Kato Koji, Miyazaki Naoyuki, Hamaguchi Tasuku, Nakajima Yoshiki, Akita Fusamichi, Yonekura Koji, Shen Jian-Ren
Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, Ibaraki, Japan.
Commun Biol. 2021 Mar 22;4(1):382. doi: 10.1038/s42003-021-01919-3.
Photosystem II (PSII) plays a key role in water-splitting and oxygen evolution. X-ray crystallography has revealed its atomic structure and some intermediate structures. However, these structures are in the crystalline state and its final state structure has not been solved. Here we analyzed the structure of PSII in solution at 1.95 Å resolution by single-particle cryo-electron microscopy (cryo-EM). The structure obtained is similar to the crystal structure, but a PsbY subunit was visible in the cryo-EM structure, indicating that it represents its physiological state more closely. Electron beam damage was observed at a high-dose in the regions that were easily affected by redox states, and reducing the beam dosage by reducing frames from 50 to 2 yielded a similar resolution but reduced the damage remarkably. This study will serve as a good indicator for determining damage-free cryo-EM structures of not only PSII but also all biological samples, especially redox-active metalloproteins.
光系统II（PSII）在水分解和氧气释放过程中起着关键作用。X射线晶体学已经揭示了其原子结构和一些中间结构。然而，这些结构处于晶体状态，其最终状态结构尚未得到解析。在此，我们通过单颗粒冷冻电子显微镜（cryo-EM）以1.95Å的分辨率分析了溶液中PSII的结构。所获得的结构与晶体结构相似，但在冷冻电镜结构中可见一个PsbY亚基，这表明它更接近其生理状态。在容易受到氧化还原状态影响的区域，高剂量时观察到了电子束损伤，通过将帧数从50帧减少到2帧来降低束剂量，得到了相似的分辨率，但显著减少了损伤。这项研究将成为一个很好的指标，不仅用于确定PSII的无损伤冷冻电镜结构，也用于确定所有生物样品，特别是氧化还原活性金属蛋白的无损伤冷冻电镜结构。
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