電子伝達系: 錯体 III および IV

The third complex of the electron transport chain, Q-cytochrome c oxidoreductase, is a dimeric protein that transfers electrons from Q to cytochrome c. Each monomer includes eleven subunits with three catalytic components- cytochrome b, cytochrome c₁, and Rieske iron-sulfur protein.

Each cytochrome b is encoded by the mitochondrial genome and has two different b-type heme groups. Each cytochrome c₁ has one c-type heme, and each Rieske iron-sulfur protein has Fe₂-S₂ clusters.

The next complex- cytochrome c-oxidase comprises heme and copper ions. These cofactors sequester an oxygen atom, enabling electron transfer from cytochrome c to the terminal electron acceptor-oxygen. This complex has thirteen subunits, with three of its largest subunits-COX I, II, and III, encoded by the mitochondrial genome.

The overall electron transport process releases free energy, which the complexes-I, III, and IV utilize for pumping protons into the intermembrane space.

The resulting proton motive force drives the rotation of complex V, or ATP synthase, which in turn catalyzes the synthesis of ATP from ADP and inorganic phosphate.