Glaser E G, Crofts A R
Biochim Biophys Acta. 1984 Aug 31;766(2):322-33. doi: 10.1016/0005-2728(84)90248-2.
Myxothiazol, an inhibitor of the ubiquinol oxidase site of the ubiquinol:cytochrome c2 oxidoreductase complex, has been shown in the present work to inhibit a part of the electrogenic process indicated by phase III of the carotenoid change, in addition to the part of the change inhibited by antimycin. This finding shows that there is an antimycin-insensitive, but myxothiazol-sensitive portion of the slow phase, which indicates the existence of an electrogenic event within the ubiquinol:cytochrome c2 oxidoreductase complex, in addition to that linked to oxidation of cytochrome b-561 which has been previously characterized. Redox titrations show that the appearance of the new electrogenic step is correlated with the amount of cytochrome b-561 available in the oxidized form before the flash. The rate of the antimycin-insensitive and myxothiazol-sensitive portion of the carotenoid change correlates well with the rate of reduction of cytochrome b-561. No carotenoid change associated with reduction of cytochrome b-566 was seen. These findings suggest that the newly identified electrogenic process is linked to electron transfer between cytochrome b-566 and b-561. Calculations of the contribution of this new electrogenic step to the total electrogenic event within the complex show that electrons passing from cytochrome b-566 to cytochrome b-561 pass about 35-50% of the distance across the whole membrane.
细胞色素c2氧化还原酶复合物泛醌氧化酶位点的抑制剂，在本研究中已表明，除了抗霉素所抑制的那部分变化外，它还能抑制类胡萝卜素变化的III期所指示的部分电生成过程。这一发现表明，慢相存在一个对抗霉素不敏感但对黏噻唑敏感的部分，这表明在泛醌：细胞色素c2氧化还原酶复合物中存在一个电生成事件，此外还与先前已被表征的细胞色素b - 561的氧化相关。氧化还原滴定表明，新电生成步骤的出现与闪光前氧化形式的细胞色素b - 561的量相关。类胡萝卜素变化中对抗霉素不敏感且对黏噻唑敏感部分的速率与细胞色素b - 561的还原速率密切相关。未观察到与细胞色素b - 566还原相关的类胡萝卜素变化。这些发现表明，新确定的电生成过程与细胞色素b - 566和b - 561之间的电子转移有关。计算该新电生成步骤对复合物内总电生成事件的贡献表明，从细胞色素b - 566传递到细胞色素b - 561的电子跨越整个膜的距离约为35 - 50%。
