner I, Kaplan A, Schuster G, Nelson N, Lubitz W, Nechushtai R. Cryo-EM photosystem I structure reveals adaptation mechanisms to extreme high light in Chlorella ohadii. Nat Plants 2021; 7:1314-1322. [PMID: 34462576 DOI: 10.1038/s41477-021-00983-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 07/07/2021] [Indexed: 05/10/2023]
Abstract
Photosynthesis in deserts is challenging since it requires fast adaptation to rapid night-to-day changes, that is, from dawn's low light (LL) to extreme high light (HL) intensities during the daytime. To understand these adaptation mechanisms, we purified photosystem I (PSI) from Chlorella ohadii, a green alga that was isolated from a desert soil crust, and identified the essential functional and structural changes that enable the photosystem to perform photosynthesis under extreme high light conditions. The cryo-electron microscopy structures of PSI from cells grown under low light (PSILL) and high light (PSIHL), obtained at 2.70 and 2.71 Å, respectively, show that part of light-harvesting antenna complex I (LHCI) and the core complex subunit (PsaO) are eliminated from PSIHL to minimize the photodamage. An additional change is in the pigment composition and their number in LHCIHL; about 50% of chlorophyll b is replaced by chlorophyll a. This leads to higher electron transfer rates in PSIHL and might enable C. ohadii PSI to act as a natural photosynthesiser in photobiocatalytic systems. PSIHL or PSILL were attached to an electrode and their induced photocurrent was determined. To obtain photocurrents comparable with PSIHL, 25 times the amount of PSILL was required, demonstrating the high efficiency of PSIHL. Hence, we suggest that C. ohadii PSIHL is an ideal candidate for the design of desert artificial photobiocatalytic systems.
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Affiliation(s)
- Ido Caspy
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ehud Neumann
- Institute of Life Science, Faculty of Science and Mathematics, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Maria Fadeeva
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Varda Liveanu
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Anton Savitsky
- Faculty of Physics, Technical University Dortmund, Dortmund, Germany
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
| | - Anna Frank
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Yael Levi Kalisman
- Institute of Life Science, Faculty of Science and Mathematics, The Hebrew University of Jerusalem, Jerusalem, Israel
- The Centre for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yoel Shkolnisky
- School of Mathematical Sciences, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Omer Murik
- Institute of Life Science, Faculty of Science and Mathematics, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Haim Treves
- Institute of Life Science, Faculty of Science and Mathematics, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Volker Hartmann
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Marc M Nowaczyk
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Wolfgang Schuhmann
- Analytical Chemistry-Centre for Electrochemical Sciences (CES), Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Matthias Rögner
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Itamar Willner
- Institute of Life Science, Faculty of Science and Mathematics, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Aaron Kaplan
- Institute of Life Science, Faculty of Science and Mathematics, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Gadi Schuster
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Nathan Nelson
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany.
| | - Rachel Nechushtai
- Institute of Life Science, Faculty of Science and Mathematics, The Hebrew University of Jerusalem, Jerusalem, Israel.
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Caspy I, Borovikova-Sheinker A, Klaiman D, Shkolnisky Y, Nelson N. The structure of a triple complex of plant photosystem I with ferredoxin and plastocyanin. Nat Plants 2020. [PMID: 33020607 DOI: 10.1038/s41477-020-00779-779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The ability of photosynthetic organisms to use sunlight as a sole source of energy is endowed by two large membrane complexes-photosystem I (PSI) and photosystem II (PSII). PSI and PSII are the fundamental components of oxygenic photosynthesis, providing oxygen, food and an energy source for most living organisms on Earth. Currently, high-resolution crystal structures of these complexes from various organisms are available. The crystal structures of megadalton complexes have revealed excitation transfer and electron-transport pathways within the various complexes. PSI is defined as plastocyanin-ferredoxin oxidoreductase but a high-resolution structure of the entire triple supercomplex is not available. Here, using a new cryo-electron microscopy technique, we solve the structure of native plant PSI in complex with its electron donor plastocyanin and the electron acceptor ferredoxin. We reveal all of the contact sites and the modes of interaction between the interacting electron carriers and PSI.
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Affiliation(s)
- Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Anna Borovikova-Sheinker
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Daniel Klaiman
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Yoel Shkolnisky
- School of Mathematical Sciences, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel.
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
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Caspy I, Borovikova-Sheinker A, Klaiman D, Shkolnisky Y, Nelson N. The structure of a triple complex of plant photosystem I with ferredoxin and plastocyanin. Nat Plants 2020; 6:1300-1305. [PMID: 33020607 DOI: 10.1038/s41477-020-00779-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 09/03/2020] [Indexed: 06/11/2023]
Abstract
The ability of photosynthetic organisms to use sunlight as a sole source of energy is endowed by two large membrane complexes-photosystem I (PSI) and photosystem II (PSII). PSI and PSII are the fundamental components of oxygenic photosynthesis, providing oxygen, food and an energy source for most living organisms on Earth. Currently, high-resolution crystal structures of these complexes from various organisms are available. The crystal structures of megadalton complexes have revealed excitation transfer and electron-transport pathways within the various complexes. PSI is defined as plastocyanin-ferredoxin oxidoreductase but a high-resolution structure of the entire triple supercomplex is not available. Here, using a new cryo-electron microscopy technique, we solve the structure of native plant PSI in complex with its electron donor plastocyanin and the electron acceptor ferredoxin. We reveal all of the contact sites and the modes of interaction between the interacting electron carriers and PSI.
