Affinage

GTPBP3

5-taurinomethyluridine-[tRNA] synthase subunit GTPB3, mitochondrial · UniProt Q969Y2

Length
492 aa
Mass
52.1 kDa
Annotated
2026-06-10
20 papers in source corpus 14 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: tie faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GTPBP3 is a mitochondria-localized GTPase that, together with MTO1, catalyzes formation of the 5-taurinomethyluridine (τm5U) modification at the wobble position (U34) of five mitochondrial tRNAs, a modification required for accurate mitochondrial translation (PMID:25434004, PMID:30916346). Biochemically, GTPBP3 binds and hydrolyzes GTP, and its catalytic competence depends on the intact mature enzyme: the isolated G domain and N-terminal truncations hydrolyze GTP poorly, while an N-terminal domain mediates a potassium-independent dimerization linked to assembly of the one-carbon-donor binding site for tRNA modification (PMID:18852288, PMID:33619562). Loss of GTPBP3 function—by knockdown, knockout, or pathogenic mutation—causes mt-tRNA hypomodification, impaired mitochondrial protein synthesis, and combined respiratory chain deficiency, with elevated mitochondrial ROS and disrupted membrane potential (PMID:18852288, PMID:25434004, PMID:30916346). These defects trigger AMPK-dependent retrograde signaling and metabolic reprogramming, including down-regulation of Complex I assembly factors and the mitochondrial pyruvate carrier alongside up-regulation of glycolysis and fatty acid oxidation (PMID:26642043, PMID:29348686). In endothelial cells, GTPBP3 loss elevates mitochondrial ROS that activates an HRI–ATF4–Sestrin2 axis and suppresses mTORC1 to disrupt angiogenesis (PMID:40533669). GTPBP3 mutations cause combined oxidative phosphorylation deficiency (COXPD23) with mitochondrial translation defects and combined respiratory chain deficiencies, and knock-in mouse models reproduce embryonic lethality and cardiac/muscular dysfunction that is reversible by AAV-mediated GTPBP3 re-expression (PMID:25434004, PMID:41957021, PMID:38515655).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 2003 Medium

    Established the subcellular address of the protein, placing GTPBP3 in mitochondria and framing its function within mitochondrial biology.

    Evidence Immunofluorescence of GTPBP3-GFP fusion in NIH3T3 cells

    PMID:14680828

    Open questions at the time
    • Single GFP-fusion method without endogenous protein validation
    • Does not define molecular activity
  2. 2004 Medium

    Placed GTPBP3 as a nuclear modifier gene whose genetic variation modulates the penetrance of pathogenic mtDNA mutations, connecting it to human mitochondrial disease before any enzymatic mechanism was known.

    Evidence Linkage and disequilibrium analysis in A1555G deafness families across multiple cohorts

    PMID:15542390

    Open questions at the time
    • Genetic association only, no biochemical experiment
    • Does not identify the molecular function modulating the phenotype
  3. 2008 High

    Defined the core biochemistry: GTPBP3 binds and slowly hydrolyzes GTP, and unlike its bacterial homologue uses a potassium-independent N-terminal dimerization rather than K+-stimulated G-domain dimerization, and linked it functionally to mitochondrial respiration and translation.

    Evidence In vitro GTPase/nucleotide-binding assays with domain truncations, plus siRNA knockdown with respiration and protein-synthesis readouts

    PMID:18852288

    Open questions at the time
    • tRNA substrates not yet identified at this stage
    • Catalytic mechanism of the modification reaction undefined
  4. 2014 High

    Demonstrated that GTPBP3 mutations cause human disease via a severe mitochondrial translation defect and combined respiratory chain deficiency, tying loss of function to the τm5U wobble modification on five mt-tRNAs.

    Evidence Exome/candidate gene sequencing in 11 patients with respiratory chain enzyme and translation assays in muscle

    PMID:25434004

    Open questions at the time
    • Direct demonstration of tRNA hypomodification not shown in patient material
    • Genotype-phenotype variability not resolved
  5. 2015 High

    Showed that GTPBP3 silencing causes measurable mt-tRNA hypomodification and selectively impairs Complex I, and connected the bioenergetic defect to AMPK-dependent retrograde signaling that reprograms nuclear gene expression.

