Beschreibung:
<jats:title>Significance</jats:title>
<jats:p>
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
<jats:italic>c</jats:italic>
. The latter transfers electrons from respiratory complex III to complex IV. In yeast, these complexes assemble into III
<jats:sub>2</jats:sub>
IV
<jats:sub>1/2</jats:sub>
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
<jats:italic>c</jats:italic>
shuttles electrons by two-dimensional diffusion, sliding along the surface of III
<jats:sub>2</jats:sub>
IV
<jats:sub>1/2</jats:sub>
. The structural arrangement of III
<jats:sub>2</jats:sub>
IV
<jats:sub>1/2</jats:sub>
supercomplexes suggests a mechanism to regulate cellular respiration.
</jats:p>