Affinage

TIMM23

Mitochondrial import inner membrane translocase subunit Tim23 · UniProt O14925

Length
209 aa
Mass
21.9 kDa
Annotated
2026-06-10
80 papers in source corpus 48 papers cited in narrative 50 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 9/9 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TIMM23 (Tim23) is the central inner-membrane subunit of the mitochondrial TIM23 presequence translocase that imports presequence-bearing precursor proteins from the cytosol into the matrix and inner membrane (PMID:9128249, PMID:37696957). It adopts a two-membrane-spanning topology in which its C-terminal domain is integrated in the inner membrane while an intrinsically disordered N-terminal/intermembrane-space (IMS) domain reaches across to the outer membrane, forming contact sites that channel precursors from TOM to TIM23 (PMID:10830167, PMID:20718036). The IMS domain serves as a dynamic organizing hub: it dimerizes in a membrane-potential-dependent manner to act as a presequence receptor, and dimer dissociation upon presequence binding is coupled to channel opening (PMID:8858146, PMID:32277989). This domain coordinates the translocase by binding Tim50, the primary presequence receptor, as well as Tim21 and Tom22, integrating substrate handover with channel gating in which presequences and Tim50 act antagonistically on the channel (PMID:12437925, PMID:22065641, PMID:25263020). Conformational rearrangements of the transmembrane segments accompany membrane potential changes and substrate trapping, and pore properties such as cation selectivity are essential for import (PMID:23832274, PMID:28857742). Tim23 recruits the matrix mtHsp70-based PAM import motor through its matrix-exposed loop, binding Tim44 and the Tim14(Pam18)/Tim16(Pam16) J-protein subcomplex that drives ATP-dependent translocation (PMID:14517234, PMID:14981506, PMID:28440746, PMID:24061477). Recent cryo-EM structures revise the long-standing channel model: Tim23 plays a primarily structural role within a Tim17–Tim23–Tim44/Mgr2 core, while the protein-conducting path is formed by the Tim17 cavity sealed laterally by Mgr2, which gates lateral release of hydrophobic stop-transfer substrates into the inner membrane (PMID:37344598, PMID:37696957, PMID:40877479). Beyond constitutive import, TIM23 interacts with PINK1 and protects it from OMA1-mediated degradation, positioning the translocase as a damage-sensing switch in PINK1–Parkin mitophagy (PMID:37160114, PMID:38416681). The translocase is a target of pathology: mutant huntingtin binds Tim23 and inhibits matrix import (PMID:31346086), and reduced TIM23 import capacity activates the CHOP branch of the mitochondrial unfolded protein response (PMID:29949403).

Mechanistic history

Synthesis pass · year-by-year structured walk · 17 steps
  1. 1996 High

    Established that Tim23 is not a static channel but a membrane-potential-regulated presequence receptor, defining the first dynamic gating principle of the translocase.

    Evidence Biochemical dimerization assays with membrane potential manipulation and leucine-repeat mutagenesis in yeast mitochondria

    PMID:8858146

    Open questions at the time
    • Did not resolve the structural basis of dimerization
    • Coupling between dimer dissociation and physical channel opening inferred indirectly
  2. 1997 High

    Linked Tim23 directly to the protein-conducting pore activity of the inner membrane, identifying it as essential for the multiple conductance channel.

    Evidence Patch-clamp electrophysiology with antibody inhibition and the tim23-1 mutant

    PMID:9128249

    Open questions at the time
    • Did not distinguish whether Tim23 itself lines the conducting pore
    • No structural assignment of pore-lining residues
  3. 2000 High

    Resolved how Tim23 bridges two membranes, explaining how precursors transfer from TOM to TIM23 at contact sites and how the IMS domain is positioned as a receptor.

    Evidence Protease accessibility, GFP topology mapping, import competition and EM in yeast

    PMID:10830167

    Open questions at the time
    • Mechanism of outer-membrane anchoring of the N-terminus not defined
    • Stoichiometry of contact-site complexes unresolved
  4. 2000 High

    Defined the chaperone requirements for Tim23 biogenesis itself, showing the small TIM8-13 complex escorts Tim23 across the IMS under low potential.

