Hirst Judy, Carroll Joe, Fearnley Ian M, Shannon Richard J, Walker John E
Medical Research Council Dunn Human Nutrition Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 2XY, UK.
Biochim Biophys Acta. 2003 Jul 10;1604(3):135-50. doi: 10.1016/s0005-2728(03)00059-8.
ubiquinone oxidoreductase (complex I) from bovine heart mitochondria is a complicated, multi-subunit, membrane-bound assembly. Recently, the subunit compositions of complex I and three of its subcomplexes have been reevaluated comprehensively. The subunits were fractionated by three independent methods, each based on a different property of the subunits. Forty-six different subunits, with a combined molecular mass of 980 kDa, were identified. The three subcomplexes, I alpha, I beta and I lambda, correlate with parts of the membrane extrinsic and membrane-bound domains of the complex. Therefore, the partitioning of subunits amongst these subcomplexes has provided information about their arrangement within the L-shaped structure. The sequences of 45 subunits of complex I have been determined. Seven of them are encoded by mitochondrial DNA, and 38 are products of the nuclear genome, imported into the mitochondrion from the cytoplasm. Post-translational modifications of many of the nuclear encoded subunits of complex I have been identified. The seven mitochondrially encoded subunits, and seven of the nuclear encoded subunits, are homologues of the 14 subunits found in prokaryotic complexes I. They are considered to be sufficient for energy transduction by complex I, and they are known as the core subunits. The core subunits bind a flavin mononucleotide (FMN) at the active site for NADH oxidation, up to eight iron-sulfur clusters, and one or more ubiquinone molecules. The locations of some of the cofactors can be inferred from the sequences of the core subunits. The remaining 31 subunits of bovine complex I are the supernumerary subunits, which may be important either for the stability of the complex, or for its assembly. Sequence relationships suggest that some of them carry out reactions unrelated to the NADH:ubiquinone oxidoreductase activity of the complex.
牛心线粒体中的NADH：泛醌氧化还原酶（复合体I）是一种复杂的、多亚基的膜结合装配体。最近，对复合体I及其三个亚复合体的亚基组成进行了全面的重新评估。通过三种独立的方法对亚基进行了分级分离，每种方法都基于亚基的不同特性。鉴定出了46种不同的亚基，其总分子量为980 kDa。三个亚复合体，Iα、Iβ和Iλ，与复合体的膜外在结构域和膜结合结构域的部分相关。因此，这些亚复合体中亚基的分配提供了有关它们在L形结构中排列的信息。已经确定了复合体I的45个亚基的序列。其中7个由线粒体DNA编码，38个是核基因组的产物，从细胞质导入线粒体。已经鉴定出复合体I许多核编码亚基的翻译后修饰。七个线粒体编码的亚基和七个核编码的亚基是原核复合体I中发现的14个亚基的同源物。它们被认为足以通过复合体I进行能量转导，并且它们被称为核心亚基。核心亚基在NADH氧化的活性位点结合一个黄素单核苷酸（FMN）、多达八个铁硫簇和一个或多个泛醌分子。一些辅因子的位置可以从核心亚基的序列中推断出来。牛复合体I的其余31个亚基是多余亚基，它们可能对复合体的稳定性或其组装很重要。序列关系表明，其中一些亚基进行的反应与复合体的NADH：泛醌氧化还原酶活性无关。
