Putative peripheral benzodiazepine receptor-related protein (TSPO)

Can bind protoporphyrin IX and may play a role in the transport of porphyrins and heme (By similarity). Promotes the transfer of cholesterol across mitochondrial membranes and might play a role in lipid metabolism (PubMed:24814875), but its exact physiological function is controversial.

It's apparently not required for steroid hormone biosynthesis. Was initially identified as peripheral-type benzodiazepine receptor; may also bind isoquinoline carboxamides (PubMed:1847678).