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Publication Abstract from PubMed

Photosynthetic water oxidation is catalyzed by the Mn4CaO5 cluster of photosystem II (PSII) with linear progression through five S-state intermediates (S0 to S4). To reveal the mechanism of water oxidation, we analyzed structures of PSII in the S1, S2, and S3 states by x-ray free-electron laser serial crystallography. No insertion of water was found in S2, but flipping of D1 Glu(189) upon transition to S3 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.

An oxyl/oxo mechanism for oxygen-oxygen coupling in PSII revealed by an x-ray free-electron laser.,Suga M, Akita F, Yamashita K, Nakajima Y, Ueno G, Li H, Yamane T, Hirata K, Umena Y, Yonekura S, Yu LJ, Murakami H, Nomura T, Kimura T, Kubo M, Baba S, Kumasaka T, Tono K, Yabashi M, Isobe H, Yamaguchi K, Yamamoto M, Ago H, Shen JR Science. 2019 Oct 18;366(6463):334-338. doi: 10.1126/science.aax6998. Epub 2019, Oct 17. PMID:31624207^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.