Affinage

MT-ATP8

ATP synthase F(0) complex subunit 8 · UniProt P03928

Length
68 aa
Mass
8.0 kDa
Annotated
2026-06-10
47 papers in source corpus 14 papers cited in narrative 13 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

MT-ATP8 encodes subunit 8 (A6L/chargerin II), an integral component of the membrane-embedded Fo domain of the mitochondrial ATP synthase (Complex V) that is required for energy transduction and oxidative ATP synthesis (PMID:6301689, PMID:3113438, PMID:3360805). The protein is the product of the URFA6L reading frame that overlaps ATP6, and was identified at the protein level by region-specific antibodies and direct peptide sequencing (PMID:6301689, PMID:3360805). Within Fo it adopts a defined topology—its short N-terminus exposed on the cytoplasmic face of the inner membrane while its C-terminal and charge-cluster regions are buried in the membrane domain—and is present in 1:1 stoichiometry with the holoenzyme (PMID:2531582, PMID:2139330). Loss of ATP8 through a homoplasmic nonsense mutation prevents assembly of the Complex V holoenzyme, leaving only ATP synthase subcomplexes with residual free F1-ATPase activity and abolishing normal Complex V function (PMID:17954552, PMID:21686774). ATP8 function is essential for mitochondrial integrity and bioenergetics in vivo: a pathogenic murine Atp8 mutation causes fragmented mitochondria, increased ROS, reduced ATP, and impaired glucose-stimulated insulin secretion in pancreatic β-cells (PMID:22919063). Allotopic nuclear expression of ATP8 restores ATP synthesis and viability, and co-expression with ATP6 fully reconstitutes Complex V assembly and ATP hydrolysis, with stable mitochondrial import and complex incorporation also achievable in transgenic mice (PMID:27596602, PMID:39659757). In yeast, translation of the bicistronic ATP8/ATP6 mRNA is gated by the inner-membrane repressor Smt1p and the activator Atp22p/Aep3p, coupling subunit synthesis to F1 availability (PMID:26823015, PMID:28404747).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 1983 High

    Established that the overlapping URFA6L reading frame is actually translated into a real mitochondrial protein, converting a predicted ORF into a bona fide gene product.

    Evidence Immunoprecipitation of mitochondrial translation products with N- and C-terminal anti-peptide antibodies plus tryptic fingerprinting in HeLa cells

    PMID:6301689

    Open questions at the time
    • Did not establish the protein's biochemical function
    • No localization within ATP synthase determined
  2. 1987 Medium

    Linked the URFA6L product (chargerin II) to active energy transduction, indicating it participates in coupling redox reactions to ATP synthesis rather than being a passive structural element.

    Evidence Antibody immunoinhibition of ATP–Pi exchange and reversed electron flow in energized vs non-energized rat liver mitoplasts

    PMID:3113438

    Open questions at the time
    • Conformational coupling inferred indirectly from antibody inhibition
    • Mechanism of redox-linked conformational change unresolved
    • Single lab
  3. 1988 High

    Confirmed chargerin II and the ATP8/URFA6L product are the same protein by direct chemistry, cementing the protein identity established immunologically.

    Evidence HPLC purification, lysylendopeptidase digestion, and peptide sequencing of rat liver chargerin II matched to the predicted URFA6L sequence

    PMID:3360805

    Open questions at the time
    • Did not map position within the synthase
    • Stoichiometry unknown at this point
  4. 1989 Medium

    Defined the membrane topology of ATP8 within Fo, showing an asymmetric arrangement with the N-terminus surface-exposed and the rest buried—key to understanding how it integrates into the complex.

    Evidence Region-specific antibody accessibility on submitochondrial particles and intact mitochondria before/after membrane disruption

    PMID:2531582

    Open questions at the time
    • No atomic structure
    • Functional consequence of buried charge cluster not tested
    • Single lab
  5. 1990 Medium

    Quantified ATP8 as a 1:1 stoichiometric subunit of the holoenzyme, establishing it as an obligate single-copy component rather than a substoichiometric accessory.

