ダイナミクス・エナジェティクス融合による光合成水分解反応機構の解明

• Project Area: Creation of novel light energy conversion system through elucidation of the molecular mechanism of photosynthesis and its artificial design in terms of time and space
• Project/Area Number: 18H05155
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Research Institution: The University of Tokyo
• Principal Investigator: 石北 央 東京大学, 先端科学技術研究センター, 教授 (00508111)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥5,200,000 (Direct Cost: ¥4,000,000、Indirect Cost: ¥1,200,000); Fiscal Year 2019: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000); Fiscal Year 2018: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000)
• Keywords: 人工光合成 / 光合成 / プロトン移動 / 電子移動 / 光化学系II / photosystem II / 水分解・酸素発生 / 結晶構造 / 理論化学

Outline of Annual Research Achievements

光合成の膜タンパク質複合体photosystem II (PSII)は、水分解酸素発生触媒部位としてMn4CaO5錯体を有する。研究期間内において、Mn4CaO5錯体を量子化学的手法で取り扱うことにより、タンパク質静電場環境下でのMn4CaO5の電位を明らかにした。また、電子移動アクセプターであるチロシン残基TyrZ、クロロフィルP680の電位もあわせて計算することで、電子移動経路Mn4CaO5→TyrZ→P680から成る電子移動カスケードの観点からMn4CaO5に要求されている電位とその妥当性を評価した。プロトン共役電子移動はプロトン移動が電子移動の電位に大きく関わっていることを示す好例であるが、それはすなわち、プロトン化状態の妥当性は、Mn4CaO5の電位からも垣間見ることができる、ということを意味している。（すでにあまたと提唱されている）各反応機構のプロトン化状態、水分子から電子を奪うのに要する電位等の観点から、機構の解析を進めた。また、各S状態遷移でのプロトン共役電子移動に関して、電子放出がプロトン放出を誘起するか（電子移動律速）、あるいはプロトン放出が電子移動放出を誘起するか（プロトン移動律速）、解析を行う。結果として、本研究では「電子の流れ」と「プロトンの流れ」の両面からの整合性から水分解反応機構を明らかにすることにも積極的に努めた。さらに本研究手法を拡張し、Ca2+-depleted PSIIでのMn4O5電位、Sr2+置換体でのMn4SrO5の電位を世界で初めて明らかにした。国際誌において複数の論文発表を行うことができた。

