UPR 407, CNRS, 91198, Gif sur Yvette Cedex, France.
Photosynth Res. 1993 Jan;38(3):387-94. doi: 10.1007/BF00046765.
Photosystem II (PS II) is the site of oxygen evolution. Activation of dark adapted samples by a train of saturating flashes produces oxygen with a yield per flash which oscillates with a periodicity of four. Damping of the oxygen oscillations is accounted for by misses and double hits. The mechanisms hidden behind these parameters are not yet fully understood. The components which participate in charge transfer and storage in PS II are believed to be anchored to the heterodimer formed by the D1 and D2 proteins. The secondary plastoquinone acceptor QB binds on D1 in a loop connecting the fourth and fifth helices (the QB pocket). Several D1 mutants, mutated in the QB binding region, have been studied over the past ten years.In the present report, our results on nine D1 mutants of Synechocystis PCC 6714 and 6803 are analyzed. When oxygen evolution is modified, it can be due to a change in the electron transfer kinetics at the level of the acceptor side of PS II and also in some specific mutants to a long ranging effect on the donor side of PS II. The different properties of the mutants enable us to propose a classification in three categories. Our results can fit in a model in which misses are substantially determined by the fraction of centers which have QA (-) before each flash due to the reversibility of the electron transfer reactions. This idea is not new but was more thoroughly studied in a recent paper by Shinkarev and Wraight (1993). However, we will show in the discussion that some doubts remain as to the true origin of misses and double hits.
光系统 II（PS II）是氧气产生的部位。用一系列饱和闪光对暗适应样品进行激活，会产生每闪光一次的氧气产量，其随四分之一的周期性波动。氧气波动的阻尼是由漏失和双击中造成的。这些参数背后隐藏的机制尚未完全理解。参与 PS II 中电荷转移和存储的组件被认为是锚定在 D1 和 D2 蛋白形成的异二聚体上。二级质体醌受体 QB 结合在 D1 上，位于连接第四和第五螺旋的环上（QB 口袋）。过去十年中，已经研究了几种在 QB 结合区域发生突变的 D1 突变体。在本报告中，我们分析了来自集胞藻 PCC 6714 和 6803 的 9 种 D1 突变体的结果。当氧气进化发生改变时，这可能是由于 PS II 受体侧的电子转移动力学的变化，并且在某些特定的突变体中，也可能是由于 PS II 供体侧的长程效应。不同的突变体特性使我们能够提出三种分类。我们的结果可以拟合在一个模型中，其中漏失主要由每个闪光前 QA（-）中心的分数决定，这是由于电子转移反应的可逆性。这个想法并不新鲜，但在 Shinkarev 和 Wraight（1993）的最近一篇论文中进行了更深入的研究。然而，我们将在讨论中表明，对于漏失和双击中的真正起源，仍然存在一些疑问。