    Evidence Stable shRNA silencing with angiogenin-digestion tRNA assay, BN-PAGE, AMPK activation, and target gene expression analysis

    PMID:26642043

    Open questions at the time
    • Mechanism linking AMPK to specific assembly-factor down-regulation not dissected
    • Direct catalytic role in modification not reconstituted
  6. 2016 Medium

    Provided in vivo loss-of-function and cross-species evidence that GTPBP3 function is conserved and required for mitochondrial ATP generation and embryonic development.

    Evidence Zebrafish morpholino knockdown with mRNA rescue, GFP localization, and yeast complementation of mss1/gtpbp3 mutants

    PMID:27184967

    Open questions at the time
    • Morpholino off-target effects not fully excluded
    • tRNA modification status not directly measured
  7. 2017 Medium

    Revealed that GTPBP3 expression is itself tuned post-transcriptionally by ROS/Ca2+-induced miRNAs, integrating the modification enzyme into a retrograde feedback loop responsive to mitochondrial stress.

    Evidence Cybrid disease models with miRNA profiling, overexpression/antagonist transfection, and OXPHOS readouts

    PMID:28740091

    Open questions at the time
    • Direct miRNA-GTPBP3 binding not demonstrated
    • Physiological relevance beyond cybrid models unclear
  8. 2018 Medium

    Distinguished GTPBP3-specific metabolic consequences from those of MTO1, indicating a role beyond the shared modification reaction.

    Evidence Comparative shRNA silencing versus patient MTO1 fibroblasts with metabolic flux and pathway markers

    PMID:29348686

    Open questions at the time
    • Molecular basis of the MTO1-independent function not identified
    • Single lab comparison
  9. 2019 High

    Provided direct in vivo proof that GTPBP3 catalyzes τm5U on specific mt-tRNAs, defined the structural and functional consequences for tRNA folding and aminoacylation, and linked the defect to hypertrophic cardiomyopathy.

    Evidence CRISPR/Cas9 knockout zebrafish with tRNA modification, S1-nuclease, aminoacylation, translation, respiratory complex, and cardiac phenotyping

    PMID:30916346

    Open questions at the time
    • Paradoxical aminoacylation increase mechanistically unexplained
    • Catalytic mechanism not reconstituted in vitro
  10. 2021 High

    Established that catalytic GTPase competence requires the intact mature enzyme and that pathogenic mutations act by altering localization, structure, or activity, while identifying a cytoplasmic isoform hinting at non-canonical function.

    Evidence In vitro GTP hydrolysis with purified domain mutants, Km/kcat determination, in vivo tRNA modification, and localization microscopy

    PMID:33619562

    Open questions at the time
    • Function of the cytoplasmic isoform undefined
    • Coupling of GTP hydrolysis to modification chemistry not resolved
  11. 2024 Medium

    Connected GTPBP3 to ER stress signaling and confirmed a loss-of-function splicing mechanism for disease, broadening the cellular stress-response context.

    Evidence siRNA knockdown in R28 cells with UPR modulators and an AOH mouse taurine model; minigene splicing assay for a COXPD23 splice variant

    PMID:38515655 PMID:39710098

    Open questions at the time
    • Mechanism linking GTPBP3 loss to UPR not defined
    • Reciprocal GTPBP3-UPR regulation correlative
  12. 2025 High

    Defined a tissue-specific consequence of GTPBP3 loss in endothelial cells, mapping a mtROS-driven HRI–ATF4–Sestrin2–mTORC1 axis that suppresses angiogenesis.

    Evidence Two conditional EC-specific knockout mouse models with retinal/ischemia angiogenesis assays, pathway Westerns, and MitoQ rescue

    PMID:40533669

    Open questions at the time
    • Whether the angiogenic defect derives solely from tRNA hypomodification not isolated
    • Upstream sensing of mtROS by HRI not detailed
  13. 2026 High

    Demonstrated that specific pathogenic mutations cause aggregation and degradation that impair GTPase activity and translation, and showed gene-replacement therapy reverses the phenotype in cells and mice.

