Zickermann Volker, Zwicker Klaus, Tocilescu Maja A, Kerscher Stefan, Brandt Ulrich
Johann Wolfgang Goethe-Universität, Fachbereich Medizin, Molekulare Bioenergetik, Centre of Excellence Frankfurt Macromolecular Complexes, D-60590 Frankfurt am Main, Germany.
Biochim Biophys Acta. 2007 May;1767(5):393-400. doi: 10.1016/j.bbabio.2007.03.005. Epub 2007 Mar 15.
Mitochondrial NADH:ubiquinone oxidoreductase is the largest and most complicated proton pump of the respiratory chain. Here we report the preparation and characterization of a subcomplex of complex I selectively lacking the flavoprotein part of the N-module. Removing the 51-kDa and the 24-kDa subunit resulted in loss of catalytic activity. The redox centers of the subcomplex could be reduced neither by NADH nor NADPH demonstrating that physiological electron input into complex I occurred exclusively via the N-module and that the NADPH binding site in the 39-kDa subunit and further potential nucleotide binding sites are isolated from the electron transfer pathway within the enzyme. Taking advantage of the selective removal of two of the eight iron-sulfur clusters of complex I and providing additional evidence by redox titration and site-directed mutagenesis, we could for the first time unambiguously assign cluster N1 of fungal complex I to mammalian cluster N1b.
线粒体NADH：泛醌氧化还原酶是呼吸链中最大且最复杂的质子泵。在此，我们报告了一种复合体I亚复合体的制备及特性，该亚复合体选择性地缺失了N模块的黄素蛋白部分。去除51 kDa和24 kDa亚基导致催化活性丧失。该亚复合体的氧化还原中心既不能被NADH也不能被NADPH还原，这表明复合体I的生理电子输入仅通过N模块发生，并且39 kDa亚基中的NADPH结合位点以及其他潜在的核苷酸结合位点与酶内的电子传递途径隔离。利用选择性去除复合体I八个铁硫簇中的两个，并通过氧化还原滴定和定点诱变提供额外证据，我们首次明确地将真菌复合体I的簇N1归为哺乳动物的簇N1b。
