Structural study on the function of chloride ion in photosystem II

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K06158
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 43040:Biophysics-related
• Research Institution: Jichi Medical University (2020); Okayama University (2018-2019)
• Principal Investigator: Umena Yasufumi 自治医科大学, 医学部, ポスト・ドクター (10468267)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 光合成 / 結晶構造解析 / 分子アニオン / 塩素イオン / 水分解反応

Outline of Final Research Achievements

In order to elucidate the role of chloride ion, which is an essential cofactor for water splitting in photosystem II (PSII) in photosynthesis reaction, we studied the inhibition mechanism from the crystal structure of PSII bound with molecular anions, which reduced PSII activity and to understand the original role of chloride ion from structural chemistry.
This study succeeded in analyzing PSII crystals substituted with molecular anions azide, nitrate, and nitrite ions at 2-2.1 angstrom resolution. The inhibition mechanism was clarified from the common structural changes associated with these substitutions compared with the original structure. We concluded that the role of the chlorine ion in PSII is for supporting the proton transfer mechanism and for sustaining the structure of the active center of the Mn-cluster.

Free Research Field

構造生物化学

Academic Significance and Societal Importance of the Research Achievements

PSIIの水分解反応は金属触媒のMnクラスターを中心に議論がされているが、補欠因子としての塩素イオンの構造化学的な役割については、はっきりしていなかった。本研究により、PSIIにおける水分解反応をより包括的に議論できる構造情報を示すことができた。この知見は、Mnクラスターを模倣したMn触媒の周辺構造が重要性を提示することで、新たな人工光合成触媒への設計指針を提供できたものと思われる。