    Evidence Patient cells and CRISPR knock-in mice with in vitro GTPase, tRNA modification, respirometry, aggregation assays, and AAV rescue

    PMID:41957021

    Open questions at the time
    • Long-term durability and safety of AAV rescue not assessed
    • Mechanism of mutation-induced aggregation not structurally resolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • The function of the cytoplasmic GTPBP3 isoform and the molecular basis of GTPBP3's MTO1-independent metabolic role remain open.
  • Cytoplasmic isoform substrate/activity unknown
  • MTO1-independent function unmapped
  • Step-by-step coupling of GTP hydrolysis to τm5U chemistry undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003924 GTPase activity 3 GO:0140098 catalytic activity, acting on RNA 3 GO:0003723 RNA binding 2
Localization
GO:0005739 mitochondrion 2 GO:0005829 cytosol 1
Pathway
R-HSA-1430728 Metabolism 2 R-HSA-392499 Metabolism of proteins 2 R-HSA-8953854 Metabolism of RNA 2
Partners
MTO1

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2008 Human GTPBP3 protein exhibits moderate affinity for guanine nucleotides and hydrolyzes GTP at a ~100-fold lower rate than its bacterial homologue MnmE. Unlike MnmE, potassium-induced dimerization of the G domain does NOT stimulate GTPase activity in GTPBP3. Instead, the N-terminal domain mediates a potassium-independent dimerization conserved across the protein family, likely related to construction of the binding site for the one-carbon-unit donor in tRNA modification. In vitro GTPase assays, guanine nucleotide binding assays, domain truncation/mutagenesis, biochemical characterization of dimerization Molecular and cellular biology High 18852288
2008 Partial inactivation of GTPBP3 by siRNA reduces oxygen consumption, ATP production, and mitochondrial protein synthesis, while mitochondria display defective membrane potential and increased superoxide levels, establishing a functional link between GTPBP3 and mitochondrial respiration and translation. siRNA knockdown with mitochondrial respiration assays (oxygen consumption, ATP production), membrane potential measurement, ROS detection, mitochondrial protein synthesis assay Molecular and cellular biology High 18852288
2003 Mouse GTPBP3 protein localizes to mitochondria, as demonstrated by immunofluorescence of NIH3T3 cells expressing GTPBP3-GFP fusion protein. Immunofluorescence microscopy of GFP-fusion protein in NIH3T3 cells Biochemical and biophysical research communications Medium 14680828
2014 Mutations in GTPBP3 cause a severe mitochondrial translation defect associated with combined respiratory chain complex deficiencies in skeletal muscle, consistent with GTPBP3's role in catalyzing formation of 5-taurinomethyluridine (τm5U) at the wobble position of five mitochondrial tRNAs (mt-tRNAGlu, mt-tRNAGln, mt-tRNALys, mt-tRNATrp, mt-tRNALeu(UUR)). Whole-exome sequencing, candidate gene sequencing in 11 patients; respiratory chain enzyme activity assays in skeletal muscle; mitochondrial translation assays American journal of human genetics High 25434004
2015 Stable silencing of GTPBP3 causes mt-tRNA hypomodification (increased sensitivity to angiogenin digestion), reduces Complex I steady-state levels and activity by ~50%, decreases cellular ATP, increases Complex V ATPase activity, elevates UCP2 levels, and triggers AMPK-dependent retrograde signaling that down-regulates Complex I assembly factors NDUFAF3 and NDUFAF4 and the mitochondrial pyruvate carrier (MPC), while up-regulating glycolysis and fatty acid oxidation genes. Stable shRNA silencing, angiogenin digestion assay for tRNA modification, BN-PAGE and spectrophotometric enzyme activity assays for respiratory complexes, AMPK activation assays, qRT-PCR and Western blot for target gene expression PloS one High 26642043
2018 GTPBP3 deficiency triggers a metabolic reprogramming pathway distinct from MTO1 deficiency: GTPBP3-depleted cells exhibit AMPK activation, increased UCP2 and PPARγ levels, HIF-1 inactivation, and stimulation of fatty acid oxidation and respiration, indicating that GTPBP3 has an additional role beyond shared mt-tRNA modification with MTO1. Stable shRNA silencing of GTPBP3; patient-derived MTO1 fibroblasts; Western blot, metabolic flux analysis, lipid droplet staining, comparison of AMPK/HIF-1/PPARγ/UCP2 pathway activation between GTPBP3- and MTO1-deficient cells Scientific reports Medium 29348686
2016 Zebrafish gtpbp3 localizes to mitochondria (three isoforms), and morpholino-mediated knockdown causes decreased mitochondrial ATP generation, increased apoptosis and ROS, and defective embryonic development; rescue with wild-type gtpbp3 mRNA partially reverses these defects. Yeast complementation shows zebrafish gtpbp3 can functionally restore growth defects of mss1/gtpbp3 mutant yeast. Antisense morpholino knockdown in zebrafish; mRNA rescue; GFP-localization; ATP assay; ROS/apoptosis detection; yeast complementation assay The international journal of biochemistry & cell biology Medium 27184967
