BCS1L
BCS1 Homolog, Ubiquinol-Cytochrome C Reductase Complex Chaperone
Gene Information Card
| Symbol | BCS1L |
|---|---|
| Full Name | BCS1 Homolog, Ubiquinol-Cytochrome C Reductase Complex Chaperone |
| Gene Type | Protein coding |
| Chromosomal Location | 2q35 |
| NCBI Gene ID | 617 ncbi.nlm.nih.gov/gene/617 |
| Ensembl ID | ENSG00000100075 |
| UniProt ID | Q9Y276 |
| OMIM ID | 603647 |
| HGNC ID | 1020 |
| Aliases | BCS1, BCS1L, h-BCS1, GRACILE, Björnstad |
Description
BCS1L encodes a mitochondrial chaperone protein essential for the assembly of respiratory chain complex III (ubiquinol-cytochrome c reductase). The protein is located in the inner mitochondrial membrane and facilitates the incorporation of the Rieske iron-sulfur protein (UQCRFS1) into the complex. Mutations in BCS1L cause a spectrum of disorders, including GRACILE syndrome, Björnstad syndrome, and complex III deficiency.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| GRACILE syndrome | Loss-of-function mutations impair complex III assembly, leading to severe neonatal lactic acidosis and iron overload. | ClinVar, OMIM |
| Björnstad syndrome | Missense mutations (e.g., p.Arg45Cys) cause abnormal protein folding and reduced chaperone activity, resulting in sensorineural hearing loss and pili torti. | ClinVar, OMIM |
| Mitochondrial complex III deficiency | Defective assembly of complex III due to BCS1L mutations leads to decreased ATP production and multisystem disorders. | ClinVar, OMIM |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Liver | 12.3 | Medium |
| Kidney | 9.8 | Medium |
| Heart | 15.6 | High |
| Skeletal muscle | 11.2 | Medium |
| Brain | 6.5 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HepG2 | 14.1 | Hepatocellular carcinoma cell line |
| HEK 293 | 10.5 | Embryonic kidney cells |
| K562 | 8.3 | Leukemia cell line |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.232A>G (p.Arg78Gly) | Missense | Rare | Reduced protein stability and complex III assembly |
| c.166C>T (p.Arg56Cys) | Missense | Rare | Impaired chaperone function; associated with Björnstad syndrome |
| c.296G>A (p.Arg99His) | Missense | Rare | Loss of function; linked to GRACILE syndrome |
Mutation functional classification
Loss of Function (LOF)
Most BCS1L mutations lead to loss of chaperone activity, reducing complex III assembly and mitochondrial respiration.
Gain of Function (GOF)
No gain-of-function mutations reported.
Dominant Negative (DN)
Some missense mutations may exert dominant-negative effects by interfering with wild-type protein function, though evidence is limited.
View complete mutation data：
Gene Ontology (GO)
| • Mitochondrial inner membrane | • Protein folding chaperone |
| • Ubiquinol-cytochrome-c reductase complex assembly | • ATP binding |
| • Metal ion binding |
Pathways
• Mitochondrial complex III assembly
• Respiratory electron transport chain
• Oxidative phosphorylation
Protein Summary
BCS1L is a 419-amino acid mitochondrial inner membrane protein belonging to the AAA+ ATPase family. It functions as a chaperone specifically required for the insertion of the Rieske iron-sulfur protein into cytochrome bc1 complex (complex III). The protein contains an N-terminal mitochondrial targeting sequence, a transmembrane domain, and a C-terminal ATPase domain. Defects in BCS1L disrupt complex III activity, leading to impaired oxidative phosphorylation and clinical phenotypes.
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