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TTC19

Tetratricopeptide repeat protein 19, mitochondrial · UniProt Q6DKK2

Length
380 aa
Mass
42.5 kDa
Annotated
2026-06-10
18 papers in source corpus 6 papers cited in narrative 8 extracted findings
Cross-family judge vs UniProt: tie faithfulness: 4/5 claims corpus-supported (80%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TTC19 is a mitochondrial inner-membrane protein that functions in the late maturation of respiratory chain complex III (cIII) (PMID:21278747). It assembles into high-molecular-weight complexes that coincide with cIII and physically associates with the holocomplex, and its loss causes accumulation of cIII-specific assembly intermediates (PMID:21278747). Mechanistically, TTC19 binds the fully assembled cIII dimer only after incorporation of the Rieske iron-sulfur protein UQCRFS1, and is required for the rapid removal of N-terminal UQCRFS1 maturation fragments that otherwise remain bound to and impair the holocomplex (PMID:28673544). Loss of TTC19 across Drosophila, mouse, and patient-derived systems produces cIII deficiency with reduced enzyme activity and elevated reactive oxygen species (PMID:28673544, PMID:23532514), and causative loss-of-function and splice-disrupting mutations link TTC19 to mitochondrial dysfunction in patients (PMID:25452764, PMID:42250897). A distinct non-mitochondrial role has been described in which XPOT-dependent tRNA export drives TTC19 translation and TTC19 is required for cytokinesis and proliferation of triple-negative breast cancer cells (PMID:37928256).

Mechanistic history

Synthesis pass · year-by-year structured walk · 6 steps
  1. 2011 High

    Established that TTC19 is a mitochondrial inner-membrane protein required for complex III biogenesis, answering whether it had any role in the respiratory chain.

    Evidence Co-IP, BN-PAGE, subcellular fractionation, and a Drosophila knockout with locomotor and biochemical readouts

    PMID:21278747

    Open questions at the time
    • Did not define the specific assembly step TTC19 acts on
    • Did not identify the molecular substrate or binding determinants
  2. 2013 Medium

    Connected human TTC19 loss to defective cIII assembly in muscle and elevated ROS in patient cells, extending the assembly role to a redox consequence.

    Evidence Western blot, biochemical cIII assembly assay, and ROS measurement in patient-derived muscle and fibroblasts

    PMID:23532514

    Open questions at the time
    • Single-lab patient study
    • Mechanism linking assembly defect to ROS not resolved
  3. 2014 Medium

    Confirmed via an independent causative frameshift that TTC19 absence leads to accumulation of cIII assembly intermediates, reinforcing its assembly/stability function.

    Evidence Western blot and BN-PAGE in patient fibroblasts carrying a homozygous frameshift

    PMID:25452764

    Open questions at the time
    • Single-lab patient study
    • Did not address the biochemical identity of the accumulating intermediate
  4. 2017 High

    Defined the precise molecular function: TTC19 acts after UQCRFS1 incorporation to clear N-terminal Rieske maturation fragments from assembled cIII, explaining how its loss destabilizes the enzyme.

    Evidence Ttc19-/- mouse model, human cell knockdown/rescue, BN-PAGE, and mass spectrometry of UQCRFS1 fragments; mouse showed reduced cIII activity and increased ROS in vivo

    PMID:28673544

    Open questions at the time
    • Did not establish a structural model of the TTC19–cIII interaction
    • Mechanism of fragment removal/degradation not detailed
  5. 2023 Medium

    Revealed a non-mitochondrial role by linking XPOT-dependent tRNA export to TTC19 translation and showing TTC19 is required for cytokinesis and proliferation in cancer cells.