Research Progress Status

令和元年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和元年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] Insights into the Protein Functions and Absorption Wavelengths of Microbial Rhodopsins (2020)
  • Author(s): Tsujimura Masaki、Ishikita Hiroshi
  • Journal Title: The Journal of Physical Chemistry B Volume: 124 Issue: 52 Pages: 11819-11826
  • DOI: 10.1021/acs.jpcb.0c08910
  • Peer Reviewed / Open Access
• [Journal Article] The Nature of the Short Oxygen?Oxygen Distance in the Mn4CaO6 Complex of Photosystem II Crystals (2020)
  • Author(s): Mandal Manoj、Saito Keisuke、Ishikita Hiroshi
  • Journal Title: The Journal of Physical Chemistry Letters Volume: 11 Issue: 23 Pages: 10262-10268
  • DOI: 10.1021/acs.jpclett.0c02868
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Redox potentials along the redox-active low-barrier H-bonds in electron transfer pathways (2020)
  • Author(s): Saito Keisuke、Mandal Manoj、Ishikita Hiroshi
  • Journal Title: Physical Chemistry Chemical Physics Volume: 22 Issue: 44 Pages: 25467-25473
  • DOI: 10.1039/d0cp04265j
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Dependence of the chlorophyll wavelength on the orientation of a charged group: Why does the accessory chlorophyll have a low site energy in photosystem II? (2020)
  • Author(s): Saito Keisuke、Mitsuhashi Koji、Ishikita Hiroshi
  • Journal Title: Journal of Photochemistry and Photobiology A: Chemistry Volume: 402 Pages: 112799-112799
  • DOI: 10.1016/j.jphotochem.2020.112799
  • Peer Reviewed / Open Access
• [Journal Article] Green-Sensitive, Long-Lived, Step-Functional Anion Channelrhodopsin-2 Variant as a High-Potential Neural Silencing Tool (2020)
  • Author(s): Kojima Keiichi、Miyoshi Natsuki、Shibukawa Atsushi、Chowdhury Srikanta、Tsujimura Masaki、Noji Tomoyasu、Ishikita Hiroshi、Yamanaka Akihiro、Sudo Yuki
  • Journal Title: The Journal of Physical Chemistry Letters Volume: 11 Issue: 15 Pages: 6214-6218
  • DOI: 10.1021/acs.jpclett.0c01406
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Energetics of Ionized Water Molecules in the H-Bond Network near the Ca2+ and Cl? Binding Sites in Photosystem II (2020)
  • Author(s): Saito Keisuke、Mandal Manoj、Ishikita Hiroshi
  • Journal Title: Biochemistry Volume: 59 Issue: 35 Pages: 3216-3224
  • DOI: 10.1021/acs.biochem.0c00177
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] pKa of the ligand water molecules in the oxygen-evolving Mn4CaO5 cluster in photosystem II (2020)
  • Author(s): Saito Keisuke、Nakagawa Minesato、Ishikita Hiroshi
  • Journal Title: Communications Chemistry Volume: 3 Issue: 1 Pages: 89-89
  • DOI: 10.1038/s42004-020-00336-7
  • Peer Reviewed / Open Access
• [Journal Article] Rigidly hydrogen-bonded water molecules facilitate proton transfer in photosystem II (2020)
  • Author(s): Sakashita Naoki、Ishikita Hiroshi、Saito Keisuke
  • Journal Title: Physical Chemistry Chemical Physics Volume: 22 Issue: 28 Pages: 15831-15841
  • DOI: 10.1039/d0cp00295j
  • Peer Reviewed / Open Access
• [Journal Article] Acquirement of water-splitting ability and alteration of the charge-separation mechanism in photosynthetic reaction centers (2020)
  • Author(s): Tamura Hiroyuki、Saito Keisuke、Ishikita Hiroshi
  • Journal Title: Proceedings of the National Academy of Sciences Volume: 117 Issue: 28 Pages: 16373-16382
  • DOI: 10.1073/pnas.2000895117
  • Peer Reviewed / Open Access
• [Journal Article] Quenching of Singlet Oxygen by Carotenoids via Ultrafast Superexchange Dynamics (2020)
  • Author(s): Tamura Hiroyuki、Ishikita Hiroshi
  • Journal Title: The Journal of Physical Chemistry A Volume: 124 Issue: 25 Pages: 5081-5088
  • DOI: 10.1021/acs.jpca.0c02228
  • Peer Reviewed
• [Journal Article] Vectorial Proton Transport Mechanism of RxR, a Phylogenetically Distinct and Thermally Stable Microbial Rhodopsin (2020)
  • Author(s): Kojima Keiichi、Ueta Tetsuya、Noji Tomoyasu、Saito Keisuke、Kanehara Kanae、Yoshizawa Susumu、Ishikita Hiroshi、Sudo Yuki
  • Journal Title: Scientific Reports Volume: 10 Issue: 1 Pages: 1-11
  • DOI: 10.1038/s41598-019-57122-2
  • NAID: 120006884916
