Figure 1.
Mitochondrial ETC complexes can generate superoxide from multiple sites. Complexes I and II release ROS primarily to the matrix compartment, where manganese superoxide dismutatase (MnSOD) converts superoxide to hydrogen peroxide (H2O2). Complex III can generate ROS at the Q0 ubiquinone binding site within the inner membrane. Superoxide generated there is ejected into the intermembrane space by the strong electrical field in the membrane (Em) that results from the electrical gradient (−180 mV).