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Affiliation(s)
- Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Anna Borovikova-Sheinker
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Daniel Klaiman
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Yoel Shkolnisky
- School of Mathematical Sciences, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel.
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
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Caspy I, Malavath T, Klaiman D, Fadeeva M, Shkolnisky Y, Nelson N. Structure and energy transfer pathways of the Dunaliella Salina photosystem I supercomplex. Biochim Biophys Acta Bioenerg 2020; 1861:148253. [PMID: 32569661 DOI: 10.1016/j.bbabio.2020.148253] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Revised: 06/14/2020] [Accepted: 06/15/2020] [Indexed: 12/30/2022]
Abstract
Oxygenic photosynthesis evolved more than 3 billion years ago in cyanobacteria. The increased complexity of photosystem I (PSI) became apparent from the high-resolution structures that were obtained for the complexes that were isolated from various organisms, ranging from cyanobacteria to plants. These complexes are all evolutionarily linked. In this paper, the researchers have uncovered the increased complexity of PSI in a single organism demonstrated by the coexistance of two distinct PSI compositions. The Large Dunaliella PSI contains eight additional subunits, six in PSI core and two light harvesting complexes. Two additional chlorophyll a molecules pertinent for efficient excitation energy transfer in state II transition were identified in PsaL and PsaO. Short distances between these newly identified chlorophylls correspond with fast excitation transfer rates previously reported during state II transition. The apparent PSI conformations could be a coping mechanism for the high salinity.
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Affiliation(s)
- Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tirupathi Malavath
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Daniel Klaiman
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Maria Fadeeva
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yoel Shkolnisky
- School of Mathematical Sciences, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
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Perez-Boerema A, Klaiman D, Caspy I, Netzer-El SY, Amunts A, Nelson N. Structure of a minimal photosystem I from the green alga Dunaliella salina. Nat Plants 2020; 6:321-327. [PMID: 32123351 DOI: 10.1038/s41477-020-0611-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 01/30/2020] [Indexed: 05/19/2023]
Abstract
Solar energy harnessed by oxygenic photosynthesis supports most of the life forms on Earth. In eukaryotes, photosynthesis occurs in chloroplasts and is achieved by membrane-embedded macromolecular complexes that contain core and peripheral antennae with multiple pigments. The structure of photosystem I (PSI) comprises the core and light-harvesting (LHCI) complexes, which together form PSI-LHCI. Here we determined the structure of PSI-LHCI from the salt-tolerant green alga Dunaliella salina using X-ray crystallography and electron cryo-microscopy. Our results reveal a previously undescribed configuration of the PSI core. It is composed of only 7 subunits, compared with 14-16 subunits in plants and the alga Chlamydomonas reinhardtii, and forms the smallest known PSI. The LHCI is poorly conserved at the sequence level and binds to pigments that form new energy pathways, and the interactions between the individual Lhca1-4 proteins are weakened. Overall, the data indicate the PSI of D. salina represents a different type of the molecular organization that provides important information for reconstructing the plasticity and evolution of PSI.
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Affiliation(s)
- Annemarie Perez-Boerema
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Daniel Klaiman
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Sigal Y Netzer-El
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Alexey Amunts
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden.
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
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Antoshvili M, Caspy I, Hippler M, Nelson N. Structure and function of photosystem I in Cyanidioschyzon merolae. Photosynth Res 2019; 139:499-508. [PMID: 29582227 DOI: 10.1007/s11120-018-0501-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 03/21/2018] [Indexed: 05/19/2023]
Abstract
The evolution of photosynthesis from primitive photosynthetic bacteria to higher plants has been driven by the need to adapt to a wide range of environmental conditions. The red alga Cyanidioschyzon merolae is a primitive organism, which is capable of performing photosynthesis in extreme acidic and hot environments. The study of its photosynthetic machinery may provide new insight on the evolutionary path of photosynthesis and on light harvesting and its regulation in eukaryotes. With that aim, the structural and functional properties of the PSI complex were investigated by biochemical characterization, mass spectrometry, and X-ray crystallography. PSI was purified from cells grown at 25 and 42 °C, crystallized and its crystal structure was solved at 4 Å resolution. The structure of C. merolae reveals a core complex with a crescent-shaped structure, formed by antenna proteins. In addition, the structural model shows the position of PsaO and PsaM. PsaG and PsaH are present in plant complex and are missing from the C. merolae model as expected. This paper sheds new light onto the evolution of photosynthesis, which gives a strong indication for the chimerical properties of red algae PSI. The subunit composition of the PSI core from C. merolae and its associated light-harvesting antennae suggests that it is an evolutionary and functional intermediate between cyanobacteria and plants.
