Humboldt-Universität zu Berlin, Department of Biology, D 10099 Berlin, Germany.
Department of Chemistry, Umeå University, SE 90187 Umeå, Sweden.
Science. 2024 Jun 21;384(6702):1349-1355. doi: 10.1126/science.adn6541. Epub 2024 Jun 20.
Photosystem II starts the photosynthetic electron transport chain that converts solar energy into chemical energy and thus sustains life on Earth. It catalyzes two chemical reactions: water oxidation to molecular oxygen and plastoquinone reduction. Coupling of electron and proton transfer is crucial for efficiency; however, the molecular basis of these processes remains speculative owing to uncertain water binding sites and the lack of experimentally determined hydrogen positions. We thus collected high-resolution cryo-electron microscopy data of fully hydrated photosystem II from the thermophilic cyanobacterium to a final resolution of 1.71 angstroms. The structure reveals several previously undetected partially occupied water binding sites and more than half of the hydrogen and proton positions. This clarifies the pathways of substrate water binding and plastoquinone B protonation.
光系统 II 启动光合作用电子传递链，将太阳能转化为化学能，从而维持地球上的生命。它催化两个化学反应：水氧化为分子氧和质体醌还原。电子和质子转移的偶联对于效率至关重要；然而，由于不确定的水结合位点和缺乏实验确定的氢位置，这些过程的分子基础仍然是推测性的。因此，我们收集了嗜热蓝藻的完全水合光系统 II 的高分辨率冷冻电镜数据，最终分辨率为 1.71 埃。该结构揭示了几个以前未检测到的部分占据的水结合位点以及超过一半的氢和质子位置。这阐明了底物水结合和质体醌 B 质子化的途径。
