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Showing TIMM50 — TIM50 is a alias.

TIMM50

Mitochondrial import inner membrane translocase subunit TIM50 · UniProt Q3ZCQ8

Length
353 aa
Mass
39.6 kDa
Annotated
2026-06-10
38 papers in source corpus 21 papers cited in narrative 21 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

TIMM50 (Tim50) is the principal presequence receptor of the mitochondrial TIM23 inner-membrane translocase, governing the import of matrix-targeted precursor proteins from the TOM complex into mitochondria (PMID:12437924, PMID:22065641). It is anchored in the inner membrane with a large intermembrane-space (IMS) domain that engages translocating preproteins and hands them to the channel protein Tim23, an interaction mediated by a protruding β-hairpin and additional surface patches of the Tim50 IMS domain (PMID:12437925, PMID:21704637, PMID:30765764). The Tim50 IMS domain enforces the inner-membrane permeability barrier by closing the Tim23 channel, while incoming presequences antagonistically open it, coupling cargo recognition to gated translocation (PMID:16763150, PMID:22065641). Beyond receptor function, Tim50 acts as a transmembrane signal transducer: its matrix domain, IMS domain, and transmembrane segment cooperate to recruit and activate the PAM import motor (including Pam17), linking IMS presequence binding to matrix-directed motor force (PMID:19139266, PMID:32130909), and its IMS region resolves into a core presequence-binding/recruitment domain and a separable domain that promotes TOM–TIM23 cooperation (PMID:37748811). Cardiolipin modulates the Tim50 receptor domain's association with membranes and Tim23 (PMID:28879236). In humans, pathogenic TIMM50 mutations destabilize TIM23 core components, lower mitochondrial membrane potential, and impair import—most severely of laterally sorted OXPHOS and mitochondrial ribosome substrates—causing reduced respiration and ATP, defective neuronal mitochondrial trafficking, and a severe neurological disease phenotype (PMID:38828998, PMID:39680434). Human TIMM50 additionally interacts with steroidogenic enzymes 3β-HSD2 and CYP11A1 within the TIM23 IMS to support their activity (PMID:21930695, PMID:30348838).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2002 High

    Established Tim50 as an essential TIM23 subunit that exposes an IMS domain to receive preproteins and hand them to the Tim23 channel, defining the entry point for presequence import.

    Evidence Genetic depletion, co-IP, and preprotein import assays in yeast, with site-specific photocrosslinking of a translocation intermediate to Tim50

    PMID:12437924 PMID:12437925

    Open questions at the time
    • Did not resolve the structural basis of presequence binding
    • Did not define how the channel is gated
  2. 2004 Medium

    Showed human TIMM50 forms a complex with human TIM23 and that its loss accelerates cytochrome c release, linking the import receptor to apoptotic sensitivity.

    Evidence Phosphatase activity assay on purified human Tim50, co-IP with Tim23, RNAi with cytochrome c release measurement

    PMID:15044455

    Open questions at the time
    • Physiological substrate of the reported phosphatase activity unidentified
    • Mechanism connecting Tim50 loss to cytochrome c release unresolved
  3. 2006 High

    Defined the regulatory logic of import by showing the Tim50 IMS domain closes the Tim23 channel and presequences antagonistically open it.

    Evidence Reconstituted Tim23 channel electrophysiology with recombinant Tim50 IMS domain and presequence peptide competition

    PMID:16763150

    Open questions at the time
    • Structural conformations of the open/closed channel not defined
    • Did not map the presequence-binding site on Tim50
  4. 2009 Medium

    Demonstrated that Tim23–Tim50 IMS contacts drive two import steps—TOM-to-TIM23 transfer and a late step promoting matrix Hsp70 motor function—extending Tim50's role beyond initial reception.

    Evidence Genetic IMS-domain mutants and import assays in isolated mitochondria; in vitro reconstitution with recombinant IMS domains, SPR, and cross-linking

    PMID:19017642 PMID:19139266

    Open questions at the time
    • Molecular link between IMS-domain contacts and matrix motor activation unresolved
    • Did not define the structural element mediating the interaction
  5. 2011 High

    Mapped the presequence-binding site on Tim50 and resolved the IMS-domain crystal structure, establishing the structural basis for Tim50 as the primary inner-membrane presequence receptor and Tim23 partner.