    Evidence Co-IP, crosslinking of translocation intermediates, and TIM8-13 depletion import assays; later supported by crystal structure

    PMID:11101512 PMID:18706423

    Open questions at the time
    • Whether TIM8-13 chaperones other substrates in this mode not addressed here
  5. 2002 High

    Identified Tim50 as the IMS partner of the Tim23 N-domain that mediates precursor handover from TOM, establishing the receptor architecture of the inner-membrane face.

    Evidence Site-specific photocrosslinking, reciprocal co-IP, depletion and antibody inhibition

    PMID:12437925

    Open questions at the time
    • Did not map the presequence-binding residues of Tim50
    • Channel-gating consequence of Tim50 binding not yet defined
  6. 2004 High

    Completed identification of the PAM import-motor co-chaperones, showing Tim14/Pam18 and Tim16/Pam16 form a J-protein subcomplex that activates mtHsp70 within the translocase.

    Evidence Protein identification, reciprocal co-IP, HPD-motif mutagenesis and depletion import assays

    PMID:14517234 PMID:14981506

    Open questions at the time
    • How motor activation is mechanically coupled to Tim23 channel dynamics not resolved
    • Quantitative ATPase kinetics within the assembled translocase not measured
  7. 2008 High

    Mapped the conformational and quaternary dynamics of Tim23 in functional membranes, showing TMS2 lines an amphipathic channel that rearranges with gating and that subunit proximities change with potential and substrate.

    Evidence Site-directed fluorescence mapping and site-specific crosslinking of Tim23 cysteine mutants in intact mitochondria

    PMID:17959826 PMID:18692467

    Open questions at the time
    • Atomic structure not obtained
    • Whether TMS2 forms a true aqueous channel vs lipid-exposed cavity unresolved at this stage
  8. 2011 High

    Defined the antagonistic regulation of the Tim23 channel by presequences and Tim50, and quantified trans-side presequence binding by Tim44 and Tim23 that supports directional import.

    Evidence Photo-affinity labeling with MS mapping, electrophysiology, and SPR/crosslinking with purified components

    PMID:21969381 PMID:22065641

    Open questions at the time
    • In situ regulation under physiological potential not directly measured
    • Affinity hierarchy across the full import pathway not fully reconstituted
  9. 2014 High

    Established the Tim23 IMS domain as an intrinsically disordered, membrane-associated interaction hub contacting Tim21, Tim50 and Tom22, and identified cardiolipin as a modulator of its membrane attachment.

    Evidence NMR with single-residue mapping and membrane model systems including cardiolipin liposomes

    PMID:25263020 PMID:25349212

    Open questions at the time
    • In vivo functional consequence of cardiolipin effect not validated
    • Dynamic interactions not captured in an intact translocase structure
  10. 2014 High

    Assigned distinct interaction sites that organize the motor and regulatory subunits, with Tim23 loop 1 anchoring Tim44 and adjacent contacts positioning Pam17.

    Evidence Site-specific in vivo photocrosslinking with genetic and co-IP validation

    PMID:24061477 PMID:25157107

    Open questions at the time
    • Precise allosteric path from motor docking to channel gating undefined
  11. 2017 High

    Detailed the Tim44 NTD/CTD bipartite engagement of presequences and the translocon, and showed cardiolipin tunes Tim50 receptor association with the membrane and Tim23.

    Evidence In vivo crosslinking with in vitro binding, plus SAXS structure and MD of the Tim50 receptor

    PMID:28440746 PMID:28879236

    Open questions at the time
    • Full assembled translocase structure not yet available at this point
    • Lipid regulation in cells not quantified
  12. 2017 High

    Demonstrated that cation selectivity of the Tim23 channel is mechanistically required for substrate recognition and import competence.

    Evidence Structure-based mutagenesis with electrophysiology and import assays

    PMID:28857742

    Open questions at the time
    • Pore-lining residue assignment later revised by cryo-EM showing the Tim17 path
  13. 2019 Medium

    Defined Mgr2 and Pam18 as controllers of the lateral gate that decide between matrix translocation and inner-membrane insertion of stop-transfer substrates.

