Cytochrome b oxidation and reduction reactions in the ubiquinone-cytochrome b/c2 oxidoreductase from Rhodopseudomonas sphaeroides.
Cytochrome b oxidation and reduction reactions in the ubiquinone-cytochrome b/c2 oxidoreductase from Rhodopseudomonas sphaeroides.
复制标题
球形红假单胞菌泛醌-细胞色素 b/c2 氧化还原酶中的细胞色素 b 氧化和还原反应。
DOI：
10.1016/0005-2728(81)90015-3
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发表时间：
1981
期刊：
影响因子：
--
通讯作者：
Dutton,PL
中科院分区：
文献类型：
--
作者：
O'Keefe,DP;Dutton,PL
1.在存在和不存在抗霉素的情况下，在细胞色素2、反应中心的氧化细菌叶绿素二聚体和天线细菌叶绿素的红移的吸收变化的贡献减去后，测定了红球藻球形色素Ga的泛醌-细胞色素B/c2氧化还原酶中细胞色素b还原和氧化的动力学.天线细菌叶绿素谱带在589 nm处有一个小的红移，这与类胡萝卜素谱带的红移在动力学上是相似的.抗霉素在所有条件下都能抑制铁细胞色素的氧化;在某些条件下（如果不是所有条件的话），它也能刺激单次闪光激活的细胞色素还原量3- 4倍。激活闪光后，每个反应中心最多减少约0.6个细胞色素b-560（Em（7）= 50 mV，n= 1，之前为细胞色素b 50）血红素。该比率表明，每个泛醌-细胞色素B/c2氧化还原酶有一个细胞色素B-560血红素功能。在这里使用的实验条件下，仅观察到细胞色素b-560在循环电子转移中起作用。我们描述了存在三种不同的状态的还原的泛醌细胞色素B/C2氧化还原酶，可以建立激活前，并导致显着不同的反应序列，涉及细胞色素后闪光激活。平衡使得特殊的泛醌（Qz）被还原并且细胞色素B-560被氧化产生通过泛醌-细胞色素B/c2氧化还原酶的最佳闪光激活电子转移速率的条件。然而，当降低环境氧化还原状态以还原细胞色素B-560或升高环境氧化还原状态以氧化Qz时，通过泛醌-细胞色素B/c2氧化还原酶的单翻转闪光诱导的电子转移似乎受到阻碍;通过从反应中心的还原仲醌（QII）到铁细胞色素b-560和从铁细胞色素b-560的电子转移步骤，初步确定了障碍点。560分别与氧化的Qz。
1. The kinetics of cytochromebreduction and oxidation in the ubiquinone-cytochrome b/c2oxidoreductase of chromatophores fromRhodopseudomonas sphaeroidesGa have been measured both in the presence and absence of anti-mycin, after subtraction of contributions due to absorption changes from cytochromec2, the oxidized bacteriochlorophyll dimer of the reaction center, and a red shift of the antenna bacteriochlorophyll.2. A small red shift of the antenna bacteriochlorophyll band centered at 589 nm has been identified and found to be kinetically similar to the carotenoid bandshift.3. Antimycin inhibits the oxidation of ferrocytochromebunder all conditions; it also stimulates the amount of single flash activated cytochromebreduction 3- to 4-fold under certain if not all conditions.4. A maximum of approximately 0.6 cytochromeb-560 (Em(7)= 50 mV,n= 1, previously cytochromeb50) hemes per reaction center are reduced following activating flashes. This ratio suggests that there is one cytochromeb-560 heme functional per ubiquinone-cytochrome b/c2oxidoreductase.5. Under the experimental conditions used here, only cytochromeb-560 is observed functional in cyclic electron transfer.6. We describe the existence of three distinct states of reduction of the ubiquinone-cytochrome b/c2oxidoreductase which can be established before activation, and result in markedly different reaction sequences involving cytochromebafter the flash activation. Poising such that the special ubiquinone (Qz) is reduced and cytochromeb-560 is oxidized yields the conditions for optimal flash activated electron transfer rates through the ubiquinone-cytochrome b/c2oxidoreductase. However when the ambient redox state is lowered to reduce cytochromeb-560 or raised to oxidize Qz, single turnover flash induced electron transfer through the ubiquinone-cytochrome b/c2oxidoreductase appears impeded; the points of the impediment are tentatively identified with the electron transfer step from the reduced secondary quinone (QII) of the reaction center to ferricytochromeb-560 and from the ferrocytochromeb-560 to oxidized Qz, respectively.