Journal
FRONTIERS IN CHEMISTRY
Volume 9, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fchem.2021.672969
Keywords
NADH dehydrogenase; respiratory complex I; bioenergetics; proton-coupled electron transfer; quinone chemistry; Escherichia coli
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Funding
- Deutsche Forschungsgemeinschaft (DFG) [278002225/RTG 2202, SPP1927 (FR 1140/11-2)]
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Energy-converting NADH:ubiquinone oxidoreductase, respiratory complex I, is crucial in cellular energy metabolism by oxidizing NADH and reducing quinone while translocating protons across the membrane. It has an overall L-shaped structure with electron transfer catalyzed by a peripheral arm and proton translocation by a membrane arm. The spatially separated reactions are tightly coupled through a mechanism that is not fully understood.
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 Escherichia coli 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(H) 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.
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