Regulation of proton-to-electron stoichiometry in photosynthetic electron transport: physiological function in photoprotection
Regulation of proton-to-electron stoichiometry in photosynthetic electron transport: physiological function in photoprotection
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DOI：
10.1007/s102650200001
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发表时间：
2002-02
影响因子：
2.8
通讯作者：
T. Shikanai;Y. Munekage;K. Kimura
中科院分区：
文献类型：
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作者：
T. Shikanai;Y. Munekage;K. Kimura
光合作用电子流的主要稳定产物是NADPH和ATP。其产生的化学计量学取决于通过类囊体膜泵浦的质子与通过电子传输途径的电子的比率(H+/e−比率)。叶绿体中各种同化反应对−/NADPH比值的灵活要求必须由电子流中的H+/e DNA比值来满足。除了众所周知的ΔpH在三磷酸腺苷合成过程中的作用外，Δ的pH也是光系统II(PSII光化学)下调的触发器。过量的光能通过这一调节过程安全地以热的形式消散，以抑制有毒活性氧物种的产生。因此，H+/e−比例的调节可能在光保护中起作用，也可能在调节ATP/NADPH的生成比例中起作用。长期以来，人们一直认为，H+/e−的比值可以通过调节细胞色素复合体中的质子传输Q循环和光系统I周围的循环电子流动来控制。尽管PSI可能具有重要的生理意义和悠久的研究历史，但Q周期调节和PSI周围的循环电子流动的分子一致性仍然不清楚。最近在研究工具方面的改进，包括使用叶绿素荧光成像的遗传方法和建立叶绿体转化技术，正在为经典主题提供新的见解。本文主要从光合作用调节的角度对H+/e−比值的调节进行了综述。
The primary stable products of photosynthetic electron flow are NADPH and ATP. Stoichiometry of their production depends on the ratio of protons pumped across the thylakoid membrane to electrons passed through the electron transport pathway (H+/e−ratio). Flexible requirements of the ATP/NADPH ratio by various assimilatory reactions in chloroplasts must be fulfilled by the H+/e−ratio during the electron flow. In addition to the well-known role of ΔpH during ATP synthesis, ΔpH also functions as a trigger of the down-regulation of photosystem II (PSII) photochemistry. Excessive light energy is safely dissipated as heat by this regulatory process to suppress the generation of toxic reactive oxygen species. Thus, regulation of the H+/e−ratio may function in the photoprotection, as well as in the regulation of the ATP/NADPH production ratio. It has long been the consensus that the H+/e−ratio can be controlled by regulating the proton-transporting Q-cycle in the cytochromeb6fcomplex and by the cyclic electron flow around photosystem I (PSI). Despite the possible physiological importance and the long history of interest, the molecular identity of Q-cycle regulation and the cyclic electron flow around PSI have been remained unclear. The recent improvements in research tools, including the genetic approach using chlorophyll fluorescence imaging and establishment of the chloroplast transformation technique, are providing new insights into classical topics. In this review, we focus on regulation of the H+/e−ratio especially from the view of photosynthetic regulation.