Functions of lipophilic quinones in photosynthetic reaction sytems of photosynthesis

Functions of plastoquinone associated with PS II Preparations isolated from the thermophilic cyanobacterium Sybechococcus sp. were studied 1。第一次用不同的PS II制备方法明确地进行了说明，将苯醇型草药结合到28 KDa Q_B蛋白和47 KDa氯基携带蛋白作为塑料激酶结合位点2。Pf Plastoquinone分子与PS II的制备有关的数字和函数是确定的。在氧进化的准备函数中，三个五聚氰胺分子存在于PS II 3反应中心的水面上，可能存在于Q_A和Q_G。“高纯度氧进化的复合物的化学成分已经被分析出来。结果显示了两个plastoquinone分子，其功能为Q_A和PS II的水面，需要氧进化4。苯并喹酮减少的单一模式是在氧气进化的准备过程中发现的。氧化物演化的高速率被脂质苯并喹啉，而更少的脂质分子是不良的电子接受者。DCMU被严格禁止减少所有电子接收器的审查。在对比度下， DBMIB对苯并喹酮的有效减少，但不包括苯丙胺和二氯酚。本建议将苯并喹啉绑定到Q_B站点，由置换铂并直接接受Q_A的电子。19 ° C5中Q_B-蛋白质发生变化的arrhenius提出了减少苯并喹酮的建议。通过PS I在青细菌细胞中氧化Duroquinol也受到DBMIB的抑制，并建议在ozygen进化复合体和细胞色素b_6-f复合体之间建立一个常见的抑制机制。

Functions of plastoquinone associated with PS II Preparations isolated from the thermophilic cyanobacterium Sybechococcus sp. were studied1. Photoaffinty labeling of various PS II preparations clearly demonstrated for the first time that a phenol-type herbicide binds to the 28 KDa Q_B-protein and the 47 KDa chlorophyll-carrying protein has a plastoquinone binding site2. Numbers and functions pf plastoquinone molecules associated with PS II preparetions were determined. Three quinone molecules present in the oxygen evolving preparations function as Q_A and Q_G and possibly on the water side of the reaction center of PS II3. Chemical composition of the highly purified oxygen evolving comolexes was analyzed. The results show that two plastoquinone molecules, which function as Q_A and on the water side of PS II,are needed for oxygen evolution4. A unigue mode of benzoquinone reduction was found in the oxygen evolving prepqrations. High rate of oxygen evolution was obtained with lipophilic benzoquinones, while less lipophilic molecules were poor electron acceptors. DCMU strongly inhibited reduction of all the electron acceptors examined. In contrast, DBMIB suppressed competitively reduction of benzoquinones but not that of ferricyanide and dichlorophenolindophenol. This suggests that benzoquinones bind to the Q_B-site, by replacing plastoquinone, and accept electrons directly from Q_A. The arrhenius plot of benzoquinone reduction suggests that a change in the conformation of the Q_B-protein occurs at 19゜C5. Duroquinol oxidation by PS I in the cyanobacterial cells was also inhibited competitively by DBMIB, suggesting a common inhibition mechanism of DBMIB between the ozygen evolving complexes and the cytochrome b_6-f complexes.