Effects of site-directed mutations on photosynthetic water oxidation reactions

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K07442
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Plant molecular biology/Plant physiology
• Research Institution: Okayama University
• Principal Investigator: Nagao Ryo 岡山大学, 異分野基礎科学研究所, 特任講師 (30633961)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 光合成 / シアノバクテリア / 赤外分光 / 水分解反応

Outline of Final Research Achievements

Photosystem II (PSII) is a multi-subunit pigment-protein complex embedded in thylakoid membranes in plants, algae, and cyanobacteria. PSII serves as light-driven water-oxidation reactions. In this study, we examined mechanisms of the water-oxidation reactions, especially proton release and charge separation, by means of infrared spectroscopy using PSII isolated from site-directed mutants.
The mutations were introduced into D1 and D2 subunits in PSII, which have important amino acid residues for the water-oxidation reactions as suggested by the X-ray crystal structure of PSII. The Fourier transformed infrared and time-resolved infrared analyses clearly showed that at least five amino acid residues, D1-Val157, D1-Ser169, D1-Asp170, D1-Asn298, and D2-Val156, contribute to the reactions, that is, D1-Val157 and D2-Val156 are involved in charge-separation reaction, and the remaining D1-Ser169, D1-Asp170, and D1-Asn298 function in water-oxidation reaction.

Free Research Field

生化学

Academic Significance and Societal Importance of the Research Achievements

本研究が完遂されることにより、水分解反応におけるアミノ酸配位子のマンガンクラスターへの寄与およびプロトン放出機構が明らかとなる。これは光に弱いPSIIを強化することによる光合成能増強に向けた基盤研究となり、将来的にはイネやトウモロコシなどの有用作物の生産量向上のための応用研究に繋がると考えられるため、その意義は大きい。また、太陽光エネルギーを電気エネルギーに変換する人工光合成デバイス、特に光を利用した水分解システムや効率的な水素発生システムの原理構築に繋がり、人工光合成分野の発展も期待できる。