Role of D1-Glu65 in Proton Transfer during Photosynthetic Water Oxidation in Photosystem II
Role of D1-Glu65 in Proton Transfer during Photosynthetic Water Oxidation in Photosystem II
复制标题
D1-Glu65 在光系统 II 光合水氧化过程中质子转移中的作用
DOI：
10.1021/acs.jpcb.2c05869
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Noguchi Takumi
中科院分区：
文献类型：
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作者：
Shimada Yuichiro;Sugiyama Ayane;Nagao Ryo;Noguchi Takumi
光系统II(PSII)中的Mn4CaO5团簇的光合作用水氧化通过称为S态(S0-S4)的5个中间产物的光驱动循环发生。尽管PSII结构已经显示出在Mn4CaO5团簇周围存在几个通向管腔的通道，但在单个S态跃迁中质子释放的途径仍然不清楚。在这里，我们利用傅里叶变换红外光谱和时间分辨红外光谱，结合热释光和延迟发光测量，研究了所谓的氯通道在水氧化过程中的质子转移，通过检测该通道的关键残基D1-Glu65的突变对ALA的影响。结果表明，D_1-Glu65Ala突变对催化中心的结构和氧化还原性质影响不大。在S2→S3转换中，D1Glu65Ala突变体的转换效率仍然很高，转换速度只有中等程度的延迟。相反，该突变显著抑制了S3→S0的转变。这些结果表明，S2→S3跃迁中的质子转移是通过包括氯通道在内的多个途径进行的，而这一通道可能是S3→S0跃迁中质子出射的单一途径。
Photosynthetic water oxidation takes place at the Mn4CaO5cluster in photosystem II (PSII) through a light-driven cycle of five intermediates called S states (S0–S4). Although the PSII structures have shown the presence of several channels around the Mn4CaO5cluster leading to the lumen, the pathways for proton release in the individual S-state transitions remain unidentified. Here, we studied the involvement of the so-called Cl channel in proton transfer during water oxidation by examining the effect of the mutation of D1-Glu65, a key residue in this channel, to Ala using Fourier transform infrared difference and time-resolved infrared spectroscopies together with thermoluminescence and delayed luminescence measurements. It was shown that the structure and the redox property of the catalytic site were little affected by the D1-Glu65Ala mutation. In the S2→ S3transition, the efficiency was still high and the transition rate was only moderately retarded in the D1-Glu65Ala mutant. In contrast, the S3→ S0transition was significantly inhibited by this mutation. These results suggest that proton transfer in the S2→ S3transition occurs through multiple pathways including the Cl channel, whereas this channel likely serves as a single pathway for proton exit in the S3→ S0transition.