    Evidence Radioimmunoassay of purified rat liver ATP synthase and submitochondrial particles

    PMID:2139330

    Open questions at the time
    • Single immunochemical method
    • Did not address assembly role
  6. 2007 High

    Demonstrated that ATP8 is required for Complex V holoenzyme assembly in humans, providing the first causal disease link and showing its loss yields abortive subcomplexes.

    Evidence Transmitochondrial cybrids from a patient with homoplasmic m.8529G>A (p.Trp55X); BN-PAGE, in-gel ATP hydrolysis, and enzyme activity assays

    PMID:17954552 PMID:21686774

    Open questions at the time
    • Precise assembly step requiring ATP8 not defined
    • Why free F1 activity persists not mechanistically explained
  7. 2012 Medium

    Showed ATP8 is required for normal mitochondrial morphology, redox balance, and tissue-level bioenergetic output in vivo, connecting subunit dysfunction to physiological β-cell phenotypes.

    Evidence Conplastic mouse strain carrying m.7778G>T Atp8 mutation; mitochondrial ROS, ATP, morphology, and glucose-stimulated insulin secretion assays

    PMID:22919063

    Open questions at the time
    • Molecular mechanism linking subunit defect to ROS/morphology unclear
    • Single lab
    • Specific to one genetic background
  8. 2016 High

    Reconstituted Complex V function by nuclear allotopic expression, proving ATP8 can be imported and integrated, and revealing that full restoration of ATP hydrolysis requires co-expression with ATP6.

    Evidence Allotopic expression in ATP8-null patient cybrids; ATP synthesis/hydrolysis, oxygen consumption, and Complex V immunoblotting assays

    PMID:27596602

    Open questions at the time
    • Why ATP8 alone restores synthesis but not hydrolysis not fully resolved
    • Import efficiency limits not defined
  9. 2016 Medium

    Identified a mitochondrial translational control circuit coupling ATP8/ATP6 synthesis to F1 availability via an inner-membrane repressor, explaining how subunit production is matched to assembly demand.

    Evidence Affinity purification of tagged Smt1p with RT-PCR detection of associated ATP8/ATP6 mRNA and genetic analysis of smt1 mutants in yeast

    PMID:26823015

    Open questions at the time
    • F1-mediated displacement of Smt1p is a model, not directly demonstrated
    • No human ortholog identified
    • Yeast model
  10. 2017 Medium

    Identified Aep3p as an ATP8-specific translational activator, sharpening the picture of dedicated factors controlling subunit 8 synthesis.

    Evidence [35S]methionine pulse labeling in temperature-sensitive aep3 yeast mutants with Northern blotting and allotopic rescue

    PMID:28404747

    Open questions at the time
    • Direct mRNA binding by Aep3p not shown
    • Human equivalent unknown
    • Yeast model
  11. 2023 Medium

    Used yeast modeling and structural analysis to discriminate benign from consequential MT-ATP8 variants, refining understanding of which residues matter for the membrane domain contribution.

    Evidence Yeast mutagenesis of conserved subunit 8 positions with ATP synthase activity assays and structural/in silico modeling

    PMID:37340059

    Open questions at the time
    • In silico structural component not experimentally validated
    • Variant effects in human cells not tested for all positions
  12. 2024 High

    Demonstrated stable in vivo allotopic delivery of ATP8 in transgenic mice with successful import and complex incorporation, advancing a gene-therapy strategy without overt toxicity.

