Isolation and properties of a mitochondrial protein that converts succinate dehydrogenase into succinate-ubiquinone oxidoreductase.
Isolation and properties of a mitochondrial protein that converts succinate dehydrogenase into succinate-ubiquinone oxidoreductase.
复制标题
将琥珀酸脱氢酶转化为琥珀酸泛醌氧化还原酶的线粒体蛋白的分离和特性。
作者：
Yu,CA;Yu,L
Chang-An Yu* and琳达Yu摘要：通过两种不同的方法从可溶性细胞色素b-cx复合物中分离出一种线粒体蛋白（QP），它将可溶性琥珀酸脱氢酶转化为琥珀酸-泛醌氧化还原酶。方法I包括在2 M尿素存在下用Triton X-100处理，然后进行磷酸钙柱层析和硫酸铵分级。该方法得到了高纯度的QPs，其具有相对较低的比活性和泛醌含量。方法Ⅱ包括在脱氧胆酸盐存在下的醋酸铵分级、在尿素存在下的硫酸铵分级和差速离心。该方法得到的QPs具有较高的比活性和较高的回收率，但纯度较低。通过方法II获得的QP中的主要污染物是变性细胞色素B。QPs的分子量（亚基）为15 000。QPs在中性pH和低温下是稳定的，但是当酶在室温下孵育时迅速变性。阐明复杂的膜结合酶复合物的结构和功能之间的关系需要充分理解系统中的每个参与组分。对琥珀酸-细胞色素c还原酶的化学组成的仔细分析（Takemori & King，1964）揭示了该酶复合物含有细胞色素B和cx、非血红素铁硫蛋白、黄素蛋白、磷脂（PL）和泛醌（Q）。1在这些基本组分中，除Q外的所有功能性辅基都被发现与特定的蛋白质相关联，并且作为全蛋白实体受到了极大的关注。另一方面，泛醌直到最近鉴定出琥珀酸脱氢酶琥珀酸-泛醌还原酶转化蛋白（QP）（Yu等人，1977 a）和在细胞色素b-cx区域中观察到泛半醌自由基（Yu等，1978）被认为作为线粒体内膜中的自由移动的分子存在（绿色，1962; Kroger & Klingenberg，1967）。
Chang-An Yu* and Linda Yu abstract: A mitochondrial protein (QPs), which converts soluble succinate dehydrogenase into succinate-ubiquinone oxidoreductase, has been isolated from the soluble cytochrome b-cx complex by using two different methods. Method I in-volves treatment with Triton X-100 in the presence of 2 M urea, followed by calcium phosphate column chromatography and ammonium sulfatefractionation. This method gave a highly purified QPs which had relatively low specific activity and ubiquinone content. Method II involves ammonium acetate fractionation in the presence of deoxycholate, am-monium sulfate fractionation inthe presence of urea, and differential centrifugation. This method yielded a QPs with high specific activity and higher recovery but with less purity. The major contaminant inQPs obtained by method II is de-natured cytochrome b. The molecular (subunit) weight of QPs is 15 000. QPs is stable at neutral pH and at low temperatures but denatures rapidly when the enzyme is incubated at roomElucidation of the relationship between structure and function of a complicated membrane-bound enzyme complex requires full understanding of each participating component in the system. Careful analysis of the chemical composition of succinate-cytochrome c reductase (Takemori & King, 1964) reveals that theenzyme complex contains cytochromes b and cx, non-heme ironsulfur proteins, flavoproteins, phospholipids (PL), and ubiquinone (Q). 1 Among these essential components, all the functional prosthetic groups except Q are found to be associated with a particular protein and have received great attention as holoprotein entities. Ubiquinone, on the other hand, until therecent identification of the succinate dehydrogenase succinate-ubiquinone reductase converting protein (QPs)(Yu et al., 1977a) and the observation of ubisemiquinone radical in the cytochrome b-cx region (Yu et al., 1978) has been believed to exist as a free mobile molecule in the mitochondrial inner membrane (Green, 1962; Kroger & Klingenberg, 1967).