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Showing PTCD3 — MS39 is a alias.

PTCD3

Small ribosomal subunit protein mS39 · UniProt Q96EY7

Length
689 aa
Mass
78.5 kDa
Annotated
2026-06-10
24 papers in source corpus 12 papers cited in narrative 12 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PTCD3 (MRPS39/mS39) is an integral protein component of the small subunit of the mitochondrial ribosome that is essential for mitochondrial protein synthesis (PMID:19427859, PMID:23908630). It forms the mRNA entry channel of the small subunit and binds single-stranded mRNA, serving as the primary docking platform through which the LRPPRC-SLIRP complex hands off mt-mRNA to the ribosome for translation; cryo-EM structures show mS39 recognizing LRPPRC helical repeats together with the N-terminus of mS31 to form a corridor for mRNA delivery (PMID:32812867, PMID:39134711, PMID:39544688). Loss of PTCD3 produces a generalized mitochondrial translation defect with selective reduction in the assembly and activity of OXPHOS Complexes I and IV, decreased oxygen consumption and ATP biosynthesis (PMID:19427859, PMID:30607703, PMID:36450274). Biallelic loss-of-function variants in PTCD3 cause combined oxidative phosphorylation deficiency in humans, with patient phenotypes rescued by wild-type PTCD3 complementation (PMID:30607703, PMID:36450274, PMID:39544688). Its requirement extends in vivo, where the Drosophila ortholog is essential for larval development (PMID:38074476), and PTCD3 is required for tumor maintenance in Myc-driven lymphoma, where mitochondrial translation inhibition is synthetic-lethal with Myc activation (PMID:27635472). A non-canonical cytoplasmic role has also been described in which PTCD3 stabilizes SLC38A2 mRNA in an IGF2BP2-dependent manner to drive glutaminolysis and metastasis in colorectal cancer (PMID:40304977).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2009 High

    Established that PTCD3 is a mitochondrial small-subunit ribosome-associated protein required for translation rather than RNA processing, distinguishing its function from RNA-stability roles.

    Evidence Subcellular fractionation, mitoribosome association assay, and siRNA knockdown with protein synthesis, respirometry, and complex activity readouts in 143B cells

    PMID:19427859

    Open questions at the time
    • Did not resolve PTCD3's structural position within the small subunit
    • Mechanism by which translation loss selectively affects specific complexes not addressed
  2. 2011 Medium

    Began positioning PTCD3 within the small subunit by linking it to transcription/translation machinery, showing an RNA-mediated association with the TEFM complex and proximity to the IF3mt binding site.

    Evidence Affinity purification/MS of TEFM with RNase dissociation; chemical cross-linking of IF3mt to the small subunit followed by MS

    PMID:21278163 PMID:22015679

    Open questions at the time
    • TEFM association is a secondary finding and RNA-mediated, not a stable direct interaction
    • Cross-linking placed PTCD3 near IF3mt but did not define its functional contribution
  3. 2013 Medium

    Formalized PTCD3 as the bona fide mitoribosomal protein MRPS39 and confirmed its essential role in synthesizing mitochondrially encoded proteins.

    Evidence MS-based identification of mitoribosome components plus siRNA knockdown with immunoblot of mt-encoded proteins

    PMID:23908630

    Open questions at the time
    • Did not define molecular mechanism of mRNA engagement
    • Single-lab nomenclature/identification study
  4. 2016 Medium

    Extended PTCD3 function to disease-relevant physiology by showing mitochondrial translation, via Ptcd3, is required for Myc-driven tumor maintenance.

    Evidence In vivo RNAi reverse-genetic screen in mouse B-cell lymphoma plus tigecycline-based mitochondrial translation inhibition

    PMID:27635472

    Open questions at the time
    • Does not establish a PTCD3-specific molecular mechanism beyond general mitochondrial translation
    • Synthetic-lethal relationship with Myc not mechanistically dissected
  5. 2019 High

    Demonstrated that human PTCD3 loss-of-function causes combined OXPHOS deficiency through reduced small-subunit assembly, with complementation establishing causality.

    Evidence Exome sequencing, patient fibroblast complex activity/oxygen consumption/ATP assays, quantitative mitoribosome proteomics, and wild-type complementation

    PMID:30607703

    Open questions at the time
    • Did not resolve why Complexes I and IV are selectively affected
    • Structural basis of the assembly defect not defined
  6. 2020 High

    Provided structural proof that PTCD3/mS39 forms the mRNA entry platform and is the mitoribosomal contact for LRPPRC-SLIRP-mediated mRNA delivery.

