日本冈山大学Shen, Jian-Ren团队报道了S1-S2-S3跃迁过程中出氧光系统II结构。相关研究成果发表在2024年1月31日出版的国际学术期刊《自然》。

光系统II（PSII）通过Mn₄CaO₅簇Si态（i=0–4）的四步循环催化水的氧化，在此过程中，额外的氧（O6）在S3态结合，形成可能的双氧。在微秒时间尺度上研究了金属团簇及其环境在S态跃迁过程中的结构变化。

该文中，研究人员使用泵浦探针串联飞秒晶体学来揭示，PSII在一次闪光（1F）或两次闪光（2F）照射后从纳秒到毫秒的结构动力学。YZ是一种连接反应中心P680和Mn₄CaO₅簇的酪氨酸残基，其周围的氨基酸残基和水分子在纳秒时间尺度上表现出结构变化，反映了闪光照射后电子和质子的快速转移。

值得注意的是，一个水分子出现在PSII的D1亚基（D1-E189）的Glu189附近，并在2F照射后的亚微秒时间尺度上与Ca²⁺离子结合。这种水分子后来随着O6的增加而消失，这表明它是O6的起源。研究人员还观察到水分子在O1、O4和Cl^-1通道及其周围氨基酸残基中的协同运动，以完成电子转移、质子释放和底物水输送的序列。这些结果为PSII在S态转变以及O–O键形成过程中的结构动力学提供了重要的见解。

附：英文原文

Title: Oxygen-evolving photosystem II structures during S1–S2–S3 transitions

Author: Li, Hongjie, Nakajima, Yoshiki, Nango, Eriko, Owada, Shigeki, Yamada, Daichi, Hashimoto, Kana, Luo, Fangjia, Tanaka, Rie, Akita, Fusamichi, Kato, Koji, Kang, Jungmin, Saitoh, Yasunori, Kishi, Shunpei, Yu, Huaxin, Matsubara, Naoki, Fujii, Hajime, Sugahara, Michihiro, Suzuki, Mamoru, Masuda, Tetsuya, Kimura, Tetsunari, Thao, Tran Nguyen, Yonekura, Shinichiro, Yu, Long-Jiang, Tosha, Takehiko, Tono, Kensuke, Joti, Yasumasa, Hatsui, Takaki, Yabashi, Makina, Kubo, Minoru, Iwata, So, Isobe, Hiroshi, Yamaguchi, Kizashi, Suga, Michihiro, Shen, Jian-Ren

Issue&Volume: 2024-01-31

Abstract: Photosystem II (PSII) catalyses the oxidation of water through a four-step cycle of Si states (i=0–4) at the Mn4CaO5 cluster1,2,3, during which an extra oxygen (O6) is incorporated at the S3 state to form a possible dioxygen4,5,6,7. Structural changes of the metal cluster and its environment during the S-state transitions have been studied on the microsecond timescale. Here we use pump-probe serial femtosecond crystallography to reveal the structural dynamics of PSII from nanoseconds to milliseconds after illumination with one flash (1F) or two flashes (2F). YZ, a tyrosine residue that connects the reaction centre P680 and the Mn4CaO5 cluster, showed structural changes on a nanosecond timescale, as did its surrounding amino acid residues and water molecules, reflecting the fast transfer of electrons and protons after flash illumination. Notably, one water molecule emerged in the vicinity of Glu189 of the D1 subunit of PSII (D1-E189), and was bound to the Ca2+ ion on a sub-microsecond timescale after 2F illumination. This water molecule disappeared later with the concomitant increase of O6, suggesting that it is the origin of O6. We also observed concerted movements of water molecules in the O1, O4 and Cl-1 channels and their surrounding amino acid residues to complete the sequence of electron transfer, proton release and substrate water delivery. These results provide crucial insights into the structural dynamics of PSII during S-state transitions as well as O–O bond formation.

DOI: 10.1038/s41586-023-06987-5

Source: https://www.nature.com/articles/s41586-023-06987-5