The function of TSPO (translocator protein, Ensembl gene identifier ENSG00000100300) is as follows. Can bind protoporphyrin IX and may play a role in the transport of porphyrins and heme (By similarity). Promotes the transport of cholesterol across mitochondrial membranes and may play a role in lipid metabolism (PubMed:24814875), but its precise physiological role is controversial. It is apparently not required for steroid hormone biosynthesis. Was initially identified as peripheral- type benzodiazepine receptor; can also bind isoquinoline carboxamides (PubMed:1847678). {ECO:0000250, ECO:0000269|PubMed:1847678, ECO:0000269|PubMed:24814875}.