This gene encodes a homolog of the S. cerevisiae bcs1 protein which is involved in the assembly of complex III of the mitochondrial respiratory chain. The encoded protein does not contain a mitochondrial targeting sequence but experimental studies confirm that it is imported into mitochondria. A conserved domain at the N-terminus of BCS1 is responsible for the import and intramitochondrial sorting.  Mutations in this gene are associated with mitochondrial complex III deficiency and the GRACILE syndrome. Two alternatively spliced transcripts encoding the same protein have been described.
^Petruzzella V, Tiranti V, Fernandez P, Ianna P, Carrozzo R, Zeviani M (Feb 1999). "Identification and characterization of human cDNAs specific to BCS1, PET112, SCO1, COX15, and COX11, five genes involved in the formation and function of the mitochondrial respiratory chain". Genomics54 (3): 494–504. doi:10.1006/geno.1998.5580. PMID9878253.
^Hinson JT, Fantin VR, Schonberger J, Breivik N, Siem G, McDonough B, Sharma P, Keogh I, Godinho R, Santos F, Esparza A, Nicolau Y, Selvaag E, Cohen BH, Hoppel CL, Tranebjaerg L, Eavey RD, Seidman JG, Seidman CE (Feb 2007). "Missense mutations in the BCS1L gene as a cause of the Bjornstad syndrome". N Engl J Med356 (8): 809–19. doi:10.1056/NEJMoa055262. PMID17314340.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K et al. (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID9373149.
de Lonlay P, Valnot I, Barrientos A et al. (2001). "A mutant mitochondrial respiratory chain assembly protein causes complex III deficiency in patients with tubulopathy, encephalopathy and liver failure". Nat. Genet.29 (1): 57–60. doi:10.1038/ng706. PMID11528392.
Fernandez-Vizarra E, Bugiani M, Goffrini P et al. (2007). "Impaired complex III assembly associated with BCS1L gene mutations in isolated mitochondrial encephalopathy". Hum. Mol. Genet.16 (10): 1241–52. doi:10.1093/hmg/ddm072. PMID17403714.