2019 CRISPR/Cas9 knockout of gtpbp3 in zebrafish leads to loss of τm5U modification on mt-tRNAGlu, mt-tRNALys, mt-tRNATrp, and mt-tRNALeu(UUR), alters tRNA functional folding (conformation changes and increased S1-nuclease sensitivity), paradoxically increases aminoacylation efficiency of mitochondrial tRNAs, impairs mitochondrial translation, causes proteostasis stress, alters respiratory chain complex activities, and produces hypertrophic cardiomyopathy phenotype (cardiomyocyte hypertrophy, myocardial fiber disarray, reduced fractional shortening). CRISPR/Cas9 knockout zebrafish; tRNA modification analysis; S1-nuclease digestion assay; aminoacylation efficiency assay; mitochondrial protein synthesis; respiratory chain complex activity; echocardiography; cardiac histology Nucleic acids research High 30916346
2021 Mature form of human GTPBP3 is an active GTPase in vitro; the isolated G domain alone and an N-terminal domain truncation mutant show only limited GTP hydrolysis with high Km, while the intact mature enzyme has substantially better catalytic efficiency. Pathogenic mutations alter GTPBP3 localization, protein structure, and/or GTPase activity in vitro and tRNA modification in vivo. A novel cytoplasm-localized isoform of hGTPBP3 was identified, suggesting a non-canonical cytoplasmic function. In vitro GTP hydrolysis assays with purified recombinant proteins (wild-type and domain truncations/mutants); tRNA modification assay in vivo; cellular localization by fluorescence microscopy; Km/kcat determination Nucleic acids research High 33619562
2017 Expression of GTPBP3 (as well as TRMU and MTO1) is regulated post-transcriptionally by specific miRNAs induced by retrograde signals (ROS and Ca2+), modulating mt-tRNA modification status in response to pathological mtDNA mutations; transfection with miRNA antagonists improves the energetic state of mutant cybrid cells. Cybrid cell models of mtDNA diseases; miRNA expression profiling; miRNA overexpression and antagonist transfection; mt-tRNA modification assays; OXPHOS activity measurements Scientific reports Medium 28740091
2004 GTPBP3 and MTO1, both involved in mitochondrial RNA modification, show strongly suggestive linkage and significant linkage disequilibrium in families with A1555G mtDNA mutation-associated deafness, placing these tRNA/rRNA modification enzymes as nuclear modifier genes that modulate the phenotypic expression of pathogenic mtDNA mutations. Multipoint non-parametric linkage analysis and transmission disequilibrium test in 214 DNA samples from Spanish, Italian, and Arab-Israeli families Molecular genetics and metabolism Medium 15542390
2024 GTPBP3 knockdown in retinal R28 cells activates the unfolded protein response (UPR/ER stress); conversely, a UPR activator downregulates GTPBP3 levels in normal cells, and a UPR inhibitor upregulates GTPBP3 in knockdown cells, indicating a reciprocal regulatory relationship between GTPBP3 and ER stress/UPR signaling. Taurine reverses the reduction of GTPBP3 expression after AOH injury and alleviates UPR activation. siRNA knockdown in R28 cells; UPR activator/inhibitor treatment; Western blot for UPR markers; in vivo AOH mouse model with intravitreal taurine injection; electroretinography Experimental eye research Medium 39710098
2025 Endothelial cell-specific conditional knockout of GTPBP3 in mice causes embryonic lethality with vascular formation defects, and inducible EC-specific knockout reduces retinal sprouting angiogenesis and neovascularization after limb ischemia. Mechanistically, GTPBP3 loss in ECs increases mitochondrial ROS (mtROS), which activates the HRI–ATF4–Sestrin2 pathway and inhibits mTORC1, suppressing angiogenesis; treatment with mtROS scavenger MitoQ rescues the angiogenic defect. Conditional EC-specific knockout mice (two models: constitutive and tamoxifen-inducible); retinal sprouting angiogenesis assay; hindlimb ischemia model; mitochondrial ROS measurement; Western blot for HRI/ATF4/Sestrin2/mTORC1 pathway; MitoQ rescue experiment Angiogenesis High 40533669
2026 Pathogenic mutations Q230P and N374D in GTPBP3 induce protein multimerization/aggregation and protease-mediated degradation, reduce GTPase activity and tRNA modification, impair mitochondrial translation, respiration, and dynamics. Homozygous N374D knock-in mice are embryonic lethal; homozygous E230P or compound heterozygous E230P/N374D knock-in mice develop cardiac and muscular dysfunction due to altered mitochondrial translation. AAV-mediated re-expression of GTPBP3 in cells and animals efficiently reverses mitochondrial dysfunction and pathology. Patient-derived cell lines; knock-in mouse models (CRISPR); in vitro GTPase assay; tRNA modification assay; mitochondrial translation assay; respirometry; protein aggregation/stability assays; AAV gene therapy rescue in cells and mice; cardiac/muscle phenotyping Nature communications High 41957021
2024 A novel splice-site mutation c.809-1_809delinsA in GTPBP3 was shown by minigene assay to disrupt normal pre-mRNA splicing, producing two aberrant transcripts with premature termination codons, establishing a loss-of-function splicing mechanism for COXPD23. Minigene splicing assay; whole-exome sequencing; Sanger sequencing Heliyon Medium 38515655

