Mitochondrial complex I couples NADH:ubiquinone oxidoreduction to proton pumping by an unknown mechanism. Here, we present cryo-electron microscopy structures of ovine complex I in five different conditions, including turnover, at resolutions up to 2.3 to 2.5 angstroms. Resolved water molecules allowed us to experimentally define the proton translocation pathways. Quinone binds at three positions along the quinone cavity, as does the inhibitor rotenone that also binds within subunit ND4. Dramatic conformational changes around the quinone cavity couple the redox reaction to proton translocation during open-to-closed state transitions of the enzyme. In the induced deactive state, the open conformation is arrested by the ND6 subunit. We propose a detailed molecular coupling mechanism of complex I, which is an unexpected combination of conformational changes and electrostatic interactions.
We thank J. Novacek (CEITEC Brno) and V.-V. Hodirnau (IST Austria) for their help with collecting cryo-EM datasets. We thank the IST Life Science and Electron Microscopy Facilities for providing equipment. This work has been supported by iNEXT,project number 653706, funded by the Horizon 2020 program of the European Union. This article reflects only the authors’view,and the European Commission is not responsible for any use that may be made of the information it contains. CIISB research infrastructure project LM2015043 funded by MEYS CR is gratefully acknowledged for the financial support of the measurements at the CF Cryo-electron Microscopy and Tomography CEITEC MU.This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement no. 665385
Kampjut D, Sazanov LA. The coupling mechanism of mammalian respiratory complex I. Science. 2020;370(6516). doi:10.1126/science.abc4209
Kampjut, D., & Sazanov, L. A. (2020). The coupling mechanism of mammalian respiratory complex I. Science, 370(6516). https://doi.org/10.1126/science.abc4209
Kampjut, Domen, and Leonid A Sazanov. “The Coupling Mechanism of Mammalian Respiratory Complex I.” Science 370, no. 6516 (2020). https://doi.org/10.1126/science.abc4209.
D. Kampjut and L. A. Sazanov, “The coupling mechanism of mammalian respiratory complex I,” Science, vol. 370, no. 6516, 2020.
Kampjut D, Sazanov LA. 2020. The coupling mechanism of mammalian respiratory complex I. Science. 370(6516).
Kampjut, Domen, and Leonid A. Sazanov. “The Coupling Mechanism of Mammalian Respiratory Complex I.” Science, vol. 370, no. 6516, eabc4209, American Association for the Advancement of Science, 2020, doi:10.1126/science.abc4209.
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