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Affiliation(s)
- Maya Antoshvili
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978, Tel Aviv, Israel
| | - Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978, Tel Aviv, Israel
| | - Michael Hippler
- Institute of Plant Biology and Biotechnology, University of Münster, 48143, Münster, Germany
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978, Tel Aviv, Israel.
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Netzer-El SY, Caspy I, Nelson N. Crystal Structure of Photosystem I Monomer From Synechocystis PCC 6803. Front Plant Sci 2019; 9:1865. [PMID: 30662446 PMCID: PMC6328476 DOI: 10.3389/fpls.2018.01865] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 12/04/2018] [Indexed: 05/25/2023]
Abstract
A single histidine addition to the C-terminus of PsaL of Synechocystis sp. PCC 6803 was previously reported by our lab to shift the trimer-to-monomer ratio of PSI in favor of the monomeric form. P700 re-reduction and NADP+ photo-reduction measurements of the PsaLHIS strain show no effect on PSI activity in comparison to the WT trimeric PSI. Crystal structure of the PsaLHIS monomeric PSI reveals several alterations that occurred in the trimerisation site of PSI, primarily a deformation of the C-terminus of PsaL and loss of chlorophyll a and β-carotene molecules.
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Malavath T, Caspy I, Netzer-El SY, Klaiman D, Nelson N. Structure and function of wild-type and subunit-depleted photosystem I in Synechocystis. Biochim Biophys Acta Bioenerg 2018; 1859:645-654. [PMID: 29414678 DOI: 10.1016/j.bbabio.2018.02.002] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 01/30/2018] [Accepted: 02/01/2018] [Indexed: 10/18/2022]
Abstract
The ability of photosynthetic organisms to use the sun's light as a sole source of energy sustains life on our planet. Photosystems I (PSI) and II (PSII) are large, multi-subunit, pigment-protein complexes that enable photosynthesis, but this intriguing process remains to be explained fully. Currently, crystal structures of these complexes are available for thermophilic prokaryotic cyanobacteria. The mega-Dalton trimeric PSI complex from thermophilic cyanobacterium, Thermosynechococcus elongatus, was solved at 2.5 Å resolution with X-ray crystallography. That structure revealed the positions of 12 protein subunits (PsaA-F, PsaI-M, and PsaX) and 127 cofactors. Although mesophilic organisms perform most of the world's photosynthesis, no well-resolved trimeric structure of a mesophilic organism exists. Our research model for a mesophilic cyanobacterium was Synechocystis sp. PCC6803. This study aimed to obtain well-resolved crystal structures of [1] a monomeric PSI with all subunits, [2] a trimeric PSI with a reduced number of subunits, and [3] the full, trimeric wild-type PSI complex. We only partially succeeded with the first two structures, but we successfully produced the trimeric PSI structure at 2.5 Å resolution. This structure was comparable to that of the thermophilic species, but we provided more detail. The PSI trimeric supercomplex consisted of 33 protein subunits, 72 carotenoids, 285 chlorophyll a molecules, 51 lipids, 9 iron-sulfur clusters, 6 plastoquinones, 6 putative calcium ions, and over 870 water molecules. This study showed that the structure of the PSI in Synechocystis sp. PCC6803 differed from previously described PSI structures. These findings have broadened our understanding of PSI structure.
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Affiliation(s)
- Tirupathi Malavath
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Sigal Y Netzer-El
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Daniel Klaiman
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
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Nelson N, Caspy I, Klaiman D. Structure of Photosystem I - Interplay between Robastness and Complexity. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Mazor Y, Borovikova A, Caspy I, Nelson N. Structure of the plant photosystem I supercomplex at 2.6 Å resolution. Nat Plants 2017; 3:17014. [PMID: 28248295 DOI: 10.1038/nplants.2017.14] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 01/25/2017] [Indexed: 05/21/2023]
Abstract
Four elaborate membrane complexes carry out the light reaction of oxygenic photosynthesis. Photosystem I (PSI) is one of two large reaction centres responsible for converting light photons into the chemical energy needed to sustain life. In the thylakoid membranes of plants, PSI is found together with its integral light-harvesting antenna, light-harvesting complex I (LHCI), in a membrane supercomplex containing hundreds of light-harvesting pigments. Here, we report the crystal structure of plant PSI-LHCI at 2.6 Å resolution. The structure reveals the configuration of PsaK, a core subunit important for state transitions in plants, a conserved network of water molecules surrounding the electron transfer centres and an elaborate structure of lipids bridging PSI and its LHCI antenna. We discuss the implications of the structure for energy transfer and the evolution of PSI.
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Affiliation(s)
- Yuval Mazor
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Anna Borovikova
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ido Caspy
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Nathan Nelson
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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