PBR (Peripheral-type Benzodiazepine Receptor) is a ubiquitous protein (18 kDa) found in most steroidogenic tissues. It is located primarily in the outer mitochondrial membrane of steroid-producing tissues and is found in association with a 34 kDa voltage-dependent anion channel protein (VDAC). PBR is involved in the regulation of cholesterol transport from the outer to the inner mitochondrial membrane. It is thoμght to be part of the mitochondrial permeability transition pore (PT) and to be involved in apoptosis.