    Evidence Photo-affinity presequence labeling with MS mapping plus import assays; X-ray crystallography at 1.83 Å with β-hairpin mutagenesis

    PMID:21704637 PMID:22065641

    Open questions at the time
    • Conformational dynamics of the binding groove not captured in a single structure
    • Did not address how signal binding is transmitted across the membrane
  6. 2011 Medium

    Identified non-import functions of human TIMM50, including steroidogenic enzyme support and transcriptional upregulation by mutant p53 driving proliferation and chemoresistance.

    Evidence Co-IP and enzymatic assays with 3β-HSD2 after Tim50 knockdown; ChIP, promoter reporter, and siRNA proliferation/chemoresistance assays in mutant-p53 cells

    PMID:21621504 PMID:21930695

    Open questions at the time
    • Whether steroidogenic support is separable from import function unresolved
    • Generality of mutant-p53 upregulation across tumor contexts untested
  7. 2017 High

    Showed cardiolipin modulates Tim50 receptor-domain association with membranes and Tim23, adding a lipid-dependent layer to receptor-channel coupling.

    Evidence In vivo assays, model-membrane reconstitution, SAXS structure of the soluble receptor domain, MD simulations, and biophysical binding measurements

    PMID:28879236

    Open questions at the time
    • In situ cardiolipin dependence within intact translocase not directly imaged
    • Functional consequence for cargo throughput not quantified
  8. 2020 Medium

    Resolved how Tim50 transduces a signal across the membrane: distinct matrix, IMS, and transmembrane elements cooperate to recruit Pam17/PAM and stimulate import force, coupling IMS recognition to matrix motor activation.

    Evidence Genetic dissection of Tim50 domains, import assays, and PAM/Pam17 recruitment analysis in isolated mitochondria

    PMID:32130909

    Open questions at the time
    • Atomic mechanism of transmembrane signal transmission undefined
    • Stoichiometry of Tim50-PAM coupling unresolved
  9. 2023 Medium

    Subdivided the Tim50 IMS region into a core presequence-binding/recruitment domain and a separable domain promoting TOM–TIM23 cooperation, refining the receptor's functional architecture.

    Evidence Domain-swap and trans-complementation experiments, import assays, and co-IP

    PMID:37748811

    Open questions at the time
    • Direct versus indirect mechanism by which the PBD aids TOM-TIM23 coupling unresolved
    • Structural interface of the two subdomains not defined
  10. 2024 Medium

    Linked TIMM50 loss-of-function to human disease by showing pathogenic mutations destabilize TIM23 components, lower membrane potential, and selectively impair laterally sorted OXPHOS and mitoribosome substrate import, explaining the neurological phenotype.

    Evidence Proteomics of patient fibroblasts and a TIMM50 CRISPR HEK293 model, import assays, membrane potential measurements; patient and mouse neuron knockdown with respirometry, trafficking, and electrophysiology

    PMID:38828998 PMID:39680434

    Open questions at the time
    • Causal chain from import defect to specific neuronal channel changes (KCNJ10/KCNA2) not fully mechanistic
    • Tissue-specific vulnerability not explained
  11. 2024 Medium

    Connected Tim50 biogenesis to translation control, showing eIF5A relieves ribosome stalling at TIM50 polyproline tracts and that Tim50 limitation triggers a mitochondrial import stress response.

