Yu C A, Xia J Z, Kachurin A M, Yu L, Xia D, Kim H, Deisenhofer J
Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater 74078-3035, USA.
Biochim Biophys Acta. 1996 Jul 18;1275(1-2):47-53. doi: 10.1016/0005-2728(96)00049-7.
The method reported for isolation of ubiquinol-cytochrome-c reductase complex from submitochondrial particles was modified to yield a preparation for crystallization. The cytochrome bc1 complex was first crystallized in large thin plate form and diffracts X-rays to 7 A resolution in the presence of mother liquor. This crystalline complex was enzymatically active and contains ten protein subunits. It had 33 mol phospholipid and 0.6 mol ubiquinone per mol protein. With slightly modified crystallization conditions, different crystal forms were obtained. Crystals grown in the presence of 20% glycerol diffracted X-rays up to 2.9 A resolution using a synchrotron source. Four heavy atom derivatives have been obtained. The 3-D structure of the cytochrome bc1 complex was solved to 3.4 A resolution. Crystalline cytochrome bc1 complex is a dimer: most of the masses of core proteins I and II protrudes from the matrix side of the membrane, whereas the cytochrome b protein is located mainly within the membrane. There are 13 transmembrane helices in each monomer. Most of the mass of cytochrome c1 and iron-sulfur protein including their redox centers are located on the cytoplasmic side of the membrane. The distances between these redox centers have been determined, and several electron transfer inhibitor binding sites in the complex have been located.
对报道的从亚线粒体颗粒中分离泛醇 - 细胞色素c还原酶复合物的方法进行了改进，以获得用于结晶的制剂。细胞色素bc1复合物首先以大的薄板形式结晶，并在母液存在下将X射线衍射至7埃分辨率。这种结晶复合物具有酶活性，包含十个蛋白质亚基。每摩尔蛋白质含有33摩尔磷脂和0.6摩尔泛醌。通过略微改变结晶条件，获得了不同的晶体形式。在20％甘油存在下生长的晶体使用同步加速器源将X射线衍射至2.9埃分辨率。已获得四种重原子衍生物。细胞色素bc1复合物的三维结构解析至3.4埃分辨率。结晶细胞色素bc1复合物是二聚体：核心蛋白I和II的大部分质量从膜的基质侧突出，而细胞色素b蛋白主要位于膜内。每个单体中有13个跨膜螺旋。细胞色素c1和铁硫蛋白的大部分质量包括它们的氧化还原中心位于膜的细胞质侧。已确定这些氧化还原中心之间的距离，并在复合物中定位了几个电子传递抑制剂结合位点。
