Mitochondrial chaperone BCS1 (BCS1L)

Mitochondrial chaperone BCS1 (BCS1L) is an essential assembly factor located in the inner mitochondrial membrane, belonging to the AAA+ ATPase family. It plays a critical role in the final steps of mitochondrial respiratory chain complex III (ubiquinol-cytochrome c reductase) assembly by facilitating the insertion of the catalytic Rieske iron-sulfur protein, thereby enabling full enzyme functionality and efficient ATP synthesis through oxidative phosphorylation. Mutations in BCS1L disrupt this process, causing varied mitochondrial diseases—including severe multisystem disorders (GRACILE syndrome) and milder conditions with sensorineural hearing loss (Björnstad syndrome)—characterized by reduced complex III activity, impaired energy production, and multi-organ impairment. BCS1L’s disease spectrum is wide, as its deficiency affects not only ATP synthesis but also leads to oxidative stress and altered iron metabolism, with pathogenic mutations serving as biomarkers for clinical diagnosis[1][2][4][5][6].

Other names

BCS1h-BCS1BCSBJSBCS1-like proteinGRACILE syndrome proteinBjörnstad syndrome proteinMC3DN1PTDFLNMSmitochondrial complex III assembly factorBC1 (ubiquinol-cytochrome c reductase) synthesis-likeBCS1 homologubiquinol-cytochrome c reductase complex chaperone