    Evidence eIF5A depletion in yeast, ribosome profiling, and polyproline-mutant rescue with mitoprotein precursor accumulation assays

    PMID:39509053

    Open questions at the time
    • Whether this regulation operates in human cells untested
    • Quantitative contribution of Tim50 stalling to the stress response unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How Tim50's distinct activities—presequence reception, channel gating, motor coupling, and its reported moonlighting nuclear/steroidogenic roles—are integrated and regulated in a single protein remains unresolved.
  • Nuclear Tim50a isoform role in snRNP biogenesis lacks functional validation (#18)
  • Senescence regulation via sirtuin1-CEBPα reported with limited mechanistic detail (#20)
  • No high-resolution structure of the assembled human translocase with Tim50 engaging cargo

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0038024 cargo receptor activity 2 GO:0098772 molecular function regulator activity 2 GO:0060089 molecular transducer activity 1 GO:0140110 transcription regulator activity 1
Localization
GO:0005739 mitochondrion 3
Pathway
R-HSA-392499 Metabolism of proteins 3 R-HSA-9609507 Protein localization 3 R-HSA-1852241 Organelle biogenesis and maintenance 2
Partners
CYP11A1HSD3B2HSPA9PAM17TIMM17ATIMM17BTIMM23
Complex memberships
PAM import motorTIM23 presequence translocase