    Evidence Transgenic C57BL/6J-mtFVB mice expressing MTS-tagged ATP8 from ROSA26; Western blotting, mitochondrial fractionation, activity assays, metabolic/behavioral testing

    PMID:39659757

    Open questions at the time
    • Rescue of an ATP8-null disease phenotype not tested in this model
    • Long-term and disease-context efficacy undetermined

Open questions

Synthesis pass · forward-looking unresolved questions
  • How ATP8 nucleates or stabilizes Complex V assembly at atomic resolution, and whether the yeast Smt1p/Aep3p translational control circuit has functional human counterparts, remain open.
  • No human structural model of ATP8 within assembled Fo from the corpus
  • No human translational regulators identified
  • Assembly intermediate requiring ATP8 not defined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 3
Localization
GO:0005739 mitochondrion 3
Pathway
R-HSA-1430728 Metabolism 3
Partners
AEP3PATP22PMT-ATP6SMT1P
Complex memberships
mitochondrial ATP synthase (Complex V) Fo domain

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1983 The unidentified reading frame A6L (URFA6L), overlapping the ATPase 6 gene, is expressed as a protein (protein #25) in human mitochondria. Antibodies against synthetic peptides corresponding to both the NH2-terminal and COOH-terminal sequences of the predicted A6L polypeptide immunoprecipitated a specific mitochondrial translation product from HeLa cells, and trypsin fingerprinting was consistent with the identification. Immunoprecipitation with anti-synthetic-peptide antibodies; tryptic fingerprinting of mitochondrial translation products Cell High 6301689
1987 Chargerin II (the URFA6L / ATP8 product) is required for energy transduction in rat liver mitochondria: antibody against chargerin II inhibited ATP–Pi exchange and reversed electron flow from succinate to NAD in mitoplasts, with greater inhibition in the energized state, indicating a conformational change coupled to redox reactions. Immunoinhibition assays in energized and non-energized mitoplasts; ATP–Pi exchange and reversed electron flow measurements Biochemical and biophysical research communications Medium 3113438
1988 Chargerin II purified from rat liver mitochondria was identified as the product of URFA6L (ATP8). Peptide sequencing of HPLC-purified chargerin II yielded 12 amino acids highly homologous to the predicted C-terminal sequence of the URFA6L polypeptide, and amino acid composition matched the predicted protein. HPLC purification from mitochondria; lysylendopeptidase digestion; peptide sequencing; amino acid composition analysis; Western blotting The Journal of biological chemistry High 3360805
1989 The orientation of chargerin II (ATP8/A6L) within the Fo sector of rat liver mitochondrial ATP synthase was determined: its N-terminal ~8 residues are exposed on the cytoplasmic (C-side) surface of Fo, while the C-terminal and charge-cluster regions are buried within Fo. Antibodies against N-terminal and C-terminal peptides applied to submitochondrial particles and intact mitochondria; immunoreactivity probed before and after membrane disruption Biochemical and biophysical research communications Medium 2531582
1990 Chargerin II (ATP8) is present in the H+-ATP synthase of rat liver mitochondria in a 1:1 molar stoichiometry relative to the holoenzyme, as determined by radioimmunoassay of purified ATP synthase and submitochondrial particles. Radioimmunoassay of purified ATP synthase and submitochondrial particles Biochemical and biophysical research communications Medium 2139330
2004 Bioinformatic sequence analysis of A6L (ATP8) across vertebrates identified a conserved aromatic residue adjacent to the N-terminal MPQL motif (MPQLX4Ar motif), proposed as functionally important for the role of A6L in the Fo membrane domain of ATP synthase. Comparative sequence alignment and homology searching Journal of bioenergetics and biomembranes Low 15692730
