| Budget Amount *help |
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1986: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1985: ¥600,000 (Direct Cost: ¥600,000)
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| Research Abstract |
The sodium-transport respiratory chain NADH:quinone reductase of a marine bacterium, Vibrio alginolyticus, was purified by high-performance liquid chromatography. The purified quinone reductase, which catalyses the reduction of ubiquinone to ubiquinol, was composed of three subunits, <alpha> , <beta> and <gamma> , with apparent molecular weights of 52 000, 46 000 and 32 000, respectively. The subunit <beta> contained one molecule of FAD per molecule and catalysed the reduction of ubiquinone to ubisemiquinone. The subunit <alpha> contained FMN as a prosthetic group. The quinone reductase was reconstituted from <alpha> and <betagamma> , but not from <alpha> and <beta> , and the maximum activity was obtained at the equimolar amounts of FAD( <beta> ) and FMN( <alpha> ). The molecular weight of quinone reductase complex was estimated to be 254 000, which corresponded to a dimer of <alphabetagamma> complex or <alpha_2bata_2gamma_2> . The subunit <gamma> increased the affinity of <beta> for ubiquinone-1. The reaction catalysed by FMN-containing <alpha> subunit was essential for the generation of membrane potential in proteoliposomes and the coupling site of sodium pump in the quinone reductase was localised to this reaction step.
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