Promotes the transport of cholesterol across mitochondrial membranes and may play a role in lipid metabolism, but its precise physiological role is controversial. It is apparently not required for steroid hormone biosynthesis. Can bind protoporphyrin IX and may play a role in the transport of porphyrins and heme (By similarity). Was initially identified as peripheral-type benzodiazepine receptor; can also bind isoquinoline carboxamides (PubMed:1649835). Interacts with TSPOAP1. Interacts with MOST-1. May interact with STAR. Belongs to the TspO/BZRP family.