BCS1 Like Protein (BCS1L)

BCS1L 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.The predicted 420-amino acid human protein is 50% identical to yeast bcs1 and, like bcs1, contains 2 conserved nucleotide-binding motifs. Although BCS1L does not contain an N-terminal mitochondrial targeting sequence, in vitro mitochondrial import and trypsin-protection assays demonstrated that it is imported into mitochondria.