Antimycin A inhibits cytochrome b(559)-mediated cyclic electron flow within photosystem II
Antimycin A inhibits cytochrome b(559)-mediated cyclic electron flow within photosystem II
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抗霉素 A 抑制光系统 II 内细胞色素 b(559) 介导的循环电子流
DOI：
10.1007/s11120-018-0519-7
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发表时间：
2019
影响因子：
3.7
通讯作者：
Takagi D. Ifuku K. Nishimura T. and Miyake C.
中科院分区：
文献类型：
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作者：
Takagi D. Ifuku K. Nishimura T. and Miyake C.
众所周知，光合作用的光反应包括线性和循环电子流，以将光能转化为NADPH和ATP形式的化学能。在光合作用研究中，抗霉素A(AA)被认为是铁还蛋白依赖的光系统I(CEF-PSI)循环电子流的抑制剂。然而，其确切的抑制机制和靶点尚不清楚。在这里，我们发现AA通过光系统II(CEF-PSII)中的细胞色素b559(Cytb559)抑制循环(交替)电子流动。当AA应用于菠菜叶片的类囊体膜时，Cytb559在黑暗中还原的高电势形式转变为低电势形式，并容易被分子氧氧化。在没有AA的情况下，还原的Cytb559在光照下被P680+氧化，在黑暗中重新还原，主要是由PSII受体侧QB位的电子还原。相反，AA抑制了Cytb559的氧化，并诱导其在光照下被还原。AA对Cytb559氧化的抑制增强了对PSII的光抑制作用。基于以上结果，我们建议谨慎使用AA来评估CEF-PSI本身，同时建议AA为理解Cytb559而不是CEF-PSI在光合作用生物中的生理意义提供了新的见解和解释。
The light reactions of photosynthesis are known to comprise both linear and cyclic electron flow in order to convert light energy into chemical energy in the form of NADPH and ATP. Antimycin A (AA) has been proposed as an inhibitor of ferredoxin-dependent cyclic electron flow around photosystem I (CEF-PSI) in photosynthesis research. However, its precise inhibitory mechanism and target site had not been elucidated yet. Here we show that AA inhibits the cyclic (alternative) electron flow via cytochromeb559(Cytb559) within photosystem II (CEF-PSII). When AA was applied to thylakoid membranes isolated from spinach leaves, the high potential form of Cytb559, which was reduced in the dark, was transformed into the lower potential forms and readily oxidized by molecular oxygen. In the absence of AA, the reduced Cytb559was oxidized by P680+upon light illumination and re-reduced in the dark, mainly by the electron from the QBsite on the acceptor side of PSII. In contrast, AA suppressed the oxidation of Cytb559and induced its reduction under the illumination. This inhibition of Cytb559oxidation by AA enhanced photoinhibition of PSII. Based on the above results, we propose caution regarding the use of AA for evaluating CEF-PSI per se and concurrently propose that AA provides for new insights into, and interpretations of, the physiological importance of Cytb559, rather than that of CEF-PSI in photosynthetic organisms.