The cytochrome bc1 complex of Rhodobacter capsulatus:: ubiquinol oxidation in a dimeric Q-cycle?
The cytochrome bc1 complex of Rhodobacter capsulatus:: ubiquinol oxidation in a dimeric Q-cycle?
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DOI：
10.1016/s0014-5793(98)00768-6
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发表时间：
1998-07-17
期刊：
影响因子：
3.5
通讯作者：
Mulkidjanian, AY
中科院分区：
文献类型：
--
作者：
Gopta, OA;Feniouk, BA;Mulkidjanian, AY
本文用闪光激发法研究了Rhonocapsulatus色素细胞的细胞色素bc（1）复合物。在第一次和第二次闪光后，分别监测细胞色素B（在561 nm处）和细胞色素c（在552 nm处）的高电位血红素B（h）的还原以及电致变色吸收瞬变（在524 nm处）。我们保持泛醌池在黑暗中氧化，并只在第二次闪光后才关注光合反应中心的泛醇形成。令人惊讶的是;第一次闪光导致每个bc二聚体氧化约一个泛醇。基于这些和其它数据，我们提出了二聚体Q-循环，其中第一泛醇分子被一个be单体的能量上不利的氧化由第二泛醇被另一个be单体的能量上有利的氧化驱动，导致泛醇分子被二聚体be在黑暗中成对氧化。剩余的未配对泛醇应该保留在酶上，然后在第一次闪光后被氧化。(C)1998年欧洲生物化学学会联合会。
We studied the cytochrome bc(1) complex (hereafter be) by flash excitation of Rhonobacter capsulatus chromatophores. The reduction of the high-potential heme b(h) of cytochrome b (at 561 nm) and of cytochromes c (at 552 nm) and the electrochromic absorption transients (at 524 nm) were monitored after the first and second flashes of light, respectively. We kept the uhiquinone pool oxidized in the dark and concerned for the ubiquinol formation in the photosynthetic reaction center only after the second flash. Surprisingly; the first flash caused the oxidation of about one ubiquinol per bc dimer, Based on these and other data we propose a dimeric Q-cycle where the energetically unfavorable oxidation of the first ubiquinol molecule by one of the be monomers is driven by the energetically favorable oxidation of the second ubiquinol by the other be monomer resulting in a pairwise oxidation of ubiquinol molecules by the dimeric be in the dark. The residual unpaired ubiquinol supposedly remains on the enzyme and is then oxidized after the first flash. (C) 1998 Federation of European Biochemical Societies.