Electron nuclear double resonance (ENDOR) of the Qc.- ubisemiquinone radical in the mitochondrial electron transport chain.
Electron nuclear double resonance (ENDOR) of the Qc.- ubisemiquinone radical in the mitochondrial electron transport chain.
复制标题
线粒体电子传递链中 Qc.-泛半醌自由基的电子核双共振 (ENDOR)。
DOI：
10.1021/bi00482a006
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发表时间：
1990
期刊：
影响因子：
2.9
通讯作者：
Scholes,CP
中科院分区：
文献类型：
--
作者：
Salerno,JC;Osgood,M;Liu,YJ;Taylor,H;Scholes,CP
修订稿于 1990 年 3 月 7 日收到摘要：我们提出了对线粒体醌醇细胞色素 c 还原酶复合物中结合的 Qc*~ 泛半醌的电子核双共振 (ENDOR) 研究。本研究使用了专门修改为插入我们的电子顺磁共振腔的 ENDOR 探针。我们观察到强超精细耦合质子，其可交换性质表明它们与醌氧形成氢键。据认为，这种氢键对于泛醌与蛋白质的结合、稳定其半醌形式以及调节线粒体醌醇细胞色素c还原酶复合物中结合的泛醌的热力学性质至关重要。其他 ENDOR 特征被分配给醌环本身的质子以及可能与附近氨基酸相关的弱耦合质子。从非常弱的超精细耦合、遥远的、可交换的质子中，还有 ENDOR 证据表明泛醌位点与溶剂的接近性和可及性。IN^ Ltochondrial quinol 细胞色素 c 还原酶（也称为细胞色素 6c，复合物）是第一个生物能复合物，其具有提出用于耦合矢量跨膜质子通量与电子传递的特定分子模型（Mitchell，1976）。最初和随后的 Q1* 循环的一个主要特征（Mitchell，1976；Crofts & Meinhardt，1982）是有效改变醌热力学性质的醌结合位点的必要性。据信 QCR 包含两个结合泛醌的位点，并且 QCR 还包含细胞色素 ¿> 566, 》 562, c1 （以及 Rieske 铁硫中心。其中一个位点，标记为 Qc 或 Q¡，相对于其醌和醌醇形式稳定泛半醌阴离子 (Qc*~)，并且对抗霉素敏感，抗霉素可淬灭 Qc 位点的半醌自由基 (Siedow 等等，1978；
Revised Manuscript Received March 7, 1990 abstract: We present an electron nuclear double resonance(ENDOR) study of the bound Qc*~ ubi-semiquinone in the mitochondrial quinol cytochrome c reductase complex. An ENDOR probe specifically modified for insertion into our electron paramagnetic resonance cavity was used for this study. We observed strongly hyperfine-coupled protons whose exchangeable natureindicated they were hydrogen-bonded to the quinone oxygen (s). It is thought that such hydrogen bonds are critical in bindingthe ubiquinone to protein, in stabilizing its semiquinone form, and in modulating the thermodynamic properties of the bound ubiquinone in the mitochondrial quinol cytochrome c reductase complex. Additional ENDOR features were assigned to protons of the quinone ringitself and to weakly coupled protons that may be associated with nearby amino acids. From very weakly hyperfine-coupled, distant, exchangeable protons there was also ENDOR evidence to suggest proximity and accessibility of the ubiquinone site to the solvent.IN^ Ltochondrial quinol cytochrome c reductase (also called the cytochrome 6c, complex) was the first bioenergetic complex to have a specific molecular model proposed for coupling vectorial transmembrane proton flux to electrontransport (Mitchell, 1976). A majorfeature of the original and subsequent Q1* cycles (Mitchell, 1976; Crofts & Meinhardt, 1982) was the necessity for quinone binding sites that effectively modify the thermodynamic properties of quinone. QCR is believed to contain two sites that bind ubiquinone, and QCR also contains cytochromes¿> 566,¿> 562, c1 (and the Rieske iron-sulfur center. One such site, labeled Qc or Q¡, stabilizes the ubisemiquinone anion (Qc*~) relative to its quinone and quinol forms and is sensitive to antimycin, which quenches the semiquinone radical of the Qc site (Siedow et al., 1978; Ohnishi