2007 A homoplasmic nonsense mutation m.8529G>A (p.Trp55X) in the mitochondrial ATP8 gene causes loss of ATP8 protein, failure to assemble Complex V holoenzyme, reduced Complex V activity, and accumulation of ATP synthase subcomplexes with residual free F1-ATPase activity. Demonstrated in patient fibroblasts, muscle, and transmitochondrial cybrid clones. Transmitochondrial cybrid generation; Blue Native PAGE with immunoblotting; in-gel ATP hydrolysis activity assay; enzyme activity measurements in fibroblasts and muscle Journal of medical genetics High 17954552 21686774
2012 A point mutation in the murine Atp8 gene (m.7778G>T in B6-mtFVB mice) causes fragmented mitochondrial morphology, increased mitochondrial ROS generation, reduced cellular ATP levels, impaired glucose-induced insulin secretion in pancreatic islets, and higher susceptibility to palmitate stress, establishing ATP8 as required for normal β-cell mitochondrial function and secretory responsiveness. Conplastic mouse strain comparison; mitochondrial ROS measurement; ATP level assay; glucose-stimulated insulin secretion assay; morphological analysis of isolated islets Endocrinology Medium 22919063
2016 Nuclear (allotopic) expression of ATP8 alone (with a mitochondrial targeting sequence) in ATP8-null cybrid cells restored viability on Krebs cycle substrates and ATP synthesis, but failed to restore ATP hydrolysis activity or inhibitor sensitivity. Co-expression of both ATP8 and ATP6 from the nucleus led to stable protein import, integration into Complex V, restored ATP hydrolysis/synthesis, oxygen consumption, and Complex V re-assembly. Allotopic expression in patient cybrid cells; ATP synthesis/hydrolysis assays; oxygen consumption measurement; Complex V immunoblotting; glycolytic/viability assays Nucleic acids research High 27596602
2016 In yeast mitochondria, translation of the bicistronic ATP8/ATP6 mRNA is repressed by Smt1p, an inner membrane protein that forms a complex with the ATP8/ATP6 mRNA (and also with COB mRNA). F1 ATPase availability is proposed to displace Smt1p and allow the Atp22p activator to promote translation, coupling ATP8 and ATP6 synthesis to F1 assembly. Affinity purification of tagged Smt1p followed by RT-PCR with gene-specific primers to detect associated mRNAs; genetic analysis of smt1 mutants; [35S]methionine incorporation assays Molecular biology of the cell Medium 26823015
2017 In yeast mitochondria, Aep3p functions as a translation activator specifically for ATP8: temperature-sensitive aep3 mutants selectively block [35S]methionine incorporation into Atp8p at non-permissive temperature without affecting transcription or mRNA processing, and the defect is partially rescued by allotopic ATP8 in high-copy plasmid. [35S]methionine pulse labeling in yeast mitochondria; Northern blotting; allotopic rescue assay; temperature-sensitive mutant analysis Molecular biology of the cell Medium 28404747
2023 In yeast, the equivalent of the human MT-ATP8 m.8403T>C variant (changing a conserved residue in subunit 8) is not detrimental to ATP synthase function. Structural analysis of this and five other MT-ATP8 variants provides evidence that subunit 8 contributes to the membrane domain of ATP synthase and that substitutions at specific positions can have structural consequences for the complex. Yeast S. cerevisiae mutagenesis model; biochemical assays of mitochondrial ATP synthase function; structural modeling/in silico analysis Scientific reports Medium 37340059
2024 Allotopic expression of ATP8 (re-engineered with a mitochondrial targeting sequence and expressed from the ROSA26 nuclear locus) in transgenic mice (C57BL/6J-mtFVB background) produced constitutive protein expression across all tested tissues, successful mitochondrial import, and incorporation into ATP synthase with activity comparable to non-transgenic controls, without negative effects on mitochondrial function, metabolism, or behavior. Transgenic mouse generation; Western blotting; mitochondrial fractionation; ATP synthase activity assay; metabolic/behavioral testing Molecular therapy. Methods & clinical development High 39659757

