An oxyl/oxo mechanism for oxygen-oxygen coupling in PSII revealed by an x-ray free-electron laser
An oxyl/oxo mechanism for oxygen-oxygen coupling in PSII revealed by an x-ray free-electron laser
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DOI：
10.1126/science.aax6998
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发表时间：
2019-10-18
期刊：
影响因子：
56.9
通讯作者：
Shen, Jian-Ren
中科院分区：
文献类型：
--
作者：
Suga, Michihiro;Akita, Fusamichi;Shen, Jian-Ren
光合水氧化是由光系统II （PSII）的Mn4CaO5簇催化的，并通过5个s态中间体（S-0到S-4）线性推进。为了揭示水氧化的机理，我们利用x射线自由电子激光连续晶体学分析了PSII在S-1、S-2和S-3态的结构。在S-2中没有发现水的插入，但D1 Glu（189）在过渡到S-3时翻转导致水渠打开，并为加入额外的氧配体提供空间，从而形成具有氧/氧桥的开放立方体Mn4CaO6簇。PSII在不同S态间的结构变化揭示了光合水氧化过程中底物取水、质子释放和双氧形成的协同作用。
Photosynthetic water oxidation is catalyzed by the Mn4CaO5 cluster of photosystem II (PSII) with linear progression through five S-state intermediates (S-0 to S-4). To reveal the mechanism of water oxidation, we analyzed structures of PSII in the S-1, S-2, and S-3 states by x-ray free-electron laser serial crystallography. No insertion of water was found in S-2, but flipping of D1 Glu(189) upon transition to S-3 leads to the opening of a water channel and provides a space for incorporation of an additional oxygen ligand, resulting in an open cubane Mn4CaO6 cluster with an oxyl/oxo bridge. Structural changes of PSII between the different S states reveal cooperative action of substrate water access, proton release, and dioxygen formation in photosynthetic water oxidation.