Binds tetrapyrroles and promotes the photooxidative degradation of protoporphyrin IX (PubMed:25635100). Can bind the benzodiazepine receptor agonist PK-11195 (in vitro); this interferes with photooxidative tetrapyrrole degradation (PubMed:25635100). May play a role in the transmembrane transport of tetrapyrroles and similar compounds (By similarity). Monomer and homodimer. May also form higher oligomers. Belongs to the TspO/BZRP family.