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- PDB-9y4d: Strand displacement state II of Human mitochondrial DNA polymeras... -

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Basic information

Entry
Database: PDB / ID: 9y4d
TitleStrand displacement state II of Human mitochondrial DNA polymerase gamma ternary complex
Components
  • DNA (59-MER)
  • DNA polymerase subunit gamma-1
  • DNA polymerase subunit gamma-2, mitochondrial
KeywordsTRANSFERASE/DNA / DNA polymerase gamma / strand displacement / mitochondria / TRANSFERASE-DNA complex
Function / homology
Function and homology information


gamma DNA polymerase complex / mitochondrial chromosome / Strand-asynchronous mitochondrial DNA replication / mitochondrial DNA replication / positive regulation of DNA-directed DNA polymerase activity / DNA replication proofreading / single-stranded DNA 3'-5' DNA exonuclease activity / Hydrolases; Acting on ester bonds; Exodeoxyribonucleases producing 5'-phosphomonoesters / DNA metabolic process / DNA polymerase processivity factor activity ...gamma DNA polymerase complex / mitochondrial chromosome / Strand-asynchronous mitochondrial DNA replication / mitochondrial DNA replication / positive regulation of DNA-directed DNA polymerase activity / DNA replication proofreading / single-stranded DNA 3'-5' DNA exonuclease activity / Hydrolases; Acting on ester bonds; Exodeoxyribonucleases producing 5'-phosphomonoesters / DNA metabolic process / DNA polymerase processivity factor activity / Lyases; Carbon-oxygen lyases; Other carbon-oxygen lyases / mitochondrial nucleoid / 5'-deoxyribose-5-phosphate lyase activity / base-excision repair, gap-filling / DNA polymerase binding / 3'-5' exonuclease activity / Transcriptional activation of mitochondrial biogenesis / base-excision repair / DNA-templated DNA replication / protease binding / double-stranded DNA binding / DNA-directed DNA polymerase / in utero embryonic development / DNA-directed DNA polymerase activity / mitochondrial matrix / intracellular membrane-bounded organelle / chromatin binding / protein-containing complex / mitochondrion / DNA binding / identical protein binding / cytoplasm
Similarity search - Function
DNA-directed DNA-polymerase, family A, mitochondria / DNA mitochondrial polymerase, exonuclease domain / POLG2, C-terminal / : / DNA mitochondrial polymerase exonuclease domain / Glycyl-tRNA synthetase/DNA polymerase subunit gamma-2 / Anticodon-binding / Anticodon binding domain / Anticodon-binding domain superfamily / DNA-directed DNA polymerase, family A, conserved site ...DNA-directed DNA-polymerase, family A, mitochondria / DNA mitochondrial polymerase, exonuclease domain / POLG2, C-terminal / : / DNA mitochondrial polymerase exonuclease domain / Glycyl-tRNA synthetase/DNA polymerase subunit gamma-2 / Anticodon-binding / Anticodon binding domain / Anticodon-binding domain superfamily / DNA-directed DNA polymerase, family A, conserved site / DNA polymerase family A signature. / DNA-directed DNA polymerase, family A, palm domain / DNA polymerase A domain / Class II Aminoacyl-tRNA synthetase/Biotinyl protein ligase (BPL) and lipoyl protein ligase (LPL) / Ribonuclease H-like superfamily / DNA/RNA polymerase superfamily
Similarity search - Domain/homology
2'-DEOXYADENOSINE 5'-TRIPHOSPHATE / DNA / DNA (> 10) / DNA polymerase subunit gamma-1 / DNA polymerase subunit gamma-2
Similarity search - Component
Biological speciesHomo sapiens (human)
synthetic construct (others)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 2.94 Å
AuthorsPark, J. / Yin, Y.W.
Funding support United States, 2items
OrganizationGrant numberCountry
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID) United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS) United States
CitationJournal: bioRxiv / Year: 2026
Title: Pol γ possesses separate metal binding sites for polymerase and strand displacement functions.
Abstract: Accurate replication of mitochondrial genome (mtDNA) integrity, which is essential for cellular metabolism and energy supply, relies primarily on DNA polymerase gamma (Pol γ), Twinkle helicase, and ...Accurate replication of mitochondrial genome (mtDNA) integrity, which is essential for cellular metabolism and energy supply, relies primarily on DNA polymerase gamma (Pol γ), Twinkle helicase, and mitochondrial single-stranded DNA binding protein (mtSSB). Twinkle alone exhibits little helicase activity while reports indicate that Pol γ displays from modest to limited unwinding activity. This led us to dissect Pol γ strand displacement activity using structural, biochemical and in silico approaches. Here, we show that human Pol γ carries out robust strand displacement synthesis at physiological concentrations of divalent metal ions which reveals that distinct metal-binding sites can independently regulate DNA synthesis and unwinding activities. We further showed that Pol γ can displace RNA/DNA hybrid with comparable efficiency as DNA/DNA duplex, representing a key implication on RNA primer removal to preserve mtDNA integrity. Our cryo-electron microscopy structures of Pol γ complexed with a template containing downstream dsDNA and an incoming nucleotide revealed the structural mechanism for the strand displacement activity. We identified four conformational states that represent successive stages of DNA unwinding, accompanied by coordinated rearrangement of the downstream DNA and Pol γ elements that mediate strand displacement. This work establishes biochemical and structural mechanisms of Pol γ strand displacement activity, providing fundamental insight into human mitochondrial DNA replication and integrity.
History
DepositionSep 3, 2025Deposition site: RCSB / Processing site: RCSB
Revision 1.0Feb 18, 2026Provider: repository / Type: Initial release
Revision 1.0Feb 18, 2026Data content type: EM metadata / Data content type: EM metadata / Provider: repository / Type: Initial release
Revision 1.0Feb 18, 2026Data content type: FSC / Data content type: FSC / Provider: repository / Type: Initial release
Revision 1.0Feb 18, 2026Data content type: Half map / Part number: 1 / Data content type: Half map / Provider: repository / Type: Initial release
Revision 1.0Feb 18, 2026Data content type: Half map / Part number: 2 / Data content type: Half map / Provider: repository / Type: Initial release
Revision 1.0Feb 18, 2026Data content type: Image / Data content type: Image / Provider: repository / Type: Initial release
Revision 1.0Feb 18, 2026Data content type: Primary map / Data content type: Primary map / Provider: repository / Type: Initial release

