Functions of lipophilic quinones in photosynthetic reaction sytems of photosynthesis

亲脂性醌在光合作用反应体系中的作用

基本信息

批准号：
61480009
负责人：
KATOH Sakae
金额：
$ 4.22万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

项目摘要

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.

Sybecococcus sp。的塑料蓝细菌的功能。是研究。各种PS II制剂的光疗法标记首次清楚地证明了酚类除草剂与28 kDa Q_b-蛋白结合，而47 kDa叶绿素携带的蛋白具有塑料奎因酮结合位点2。确定了与PS II制剂相关的数字和功能PF塑料醌分子。氧气进化制剂中存在的三个醌分子起着Q_A和Q_G的作用，并且可能在PS II3的反应中心的水侧。分析了高纯化的氧气不断发展的Comolexes的化学组成。结果表明，氧气进化需要两个塑料喹酮分子，它们充当Q_A，在PS II的水面上作用4。在氧气进化预验中发现了苯喹酮还原模式。用亲脂性苯喹酮获得了高氧气的速度，而亲脂性分子较少的是电子受体。 DCMU强烈抑制了所检查的所有电子受体的减少。相比之下，DBMIB抑制了苯喹酮的竞争性减少，但没有抑制铁苯胺和二氯苯酚烯醇。这表明苯喹酮通过替换静态喹酮并直接从Q_A接受电子来结合Q_B位点。苯喹酮还原的Arrhenius图表明，Q_B蛋白质构象的变化发生在19°C5。 DBMIB还竞争性地抑制了蓝细菌细胞中PS I的氧化酚氧化物，这表明Ozygen Evolving Complvinges和细胞色素B_6-F复合物之间的DBMIB的常见抑制作用机制。