Source papers

Stage 0 corpus · 47 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2001 Trichinella spiralis mtDNA: a nematode mitochondrial genome that encodes a putative ATP8 and normally structured tRNAS and has a gene arrangement relatable to those of coelomate metazoans. Genetics 174 11156984
2007 A novel mitochondrial ATP8 gene mutation in a patient with apical hypertrophic cardiomyopathy and neuropathy. Journal of medical genetics 87 17954552
2009 The complete mitochondrial genome of Evania appendigaster (Hymenoptera: Evaniidae) has low A+T content and a long intergenic spacer between atp8 and atp6. Molecular biology reports 82 19655273
1983 Antibodies against synthetic peptides reveal that the unidentified reading frame A6L, overlapping the ATPase 6 gene, is expressed in human mitochondria. Cell 54 6301689
2012 The mitochondrial Atp8 mutation induces mitochondrial ROS generation, secretory dysfunction, and β-cell mass adaptation in conplastic B6-mtFVB mice. Endocrinology 47 22919063
2010 Comparative genomics of marine mussels (Mytilus spp.) gender associated mtDNA: rapidly evolving atp8. Journal of molecular evolution 45 20931184
2016 Stable nuclear expression of ATP8 and ATP6 genes rescues a mtDNA Complex V null mutant. Nucleic acids research 43 27596602
2013 The complete mitochondrial genomes of two rice planthoppers, Nilaparvata lugens and Laodelphax striatellus: conserved genome rearrangement in Delphacidae and discovery of new characteristics of atp8 and tRNA genes. BMC genomics 43 23799924
2007 The complete mitochondrial genomes of needle corals, Seriatopora spp. (Scleractinia: Pocilloporidae): an idiosyncratic atp8, duplicated trnW gene, and hypervariable regions used to determine species phylogenies and recently diverged populations. Molecular phylogenetics and evolution 42 18042404
2004 Complete mtDNA of Ciona intestinalis reveals extensive gene rearrangement and the presence of an atp8 and an extra trnM gene in ascidians. Journal of molecular evolution 41 15114417
2017 Atp8 is in the ground pattern of flatworm mitochondrial genomes. BMC genomics 38 28549457
2014 Novel mitochondrial mutations in the ATP6 and ATP8 genes in patients with breast cancer. Molecular medicine reports 34 25110199
2010 Complete mtDNA of Meretrix lusoria (Bivalvia: Veneridae) reveals the presence of an atp8 gene, length variation and heteroplasmy in the control region. Comparative biochemistry and physiology. Part D, Genomics & proteomics 31 20797924
1988 A hydrophobic protein, chargerin II, purified from rat liver mitochondria is encoded in the unidentified reading frame A6L of mitochondrial DNA. The Journal of biological chemistry 24 3360805
2017 Genetic diversity of ATP8 and ATP6 genes is associated with high-altitude adaptation in yak. Mitochondrial DNA. Part A, DNA mapping, sequencing, and analysis 22 28306370
2016 Regulation of mitochondrial translation of the ATP8/ATP6 mRNA by Smt1p. Molecular biology of the cell 21 26823015
2002 Impact of 4-chlorophenol contamination and/or inoculation with the 4-chlorophenol-degrading strain, Arthrobacter chlorophenolicus A6L, on soil bacterial community structure. FEMS microbiology ecology 21 19709298
2006 Vaccinia virus A6L encodes a virion core protein required for formation of mature virion. Journal of virology 20 17108027
2003 Sequence polymorphisms within the human mitochondrial genes MTATP6, MTATP8 and MTND4. International journal of legal medicine 20 12734709
2022 Mitochondrial genomic analyses provide new insights into the "missing" atp8 and adaptive evolution of Mytilidae. BMC genomics 19 36324074
2020 The first mitochondrial genomes of endosymbiotic rhabdocoels illustrate evolutionary relaxation of atp8 and genome plasticity in flatworms. International journal of biological macromolecules 19 32512097
1989 Orientation of chargerin II (A6L) in the ATP synthase of rat liver mitochondria determined with antibodies against peptides of the protein. Biochemical and biophysical research communications 18 2531582
1990 Stoichiometry of chargerin II (A6L) in the H(+)-ATP synthase of rat liver mitochondria. Biochemical and biophysical research communications 17 2139330