Evidence

Reading pass · 21 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2002 Tim50 is an essential subunit of the TIM23 presequence translocase that exposes its major domain to the intermembrane space, interacts with preproteins in transit, and directs them to the channel protein Tim23. Inactivation of Tim50 strongly inhibits import of matrix-targeting preproteins but does not strictly affect preproteins with additional inner membrane-sorting signals. Genetic depletion, co-immunoprecipitation, preprotein import assays in yeast Cell High 12437924
2002 Tim50 is anchored to the inner mitochondrial membrane with its C-terminal domain in the intermembrane space (IMS), interacts with the N-terminal IMS domain of Tim23, and facilitates transfer of translocating preproteins from the TOM complex to the TIM23 complex. A translocation intermediate was crosslinked to Tim50. Site-specific photocrosslinking of translocation intermediates, co-immunoprecipitation, anti-Tim50 antibody inhibition Cell High 12437925
2006 The IMS domain of Tim50 closes the Tim23 channel to maintain the permeability barrier of the mitochondrial inner membrane; presequences overcome this effect and activate the channel for translocation, establishing an antagonistic regulatory mechanism. Reconstituted Tim23 channel electrophysiology, addition of recombinant Tim50 IMS domain, presequence peptide competition assay Science High 16763150
2004 Human TIMM50 possesses phosphatase activity and forms a complex with human TIM23. Knockdown of human TIMM50 by RNAi increases sensitivity to death stimuli by accelerating cytochrome c release from mitochondria. Phosphatase activity assay on purified human Tim50, co-immunoprecipitation with Tim23, RNAi knockdown with cytochrome c release measurement The Journal of biological chemistry Medium 15044455
2008 The IMS domains of Tim50 and Tim23 directly interact in vitro; specific mutations in Tim23 that abolish this interaction in vitro also destabilize it in vivo and cause defective TIM23-dependent preprotein import and temperature-sensitive lethality. In vitro reconstitution with recombinant IMS domains, chemical cross-linking, surface plasmon resonance, in vivo mutagenesis The Journal of biological chemistry High 19017642
2009 Tim23-Tim50 IMS domain interactions facilitate two steps of protein import: transfer of precursors from TOM40 to TIM23, and a late step promoting motor functions of mitochondrial Hsp70 in the matrix. Genetic analysis of IMS domain mutants, import assays with isolated mitochondria, analysis of TOM40-TIM23 cooperation The Journal of cell biology Medium 19139266
2011 Photo-affinity cross-linking with engineered presequence probes mapped a specific presequence-binding domain on Tim50, establishing Tim50 as the primary presequence receptor at the inner membrane. Targeting signals and Tim50 regulate the Tim23 channel antagonistically. Photo-affinity labeling with presequence probes, mass spectrometric mapping of cross-linking sites, import assays The Journal of cell biology High 22065641
2011 Crystal structure of the yeast Tim50 IMS domain resolved to 1.83 Å reveals a protruding β-hairpin critical for interaction with Tim23, providing a structural basis for Tim50-Tim23 cooperation in preprotein translocation. X-ray crystallography at 1.83 Å, mutagenesis of the β-hairpin, functional import assays Journal of molecular biology High 21704637
2011 Human TIMM50 interacts with 3β-HSD2 primarily through the Tim50 N-terminus; Tim50 knockdown inhibited 3β-HSD2 enzymatic activity (conversion of DHEA to androstenedione and pregnenolone to progesterone) and reduced 3β-HSD2 expression, demonstrating a role for Tim50 in steroidogenesis beyond protein import. Mass spectrometry, co-immunoprecipitation, density-gradient ultracentrifugation, Tim50 siRNA knockdown with enzymatic activity assays, CD spectroscopy The Journal of biological chemistry Medium 21930695
2015 Crystal structure of Tim50(164-361) at 2.67 Å reveals significant structural plasticity within the putative presequence-binding groove and in the β-hairpin; crystal packing shows helix A1 from a neighboring monomer docking into the groove, suggesting a hydrophobic mechanism for presequence recognition. X-ray crystallography at 2.67 Å, structural comparison with prior 1.83 Å structure Acta crystallographica Section F Medium 26323300
2017 Cardiolipin modulates the interaction between the soluble Tim50 receptor domain and the Tim23 channel. The Tim50 receptor domain interacts with membranes and specific sites on Tim23 in a cardiolipin-dependent manner; SAXS-based structure of the full soluble Tim50 receptor domain was obtained, and MD simulations confirmed cardiolipin-driven association with concomitant structural changes. In vivo assays, isolated mitochondria reconstitution, nanoscale model membrane systems, SAXS structure determination, molecular dynamics simulations, biophysical binding measurements Science advances High 28879236
