Proton-Coupled Electron-Transfer Processes in Photosystem II Probed by Highly Resolved g-Anisotropy of Redox-Active Tyrosine YZ

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• 作者：Hideto Matsuoka ; Jian-Ren Shen ; Asako Kawamori ; Kei Nishiyama ; Yasunori Ohba ; Seigo Yamauchi
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：March 30, 2011
• 年：2011
• 卷：133
• 期：12
• 页码：4655-4660
• 全文大小：846K
• 年卷期：v.133,no.12(March 30, 2011)
• ISSN：1520-5126

文摘

The oxidation of a redox-active tyrosine residue Y_Z in photosystem II (PSII) is coupled with proton transfer to a hydrogen-bonded D1-His190 residue. Because of the apparent proximity of Y_Z to the water-oxidizing complex and its redox activity, it is believed that Y_Z plays a significant role in water oxidation in PSII. We investigated the g-anisotropy of the tyrosine radical Y_Z^{鈥?/sup> to provide insight into the mechanism of Y_Z鈥?/sup> proton-coupled electron transfer in Mn-depleted PSII. The anisotropy was highly resolved by electron paramagnetic resonance spectroscopy at the W-band (94.9 GHz) using PSII single crystals. The g_X-component along the phenolic C鈭扥 bond of Y_Z鈥?/sup> was calculated by density functional theory (DFT). It was concluded from the highly resolved g-anisotropy that Y_Z loses a phenol proton to D1-His190 upon tyrosine oxidation, and D1-His190 redonates the same proton back to Y_Z鈥?/sup> upon reduction.}