    Evidence Electrophysiology, substrate-specific import assays and co-IP in Mgr2/Pam18 perturbation strains

    PMID:30279421 PMID:30697167 PMID:31764998

    Open questions at the time
    • Structural basis of lateral gating not resolved here
    • Hydrophobicity threshold values determined in single systems
  14. 2021 High

    Captured the TOM-TIM23 interface at amino-acid resolution by crosslinking a stalled supercomplex, defining the physical map of precursor transfer.

    Evidence Chemical crosslinking-MS with structural modeling of a stalled translocation intermediate

    PMID:34588454

    Open questions at the time
    • Static snapshot of one stalled state
    • Did not resolve gating transitions during active translocation
  15. 2023 High

    Revised the core channel model by cryo-EM, showing Tim23 is primarily structural while the Tim17 cavity sealed by Mgr2 forms the protein-conducting path.

    Evidence Cryo-EM of core TIM23 heterotrimer and active TOM-TIM23 supercomplex with translocating substrate, with biochemical validation

    PMID:37344598 PMID:37696957 PMID:40877479

    Open questions at the time
    • How earlier electrophysiology-defined Tim23 channel properties reconcile with the Tim17 path not fully integrated
    • Human translocase structure not directly determined
  16. 2024 High

    Connected TIM23 to mitophagy initiation, showing it interacts with PINK1, protects it from OMA1 degradation, and tethers TOM to TIM23 as a stress-sensing switch.

    Evidence Co-IP, MS, BN-PAGE, PINK1 mutagenesis and mitophagy assays across cell models including organoids; OMA1 inactivation rescue

    PMID:37160114 PMID:38416681

    Open questions at the time
    • Whether import-channel activity per se versus the physical tether drives PINK1 sensing partly unresolved
    • Role distinct from TOM not fully separated in all conditions
  17. 2024 Medium

    Linked TIM23 translocase integrity to disease and quality control, showing prohibitin/OCIAD1 and DNAJC15/OMA1 regulate TIM23 variant stability and that TIMM50 loss preferentially depletes laterally sorted OXPHOS substrates.

    Evidence Quantitative proteomics, co-IP, protease perturbation and import assays in patient and engineered cells

    PMID:31346086 PMID:38828998 PMID:39630581 PMID:40877479

    Open questions at the time
    • Mechanistic detail of variant-selective protease targeting incomplete
    • Two preprint findings on DNAJC15/PINK1 import not yet peer-reviewed

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved how the historically defined Tim23 channel and gating properties are reconciled with the cryo-EM Tim17-conducting-path model, and how TIM23 substrate selection is regulated dynamically during physiological import and stress.
  • No integrated structural-electrophysiological model of Tim23's structural role
  • Regulation of TIM23 import capacity in human disease contexts only partially mapped

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 3 GO:0060089 molecular transducer activity 3 GO:0140096 catalytic activity, acting on a protein 3 GO:0008289 lipid binding 2
Localization
GO:0005739 mitochondrion 3
Pathway
R-HSA-392499 Metabolism of proteins 3 R-HSA-9609507 Protein localization 3 R-HSA-9612973 Autophagy 2
Partners
MGR2PAM16PAM18PINK1TIMM17TIMM21TIMM44TIMM50
Complex memberships
PAM import motorPINK1-TOM-TIM23 supercomplexTIM23 presequence translocaseTOM-TIM23 supercomplex

