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光合系统II中O2形成过程中中间体的结构证据
作者:小柯机器人 发布时间:2023/5/6 14:54:44


美国劳伦斯伯克利国家实验室Yachandra, Vittal K.团队报道了光合系统II中O2形成过程中中间体的结构证据。相关研究成果于2023年5月3日发表于国际顶尖学术期刊《自然》。

在自然光合作用中,光驱动水分解为电子、质子和分子氧,形成了太阳能转化为化学能过程的第一步。反应发生在光系统II中,其中Mn4CaO5簇首先存储四个氧化当量,即Kok循环中的S0至S4中间态,通过反应中心的光化学电荷分离依次产生,然后催化O–O键的形成。

该文中,研究人员通过连续飞秒X射线晶体学报道了室温快照,以提供对Kok光合水氧化循环的最后反应步骤S3→[S4]→S0转变的结构见解,其中O2形成并且Kok的水氧化时钟复位。该数据揭示了一系列复杂的事件,这些事件发生在微米到毫秒之间,包括Mn4CaO5簇、其配体和水通道的变化,以及通过Cl1通道的氢键网络控制的质子释放。重要的是,额外的O原子Ox,在Ca和Mn1之间S2→S3跃迁过程中被引入作为桥接配体,在第三次闪光后约700μs开始消失或重新定位,与Yz还原平行。如Mn1–Mn4距离缩短所示,O2析出的开始发生在1200μs左右,这表明存在还原的中间体,可能是结合的过氧化物。

附:英文原文

Title: Structural evidence for intermediates during O2 formation in photosystem II

Author: Bhowmick, Asmit, Hussein, Rana, Bogacz, Isabel, Simon, Philipp S., Ibrahim, Mohamed, Chatterjee, Ruchira, Doyle, Margaret D., Cheah, Mun Hon, Fransson, Thomas, Chernev, Petko, Kim, In-Sik, Makita, Hiroki, Dasgupta, Medhanjali, Kaminsky, Corey J., Zhang, Miao, Gtcke, Julia, Haupt, Stephanie, Nangca, Isabela I., Keable, Stephen M., Aydin, A. Orkun, Tono, Kensuke, Owada, Shigeki, Gee, Leland B., Fuller, Franklin D., Batyuk, Alexander, Alonso-Mori, Roberto, Holton, James M., Paley, Daniel W., Moriarty, Nigel W., Mamedov, Fikret, Adams, Paul D., Brewster, Aaron S., Dobbek, Holger, Sauter, Nicholas K., Bergmann, Uwe, Zouni, Athina, Messinger, Johannes, Kern, Jan, Yano, Junko, Yachandra, Vittal K.

Issue&Volume: 2023-05-03

Abstract: In natural photosynthesis, the light-driven splitting of water into electrons, protons and molecular oxygen forms the first step of the solar-to-chemical energy conversion process. The reaction takes place in photosystem II, where the Mn4CaO5 cluster first stores four oxidizing equivalents, the S0 to S4 intermediate states in the Kok cycle, sequentially generated by photochemical charge separations in the reaction center and then catalyzes the O–O bond formation chemistry1,2,3. Here, we report room temperature snapshots by serial femtosecond X-ray crystallography to provide structural insights into the final reaction step of Kok’s photosynthetic water oxidation cycle, the S3→[S4]→S0 transition where O2 is formed and Kok’s water oxidation clock is reset. Our data reveal a complex sequence of events, which occur over micro- to milliseconds, comprising changes at the Mn4CaO5 cluster, its ligands and water pathways as well as controlled proton release through the hydrogen-bonding network of the Cl1 channel. Importantly, the extra O atom Ox, which was introduced as a bridging ligand between Ca and Mn1 during the S2→S3 transition4,5,6, disappears or relocates in parallel with Yz reduction starting at approximately 700μs after the third flash. The onset of O2 evolution, as indicated by the shortening of the Mn1–Mn4 distance, occurs at around 1,200μs, signifying the presence of a reduced intermediate, possibly a bound peroxide.

DOI: 10.1038/s41586-023-06038-z

Source: https://www.nature.com/articles/s41586-023-06038-z

期刊信息
Nature:《自然》,创刊于1869年。隶属于施普林格·自然出版集团,最新IF:69.504
官方网址:http://www.nature.com/