Structure and assembly of the mammalian mitochondrial supercomplex CIII2CIV

Vercellino I, Sazanov LA. 2021. Structure and assembly of the mammalian mitochondrial supercomplex CIII2CIV. Nature. 598(7880), 364–367.

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Abstract
The enzymes of the mitochondrial electron transport chain are key players of cell metabolism. Despite being active when isolated, in vivo they associate into supercomplexes1, whose precise role is debated. Supercomplexes CIII2CIV1-2 (refs. 2,3), CICIII2 (ref. 4) and CICIII2CIV (respirasome)5,6,7,8,9,10 exist in mammals, but in contrast to CICIII2 and the respirasome, to date the only known eukaryotic structures of CIII2CIV1-2 come from Saccharomyces cerevisiae11,12 and plants13, which have different organization. Here we present the first, to our knowledge, structures of mammalian (mouse and ovine) CIII2CIV and its assembly intermediates, in different conformations. We describe the assembly of CIII2CIV from the CIII2 precursor to the final CIII2CIV conformation, driven by the insertion of the N terminus of the assembly factor SCAF1 (ref. 14) deep into CIII2, while its C terminus is integrated into CIV. Our structures (which include CICIII2 and the respirasome) also confirm that SCAF1 is exclusively required for the assembly of CIII2CIV and has no role in the assembly of the respirasome. We show that CIII2 is asymmetric due to the presence of only one copy of subunit 9, which straddles both monomers and prevents the attachment of a second copy of SCAF1 to CIII2, explaining the presence of one copy of CIV in CIII2CIV in mammals. Finally, we show that CIII2 and CIV gain catalytic advantage when assembled into the supercomplex and propose a role for CIII2CIV in fine tuning the efficiency of electron transfer in the electron transport chain.
Publishing Year
Date Published
2021-10-14
Journal Title
Nature
Acknowledgement
We thank the pre-clinical facility of the IST Austria and A. Venturino for assistance with the animals; and V.-V. Hodirnau for assistance during the Titan Krios data collection, performed at the IST Austria. The data processing was performed at the IST high-performance computing cluster. This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 754411.
Volume
598
Issue
7880
Page
364-367
ISSN
eISSN
IST-REx-ID

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Vercellino I, Sazanov LA. Structure and assembly of the mammalian mitochondrial supercomplex CIII2CIV. Nature. 2021;598(7880):364-367. doi:10.1038/s41586-021-03927-z
Vercellino, I., & Sazanov, L. A. (2021). Structure and assembly of the mammalian mitochondrial supercomplex CIII2CIV. Nature. Springer Nature. https://doi.org/10.1038/s41586-021-03927-z
Vercellino, Irene, and Leonid A Sazanov. “Structure and Assembly of the Mammalian Mitochondrial Supercomplex CIII2CIV.” Nature. Springer Nature, 2021. https://doi.org/10.1038/s41586-021-03927-z.
I. Vercellino and L. A. Sazanov, “Structure and assembly of the mammalian mitochondrial supercomplex CIII2CIV,” Nature, vol. 598, no. 7880. Springer Nature, pp. 364–367, 2021.
Vercellino I, Sazanov LA. 2021. Structure and assembly of the mammalian mitochondrial supercomplex CIII2CIV. Nature. 598(7880), 364–367.
Vercellino, Irene, and Leonid A. Sazanov. “Structure and Assembly of the Mammalian Mitochondrial Supercomplex CIII2CIV.” Nature, vol. 598, no. 7880, Springer Nature, 2021, pp. 364–67, doi:10.1038/s41586-021-03927-z.

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