Translocator protein (TSPO) is an 18 kDa protein mainly found on the outer mitochondrial membrane. It was first described as peripheral benzodiazepine receptor (PBR), a secondary binding site for diazepam, but subsequent research has found the receptor to be expressed throughout the body and brain. In humans, the translocator protein is encoded by the TSPO gene. It belongs to a family of tryptophan-rich sensory proteins. Regarding intramitochondrial cholesterol transport, TSPO has been proposed to interact with StAR (steroidogenic acute regulatory protein) to transport cholesterol into mitochondria, though evidence is mixed. TSPO as a biomarker is a newly discovered non-invasive procedure, and has also been linked as a biomarker for other cardiovascular related diseases including: myocardial infarction (due to ischemic reperfusion), cardiac hypertrophy, atherosclerosis, arrhythmias, and large vessel vasculitis.