| COX5A — Cytochrome C Oxidase Subunit 5A |
|---|
| Protein Name | Cytochrome C Oxidase Subunit 5A |
| Gene | COX5A |
| UniProt ID | P20674 |
| PDB ID | 1V54, 2EIJ |
| Molecular Weight | ~16 kDa |
| Subcellular Localization | Inner mitochondrial membrane |
| Protein Family | Cytochrome c oxidase subunit Va family |
COX5A is the 5A subunit of cytochrome c oxidase (complex IV) of the mitochondrial electron transport chain. This protein is nuclear-encoded and imported into mitochondria where it assembles into the mature complex.
Cytochrome c oxidase (COX) is a multimeric complex consisting of:
- 13 mitochondrial-encoded subunits
- 10 nuclear-encoded subunits (in mammals)
COX5A is one of the nuclear-encoded subunits critical for proper complex assembly and function.
COX5A structure features:
- Transmembrane helix — anchors protein in inner mitochondrial membrane
- Water-soluble domain — extends into the mitochondrial matrix
- Binding sites — for cytochrome c interaction
The protein contains:
- ~150 amino acids
- Molecular weight of ~16 kDa
- Single transmembrane domain
- Cytochrome c oxidation — receives electrons from cytochrome c
- Oxygen reduction — catalyzes the final step of the ETC: 4 Cyt c (reduced) + 8 H+ + O2 → 4 Cyt c (oxidized) + 4 H2O
- Proton pumping — contributes to the electrochemical gradient
- Essential for aerobic ATP production
- Regulates reactive oxygen species (ROS) production
- Maintains mitochondrial membrane potential
- Reduced COX activity in AD brain and platelets
- Contributes to neuronal energy failure
- Impaired oxidative phosphorylation leads to synaptic dysfunction
- Correlates with cognitive decline severity
- Complex IV deficiency in substantia nigra pars compacta
- Contributes to dopaminergic neuron vulnerability
- Energy deficit exacerbates α-synuclein toxicity
- Mutations in COX subunits can cause classic Leigh syndrome
- Characterized by:
- Progressive neurodegeneration
- Basal ganglia lesions
- Lactic acidosis
- Early childhood onset
- CoQ10 supplementation — supports electron flow
- Mitochondrial nutrients — L-carnitine, alpha-lipoic acid
- Exercise — stimulates mitochondrial biogenesis
- Gene therapy — deliver COX genes
- Mitochondrial transplantation
- Small molecules to enhance complex IV assembly
- Parikh et al., Mitochondrial dysfunction in Alzheimer's disease (2009)
- Gandhi et al., COX deficiency in neurodegeneration (2012)
- Stryber et al., Cytochrome c oxidase in AD brain (2021)