TK2 Protein is a protein that tk2 is essential for mitochondrial dna (mtdna) maintenance:. This page describes its structure, normal nervous system function, role in neurodegenerative disease, and potential as a therapeutic target.
| Protein Name | Thymidine Kinase 2 (TK2) |
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| Gene | [TK2](/genes/tk2) |
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| UniProt ID | Q9Y2H5 |
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| PDB Structure | 6G2J, 6G2K |
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| Molecular Weight | ~62 kDa |
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| Subcellular Localization | Mitochondrial matrix |
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| Protein Family | Thymidine kinase family |
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TK2 is a mitochondrial matrix enzyme with a characteristic kinase fold:
- Kinase Domain: Central catalytic domain with ATP-binding site
- Targeting Sequence: N-terminal mitochondrial targeting peptide (cleaved upon import)
- Dimerization Domain: Forms functional dimers in the mitochondrial matrix
- Substrate Binding Pocket: Recognizes thymidine and other nucleosides
TK2 is essential for mitochondrial DNA (mtDNA) maintenance:
- mtDNA Synthesis: Provides dTMP for mitochondrial DNA replication
- Nucleotide Recycling: Salvages nucleosides from mtDNA turnover for reuse
- Mitochondrial Biogenesis: Essential for maintaining mtDNA copy number
- Energy Metabolism: Supports proper function of the electron transport chain
TK2 mutations cause mtDNA depletion syndrome:
- Myopathic Form: Primary involvement of skeletal muscle with progressive weakness
- Encephalomyopathic Form: Additional neurological involvement
- Clinical Features: Exercise intolerance, muscle weakness, respiratory failure
- Biochemical Markers: Reduced mtDNA copy number in muscle, elevated mtDNA mutations
- Progressive External Ophthalmoplegia (PEO): TK2 mutations can cause PEO with mtDNA deletions
- ** Infantile-onset Spinocerebellar Ataxia (IOSCA)**: Severe early-onset neurodegeneration
Current therapeutic approaches include:
- Gene Therapy: AAV vector delivery of wild-type TK2
- Nucleotide Supplementation: Oral dTMP/dTDP supplementation
- Enzyme Replacement: Recombinant TK2 protein delivery
- Mitochondrial Biogenesis Stimulators: PGC-1α activators to increase mtDNA replication
- TK2 mutations cause mtDNA depletion (2000)
- TK2 structure and function (2018)
- Gene therapy for TK2 deficiency (2020)
- Nucleotide therapy for mtDNA depletion (2021)