2019 A novel variant m.8561C>T in the overlapping region of MT-ATP6 and MT-ATP8 in a child with early-onset severe neurological signs. Molecular genetics and metabolism reports 16 31788426
2017 Aep3p-dependent translation of yeast mitochondrial ATP8. Molecular biology of the cell 16 28404747
2010 Mutation of mitochondrial ATP8 gene improves hepatic energy status in a murine model of acute endotoxemic liver failure. Life sciences 16 21167184
1987 Immunochemical study of role of chargerin II, a product of URFA6L of mitochondrial DNA in energy transduction of rat liver mitochondria. Biochemical and biophysical research communications 16 3113438
2018 Actively transcribed and expressed atp8 gene in Mytilus edulis mussels. PeerJ 15 29900071
2018 Reversible Valproate-Induced Subacute Encephalopathy Associated With a MT-ATP8 Variant in the Mitochondrial Genome. Frontiers in neurology 14 30214424
2025 Lipid nanoparticle delivery of the CRISPR/Cas9 system directly into the mitochondria of cells carrying m.7778G>T mutation in MtDNA (mt-Atp8). Scientific reports 11 40537532
2013 A novel ATP8 gene mutation in an infant with tetralogy of Fallot. Cardiology in the young 11 23735083
2009 A novel mitochondrial ATP8 gene mutation in a patient with apical hypertrophic cardiomyopathy and neuropathy. BMJ case reports 11 21686774
2004 Mitochondrial ATP synthase: a bioinformatic approach reveals new insights about the roles of supernumerary subunits g and A6L. Journal of bioenergetics and biomembranes 11 15692730
2025 Natural History of Patients With Mitochondrial ATPase Deficiency Due to Pathogenic Variants of MT-ATP6 and MT-ATP8. Neurology 10 40112238
2023 Two-Fold ND5 Genes, Three-Fold Control Regions, lncRNA, and the "Missing" ATP8 Found in the Mitogenomes of Polypedates megacephalus (Rhacophridae: Polypedates). Animals : an open access journal from MDPI 10 37760257
2013 The complete mitochondrial genome of the clam Mactra veneriformis (Bivalvia: Mactridae): has a unique non-coding region, missing atp8 and typical tRNA Ser. Mitochondrial DNA 7 23520998
2009 [Comparison on mitochondrial ATP6, ATP8 and Cyt b genes between Chinese Tibetans in three different zones: detecting the signature of natural selection on mitochondrial genome]. Yi chuan = Hereditas 6 19273422
2021 Genetic differentiation of Indian dromedary and Bactrian camel populations based on mitochondrial ATP8 and ATP6 genes. Animal biotechnology 5 34678134
2006 Petaloid-type cms in carrot is not associated with expression of atp8 (orfB). TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik 5 16550397
2023 Analysis of MT-ATP8 gene variants reported in patients by modeling in silico and in yeast model organism. Scientific reports 4 37340059
2022 A lack of a definite correlation between male sub-fertility and single nucleotide polymorphisms in sperm mitochondrial genes MT-CO3, MT-ATP6 and MT-ATP8. Molecular biology reports 3 36066780
2021 The complete mitogenome of the inarticulate brachiopod Glottidia pyramidata reveals insights into gene order variation, deviant ATP8 and mtORFans in the Brachiopoda. Mitochondrial DNA. Part B, Resources 3 34435125
2016 Polymorphism in Murine mtATP8 Gene Correlates with Decreased Reactive Oxygen Species in Aging Hematopoietic Cells. In vivo (Athens, Greece) 2 27815458
2010 Genetic variations and sequences analysis of MTATP6 and MTATP8 genes among different Chinese pig breeds. Journal of animal breeding and genetics = Zeitschrift fur Tierzuchtung und Zuchtungsbiologie 2 21077971
2024 Exogenous expression of ATP8, a mitochondrial encoded protein, from the nucleus in vivo. Molecular therapy. Methods & clinical development 1 39659757
2018 Sequence analysis of the ATP synthase of subunits (ATP8 and ATP6) genes of mitochondrial DNA genome from Ailuropoda melanoleuca. Mitochondrial DNA. Part B, Resources 1 33474428
1992 Structure of the mitochondrial URFA6L gene and tRNA(Lys) gene from CARP. Science in China. Series B, Chemistry, life sciences & earth sciences 1 1580999

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