Cryo-EM structure and kinetics reveal electron transfer by 2D diffusion of cytochrome <i>c</i> in the yeast III-IV respiratory supercomplex
Agnes Moe, Justin M. Di Trani, John L. Rubinstein, Peter Brzezinski
Abstract
Significance 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 III 2 IV 1/2 supercomplexes, but its role has remained enigmatic. This study establishes a functional role for this supramolecular assembly in the mitochondrial membrane. We used cryo-EM and kinetic studies to show that cytochrome c shuttles electrons by two-dimensional diffusion, sliding along the surface of III 2 IV 1/2 . The structural arrangement of III 2 IV 1/2 supercomplexes suggests a mechanism to regulate cellular respiration.