Evidence

Reading pass · 50 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1996 Tim23 forms dimers promoted by membrane potential (ΔΨ); binding of a matrix targeting sequence to Tim23 triggers dimer dissociation. Dimerization depends on a heptad leucine repeat motif in the N-terminal hydrophilic domain (IMS-exposed). Monomeric Tim23 is present when a preprotein is in transit, suggesting Tim23 dimers act as receptors for matrix targeting sequences and dimer dissociation triggers TIM channel opening. Biochemical dimerization assays, membrane potential manipulation, preprotein binding experiments, mutational analysis of leucine repeat motif Cell High 8858146
2000 Tim23 has a two-membrane-spanning topology: its C-terminal domain is anchored in the inner membrane, an intermediate domain is exposed in the IMS as a presequence receptor, and the N-terminal domain is exposed on the surface of the outer mitochondrial membrane. This simultaneous integration into two membranes forms contact sites between outer and inner membranes, facilitating transfer of precursors from TOM to TIM23. Protease accessibility assays, GFP fusion topology mapping, import competition, electron microscopy Cell High 10830167
2000 The TIM8-Tim13 complex in the IMS interacts with translocation intermediates of Tim23 (partially translocated across the outer membrane), binding to the N-terminal or intermediate domain of Tim23 to prevent retrograde translocation. The TIM8-13 complex is required for Tim23 import under low membrane potential conditions. Co-immunoprecipitation, import assays with TIM8-13 deletion/depletion strains, crosslinking of translocation intermediates The EMBO journal High 11101512
1997 Tim23 is required for normal activity of the multiple conductance channel (MCC) of the mitochondrial inner membrane. Anti-Tim23 antibodies that inhibit protein import also inhibit MCC activity; the tim23-1 mutation alters MCC conductance and abolishes presequence-peptide blockage of MCC, identifying Tim23 as essential for the protein-conducting pore activity. Electrophysiology (patch clamp), antibody inhibition, yeast tim23-1 mutant analysis The Journal of cell biology High 9128249
2002 Tim50 is a subunit of the TIM23 complex anchored to the inner membrane with its C-terminal domain exposed to the IMS. Tim50 interacts with the N-terminal IMS domain of Tim23. Tim50 depletion or antibody addition blocks protein translocation across the inner membrane. A translocation intermediate at TOM is crosslinked to Tim50, establishing Tim50 as a component that mediates transfer of translocating proteins from TOM to TIM23. Site-specific photocrosslinking, co-immunoprecipitation, protein depletion, antibody inhibition assays Cell High 12437925
2003 Tim14 (Pam18) is an integral inner membrane protein with a J-domain exposed to the matrix. It is an essential component of the TIM23 import motor, interacting with Tim44 and mtHsp70 in an ATP-dependent manner. A mutation in the HPD motif of the J-domain is lethal, establishing Tim14 as the J-protein co-chaperone that activates mtHsp70 ATPase activity within the TIM23 motor. Gene depletion, import assays, co-immunoprecipitation, HPD motif mutagenesis, ATP-dependence studies The EMBO journal High 14517234
2004 Tim16 (Pam16) is a novel J-domain-related cochaperone that forms a stable subcomplex with Tim14 within the TIM23 translocase. Depletion of Tim16 markedly impairs matrix protein import and disrupts Tim14 interaction with the TIM23 complex, leading to severe structural changes of the import motor. Protein identification, co-immunoprecipitation, gene depletion, import assays Nature structural & molecular biology High 14981506
1998 Tim23 contains two independent import signals: one in the first 62 residues of the N-terminal hydrophilic domain mediating ΔΨ-independent outer membrane translocation, and a second in the C-terminal membrane-integrated domain mediating ΔΨ-dependent translocation and inner membrane insertion. Import of Tim23 into the inner membrane requires Tim22 (not functional Tim23), establishing that TIM23 biogenesis depends on the TIM22 complex. Deletion mutagenesis, import assays with ΔΨ manipulation, genetic epistasis with Tim22/Tim23 depletion strains The EMBO journal High 9501078
2006 Tim17p regulates twin-pore structure and voltage gating of TIM23. Patch clamp of reconstituted inner membranes showed TIM23 has twin pores that cooperatively gate. Tim17p depletion collapses the twin pores into a single pore; N-terminal deletion or C-terminal truncation of Tim17p produces variable-sized pores. Tim17p N-terminus is vital for voltage sensing and protein sorting, while Tim23p is the main structural unit of the pore. Patch clamp electrophysiology of reconstituted inner membranes, Tim17p deletion and truncation mutants The Journal of biological chemistry High 17148445