    Evidence XPOT knockdown, RNA-seq, tRNA-seq, codon analysis, mass spectrometry, and TTC19 knockdown with cytokinesis/proliferation readouts in TNBC lines

    PMID:37928256

    Open questions at the time
    • Not independently replicated
    • Molecular basis of the cytokinesis role undefined
    • Relationship to the mitochondrial function unclear
  6. 2026 Medium

    Functionally validated a splice-disrupting intronic variant as pathogenic, showing aberrant transcripts and mitochondrial dysfunction.

    Evidence Splicing assay, RT-PCR, expression analysis, and mitochondrial function assay in patient fibroblasts

    PMID:42250897

    Open questions at the time
    • Single-lab patient study
    • Did not assess cIII-specific assembly intermediates directly

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the mitochondrial cIII maturation role and the reported XPOT-linked cytokinesis function are mechanistically related, if at all, remains unresolved.
  • No structural model of TTC19 bound to cIII
  • Mechanism of UQCRFS1 fragment removal not defined
  • Non-mitochondrial cytokinesis role not independently confirmed

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 1
Localization
GO:0005739 mitochondrion 3
Pathway
R-HSA-1852241 Organelle biogenesis and maintenance 2
Partners
UQCRFS1XPOT
Complex memberships
respiratory chain complex III

Evidence

Reading pass · 8 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 TTC19 is embedded in the inner mitochondrial membrane as part of two high-molecular-weight complexes, one of which coincides with complex III (cIII), and physically interacts with cIII as demonstrated by coimmunoprecipitation. Loss of TTC19 causes accumulation of cIII-specific assembly intermediates, establishing TTC19 as a cIII assembly factor. Coimmunoprecipitation, Blue-Native gel electrophoresis, subcellular fractionation, Drosophila knockout model with locomotor/biochemical readouts Nature genetics High 21278747
2017 TTC19 binds to the fully assembled complex III dimer only after incorporation of the iron-sulfur Rieske protein (UQCRFS1). During in situ maturation of UQCRFS1, N-terminal polypeptide fragments are produced and remain bound to the holocomplex; TTC19 is required for their rapid removal. In the absence of TTC19 these fragments accumulate within complex III, causing structural and functional impairment of the enzyme. Ttc19−/− mouse model biochemical characterization, BN-PAGE, mass spectrometry of UQCRFS1 fragments, human cell line knockdown/rescue experiments Molecular cell High 28673544
2011 Drosophila melanogaster knockout of TTC19 results in low fertility, adult-onset locomotor impairment, and bang sensitivity, associated with cIII deficiency, establishing a causal in vivo link between TTC19 loss and mitochondrial complex III dysfunction. Drosophila knockout model; locomotor assays; biochemical cIII activity measurement Nature genetics High 21278747
2013 Loss-of-function mutation in TTC19 results in near-complete absence of TTC19 protein, defective assembly of complex III in muscle, and enhanced production of reactive oxygen species in cultured skin fibroblasts, linking TTC19 to ROS regulation downstream of cIII assembly. Western blot (protein absence), biochemical cIII assembly assay (muscle), ROS measurement in fibroblasts Neurogenetics Medium 23532514
2014 A novel homozygous frameshift rearrangement in TTC19 (c.213_229dup) causes absence of TTC19 protein and accumulation of cIII-specific assembly intermediates detectable by Blue-Native Gel Electrophoresis, confirming that TTC19 is required for normal cIII assembly/stability. Western blot, Blue-Native Gel Electrophoresis in patient fibroblasts Frontiers in genetics Medium 25452764
2017 TTC19-deficient mice show progressive neurological and metabolic decline, decreased complex III activity, and increased production of reactive oxygen species, confirming the mammalian in vivo role of TTC19 in complex III function and ROS homeostasis. Ttc19−/− mouse model; spectrophotometric cIII activity assay; ROS measurement Molecular cell High 28673544
2023 XPOT (Exportin-T) preferentially transports tRNA-Ala-AGC-10-1 to the cytoplasm, driving translation of TTC19; knockdown of TTC19 is indispensable for cytokinesis completion and proliferation of triple-negative breast cancer (TNBC) cells, revealing a non-mitochondrial role for TTC19 in cell division. XPOT knockdown, RNA-seq, high-throughput tRNA sequencing, codon preferential analysis, protein mass spectrometry, TTC19 knockdown with cytokinesis/proliferation readouts in TNBC cell lines International journal of biological sciences Medium 37928256
2026 A novel intronic 31 bp deletion in TTC19 disrupts splicing, producing aberrant transcripts, reduced TTC19 gene expression, and mitochondrial dysfunction in patient-derived fibroblasts, functionally confirming the pathogenicity of a splice-site variant. Splicing assay, RT-PCR for aberrant transcript, gene expression analysis, mitochondrial function assay in patient fibroblasts Mitochondrion Medium 42250897

