REDOX PROPERTIES OF ELECTRON-TRANSFER FLAVOPROTEIN UBIQUINONE OXIDOREDUCTASE AS DETERMINED BY EPR-SPECTROELECTROCHEMISTRY
REDOX PROPERTIES OF ELECTRON-TRANSFER FLAVOPROTEIN UBIQUINONE OXIDOREDUCTASE AS DETERMINED BY EPR-SPECTROELECTROCHEMISTRY
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DOI：
10.1021/bi00162a012
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发表时间：
1992-12-01
期刊：
影响因子：
2.9
通讯作者：
STANKOVICH, MT
中科院分区：
文献类型：
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作者：
PAULSEN, KE;ORVILLE, AM;STANKOVICH, MT
我们测定了每个电子转移到电子转移的形式电位值黄素蛋白-泛醌氧化还原酶(ETF-QO)，以进一步表征从不同的酰基辅酶A硫酯到线粒体泛醌池的电子转移的热力学。ETF-QO含有一个[4Fe-4S]2+，1+簇和一个FAD修复基。初步的可见光谱电化学滴定表明，两个氧化还原中心几乎同时被还原。因为发色团的可见光谱重叠，所以不可能用这种方法来计算每个电子转移到蛋白质的形式电位值。因此，设计了一个EPR光谱电化学池，使每个形式电位值可以通过EPR定量测定黄素半喹酮和滴定过程中还原的铁硫团簇来确定。在pH7.5和4℃时，电子转移到ETF-泛醌氧化还原酶的形式电位值分别为E‘=+0.028 V和E’=-0.006 V，对于铁-硫团簇，E‘=+0.047 V。随着这项工作的完成，从β-氧化的酰基辅酶A底物到线粒体电子传输链的电子传递的热力学已经完全解决。讨论了这些结果对整个β-氧化电子传递过程的意义。
We have determined the formal potential values for each electron transfer to electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO), in order to further characterize the thermodynamics of electron transport from various acyl-CoA thioesters to the mitochondrial ubiquinone pool. ETF-QO contains one [4Fe-4S]2+,1+ cluster and one FAD prosthetic group. A preliminary visible-spectroelectrochemical titration showed that the two redox centers were reduced almost simultaneously. Since the visible spectra of the chromophores overlap, it was not possible to resolve the formal potential value for each electron transfer to the protein using this method. Accordingly, an EPR-spectroelectrochemical cell was designed so that each formal potential value could be resolved by EPR quantitation of the flavin semiquinone and the reduced iron-sulfur cluster during the titration. The formal potential values for electron transfer to ETF-ubiquinone oxidoreductase at pH 7.5 and 4-degrees-C were E1-degrees' = +0.028 V and E2-degrees' = -0.006 V for the first and second electron transfers, respectively, to the FAD and E-degrees' = +0.047 V for the iron-sulfur cluster. The thermodynamics of electron transport from the acyl-CoA substrates of beta-oxidation to the mitochondrial electron transport chain have been fully resolved with completion of this work. The results are discussed in terms of their significance to the overall electron transport process from beta-oxidation.