The protein encoded by this gene is a member of the immunophilin protein family| which play a role in immunoregulation and basic cellular processes involving protein folding and trafficking. The protein is a cis-trans prolyl isomerase that binds the immunosuppressants FK506 and rapamycin. It interacts with several intracellular signal transduction proteins including type I TGF-beta receptor. It also interacts with multiple intracellular calcium release channels| and coordinates multi-protein complex formation of the tetrameric skeletal muscle ryanodine receptor. In mouse| deletion of this homologous gene causes congenital heart disorder known as noncompaction of left ventricular myocardium. Multiple alternatively spliced variants| encoding the same protein| have been identified. The human genome contains five pseudogenes related to this gene| at least one of which is transcribed.