Nuber Franziska, Mérono Luca, Oppermann Sabrina, Schimpf Johannes, Wohlwend Daniel, Friedrich Thorsten
Institut für Biochemie, Albert-Ludwigs-Universität, Freiburg, Germany.
Front Chem. 2021 May 7;9:672969. doi: 10.3389/fchem.2021.672969. eCollection 2021.
Energy-converting NADH:ubiquinone oxidoreductase, respiratory complex I, plays a major role in cellular energy metabolism. It couples NADH oxidation and quinone reduction with the translocation of protons across the membrane, thus contributing to the protonmotive force. Complex I has an overall L-shaped structure with a peripheral arm catalyzing electron transfer and a membrane arm engaged in proton translocation. Although both reactions are arranged spatially separated, they are tightly coupled by a mechanism that is not fully understood. Using redox-difference UV-vis spectroscopy, an unknown redox component was identified in complex I as reported earlier. A comparison of its spectrum with those obtained for different quinone species indicates features of a quinol anion. The re-oxidation kinetics of the quinol anion intermediate is significantly slower in the D213G variant that was previously shown to operate with disturbed quinone chemistry. Addition of the quinone-site inhibitor piericidin A led to strongly decreased absorption peaks in the difference spectrum. A hypothesis for a mechanism of proton-coupled electron transfer with the quinol anion as catalytically important intermediate in complex I is discussed.
能量转换型NADH：泛醌氧化还原酶，即呼吸链复合体I，在细胞能量代谢中起主要作用。它将NADH氧化和醌还原与质子跨膜转运相偶联，从而产生质子动力。复合体I具有整体L形结构，其外周臂催化电子传递，膜臂参与质子转运。虽然这两个反应在空间上是分开排列的，但它们通过一种尚未完全理解的机制紧密偶联。如先前报道，利用氧化还原差紫外可见光谱法在复合体I中鉴定出一种未知的氧化还原成分。将其光谱与不同醌类物质的光谱进行比较，表明其具有喹啉阴离子的特征。喹啉阴离子中间体的再氧化动力学在先前显示醌化学受到干扰的D213G变体中明显较慢。醌位点抑制剂匹里卡菌素A的添加导致差光谱中的吸收峰大幅降低。本文讨论了一种以喹啉阴离子作为复合体I中催化重要中间体的质子偶联电子传递机制的假说。
