Zhu Q S, Sprague S G, Beattie D S
Department of Biochemistry, West Virginia University School of Medicine, Morgantown 26506.
Arch Biochem Biophys. 1988 Sep;265(2):447-53. doi: 10.1016/0003-9861(88)90148-8.
The reduction of duroquinone (DQ), 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (DB), and dichlorophenol indophenol (DCIP) by succinate and NADH was investigated in yeast mitochondria which have no spectrally detectable cytochrome b. Succinate reduces DB in the cytochrome b-deficient mitochondria at rates comparable to that observed in wild-type mitochondria, suggesting that succinate:ubiquinone oxidoreductase is unaffected by the lack of cytochrome b. In the mutant mitochondria, succinate does not reduce DQ or DCIP at significant rates; however, NADH reduces both DQ and DCIP at rates similar to that of the wild-type mitochondria in a myxothiazol, but not antimycin, sensitive reaction. The Ki for myxothiazol in this reaction is close to that for electron transfer through the cytochrome b-c1 complex. In addition, myxothiazol does not inhibit NADH:ubiquinone oxidoreductase. These results confirm our previous suggestion that the cytochrome b-c1 complex is involved in electron transfer from the primary dehydrogenases to DQ and DCIP and suggest that cytochrome b is not the binding site for myxothiazol.
在没有光谱可检测细胞色素b的酵母线粒体中，研究了琥珀酸和NADH对二氢泛醌（DQ）、2,3 - 二甲氧基 - 5 - 甲基 - 6 - 癸基 - 1,4 - 苯醌（DB）和二氯酚靛酚（DCIP）的还原作用。琥珀酸在缺乏细胞色素b的线粒体中还原DB的速率与在野生型线粒体中观察到的速率相当，这表明琥珀酸：泛醌氧化还原酶不受细胞色素b缺乏的影响。在突变体线粒体中，琥珀酸不会以显著速率还原DQ或DCIP；然而，NADH在一种抗霉素不敏感但黏噻唑敏感的反应中，以与野生型线粒体相似的速率还原DQ和DCIP。该反应中黏噻唑的Ki值接近通过细胞色素b - c1复合物进行电子传递的Ki值。此外，黏噻唑不抑制NADH：泛醌氧化还原酶。这些结果证实了我们之前的推测，即细胞色素b - c1复合物参与从初级脱氢酶到DQ和DCIP的电子传递，并表明细胞色素b不是黏噻唑的结合位点。
