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.

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. [provided by RefSeq, Jul 2008]