The ADP/ATP transport system: a paradigm of metabolite transport in mitochondria

The eukaryotic ADP/ATP carrier regulates the transport of energy-rich substances, ADP, phosphate and O2 into the mitochondria. However, the carrier regulates ATP, CO2 and H2O out of the mitochondria. The carrier has two conformations which are recognized by the toxins carboxyatractyloside and bongkrekic acid, respectively. The outer membrane transport mechanism is electrogenic. Thirty percent of the energy needed for ATP export comes from mitochondrial respiration. The carrier is present as a tetramer and is probably compact with hydrophilic loops.