    Evidence ~3.0 Å cryo-EM structures of human mitoribosome functional complexes

    PMID:32812867

    Open questions at the time
    • Atomic details of the LRPPRC-mS39 interface not yet resolved
    • Dynamics of mRNA handoff not captured
  7. 2022 High

    Independently corroborated PTCD3 pathogenicity across multiple patients, confirming reduced protein leads to Complex I/IV deficits reversible by complementation.

    Evidence Patient fibroblast western blot, complex activity, high-resolution respirometry, minigene splicing, and complementation

    PMID:36450274

    Open questions at the time
    • Genotype-phenotype correlation across variants not fully mapped
    • Does not add structural mechanism beyond prior work
  8. 2024 High

    Defined the molecular interface of mRNA handoff, showing mS39 recognizes LRPPRC helical repeats with mS31 to form a delivery corridor, and that pathogenic variants disrupting this region cause OXPHOS deficiency.

    Evidence High-resolution cryo-EM of LRPPRC-SLIRP-mRNA-mitoribosome complex with ribosome profiling and metabolic labeling; plus WGS, splicing/respirometry and in silico variant modelling in patients

    PMID:39134711 PMID:39544688

    Open questions at the time
    • Variant-level mechanism partly relies on in silico modelling
    • Selectivity of mRNA recognition by mS39 not fully defined
  9. 2023 Medium

    Confirmed an in vivo developmental requirement for PTCD3 conserved beyond humans, linking loss to defective mitochondrial and ribosome-biogenesis gene expression.

    Evidence Loss-of-function genetic mutant analysis and transcriptomic profiling in Drosophila

    PMID:38074476

    Open questions at the time
    • Transcriptomic changes are downstream and not mechanistically resolved
    • Single ortholog study
  10. 2025 Medium

    Identified a non-canonical cytoplasmic role for PTCD3 in stabilizing SLC38A2 mRNA to drive glutaminolysis and metastasis, expanding its function beyond the mitoribosome.

    Evidence Co-IP, RIP, dual-luciferase, ChIP for H3K27ac, and xenograft and migration/invasion assays in colorectal cancer cells

    PMID:40304977

    Open questions at the time
    • Direct RNA binding versus IGF2BP2-bridged interaction not fully separated
    • Single-lab study; reconciliation with mitochondrial localization not addressed

Open questions

Synthesis pass · forward-looking unresolved questions
  • How a single protein reconciles its dedicated mitoribosomal mRNA-entry role with a reported cytoplasmic mRNA-stabilization activity, and why its loss selectively impairs Complexes I and IV, remain open.
  • No mechanism explaining complex-selective OXPHOS loss
  • Subcellular partitioning between mitochondrial and cytoplasmic functions undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003723 RNA binding 3 GO:0005198 structural molecule activity 3
Localization
GO:0005840 ribosome 3 GO:0005739 mitochondrion 2
Pathway
R-HSA-1643685 Disease 3 R-HSA-392499 Metabolism of proteins 3
Partners
IGF2BP2LRPPRCMRPS31SLIRP
Complex memberships
mitochondrial small ribosomal subunit (mitoribosome 28S)

