| Project/Area Number |
10670054
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General physiology
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| Research Institution | Tokyo Metropolitan Organization for Medical Research |
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Principal Investigator |
MIKI Toshiaki Tokyo Metropolitan Organization for Medical Research, The Tokyo Metropolitan Institute of Medical Science Research Scientist, 東京都臨床医学総合研究所, 研究員 (10239204)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAKITA Masao Tokyo Metropolitan Organization for Medical Research, The Tokyo Metropolitan Institute of Medical Science Research Scientist, 東京都臨床医学総合研究所, 研究員 (00012740)
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| Project Period (FY) |
1997 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1998: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Keywords | oxidoreductase / proton pump / reconstituted vesicles / diffusion potential / ubiquinone / polyamine / cation transporter / erythrocyte / 輸送体 |
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| Research Abstract |
We have obtained following results on a polyamine transporter and ubiquinol-cytochrome c reductase, respectively.
1. Polyamine transporter.
Rabbit erythrocytes took up spermidine from a reaction medium in a time- and temperature-dependent manner. Kinetic analysis estimated the Km value of about 2μM for the spermidine uptake. The uptake of spermidine was inhibited 70% by spermine, but putrescine did not exert any effect on the spermidine uptake. These results indicate that a transporter specific for spermidine and spermine is present in erthrocyte membranes. Inhibition of the glycolytic pathway inside erythrocytes decreased the spermidine uptake, suggesting that ATP is required for the uptake of spermidine in rabbit erythrocytes.
2. Ubiquinol-cytochrome c reductase.
QCR purified from photosynthetic bacteria Rhodobacter sphaeroides was reconstituted into liposomes containing KC1 inside. Generation of a valinomycin-mediated KィイD1+ィエD1 diffusion potential across the phospholipid membranes induced the reversed electron transfer in the reconstituted QCR. Contrary to QCR derived from bovine heart mitochondria, exogenous ubiquinone was an essential component for the potential-induced redox reaction in the bacterial enzyme. Inhibitors of the catalytic reaction of QCR such as antimycin A and myxothiazol also inhibited the reverse reaction of electron transfer. These results indicate that a membrane potential induces the reversed electron transfer in bacterial QCR as well as in the mammalian enzyme, and that ubiquinone was essential for the reverse reaction of electron transfer.
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