Kmita Katarzyna, Wirth Christophe, Warnau Judith, Guerrero-Castillo Sergio, Hunte Carola, Hummer Gerhard, Kaila Ville R I, Zwicker Klaus, Brandt Ulrich, Zickermann Volker
Structural Bioenergetics Group, Institute of Biochemistry II, Medical School, Goethe University, 60438 Frankfurt am Main, Germany;
Institute for Biochemistry and Molecular Biology, ZBMZ, BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg Germany;
Proc Natl Acad Sci U S A. 2015 May 5;112(18):5685-90. doi: 10.1073/pnas.1424353112. Epub 2015 Apr 20.
Mitochondrial proton-pumping NADH:ubiquinone oxidoreductase (respiratory complex I) comprises more than 40 polypeptides and contains eight canonical FeS clusters. The integration of subunits and insertion of cofactors into the nascent complex is a complicated multistep process that is aided by assembly factors. We show that the accessory NUMM subunit of complex I (human NDUFS6) harbors a Zn-binding site and resolve its position by X-ray crystallography. Chromosomal deletion of the NUMM gene or mutation of Zn-binding residues blocked a late step of complex I assembly. An accumulating assembly intermediate lacked accessory subunit N7BM (NDUFA12), whereas a paralog of this subunit, the assembly factor N7BML (NDUFAF2), was found firmly bound instead. EPR spectroscopic analysis and metal content determination after chromatographic purification of the assembly intermediate showed that NUMM is required for insertion or stabilization of FeS cluster N4.
线粒体质子泵NADH：泛醌氧化还原酶（呼吸链复合体I）由40多种多肽组成，包含8个典型的铁硫簇。亚基的整合以及辅因子插入新生复合体是一个复杂的多步骤过程，这一过程由组装因子辅助完成。我们发现复合体I的辅助亚基NUMM（人类的NDUFS6）含有一个锌结合位点，并通过X射线晶体学解析了其位置。NUMM基因的染色体缺失或锌结合残基的突变阻碍了复合体I组装的后期步骤。一个积累的组装中间体缺少辅助亚基N7BM（NDUFA12），取而代之的是发现该亚基的一个旁系同源物，即组装因子N7BML（NDUFAF2）牢固地结合在上面。对组装中间体进行色谱纯化后的电子顺磁共振光谱分析和金属含量测定表明，NUMM是铁硫簇N4插入或稳定所必需的。