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 PTCD3 is a mitochondrial protein that associates with the small subunit of mitochondrial ribosomes. Knockdown of PTCD3 in 143B osteosarcoma cells decreased mitochondrial protein synthesis, mitochondrial respiration, and the activity of Complexes III and IV, without affecting mitochondrial mRNA levels, indicating PTCD3 has a role in mitochondrial translation but not RNA processing/stability. Subcellular fractionation, mitoribosome subunit association assay, siRNA knockdown with mitochondrial protein synthesis assay, respirometry, and complex activity assays FEBS letters High 19427859
2011 PTCD3 co-purifies with the mitochondrial transcription elongation factor TEFM complex, which also contains mitochondrial RNA polymerase (POLRMT), mitochondrial transcripts, and DHX30; after RNase treatment only POLRMT remained associated with TEFM, indicating PTCD3's association with TEFM is RNA-mediated. Affinity purification of TEFM from human mitochondria followed by mass spectrometry; RNase treatment dissociation experiment Nucleic acids research Medium 21278163
2011 PTCD3 (Pet309 ortholog) cross-links to mitochondrial translation initiation factor IF3mt, placing it near the IF3mt binding site on the mitochondrial small ribosomal subunit. This cross-linking was confirmed by mass spectrometry and establishes PTCD3 as a small subunit ribosomal protein positioned at the IF3mt interface. Chemical cross-linking of IF3mt to mitoribosome small subunit followed by mass spectrometry identification; truncation mutant controls Biochimica et biophysica acta Medium 22015679
2013 PTCD3 was formally identified as MRPS39, a component of the mitochondrial ribosome small subunit. siRNA knockdown confirmed an essential role in mitochondrial protein synthesis, as demonstrated by significant effects on mitochondrially encoded protein expression. Mass spectrometry-based identification of mitoribosome components; siRNA knockdown with immunoblot analysis of mitochondrially encoded proteins Frontiers in physiology Medium 23908630
2016 Ptcd3 is required for tumor maintenance in Myc-driven mouse B-cell lymphomas, as identified through an in vivo reverse-genetic screen targeting Myc-activated mRNAs; inhibition of mitochondrial translation was synthetic-lethal with Myc activation. In vivo reverse-genetic RNAi screen in mouse B-cell lymphoma model; mitochondrial translation inhibition with tigecycline in vitro and in vivo Oncotarget Medium 27635472
2019 Biallelic loss-of-function variants in PTCD3 cause combined oxidative phosphorylation deficiency (reduced Complex I and IV levels and activities, decreased oxygen consumption and ATP biosynthesis) and generalized mitochondrial translation defects in patient fibroblasts. Complementation with wild-type PTCD3 rescued these defects, functionally validating pathogenicity. Quantitative proteomics showed decreased levels of small mitoribosomal subunits. Exome sequencing, patient fibroblast biochemical assays (complex activity, oxygen consumption, ATP biosynthesis), quantitative proteomics of mitoribosome subunits, complementation experiments with wild-type PTCD3 Neurogenetics High 30607703
2020 PTCD3 (mS39) forms a dedicated mRNA entry platform on the mitochondrial small ribosomal subunit. Cryo-EM structure (~3.0 Å) of the human mitoribosome revealed that mS39 is the contact site through which the LRPPRC-SLIRP complex delivers mt-mRNA to the ribosome for translation. Cryo-electron microscopy structural determination of human mitoribosome functional complexes at ~3.0 Å resolution eLife High 32812867
2022 PTCD3 deficiency caused by compound heterozygous variants leads to severely reduced PTCD3 protein levels in patient fibroblasts, reduction in steady-state levels of complexes I and IV subunits and their activities, and decreased mitochondrial respiratory capacity. Functional complementation with wild-type PTCD3 restored complex levels and respiratory capacity, confirming PTCD3's essential role in mitochondrial translation. Patient fibroblast biochemical characterization (western blot, complex activity, high-resolution respirometry), minigene splicing assays, complementation experiments Brain pathology (Zurich, Switzerland) High 36450274
2024 PTCD3/mS39 directly associates with LRPPRC through recognition of LRPPRC helical repeats, together with the N-terminus of mS31, forming a corridor for handoff of mRNA to the mitoribosome. Cryo-EM structure of LRPPRC-SLIRP-mRNA-mitoribosome complex at high resolution showed that mS39 is the primary mitoribosomal contact for LRPPRC-mediated mRNA delivery. Cryo-electron microscopy structure of LRPPRC-SLIRP-mRNA-mitoribosome complex; RNA sequencing, metabolic labeling, and mitoribosome profiling for functional validation Nature structural & molecular biology High 39134711
2024 PTCD3/MRPS39 forms the entry channel of the mitochondrial small ribosomal subunit and binds to single-stranded mRNA. Pathogenic variants including a nonsense variant (p.Tyr394Ter) that ablates the C-terminal half (including the central fold) and a missense variant (p.His269Tyr) cause combined oxidative phosphorylation deficiency with decreased basal respiration rate. Whole genome sequencing, RT-PCR splicing assay, in silico structural modelling of variants, respirometry of patient-derived cells JIMD reports Medium 39544688
2023 The Drosophila melanogaster ortholog of PTCD3 (encoded by CG4679) is essential for development; loss-of-function mutants are lethal at the second instar larval stage, with reduced expression of mitochondrial function and ribosome biogenesis genes, confirming an in vivo requirement for PTCD3 in mitochondrial RNA metabolism and development. Loss-of-function genetic mutant analysis in Drosophila; transcriptomic profiling of mutant larvae microPublication biology Medium 38074476
2025 PTCD3 promotes SLC38A2 mRNA stability in colorectal cancer cells in an IGF2BP2-dependent manner, enhancing glutaminolysis and cancer cell migration and invasion. KAT2A promotes PTCD3 expression by increasing H3K27 acetylation at the PTCD3 locus. PTCD3 knockdown suppressed CRC glutaminolysis, proliferation, and metastasis in vitro and in vivo. Co-IP, RIP (RNA immunoprecipitation), dual-luciferase assay for PTCD3-IGF2BP2-SLC38A2 interaction; ChIP for H3K27 acetylation; xenograft mouse model; CCK-8, scratch, Transwell assays FASEB journal Medium 40304977

