Yang X H, Trumpower B L
J Biol Chem. 1986 Sep 15;261(26):12282-9.
A ubiquinol-cytochrome c oxidoreductase (cytochrome bc1) complex has been purified from the plasma membrane of aerobically grown Paracoccus denitrificans by extraction with dodecyl maltoside and ion exchange chromatography of the extract. The purified complex contains two spectrally and thermodynamically distinct b cytochromes, cytochrome c1, and a Rieske-type iron-sulfur protein. Optical spectra indicate absorption peaks at 553 nm for cytochrome c1 and at 560 and 566 nm for the high and low potential hemes of cytochrome b. The spectrum of cytochrome b560 is shifted to longer wavelength by antimycin. The Paracoccus bc1 complex consists of only three polypeptide subunits. On the basis of their relative electrophoretic mobilities, these have apparent molecular masses of 62, 39, and 20 kDa. The 62- and 39-kDa subunits have been identified as cytochromes c1 and b, respectively. The 20-kDa subunit is assumed to be the Rieske-type iron-sulfur protein on the basis of its molecular weight and the presence of an EPR-detectable signal typical of this iron-sulfur protein in the three-subunit complex. The Paracoccus bc1 complex catalyzes reduction of cytochrome c by ubiquinol with a turnover of 470 s-1. This activity is inhibited by antimycin, myxothiazol, stigmatellin, and hydroxyquinone analogues of ubiquinone, all of which inhibit electron transfer in the cytochrome bc1 complex of the mitochondrial respiratory chain. The electron transfer functions of the Paracoccus complex thus appear to be similar, and possibly identical, to those of the bc1 complex of eukaryotic mitochondria. The Paracoccus bc1 complex has the simplest subunit composition and one of the highest turnover numbers of any bc1 complex isolated from any species to date. These properties suggest that the structural requirements for electron transfer from ubiquinol to cytochrome c are met by a small number of peptides and that the "extra" peptides occurring in the mitochondrial bc1 complexes serve some other function(s), possibly in biogenesis or insertion of the complex into that organelle.
通过用十二烷基麦芽糖苷提取以及对提取物进行离子交换色谱法，已从好氧生长的反硝化副球菌的质膜中纯化出泛醇 - 细胞色素c氧化还原酶（细胞色素bc1）复合物。纯化后的复合物包含两种在光谱和热力学上不同的b型细胞色素、细胞色素c1和一种 Rieske 型铁硫蛋白。光谱表明，细胞色素c1在553 nm处有吸收峰，细胞色素b的高电位和低电位血红素分别在560和566 nm处有吸收峰。抗霉素可使细胞色素b560的光谱向更长波长移动。反硝化副球菌的bc1复合物仅由三个多肽亚基组成。根据它们相对的电泳迁移率，这些亚基的表观分子量分别为62、39和20 kDa。已分别将62 kDa和39 kDa的亚基鉴定为细胞色素c1和b。基于其分子量以及在三亚基复合物中存在这种铁硫蛋白典型的可通过电子顺磁共振检测到的信号，推测20 kDa的亚基为 Rieske 型铁硫蛋白。反硝化副球菌的bc1复合物催化泛醇将细胞色素c还原，周转数为470 s⁻¹。该活性受到抗霉素、粘噻唑、抑霉素和泛醌的羟基醌类似物的抑制，所有这些物质均抑制线粒体呼吸链细胞色素bc1复合物中的电子传递。因此，反硝化副球菌复合物的电子传递功能似乎与真核线粒体的bc1复合物相似，甚至可能相同。反硝化副球菌的bc1复合物具有迄今从任何物种分离出的任何bc1复合物中最简单的亚基组成和最高的周转数之一。这些特性表明，从泛醇到细胞色素c的电子传递的结构要求可由少数几种肽满足，而线粒体bc1复合物中出现的“额外”肽发挥其他一些功能，可能与该复合物的生物发生或插入该细胞器有关。