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Structure visualization

Structure viewerMolecule:
MolmilJmol/JSmol

Downloads & links

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Assembly

Deposited unit
A: DNA polymerase subunit gamma-1
B: DNA polymerase subunit gamma-2, mitochondrial
C: DNA polymerase subunit gamma-2, mitochondrial
D: DNA (59-MER)
hetero molecules


Theoretical massNumber of molelcules
Total (without water)273,9496
Polymers273,4184
Non-polymers5312
Water00
1


  • Idetical with deposited unit
  • defined by author
  • Evidence: gel filtration, not applicable
TypeNameSymmetry operationNumber
identity operation1_5551

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Components

#1: Protein DNA polymerase subunit gamma-1 / Mitochondrial DNA polymerase catalytic subunit / PolG-alpha


Mass: 139628.672 Da / Num. of mol.: 1 / Mutation: D198A, E200A
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: POLG, MDP1, POLG1, POLGA
Production host: Insect cell expression vector pTIE1 (others)
References: UniProt: P54098, DNA-directed DNA polymerase
#2: Protein DNA polymerase subunit gamma-2, mitochondrial / DNA polymerase gamma accessory 55 kDa subunit / p55 / Mitochondrial DNA polymerase accessory ...DNA polymerase gamma accessory 55 kDa subunit / p55 / Mitochondrial DNA polymerase accessory subunit / MtPolB / PolG-beta


Mass: 54991.000 Da / Num. of mol.: 2
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: POLG2, MTPOLB / Production host: Escherichia coli BL21(DE3) (bacteria) / References: UniProt: Q9UHN1, DNA-directed DNA polymerase
#3: DNA chain DNA (59-MER)


Mass: 23807.139 Da / Num. of mol.: 1 / Source method: obtained synthetically / Source: (synth.) synthetic construct (others)
#4: Chemical ChemComp-CA / CALCIUM ION


Mass: 40.078 Da / Num. of mol.: 1 / Source method: obtained synthetically / Formula: Ca / Feature type: SUBJECT OF INVESTIGATION
#5: Chemical ChemComp-DTP / 2'-DEOXYADENOSINE 5'-TRIPHOSPHATE


Mass: 491.182 Da / Num. of mol.: 1 / Source method: obtained synthetically / Formula: C10H16N5O12P3 / Feature type: SUBJECT OF INVESTIGATION
Has ligand of interestY
Has protein modificationY

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Experimental details

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Experiment

ExperimentMethod: ELECTRON MICROSCOPY
EM experimentAggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction

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Sample preparation

ComponentName: Ternary complex of human mitochondrial DNA polymerase gamma bound to dumbbell DNA and dATP
Type: COMPLEX / Entity ID: #1-#3 / Source: MULTIPLE SOURCES
Source (natural)Organism: Homo sapiens (human)
Source (recombinant)Organism: Insect cell expression vector pTIE1 (others)
Buffer solutionpH: 7.5
SpecimenEmbedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
VitrificationCryogen name: ETHANE

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Electron microscopy imaging

Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
MicroscopyModel: TFS KRIOS
Electron gunElectron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM
Electron lensMode: BRIGHT FIELD / Nominal defocus max: 2500 nm / Nominal defocus min: 1000 nm
Image recordingElectron dose: 49.6 e/Å2 / Film or detector model: GATAN K3 BIOQUANTUM (6k x 4k)

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Processing

EM software
IDNameCategory
1cryoSPARCparticle selection
13cryoSPARC3D reconstruction
CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
3D reconstructionResolution: 2.94 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 146060 / Symmetry type: POINT

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