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Imaizumi K, Ifuku K. Binding and functions of the two chloride ions in the oxygen-evolving center of photosystem II. PHOTOSYNTHESIS RESEARCH 2022; 153:135-156. [PMID: 35698013 DOI: 10.1007/s11120-022-00921-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 05/02/2022] [Indexed: 06/15/2023]
Abstract
Light-driven water oxidation in photosynthesis occurs at the oxygen-evolving center (OEC) of photosystem II (PSII). Chloride ions (Cl-) are essential for oxygen evolution by PSII, and two Cl- ions have been found to specifically bind near the Mn4CaO5 cluster in the OEC. The retention of these Cl- ions within the OEC is critically supported by some of the membrane-extrinsic subunits of PSII. The functions of these two Cl- ions and the mechanisms of their retention both remain to be fully elucidated. However, intensive studies performed recently have advanced our understanding of the functions of these Cl- ions, and PSII structures from various species have been reported, aiding the interpretation of previous findings regarding Cl- retention by extrinsic subunits. In this review, we summarize the findings to date on the roles of the two Cl- ions bound within the OEC. Additionally, together with a short summary of the functions of PSII membrane-extrinsic subunits, we discuss the mechanisms of Cl- retention by these extrinsic subunits.
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Affiliation(s)
- Ko Imaizumi
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502, Japan
| | - Kentaro Ifuku
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan.
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Nagao R, Kato K, Kumazawa M, Ifuku K, Yokono M, Suzuki T, Dohmae N, Akita F, Akimoto S, Miyazaki N, Shen JR. Structural basis for different types of hetero-tetrameric light-harvesting complexes in a diatom PSII-FCPII supercomplex. Nat Commun 2022; 13:1764. [PMID: 35365610 PMCID: PMC8976053 DOI: 10.1038/s41467-022-29294-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 03/03/2022] [Indexed: 11/09/2022] Open
Abstract
Fucoxanthin chlorophyll (Chl) a/c-binding proteins (FCPs) function as light harvesters in diatoms. The structure of a diatom photosystem II-FCPII (PSII-FCPII) supercomplex have been solved by cryo-electron microscopy (cryo-EM) previously; however, the FCPII subunits that constitute the FCPII tetramers and monomers are not identified individually due to their low resolutions. Here, we report a 2.5 Å resolution structure of the PSII-FCPII supercomplex using cryo-EM. Two types of tetrameric FCPs, S-tetramer, and M-tetramer, are identified as different types of hetero-tetrameric complexes. In addition, three FCP monomers, m1, m2, and m3, are assigned to different gene products of FCP. The present structure also identifies the positions of most Chls c and diadinoxanthins, which form a complicated pigment network. Excitation-energy transfer from FCPII to PSII is revealed by time-resolved fluorescence spectroscopy. These structural and spectroscopic findings provide insights into an assembly model of FCPII and its excitation-energy transfer and quenching processes. Fucoxanthin chlorophyll a/c-binding proteins (FCPs) harvest light energy in diatoms. The authors analyzed a structure of PSII-FCPII supercomplex at high resolution by cryo-EM, which identified each FCP subunit and pigment network in the supercomplex.
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Affiliation(s)
- Ryo Nagao
- Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan.
| | - Koji Kato
- Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan
| | - Minoru Kumazawa
- Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502, Japan
| | - Kentaro Ifuku
- Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan
| | - Makio Yokono
- Institute of Low Temperature Science, Hokkaido University, Hokkaido, 060-0819, Japan
| | - Takehiro Suzuki
- Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, Saitama, 351-0198, Japan
| | - Naoshi Dohmae
- Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, Saitama, 351-0198, Japan
| | - Fusamichi Akita
- Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan
| | - Seiji Akimoto
- Graduate School of Science, Kobe University, Hyogo, 657-8501, Japan.
| | - Naoyuki Miyazaki
- Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, Ibaraki, 305-8577, Japan.
| | - Jian-Ren Shen
- Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan.
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Nagao R, Kato K, Suzuki T, Ifuku K, Uchiyama I, Kashino Y, Dohmae N, Akimoto S, Shen JR, Miyazaki N, Akita F. Structural basis for energy harvesting and dissipation in a diatom PSII-FCPII supercomplex. NATURE PLANTS 2019; 5:890-901. [PMID: 31358960 DOI: 10.1038/s41477-019-0477-x] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 06/13/2019] [Indexed: 05/07/2023]
Abstract
Light-harvesting antenna systems in photosynthetic organisms harvest solar energy and transfer it to the photosynthetic reaction centres to initiate charge-separation and electron-transfer reactions. Diatoms are one of the important groups of oxyphototrophs and possess fucoxanthin chlorophyll a/c-binding proteins (FCPs) as light harvesters. The organization and association pattern of FCP with the photosystem II (PSII) core are unknown. Here we solved the structure of PSII-FCPII supercomplexes isolated from a diatom, Chaetoceros gracilis, by single-particle cryoelectron microscopy. The PSII-FCPII forms a homodimer. In each monomer, two FCP homotetramers and three FCP monomers are associated with one PSII core. The structure reveals a highly complicated protein-pigment network that is different from the green-type light-harvesting apparatus. Comparing these two systems allows the identification of energy transfer and quenching pathways. These findings provide structural insights into not only excitation-energy transfer mechanisms in the diatom PSII-FCPII, but also changes of light harvesters between the red- and green-lineage oxyphototrophs during evolution.
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Affiliation(s)
- Ryo Nagao
- Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Koji Kato
- Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Takehiro Suzuki
- Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, Saitama, Japan
| | - Kentaro Ifuku
- Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Ikuo Uchiyama
- National Institute for Basic Biology, National Institutes of Natural Sciences, Aichi, Japan
| | - Yasuhiro Kashino
- Graduate School of Life Science, University of Hyogo, Hyogo, Japan
| | - Naoshi Dohmae
- Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, Saitama, Japan
| | - Seiji Akimoto
- Graduate School of Science, Kobe University, Hyogo, Japan
| | - Jian-Ren Shen
- Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
| | - Naoyuki Miyazaki
- Institute for Protein Research, Osaka University, Osaka, Japan.
- Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan.
| | - Fusamichi Akita
- Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
- Japan Science and Technology Agency, PRESTO, Saitama, Japan.
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