  • Peer Reviewed / Open Access
• [Journal Article] Redox Potential of the Oxygen-Evolving Complex in the Electron Transfer Cascade of Photosystem II (2019)
  • Author(s): Mandal Manoj、Kawashima Keisuke、Saito Keisuke、Ishikita Hiroshi
  • Journal Title: The Journal of Physical Chemistry Letters Volume: 11 Issue: 1 Pages: 249-255
  • DOI: 10.1021/acs.jpclett.9b02831
  • Peer Reviewed / Open Access
• [Journal Article] Long-Range Exciton Diffusion via Singlet Revival Mechanism (2019)
  • Author(s): Tamura Hiroyuki、Azumaya Koki、Ishikita Hiroshi
  • Journal Title: The Journal of Physical Chemistry Letters Volume: 10 Issue: 24 Pages: 7623-7628
  • DOI: 10.1021/acs.jpclett.9b03029
  • Peer Reviewed
• [Journal Article] Mechanism of protonation of the over-reduced Mn4CaO5 cluster in photosystem II (2019)
  • Author(s): Saito Keisuke、Ishikita Hiroshi
  • Journal Title: Biochimica et Biophysica Acta (BBA) - Bioenergetics Volume: 1860 Issue: 10 Pages: 148059-148059
  • DOI: 10.1016/j.bbabio.2019.148059
  • Peer Reviewed / Open Access
• [Journal Article] O2 evolution and recovery of the water-oxidizing enzyme (2018)
  • Author(s): Kawashima Keisuke、Takaoka Tomohiro、Kimura Hiroki、Saito Keisuke、Ishikita Hiroshi
  • Journal Title: Nature Communications Volume: 9 Issue: 1 Pages: 1247-1247
  • DOI: 10.1038/s41467-018-03545-w
  • Peer Reviewed / Open Access
• [Journal Article] Energetic insights into two electron transfer pathways in light-driven energy-converting enzymes (2018)
  • Author(s): K. Kawashima, H. Ishikita
  • Journal Title: Chem. Sci. Volume: 9 Issue: 17 Pages: 4083-4092
  • DOI: 10.1039/c8sc00424b
  • Peer Reviewed / Open Access
• [Journal Article] Selective Removal of B800 Bacteriochlorophyll a from Light-Harvesting Complex 2 of the Purple Photosynthetic Bacterium Phaeospirillum molischianum (2018)
  • Author(s): Saga Yoshitaka、Hirota Keiya、Matsui Sayaka、Asakawa Hitoshi、Ishikita Hiroshi、Saito Keisuke
  • Journal Title: Biochemistry Volume: 57 Issue: 21 Pages: 3075-3083
  • DOI: 10.1021/acs.biochem.8b00259
  • Peer Reviewed
• [Journal Article] Mechanism of Radical Formation in the H-Bond Network of D1-Asn298 in Photosystem II (2018)
  • Author(s): Kawashima Keisuke、Saito Keisuke、Ishikita Hiroshi
  • Journal Title: Biochemistry Volume: 57 Issue: 33 Pages: 4997-5004
  • DOI: 10.1021/acs.biochem.8b00574
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Mutational analysis of the conserved carboxylates of anion channelrhodopsin-2 (ACR2) expressed in <i>Escherichia coli</i> and their roles in anion transport (2018)
  • Author(s): Kojima Keiichi、C. Watanabe Hiroshi、Doi Satoko、Miyoshi Natsuki、Kato Misaki、Ishikita Hiroshi、Sudo Yuki
  • Journal Title: Biophysics and Physicobiology Volume: 15 Issue: 0 Pages: 179-188
  • DOI: 10.2142/biophysico.15.0_179
  • NAID: 130007472538
  • ISSN: 2189-4779
  • Peer Reviewed / Open Access
• [Presentation] Proton transfer in photosystem II (2019)
  • Author(s): Hiroshi Ishikita
  • Organizer: Gordon Research Conference
  • Int'l Joint Research / Invited
• [Presentation] Proton transfer and electron transfer in the same protein electrostatic environment (2019)
  • Author(s): 石北 央
  • Organizer: 第19回日本蛋白質科学会年会
  • Invited
• [Presentation] 基礎的な分子化学からタンパク質内反応を理解する (2019)
  • Author(s): 石北 央
  • Organizer: 第46回生体分子科学討論会
  • Invited
• [Presentation] 実験結果ありきではない蛋白質分子の理論研究をめざして (2018)
  • Author(s): 石北 央
  • Organizer: 理研シンポジウム 計算で物事を理解する予測する
  • Invited
• [Presentation] Electron and proton transfer reactions in photosynthetic reaction centers (2018)
  • Author(s): Hiroshi Ishikita
  • Organizer: 10th symposium on Discovery, Fusion, Creation of New Knowledge by Multidisciplinary Computational Sciences: CCS International Symposium 2018
  • Int'l Joint Research / Invited
• [Presentation] Redox potentials of cofactors in electron transfer branches in photosynthetic reaction centers (2018)
  • Author(s): Hiroshi Ishikita
  • Organizer: 光合成反応中心の構築および作動原理：キノンは必須か
  • Invited
• [Presentation] Molecular structure and function of photosystem II (2018)
  • Author(s): Hiroshi Ishikita
  • Organizer: 1st Asia-Oceania International Congress on Photosynthesis
  • Invited