Shinzawa-Itoh Kyoko, Shimomura Harunobu, Yanagisawa Sachiko, Shimada Satoru, Takahashi Ryoko, Oosaki Marika, Ogura Takashi, Tsukihara Tomitake
From the Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1, Koto, Kamighori, Akoh, Hyogo, 678-1297, Japan,
From the Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1, Koto, Kamighori, Akoh, Hyogo, 678-1297, Japan.
J Biol Chem. 2016 Feb 19;291(8):4178-84. doi: 10.1074/jbc.M115.680553. Epub 2015 Dec 23.
To understand the roles of mitochondrial respiratory chain supercomplexes, methods for consistently separating and preparing supercomplexes must be established. To this end, we solubilized supercomplexes from bovine heart mitochondria with digitonin and then replaced digitonin with amphipol (A8-35), an amphiphilic polymer. Afterward, supercomplexes were separated from other complexes by sucrose density gradient centrifugation. Twenty-six grams of bovine myocardium yielded 3.2 mg of amphipol-stabilized supercomplex. The purified supercomplexes were analyzed based on their absorption spectra as well as Q10 (ubiquinone with ten isoprene units) and lipid assays. The supercomplex sample did not contain cytochrome c but did contain complexes I, III, and IV at a ratio of 1:2:1, 6 molecules of Q10, and 623 atoms of phosphorus. When cytochrome c was added, the supercomplex exhibited KCN-sensitive NADH oxidation; thus, the purified supercomplex was active. Reduced complex IV absorbs at 444 nm, so we measured the resonance Raman spectrum of the reduced amphipol-solubilized supercomplex and the mixture of amphipol-solubilized complexes I1, III2, and IV1 using an excitation wavelength of 441.6 nm, allowing measurement precision comparable with that obtained for complex IV alone. Use of the purified active sample provides insights into the effects of supercomplex formation.
为了了解线粒体呼吸链超复合物的作用,必须建立能够持续分离和制备超复合物的方法。为此,我们先用洋地黄皂苷溶解牛心线粒体中的超复合物,然后用两亲聚合物两性离子聚合物(A8 - 35)取代洋地黄皂苷。之后,通过蔗糖密度梯度离心将超复合物与其他复合物分离。26克牛心肌组织可产生3.2毫克两性离子聚合物稳定的超复合物。基于其吸收光谱以及辅酶Q10(含有十个异戊二烯单元的泛醌)和脂质分析对纯化后的超复合物进行分析。超复合物样品不含细胞色素c,但含有比例为1:2:1的复合物I、III和IV、6个辅酶Q10分子以及623个磷原子。当加入细胞色素c时,超复合物表现出对氰化钾敏感的NADH氧化作用;因此,纯化后的超复合物具有活性。还原态的复合物IV在444纳米处有吸收峰,所以我们使用441.6纳米的激发波长测量了还原态两性离子聚合物溶解的超复合物以及两性离子聚合物溶解的复合物I1、III2和IV1混合物的共振拉曼光谱,测量精度与单独测量复合物IV时相当。使用纯化后的活性样品有助于深入了解超复合物形成所产生的影响。