Source papers

Stage 0 corpus · 24 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 TEFM (c17orf42) is necessary for transcription of human mtDNA. Nucleic acids research 145 21278163
2020 Discovery of Potent and Selective Epidermal Growth Factor Receptor (EGFR) Bifunctional Small-Molecule Degraders. Journal of medicinal chemistry 144 31895569
2020 Structural basis of mitochondrial translation. eLife 87 32812867
2009 Pentatricopeptide repeat domain protein 3 associates with the mitochondrial small ribosomal subunit and regulates translation. FEBS letters 87 19427859
2013 Identification and characterization of CHCHD1, AURKAIP1, and CRIF1 as new members of the mammalian mitochondrial ribosome. Frontiers in physiology 72 23908630
2016 The mitochondrial translation machinery as a therapeutic target in Myc-driven lymphomas. Oncotarget 58 27635472
2019 Mitochondrial ribosomal protein PTCD3 mutations cause oxidative phosphorylation defects with Leigh syndrome. Neurogenetics 49 30607703
2024 Structural basis of LRPPRC-SLIRP-dependent translation by the mitoribosome. Nature structural & molecular biology 34 39134711
2022 Exploring Degradation of Mutant and Wild-Type Epidermal Growth Factor Receptors Induced by Proteolysis-Targeting Chimeras. Journal of medicinal chemistry 30 35675209
2019 The role of the protein-RNA recognition code in neurodegeneration. Cellular and molecular life sciences : CMLS 21 30980111
2011 Contacts between mammalian mitochondrial translational initiation factor 3 and ribosomal proteins in the small subunit. Biochimica et biophysica acta 19 22015679
2020 Comparative pharmacoproteomics reveals potential targets for berberine, a promising therapy for colorectal cancer. Biochemical and biophysical research communications 16 32087971
2022 Leigh syndrome is the main clinical characteristic of PTCD3 deficiency. Brain pathology (Zurich, Switzerland) 12 36450274
2012 Multiple-locus variable-number tandem-repeat analysis of Streptococcus pneumoniae and comparison with multiple loci sequence typing. BMC microbiology 12 23088225
2020 Genetic determinants of ammonia-induced acute lung injury in mice. American journal of physiology. Lung cellular and molecular physiology 11 33050709
2012 Combining ability analysis for within-boll yield components in upland cotton (Gossypium hirsutum L.). Genetics and molecular research : GMR 6 23007974
2025 Epigenetic Activation of PTCD3 Promotes CRC Glutamine Metabolism and Metastasis via IGF2BP2-Mediated SLC38A2 m6A Modification. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 4 40304977
2022 RNA-sequencing for transcriptional profiling of whole blood in early stage and metastatic pancreatic cancer patients. Cell biology international 3 36229929
2023 A Drosophila melanogaster ortholog of pentatricopeptide repeat domain 3 ( PTCD3 ) is essential for development. microPublication biology 2 38074476
2014 First Report of the NA2 Lineage of Phytophthora ramorum from an Ornamental Rhododendron in the Interior of California. Plant disease 2 30708650
2025 [Clinical and genetic characteristics analysis of 18 children with infantile epileptic spasms syndrome associated with mitochondrial gene variants]. Zhonghua er ke za zhi = Chinese journal of pediatrics 0 40962542
2025 Bioinformatics-based screening and validation of ferroptosis-related genes in sepsis and type 2 diabetes mellitus. Experimental biology and medicine (Maywood, N.J.) 0 41194984
2024 The phenotypic spectrum of PTCD3 deficiency. JIMD reports 0 39544688
2022 Semilunar sign of cornea: A multimodal analysis of the posterior corneal opacity in non-infectious anterior scleritis. Indian journal of ophthalmology 0 35326015

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