New control of mitochondrial membrane potential and ROS formation - A hypothesis

A new control of mitochondrial membrane potential DeltaPsi(m) and formation of reactive oxygen species (ROS) is presented, based on allosteric ATP-inhibition of cytochrome c oxidase at high intramitochondrial ATP/ADP ratios. Since the rate of ATP synthesis by the ATP synthase is already maximal at low membrane potentials (100 - 120 mV), the ATP/ADP ratio will also be maximal at this DeltaPsi(m) (at constant rate of ATP consumption). Therefore the control of respiration by the ATP/ADP-ratio keeps DeltaPsi(m) low. In contrast, the known 'respiratory control' leads to an inhibition of respiration only at high DeltaPsi(m) values (150-200 mV) which cause ROS formation. ATP-inhibition of cytochrome c oxidase is switched on and off by reversible phosphorylation (via cAMP and calcium, respectively). We propose that 'stress hormones' which increase intracellular [Ca2+] also increase DeltaPsi(m) and ROS formation, which promote degenerative diseases and accelerate aging.