Source papers

Stage 0 corpus · 18 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 Mutations in TTC19 cause mitochondrial complex III deficiency and neurological impairment in humans and flies. Nature genetics 133 21278747
2017 TTC19 Plays a Husbandry Role on UQCRFS1 Turnover in the Biogenesis of Mitochondrial Respiratory Complex III. Molecular cell 69 28673544
2013 Novel TTC19 mutation in a family with severe psychiatric manifestations and complex III deficiency. Neurogenetics 42 23532514
2014 Exome sequencing reveals a novel TTC19 mutation in an autosomal recessive spinocerebellar ataxia patient. BMC neurology 31 24397319
2015 Phenotypic variation of TTC19-deficient mitochondrial complex III deficiency: a case report and literature review. American journal of medical genetics. Part A 29 25899669
2013 Mutations in the Complex III Assembly Factor Tetratricopeptide 19 Gene TTC19 Are a Rare Cause of Leigh Syndrome. JIMD reports 29 24368687
2015 Mutations in TTC19: expanding the molecular, clinical and biochemical phenotype. Orphanet journal of rare diseases 26 25887401
2019 A Novel TTC19 Mutation in a Patient With Neurological, Psychological, and Gastrointestinal Impairment. Frontiers in neurology 19 31551910
2014 A novel mutation in TTC19 associated with isolated complex III deficiency, cerebellar hypoplasia, and bilateral basal ganglia lesions. Frontiers in genetics 18 25452764
2015 A Japanese case of cerebellar ataxia, spastic paraparesis and deep sensory impairment associated with a novel homozygous TTC19 mutation. Journal of human genetics 17 25652355
2015 Mitochondrial Complex III Deficiency Caused by TTC19 Defects: Report of a Novel Mutation and Review of Literature. JIMD reports 16 25772319
2018 Novel Homozygous Variant in TTC19 Causing Mitochondrial Complex III Deficiency with Recurrent Stroke-Like Episodes: Expanding the Phenotype. Seminars in pediatric neurology 15 29961508
2023 XPOT Disruption Suppresses TNBC Growth through Inhibition of Specific tRNA Nuclear Exportation and TTC19 Expression to Induce Cytokinesis Failure. International journal of biological sciences 7 37928256
2023 A TTC19 mutation associated with progressive movement disorders and peripheral neuropathy: Case report and systematic review. CNS neuroscience & therapeutics 6 37927170
2026 TTC19-related mitochondrial complex III deficiency: Clinical and genetic characterization of 10 patients from 5 unrelated Arab families. Molecular genetics and metabolism 1 41818954
2025 Motor Neuropathy in a Patient With Mitochondrial Disease and a Novel TTC19 Variant: An Underrecognized Phenotypic Feature. Journal of the peripheral nervous system : JPNS 1 40946707
2026 TTC19 and FMNL2 gene variants in a pediatric case of mitochondrial disorder with renal tubular acidosis. Mitochondrion 0 42250897
2025 Expanding the Clinical, Pathological, and Molecular Phenotypes of Tetratricopeptide 19 (TTC19) Gene Mutations: A Case Report from India. Neurology India 0 40652486

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