Mamedov M D, Drachev L A
A.N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, USSR.
FEBS Lett. 1991 Jun 24;284(2):227-31. doi: 10.1016/0014-5793(91)80691-u.
The flash-induced formation of transmembrane electric potential differences (measured by carotenoid bandshift) and redox changes of cytochrome bh (b561) were monitored spectrophotometrically in Rb. sphaeroides chromatophores in a pH range from 7.5 to 10.0. It is shown that in the presence of antimycin A and at pH less than 8.3 the myxothiazol-sensitive, antimycin-insensitive component of the carotenoid bandshift is kinetically coupled to cytochrome bh reduction. The kinetics of both processes can be described by a single exponent with a rise time of about 10 ms. Alkalization of the medium (8.3 less than or equal to pH less than or equal to 9.2) causes the appearance of an additional constituent in this phase of the carotenoid response with the rise time varying in the range of 100-300 ms. With a further pH increase (pH greater than 9.2), the electrogenic constituent, kinetically linked to cytochrome bh reduction, diminishes. The obtained data are discussed within the framework of the scheme, assuming that the electron transfer between bl and bh hemes in the bc1 complex is, under certain conditions, accompanied by proton transfer in the same direction.
在7.5至10.0的pH范围内，用分光光度法监测了球形红细菌（Rb. sphaeroides）载色体中闪光诱导的跨膜电位差（通过类胡萝卜素带移测量）和细胞色素bh（b561）的氧化还原变化。结果表明，在存在抗霉素A且pH小于8.3的情况下，类胡萝卜素带移中对粘噻唑敏感、对抗霉素不敏感的成分在动力学上与细胞色素bh的还原相关联。这两个过程的动力学都可以用一个上升时间约为10毫秒的单指数来描述。介质碱化（8.3≤pH≤9.2）会导致类胡萝卜素响应的这个阶段出现一个额外的成分，其上升时间在100 - 300毫秒范围内变化。随着pH进一步升高（pH＞9.2），与细胞色素bh还原在动力学上相关联的产电成分减少。在假设bc1复合物中bl和bh血红素之间的电子转移在某些条件下伴随着同向质子转移的方案框架内，对所得数据进行了讨论。
