View source for 12sl


==Structure of a Strand-Displacement Complex of Human Mitochondrial DNA Polymerase Gamma==
<StructureSection load='12sl' size='340' side='right'caption='[[12sl]], [[Resolution|resolution]] 2.93&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[12sl]] is a 5 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] and [https://en.wikipedia.org/wiki/Synthetic_construct Synthetic construct]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=12SL OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=12SL FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Electron Microscopy, [[Resolution|Resolution]] 2.93&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=2DT:3-DEOXYTHYMIDINE-5-MONOPHOSPHATE'>2DT</scene>, <scene name='pdbligand=DTP:2-DEOXYADENOSINE+5-TRIPHOSPHATE'>DTP</scene>, <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=12sl FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=12sl OCA], [https://pdbe.org/12sl PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=12sl RCSB], [https://www.ebi.ac.uk/pdbsum/12sl PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=12sl ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/DPOG1_HUMAN DPOG1_HUMAN] Defects in POLG are the cause of progressive external ophthalmoplegia with mitochondrial DNA deletions autosomal dominant type 1 (PEOA1) [MIM:[https://omim.org/entry/157640 157640]. Progressive external ophthalmoplegia is 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.<ref>PMID:12210792</ref> <ref>PMID:11897778</ref> <ref>PMID:15534189</ref> <ref>PMID:15351195</ref> <ref>PMID:17420318</ref> <ref>PMID:18575922</ref>   Defects in POLG are a cause of progressive external ophthalmoplegia with mitochondrial DNA deletions autosomal recessive (PEOB) [MIM:[https://omim.org/entry/258450 258450]. PEOB is a severe form of progressive external ophthalmoplegia. It is clinically more heterogeneous than the autosomal dominant forms. Can be more severe.<ref>PMID:15351195</ref> <ref>PMID:11431686</ref> <ref>PMID:12975295</ref> <ref>PMID:12872260</ref> <ref>PMID:14635118</ref> <ref>PMID:12707443</ref> <ref>PMID:12565911</ref> <ref>PMID:15349879</ref> <ref>PMID:15477547</ref> <ref>PMID:15917273</ref> <ref>PMID:16634032</ref> <ref>PMID:16401742</ref> <ref>PMID:16621917</ref> <ref>PMID:16639411</ref>   Defects in POLG are a cause of sensory ataxic neuropathy dysarthria and ophthalmoparesis (SANDO) [MIM:[https://omim.org/entry/607459 607459]. SANDO is 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. An atypical form of the disease is characterized by headaches and/or seizures manifesting in childhood or adolescence, followed by development of cerebellar and sensory ataxia, dysarthria, progressive external ophthalmoplegia, and myoclonus in early adulthood.<ref>PMID:12565911</ref> <ref>PMID:15477547</ref> <ref>PMID:15917273</ref> <ref>PMID:16621917</ref> <ref>PMID:16639411</ref> <ref>PMID:14745080</ref> <ref>PMID:16080118</ref> <ref>PMID:15824347</ref> <ref>PMID:16919951</ref>   Defects in POLG are the cause of mitochondrial DNA depletion syndrome type 4A (MTDPS4A) [MIM:[https://omim.org/entry/203700 203700]; also called Alpers diffuse degeneration of cerebral gray matter with hepatic cirrhosis. An autosomal recessive hepatocerebral syndrome. 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.<ref>PMID:16621917</ref> <ref>PMID:16639411</ref> <ref>PMID:15122711</ref> <ref>PMID:15929042</ref> <ref>PMID:15689359</ref> <ref>PMID:18828154</ref>   Defects in POLG are the cause of mitochondrial DNA depletion syndrome type 4B (MTDPS4B) [MIM:[https://omim.org/entry/613662 613662]; also known as mitochondrial DNA depletion syndrome 4B MNGIE type or mitochondrial neurogastrointestinal encephalopathy syndrome POLG-related. An autosomal recessive progressive multisystem disorder clinically characterized by chronic gastrointestinal dysmotility and pseudo-obstruction, cachexia, progressive external ophthalmoplegia, axonal sensory ataxic neuropathy, and muscle weakness.  Defects in POLG are a cause of Leigh syndrome (LS) [MIM:[https://omim.org/entry/256000 256000]. LS is a severe neurological disorder characterized by bilaterally symmetrical necrotic lesions in subcortical brain regions.<ref>PMID:18828154</ref> 
== Function ==
[https://www.uniprot.org/uniprot/DPOG1_HUMAN DPOG1_HUMAN] Involved in the replication of mitochondrial DNA. Associates with mitochondrial DNA.
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Defects in human mitochondrial DNA (mtDNA) replication can lead to somatic mutations associated with a range of devastating mitochondrial diseases. However, the molecular mechanisms governing the earliest steps of mtDNA replication and their fidelity remain poorly understood. Here, we found that DNA polymerase gamma (Polgamma) forms stable complexes with RNA-DNA primer-template substrates, exhibiting greater stability and lower misincorporation than on DNA-primed substrates. Structural analysis revealed that Polgamma interacts with the 2'-OH groups of ribose within the first four nucleotides of the primer, explaining the stability of complexes that utilize RNA primers. Although Polgamma requires TWINKLE to extend RNA primers, its intrinsic strand-displacement activity allows it to extend DNA primers independently. Structural data further show that the strand-separation mechanism in human Polgamma is distinct from that of its yeast paralog, Mip1, and involves previously unresolved elements-the catcher and a GP loop in the exonuclease domain-that support intrinsic strand-displacement synthesis by Polgamma. Structure-guided mutagenesis of elements involved in strand separation supports these structural observations. Together, our study provides mechanistic insight into mtDNA replication initiation and strand separation and has implications for understanding the molecular basis of mitochondrial disease.

Molecular and structural basis for replication initiation and strand separation by human mitochondrial DNA polymerase gamma.,Sokolova V, Buchel G, Strock S, Nayak AR, Temiakov D Nucleic Acids Res. 2026 Sep 22;54(18):gkag925. doi: 10.1093/nar/gkag925. PMID:42788360<ref>PMID:42788360</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 12sl" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Synthetic construct]]
[[Category: Nayak AR]]
[[Category: Sokolova VO]]
[[Category: Temiakov D]]