2018 Tim50 directly interacts with SCC (CYP11A1) amino acids 141-146 in the TIM23 complex IMS; absence of Tim50 or its mutation reduced SCC enzymatic activity. SCC is imported to the matrix, undergoes sequential N-terminal cleavage, then its C-terminus integrates into TIM23 and aligns with Tim50. Co-immunoprecipitation, Tim50 knockdown with enzymatic activity assay, domain mapping Molecular and cellular biology Medium 30348838
2019 Random mutagenesis of Tim50 identified two distinct surface patches whose mutation impairs TIM23-dependent precursor import and disrupts Tim50-Tim23 interaction; these patches map onto the Tim50 surface structure, suggesting two regions mediate Tim23 binding. Random mutagenesis, temperature-sensitive growth assays, import assays, co-immunoprecipitation Scientific reports Medium 30765764
2020 Tim50 coordinates preprotein recognition with motor activation via three structural elements: (1) the matrix domain facilitates recruitment of the coupling factor Pam17; (2) the IMS domain promotes PAM recruitment to TIM23; (3) the transmembrane segment stimulates the matrix-directed import force by PAM. This establishes Tim50 as a transmembrane signal transducer coupling IMS presequence recognition to matrix motor activation. Genetic dissection of Tim50 domains, import assays, analysis of PAM/Pam17 recruitment in isolated mitochondria Cell reports Medium 32130909
2023 The Tim50 IMS region contains two functionally distinct domains (core and PBD): the core domain carries the main presequence-binding site and is the main recruitment point to TIM23, while the PBD directly or indirectly facilitates cooperation between TOM and TIM23 complexes. The two domains can complement each other in trans. Domain-swap and trans-complementation experiments, import assays, co-immunoprecipitation Life science alliance Medium 37748811
2024 TIMM50 pathogenic mutations reduce levels of TIM23 core components (TIMM50, TIMM17A/B, TIMM23), decrease mitochondrial membrane potential, and impair TIM23-dependent protein import. Substrates imported via TIM23SORT (lateral release pathway) are most sensitive to TIMM50 loss. OXPHOS and mitochondrial ultrastructure proteins are enriched in the TIM23SORT substrate pool, explaining the specific clinical defects. Proteomics of patient fibroblasts and TIMM50 HEK293 CRISPR/Cas9 model, import assays, mitochondrial membrane potential measurement Molecular and cellular biology Medium 38828998
2024 TIMM50 deficiency in human fibroblasts and mouse neurons selectively reduces steady-state levels of OXPHOS and mitochondrial ribosome components, leading to declined respiration, reduced ATP, and defective mitochondrial trafficking in neuronal processes. TIMM50 knockdown in neurons correlates with reduced KCNJ10 and KCNA2 potassium channel levels and increased electrical activity. Patient fibroblast characterization, mouse neuron knockdown, respirometry, ATP measurement, live neuronal mitochondrial trafficking assay, proteomics, electrophysiology eLife Medium 39680434
2024 eIF5A alleviates ribosome stalling at polyproline-encoding sequences in TIM50 mRNA at the mitochondrial surface. eIF5A depletion reduces Tim50 translation and protein levels, causing accumulation of mitoprotein precursors in the cytosol and triggering a mitochondrial import stress response; removal of polyprolines from Tim50 partially rescues this response. eIF5A depletion in yeast, ribosome profiling, Tim50 polyproline mutant rescue experiments, mitoprotein precursor accumulation assay The Journal of cell biology Medium 39509053
2005 A nuclear isoform of Tim50, Tim50a, contains an N-terminal extension with a nuclear localization signal and localizes to nuclear speckles. Tim50a interacts with coilin, snRNPs, and SMN; coilin competes with Sm proteins and SMN for binding sites on Tim50a, suggesting a role in snRNP biogenesis distinct from the mitochondrial function of Tim50. Subcellular localization by immunofluorescence, co-immunoprecipitation, competition binding experiments BMC cell biology Low 16008839
2011 Mutant p53 (R175H and R273H) upregulates Tim50 expression by increasing histone acetylation and recruiting transcription factors Ets-1, CREB, and CBP to the Tim50 promoter. Reduction of Tim50 in cells harboring mutant p53 reduced growth rate and chemoresistance. Chromatin immunoprecipitation (ChIP), Tim50 promoter reporter assay, siRNA knockdown with proliferation and chemoresistance assays Archives of biochemistry and biophysics Medium 21621504
2025 TIMM50 downregulation in cellular senescence models is mediated by sirtuin1-dependent downregulation of the transcription factor CEBPα (a transcriptional activator of TIMM50). TIMM50 loss triggers all hallmarks of senescence via impaired mitochondrial function. Multiple senescence models, TIMM50 knockdown and overexpression, pathway analysis identifying sirtuin1-CEBPα axis, mitochondrial function assays Advanced biology Low 40128440

