Edited by Yifan Cheng, University of California, San Francisco, CA, and approved January 19, 2021 (received for review October 11, 2020)In the last steps of food oxidation in living organisms, electrons are transferred to oxygen through the membrane-bound respiratory chain. This electron transfer is mediated by mobile carriers, such as membrane-bound quinone and water-soluble cytochrome c. The latter transfers electrons from respiratory complex III to complex IV. In yeast, these complexes assemble into III2IV1/2 supercomplexes, but its role has remained enigmatic. This study establishes a...…Edited by Yifan Cheng, University of California, San Francisco, CA, and approved January 19, 2021 (received for review October 11, 2020)In the last steps of food oxidation in living organisms, electrons are transferred to oxygen through the membrane-bound respiratory chain. This electron transfer is mediated by mobile carriers, such as membrane-bound quinone and water-soluble cytochrome c. The latter transfers electrons from respiratory complex III to complex IV. In yeast, these complexes assemble into III2IV1/2 supercomplexes, but its role has remained enigmatic. This study establishes a...WW…