Structural Bioenergetics Group, Institute of Biochemistry II, Medical School, Goethe-University, Frankfurt am Main, Germany; Centre for Biomolecular Magnetic Resonance, Institute for Biophysical Chemistry, University of Frankfurt, Frankfurt am Main, Germany.
Department of Physics, University of Helsinki, Helsinki, Finland.
Biochim Biophys Acta Bioenerg. 2019 Jul 1;1860(7):573-581. doi: 10.1016/j.bbabio.2019.06.006. Epub 2019 Jun 19.
Respiratory complex I catalyses the reduction of ubiquinone (Q) from NADH coupled to proton pumping across the inner membrane of mitochondria. The electrical charging of the inner mitochondrial membrane drives the synthesis of ATP, which is used to power biochemical reactions of the cell. The recent surge in structural data on complex I from bacteria and mitochondria have contributed to significant understanding of its molecular architecture. However, despite these accomplishments, the role of various subdomains in redox-coupled proton pumping remains entirely unclear. In this work, we have mutated conserved residues in the loop of the PSST subunit that faces the ~30 Å long unique Q-binding tunnel of respiratory complex I. The data show a drastic decrease in Q reductase activity upon mutating several residues despite full assembly of the complex. In-silico modeling and multiple microsecond long molecular dynamics simulations of wild-type and enzyme variants with exchanges of conserved arginine residues revealed remarkable ejection of the bound Q from the site near terminal electron donor N2. Based on experiments and long-time scale molecular simulations, we identify microscopic elements that dynamically control the diffusion of Q and are central to redox-coupled proton pumping in respiratory complex I.
呼吸复合物 I 催化 NADH 还原与质子跨线粒体内膜泵出耦联。线粒体内膜的电充电驱动 ATP 的合成，用于为细胞的生化反应提供动力。最近，来自细菌和线粒体的复合物 I 的结构数据的激增，有助于对其分子结构的深入理解。然而，尽管取得了这些成就，各种亚结构域在氧化还原偶联质子泵中的作用仍然完全不清楚。在这项工作中，我们突变了 PSST 亚基loop 中面对呼吸复合物 I 独特的~30 Å 长 Q 结合隧道的保守残基。尽管复合物完全组装，但数据显示，在突变几个残基后，Q 还原酶活性急剧下降。野生型和酶变体的计算建模和多个微秒长分子动力学模拟以及保守精氨酸残基的交换，揭示了结合 Q 从靠近末端电子供体 N2 的位点的显著逐出。基于实验和长时间尺度分子模拟，我们确定了动态控制 Q 扩散的微观元素，这些元素是呼吸复合物 I 中氧化还原偶联质子泵的核心。