Source papers

Stage 0 corpus · 38 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2002 The mitochondrial presequence translocase: an essential role of Tim50 in directing preproteins to the import channel. Cell 217 12437924
2002 Tim50 is a subunit of the TIM23 complex that links protein translocation across the outer and inner mitochondrial membranes. Cell 211 12437925
2006 Tim50 maintains the permeability barrier of the mitochondrial inner membrane. Science (New York, N.Y.) 152 16763150
2009 Tim23-Tim50 pair coordinates functions of translocators and motor proteins in mitochondrial protein import. The Journal of cell biology 117 19139266
2004 Tim50, a component of the mitochondrial translocator, regulates mitochondrial integrity and cell death. The Journal of biological chemistry 83 15044455
2011 Tim50's presequence receptor domain is essential for signal driven transport across the TIM23 complex. The Journal of cell biology 79 22065641
2008 Interaction of Tim23 with Tim50 Is essential for protein translocation by the mitochondrial TIM23 complex. The Journal of biological chemistry 55 19017642
2017 Cardiolipin mediates membrane and channel interactions of the mitochondrial TIM23 protein import complex receptor Tim50. Science advances 54 28879236
2011 Structural basis for the function of Tim50 in the mitochondrial presequence translocase. Journal of molecular biology 41 21704637
2011 Inner mitochondrial translocase Tim50 interacts with 3β-hydroxysteroid dehydrogenase type 2 to regulate adrenal and gonadal steroidogenesis. The Journal of biological chemistry 34 21930695
2007 Involvement of the mitochondrial protein translocator component tim50 in growth, cell proliferation and the modulation of respiration in Drosophila. Genetics 34 17435247
2016 Mitochondrial epileptic encephalopathy, 3-methylglutaconic aciduria and variable complex V deficiency associated with TIMM50 mutations. Clinical genetics 33 27573165
2018 Mutations in TIMM50 compromise cell survival in OxPhos-dependent metabolic conditions. EMBO molecular medicine 32 30190335
2011 Upregulation of the mitochondrial transport protein, Tim50, by mutant p53 contributes to cell growth and chemoresistance. Archives of biochemistry and biophysics 31 21621504
2012 Tim50 in Trypanosoma brucei possesses a dual specificity phosphatase activity and is critical for mitochondrial protein import. The Journal of biological chemistry 25 23212919
2015 Loss of TIM50 suppresses proliferation and induces apoptosis in breast cancer. Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine 23 26289846
2019 Mutations in TIMM50 cause severe mitochondrial dysfunction by targeting key aspects of mitochondrial physiology. Human mutation 18 31058414
2019 A mutagenesis analysis of Tim50, the major receptor of the TIM23 complex, identifies regions that affect its interaction with Tim23. Scientific reports 15 30765764
2020 Transmembrane Coordination of Preprotein Recognition and Motor Coupling by the Mitochondrial Presequence Receptor Tim50. Cell reports 14 32130909
2021 Diverse Functions of Tim50, a Component of the Mitochondrial Inner Membrane Protein Translocase. International journal of molecular sciences 12 34360547
2015 The structure of Tim50(164-361) suggests the mechanism by which Tim50 receives mitochondrial presequences. Acta crystallographica. Section F, Structural biology communications 12 26323300
2005 Tim50a, a nuclear isoform of the mitochondrial Tim50, interacts with proteins involved in snRNP biogenesis. BMC cell biology 11 16008839
2024 eIF5A controls mitoprotein import by relieving ribosome stalling at TIM50 translocase mRNA. The Journal of cell biology 10 39509053
2018 Inner Mitochondrial Translocase Tim50 Is Central in Adrenal and Testicular Steroid Synthesis. Molecular and cellular biology 10 30348838
2015 Down regulation of Tim50 in Trypanosoma brucei increases tolerance to oxidative stress. Molecular and biochemical parasitology 10 25791316
2012 Interaction of presequence with human translocase of the inner membrane of mitochondria Tim50. The journal of physical chemistry. B 10 22335443
2011 Expression and structural characterization of human translocase of inner membrane of mitochondria Tim50. Protein expression and purification 8 21742040
2024 Reduced Protein Import via TIM23 SORT Drives Disease Pathology in TIMM50-Associated Mitochondrial Disease. Molecular and cellular biology 7 38828998
2023 Two domains of Tim50 coordinate translocation of proteins across the two mitochondrial membranes. Life science alliance 7 37748811
2022 A High-Throughput Search for SFXN1 Physical Partners Led to the Identification of ATAD3, HSD10 and TIM50. Biology 6 36138777
2012 Interaction of divalent metal ions with human translocase of inner membrane of mitochondria Tim50. Biochemical and biophysical research communications 6 23098911
2024 Biochemical and neurophysiological effects of deficiency of the mitochondrial import protein TIMM50. eLife 4 39680434
2021 Outer and inner mitochondrial membrane proteins TOMM40 and TIMM50 are intensively concentrated and localized at Purkinje and pyramidal neurons in the New Zealand white rabbit brain. Anatomical record (Hoboken, N.J. : 2007) 3 34041863
2021 Trypanosoma brucei Tim50 Possesses PAP Activity and Plays a Critical Role in Cell Cycle Regulation and Parasite Infectivity. mBio 3 34517757
2024 Biochemical and neurophysiological effects of deficiency of the mitochondrial import protein TIMM50. bioRxiv : the preprint server for biology 1 38826427
2023 eIF5A controls mitoprotein import by relieving ribosome stalling at the TIM50 translocase mRNA. bioRxiv : the preprint server for biology 1 38187585
2022 Correction: Chaudhuri et al. Diverse Functions of Tim50, a Component of the Mitochondrial Inner Membrane Protein Translocase. Int. J. Mol. Sci. 2021, 22, 7779. International journal of molecular sciences 1 35887402
2025 Ameliorating TIMM50 Loss Slows Senescence by Improving Mitochondrial Structure and Function. Advanced biology 0 40128440

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