Source papers

Stage 0 corpus · 20 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2014 Mutations in GTPBP3 cause a mitochondrial translation defect associated with hypertrophic cardiomyopathy, lactic acidosis, and encephalopathy. American journal of human genetics 132 25434004
2004 Phenotype of non-syndromic deafness associated with the mitochondrial A1555G mutation is modulated by mitochondrial RNA modifying enzymes MTO1 and GTPBP3. Molecular genetics and metabolism 58 15542390
2019 Deletion of Gtpbp3 in zebrafish revealed the hypertrophic cardiomyopathy manifested by aberrant mitochondrial tRNA metabolism. Nucleic acids research 53 30916346
2008 Characterization of human GTPBP3, a GTP-binding protein involved in mitochondrial tRNA modification. Molecular and cellular biology 51 18852288
2021 The human tRNA taurine modification enzyme GTPBP3 is an active GTPase linked to mitochondrial diseases. Nucleic acids research 33 33619562
2015 Defective Expression of the Mitochondrial-tRNA Modifying Enzyme GTPBP3 Triggers AMPK-Mediated Adaptive Responses Involving Complex I Assembly Factors, Uncoupling Protein 2, and the Mitochondrial Pyruvate Carrier. PloS one 27 26642043
2018 Defects in the mitochondrial-tRNA modification enzymes MTO1 and GTPBP3 promote different metabolic reprogramming through a HIF-PPARγ-UCP2-AMPK axis. Scientific reports 26 29348686
2016 The defective expression of gtpbp3 related to tRNA modification alters the mitochondrial function and development of zebrafish. The international journal of biochemistry & cell biology 25 27184967
2021 Novel Mutations in the GTPBP3 Gene for Mitochondrial Disease and Characteristics of Related Phenotypic Spectrum: The First Three Cases From China. Frontiers in genetics 13 34276756
2017 microRNA-mediated differential expression of TRMU, GTPBP3 and MTO1 in cell models of mitochondrial-DNA diseases. Scientific reports 9 28740091
2023 Pathogenicity Analysis of a Novel Variant in GTPBP3 Causing Mitochondrial Disease and Systematic Literature Review. Genes 7 36980825
2003 Identification and characterization of mouse GTPBP3 gene encoding a mitochondrial GTP-binding protein involved in tRNA modification. Biochemical and biophysical research communications 6 14680828
2024 A novel mutation in GTPBP3 causes combined oxidative phosphorylation deficiency 23 by affecting pre-mRNA splicing. Heliyon 4 38515655
2022 Generation of patient-derived IPSC lines from a girl with Combined Oxidative Phosphorylation Deficiency 23 (COXPD23) caused by compound heterozygous GTPBP3 variants. Stem cell research 4 35413567
2024 Taurine mechanism in preventing retinal cell damage from acute ocular hypertension through GTPBP3 regulation. Experimental eye research 3 39710098
2025 Endothelial GTPBP3 directs developmental angiogenesis and neovascularization after limb ischemia via the mtROS/HRl/ATF4/mTORC1 axis. Angiogenesis 2 40533669
2023 Novel insights on GTPBP3-associated hypertrophic cardiomyopathy. American journal of medical genetics. Part A 2 37029485
2024 Echocardiographic manifestations of mitochondrial disease with GTPBP3 gene mutations: A case report. Medicine 1 38701254
2024 Expanding the phenotypic and genetic spectrum of GTPBP3 deficiency: findings from nine Chinese pedigrees. Orphanet journal of rare diseases 1 39719609
2026 Molecular pathogenesis and gene therapy-based intervention of GTPBP3-related mitochondrial disease. Nature communications 0 41957021

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