Voltage-dependent anion-selective channel protein 1 (VDAC-1) forms a channel through the mitochondrial outer membrane and also the plasma membrane. The channel at the outer mitochondrial membrane allows diffusion of small hydrophilic molecules; whereas in the plasma membrane it is involved in cell volume regulation and apoptosis. VDAC-1 adopts an open conformation at low or zero membrane potential and a closed conformation at potentials above 30-40 mV. The open state has weak anion selectivity whereas the closed state is cation-selective. VDAC-1 participates in the formation of the permeability transition pore comple, Xenopus/Amphibian, (PTPC) responsible for the release of mitochondrial products that triggers apoptosis.