Complex I is the first and the largest enzyme of respiratory chains in bacteria and mitochondria. The mechanism which couples spatially separated transfer of electrons to proton translocation in complex I is not known. Here we report five crystal structures of T. thermophilus enzyme in complex with NADH or quinone-like compounds. We also determined cryo-EM structures of major and minor native states of the complex, differing in the position of the peripheral arm. Crystal structures show that binding of quinone-like compounds (but not of NADH) leads to a related global conformational change, accompanied by local re-arrangements propagating from the quinone site to the nearest proton channel. Normal mode and molecular dynamics analyses indicate that these are likely to represent the first steps in the proton translocation mechanism. Our results suggest that quinone binding and chemistry play a key role in the coupling mechanism of complex I.
This work was funded by the Medical Research Council, UK and IST Austria. We thank the European Synchrotron Radiation Facility and the Diamond Light Source for provision of synchrotron radiation facilities. We are grateful to the staff of beamlines ID29, ID23-2 (ESRF, Grenoble, France) and I03 (Diamond Light Source, Didcot, UK) for assistance. Data processing was performed at the IST high-performance computing cluster.
Gutierrez-Fernandez J, Kaszuba K, Minhas GS, et al. Key role of quinone in the mechanism of respiratory complex I. Nature Communications. 2020;11(1). doi:10.1038/s41467-020-17957-0
Gutierrez-Fernandez, J., Kaszuba, K., Minhas, G. S., Baradaran, R., Tambalo, M., Gallagher, D. T., & Sazanov, L. A. (2020). Key role of quinone in the mechanism of respiratory complex I. Nature Communications. Springer Nature. https://doi.org/10.1038/s41467-020-17957-0
Gutierrez-Fernandez, Javier, Karol Kaszuba, Gurdeep S. Minhas, Rozbeh Baradaran, Margherita Tambalo, David T. Gallagher, and Leonid A Sazanov. “Key Role of Quinone in the Mechanism of Respiratory Complex I.” Nature Communications. Springer Nature, 2020. https://doi.org/10.1038/s41467-020-17957-0.
J. Gutierrez-Fernandez et al., “Key role of quinone in the mechanism of respiratory complex I,” Nature Communications, vol. 11, no. 1. Springer Nature, 2020.
Gutierrez-Fernandez J, Kaszuba K, Minhas GS, Baradaran R, Tambalo M, Gallagher DT, Sazanov LA. 2020. Key role of quinone in the mechanism of respiratory complex I. Nature Communications. 11(1), 4135.
Gutierrez-Fernandez, Javier, et al. “Key Role of Quinone in the Mechanism of Respiratory Complex I.” Nature Communications, vol. 11, no. 1, 4135, Springer Nature, 2020, doi:10.1038/s41467-020-17957-0.
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