Functions of lipophilic quinones in photosynthetic reaction sytems of photosynthesis
| Project/Area Number |
61480009
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
植物生理学
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| Research Institution | University of Tokyo |
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Principal Investigator |
KATOH Sakae College of Arts and Sciences, University of Tokyo, 教養学部, 教授 (50011515)
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| Co-Investigator(Kenkyū-buntansha) |
SATOH Kazuhiko College of Arts and Sciences, University of Tokyo, 教養学部, 助手 (00090522)
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| Project Period (FY) |
1986 – 1987
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| Project Status |
Completed (Fiscal Year 1987)
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| Budget Amount *help |
¥6,600,000 (Direct Cost: ¥6,600,000)
Fiscal Year 1987: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1986: ¥5,800,000 (Direct Cost: ¥5,800,000)
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| Keywords | Pastoquinone / Photosystem II / Oxygen evolving preparation / Q_B-protein / DBMIB / Benzoquinone / Photoaffinity labeling / シネココッカス / ビタミン【K_1】 / 系【II】反応中心複合体 / 電子伝達体 / 系I反応中心複合体 / 光標識実験 |
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| Research Abstract |
Functions of plastoquinone associated with PS II Preparations isolated from the thermophilic cyanobacterium Sybechococcus sp. were studied
1. 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 site
2. 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 II
3. 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 evolution
4. 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゜C
5. 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.
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Report
(2 results)
Research Products
(17 results)
