The polymerase domain encompasses three conserved active site motifs: Pol A (residues 887-896), Pol B (residues 943-958) and Pol C (residues 1134-1141). Binds the incoming dNTPs and undergoes an open to close coformation change to catalyze the formation of phosphodiester bond.
The 3' -> 5' exonuclease domain comprises three conserved active site motifs: Exo I (residues 196-200), Exo II (residues 267-275) and Exo III (residues 395-403). Proofreads the newly synthesized DNA strand.
The trigger loop contracts to enable correctly matched primer-template pair entry into the polymerase domain and extends to preclude the mismatched one.
The accessory determinant domain (AID) interacts with POLG2 proximal monomer.
Catalytic subunit of DNA polymerase gamma solely responsible for replication of mitochondrial DNA (mtDNA). Replicates both heavy and light strands of the circular mtDNA genome using a single-stranded DNA template, RNA primers and the four deoxyribonucleoside triphosphates as substrates (PubMed:11477093, PubMed:11897778, PubMed:15917273, PubMed:19837034, PubMed:9558343). Has 5' -> 3' polymerase activity. Functionally interacts with TWNK and SSBP1 at the replication fork to form a highly processive replisome, where TWNK unwinds the double-stranded DNA template prior to replication and SSBP1 covers the parental heavy strand to enable continuous replication of the entire mitochondrial genome. A single nucleotide incorporation cycle includes binding of the incoming nucleotide at the insertion site, a phosphodiester bond formation reaction that extends the 3'-end of the primer DNA, and translocation of the primer terminus to the post-insertion site. After completing replication of a mtDNA strand, mediates 3' -> 5' exonucleolytic degradation at the nick to enable proper ligation (PubMed:11477093, PubMed:11897778, PubMed:15167897, PubMed:15917273, PubMed:19837034, PubMed:26095671, PubMed:9558343). Highly accurate due to high nucleotide selectivity and 3' -> 5' exonucleolytic proofreading. Proficiently corrects base substitutions, single-base additions and deletions in non-repetitive sequences and short repeats, but displays lower proofreading activity when replicating longer homopolymeric stretches. Exerts exonuclease activity toward single-stranded DNA and double-stranded DNA containing 3'-terminal mispairs. When a misincorporation occurs, transitions from replication to a pro-nucleolytic editing mode and removes the missincorporated nucleoside in the exonuclease active site. Proceeds via an SN2 nucleolytic mechanism in which Asp-198 catalyzes phosphodiester bond hydrolysis and Glu-200 stabilizes the leaving group. As a result the primer strand becomes one nucleotide shorter and is positioned in the post-insertion site, ready to resume DNA synthesis (PubMed:10827171, PubMed:11477094, PubMed:11504725, PubMed:37202477). Exerts 5'-deoxyribose phosphate (dRP) lyase activity and mediates repair-associated mtDNA synthesis (gap filling) in base-excision repair pathway. Catalyzes the release of the 5'-terminal 2-deoxyribose-5-phosphate sugar moiety from incised apurinic/apyrimidinic (AP) sites to produce a substrate for DNA ligase. The dRP lyase reaction does not require divalent metal ions and likely proceeds via a Schiff base intermediate in a beta-elimination reaction mechanism (PubMed:9770471).
Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant, 1
PEOA1
A disorder characterized by progressive weakness of ocular muscles and levator muscle of the upper eyelid. In a minority of cases, it is associated with skeletal myopathy, which predominantly involves axial or proximal muscles and which causes abnormal fatigability and even permanent muscle weakness. Ragged-red fibers and atrophy are found on muscle biopsy. A large proportion of chronic ophthalmoplegias are associated with other symptoms, leading to a multisystemic pattern of this disease. Additional symptoms are variable, and may include cataracts, hearing loss, sensory axonal neuropathy, ataxia, depression, hypogonadism, and parkinsonism.
None
The disease is caused by variants affecting the gene represented in this entry.
Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal recessive, 1
PEOB1
A severe form of progressive external ophthalmoplegia, a disorder characterized by progressive weakness of ocular muscles and levator muscle of the upper eyelid. It is clinically more heterogeneous than the autosomal dominant forms.
None
The disease is caused by variants affecting the gene represented in this entry.
Sensory ataxic neuropathy dysarthria and ophthalmoparesis
SANDO
A systemic disorder resulting from mitochondrial dysfunction associated with mitochondrial depletion in skeletal muscle and peripheral nerve tissue. The clinical triad of symptoms consists of sensory ataxic neuropathy, dysarthria, and ophthalmoparesis. However, the phenotype varies widely, even within the same family, and can also include myopathy, seizures, and hearing loss.
None
The disease is caused by variants affecting the gene represented in this entry.
Mitochondrial DNA depletion syndrome 4A
MTDPS4A
An autosomal recessive hepatocerebral syndrome due to mitochondrial dysfunction. The typical course of the disease includes severe developmental delay, intractable seizures, liver failure, and death in childhood. Refractory seizures, cortical blindness, progressive liver dysfunction, and acute liver failure after exposure to valproic acid are considered diagnostic features. The neuropathological hallmarks are neuronal loss, spongiform degeneration, and astrocytosis of the visual cortex. Liver biopsy results show steatosis, often progressing to cirrhosis.
None
The disease is caused by variants affecting the gene represented in this entry.
Mitochondrial DNA depletion syndrome 4B
MTDPS4B
An autosomal recessive progressive multisystem disorder due to mitochondrial dysfunction. It is clinically characterized by chronic gastrointestinal dysmotility and pseudo-obstruction, cachexia, progressive external ophthalmoplegia, axonal sensory ataxic neuropathy, and muscle weakness.
None
The disease is caused by variants affecting the gene represented in this entry.
Leigh syndrome
LS
An early-onset progressive neurodegenerative disorder characterized by the presence of focal, bilateral lesions in one or more areas of the central nervous system including the brainstem, thalamus, basal ganglia, cerebellum and spinal cord. Clinical features depend on which areas of the central nervous system are involved and include subacute onset of psychomotor retardation, hypotonia, ataxia, weakness, vision loss, eye movement abnormalities, seizures, and dysphagia.
None
The disease is caused by variants affecting the gene represented in this entry.
Spinocerebellar ataxia with epilepsy
SCAE
An autosomal recessive syndrome characterized by headaches and/or seizures manifesting in childhood or adolescence, cerebellar and sensory ataxia, dysarthria, and myoclonus manifesting in early adulthood. Neuropathological findings include spinocerebellar degeneration associated with cortical neuronal degeneration in advanced cases.
None
The disease is caused by variants affecting the gene represented in this entry.
Belongs to the DNA polymerase type-A family.
MDP1, POLG1, POLGA, POLG, DNA polymerase subunit gamma-1, 3'-5' exodeoxyribonuclease, 5'-deoxyribose-phosphate lyase, Mitochondrial DNA polymerase catalytic subunit, PolG-alpha
Proteins
Immunology & Infectious Disease
139562Da
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