| PARKIN Protein | |
|---|---|
| Gene | [PARK2](/genes/park2) |
| Full Name | Parkin RBR E3 Ubiquitin Protein Ligase |
| UniProt ID | [O60260](https://www.uniprot.org/uniprot/O60260) |
| PDB Structure IDs | 1MG8, 1N4M, 2JMO, 4K7D, 5CAW |
| Molecular Weight | 51.5 kDa (465 aa) |
| Subcellular Localization | Cytoplasm, Mitochondria outer membrane |
| Protein Family | RING-between-RING (RBR) family |
Parkin is an E3 ubiquitin ligase encoded by the PARK2 gene, one of the most frequently mutated genes in early-onset autosomal recessive Parkinson's disease[1]. Parkin plays a critical role in mitochondrial quality control through the regulation of mitophagy—the selective degradation of damaged mitochondria[2]. The PINK1-Parkin pathway is one of the best-characterized mechanisms linking mitochondrial dysfunction to neurodegeneration in Parkinson's disease.
Parkin has a complex multi-domain architecture characteristic of the RING-between-RING (RBR) family of E3 ubiquitin ligases:
| Domain | Amino Acids | Function | Clinical Significance |
|---|---|---|---|
| Ubl Domain | 1-76 | Phosphorylation by PINK1, ubiquitin binding | Phosphorylation site Ser65 is disease-relevant |
| RING0 | 77-165 | Structural domain, interacts with RING1 | Mutations disrupt E3 activity |
| RING1 | 212-286 | E2 binding, ubiquitin transfer | Core catalytic component |
| IBR Domain | 327-416 | In-between-RING,桥梁作用 | Mutations cause loss of function |
| RING2 | 418-465 | Catalytic cysteine, thioester formation | Catalytic core for ubiquitination |
Parkin exists in an auto-inhibited conformation in the cytosol. Activation requires phosphorylation by PINK1 and binding to phosphorylated ubiquitin, which induces dramatic conformational changes that reposition the RING domains for catalytic activity[3].
Parkin's primary function is in mitochondrial quality control through mitophagy:
Mitochondrial Damage Sensing: Upon mitochondrial damage (e.g., oxidative stress, depolarization), PINK1 accumulates on the outer mitochondrial membrane[4].
Parkin Activation: PINK1 phosphorylates ubiquitin and Parkin's Ubl domain at Ser65. This phosphorylation triggers conformational changes that activate Parkin's E3 ligase activity[5].
Substrate Ubiquitination: Activated Parkin ubiquitinates numerous mitochondrial outer membrane proteins, including VDAC1, Mfn1/2, and TOM complex components[6].
Autophagic Clearance: Ubiquitinated mitochondria are recognized by autophagic receptors (p62/SQSTM1, OPTN, NDP52) that recruit LC3-positive autophagosomes, leading to mitochondrial degradation[7].
PARK2 mutations are the most common cause of autosomal recessive early-onset Parkinson's disease (age of onset <40 years)[8]. Over 200 pathogenic mutations have been identified, including:
Common pathogenic mutations include:
Loss of Mitophagy Function: Mutations impair Parkin's ability to initiate mitophagy, leading to accumulation of dysfunctional mitochondria[9].
Mitochondrial DNA Damage: Parkin-deficient cells show increased susceptibility to mitochondrial DNA damage.
Dysregulated Mitochondrial Dynamics: Loss of Parkin leads to excessive fission and fragmentation.
Impaired Mitochondrial Biogenesis: Reduced PGC-1α expression and decreased mitochondrial biogenesis.
Increased Apoptosis: Altered regulation of pro-apoptotic proteins.
The PINK1-Parkin pathway represents one of the best-characterized mechanisms in PD:
| Partner | Interaction Type | Functional Consequence |
|---|---|---|
| PINK1 | Phosphorylation | Activates Parkin |
| Phospho-ubiquitin | Binding | Activates Parkin |
| E2 enzymes | Catalysis | UbcH7, UbcH8 |
| p62/SQSTM1 | Autophagy receptor | Links to autophagosomes |
| Mfn1/2 | Substrate | Regulates fusion |
| VDAC1 | Substrate | Permeability control |
| BCL-2 | Anti-apoptotic | Regulates cell death |
The Parkin protein continues to be a major focus of PD research and therapeutic development.
Lücking CB, et al. (2000). New England Journal of Medicine. 2000. ↩︎
Narendra D, Tanaka A, Suen DF, Youle RJ. (2008). Journal of Cell Biology. 2008. ↩︎
Scarffe LA, et al. (2014). Molecular Neurodegeneration. 2014. ↩︎
Choudhury SR, et al. (2017). AAV-PARKIN therapy for Parkinson's disease. Molecular Therapy. 25(1):A26. PMC5385414. 2017. ↩︎
Hattori N, et al. (1998). American Journal of Human Genetics. 1998. ↩︎
Kim Y, et al. (2008). Biochemical and Biophysical Research Communications. 2008. ↩︎