2008 Fluorescence mapping using environment-sensitive probes positioned along transmembrane segment 2 (TMS2) of Tim23 revealed an amphipathic alpha-helix in the protein-conducting channel region. Probes on the aqueous-facing helical surface underwent spectral changes during active protein import, and their accessibility to hydrophilic quenchers changes with channel gating, defining the channel-lining face of Tim23 TMS2. Site-directed fluorescence labeling, multiple spectral analyses (polarization, intensity, lifetime), hydrophilic quenching in functional intact mitochondria Cell High 18692467
2008 The Tim8-Tim13 complex assembles as a hexamer and binds Tim23 cooperatively with ~6 binding sites, exhibiting positive cooperativity. The crystal structure (2.6 Å) reveals tentacle-like helices with hydrophobic pockets that interact with Tim23 transmembrane helices, shielding them during chaperoned translocation across the IMS. X-ray crystallography (2.6 Å), surface plasmon resonance binding kinetics Journal of molecular biology High 18706423
2008 Tim23 cross-links to Tim17 at its first transmembrane segment, to Tim50 at the C-terminal end of its hydrophilic IMS region, and Tim23 IMS domains cross-link to each other (dimerization). These proximity relationships reversibly change upon membrane potential alterations and when a translocating substrate is trapped, demonstrating dynamic conformational rearrangements of the TIM23 quaternary structure. Site-specific chemical cross-linking of radiolabeled Tim23 monocysteine mutants imported into functional mitochondria Molecular biology of the cell High 17959826
2008 Yeast Aac2 (ADP/ATP carrier) physically associates with both the cytochrome bc1-COX supercomplex and the TIM23 machinery. Affinity purification with His-tagged Aac2 co-purifies TIM23 components. This association can occur independently of the fully assembled cytochrome bc1-COX supercomplex. Affinity purification (His-tag), co-immunoprecipitation, blue native gel electrophoresis Molecular biology of the cell Medium 18614795
2009 Tim23-Tim50 interactions in the IMS facilitate both transfer of precursor proteins from TOM40 to TIM23 and a late step of translocation across the inner membrane by promoting mtHsp70 motor functions. The Tim23-Tim50 pair thus coordinates actions of TOM40 and TIM23 complexes together with the import motor. Genetic analysis of Tim23/Tim50 IMS domain mutants, co-immunoprecipitation, import assays, crosslinking The Journal of cell biology High 19139266
2008 In vitro reconstitution of the Tim23-Tim50 IMS domain interaction using purified recombinant proteins. Chemical cross-linking and surface plasmon resonance defined the interaction. Mutations in Tim23 that abolish Tim50 binding in vitro also destabilize the interaction in vivo, causing defective protein import and temperature-sensitive lethality. In vitro reconstitution with purified recombinant proteins, chemical cross-linking, surface plasmon resonance, in vivo import assays The Journal of biological chemistry High 19017642
2010 The IMS domain of Tim23 (residues 1-96, Tim23N) is an intrinsically disordered protein. NMR titrations with two presequences identified a distinct presequence-binding region formed by residues 71-84, making Tim23N the only IMS-exposed domain of TOM/TIM23 predicted to be intrinsically disordered. NMR spectroscopy, NMR titrations with presequence peptides, charge-hydropathy analysis Protein science High 20718036
2011 Tim50's presequence-binding domain was mapped by photo-affinity labeling with engineered presequence probes and mass spectrometric identification of cross-linking sites. Tim50 is established as the primary presequence receptor at the inner membrane. Targeting signals and Tim50 regulate the Tim23 channel in an antagonistic manner: presequences promote channel opening while Tim50 keeps the channel closed. Photo-affinity labeling, mass spectrometric mapping, in vitro import assays, electrophysiology The Journal of cell biology High 22065641
2011 Purified Tim50IMS and Tim44 directly bind presequence peptides (Hsp60, mHsp70, cytochrome P450SCC presequences), demonstrated by chemical cross-linking and surface plasmon resonance with defined KD values. Tim23IMS binding to presequences was also characterized. These stronger interactions on the trans side of the channel support directional import. Chemical cross-linking of purified recombinant proteins, surface plasmon resonance with KD determination The Journal of biological chemistry High 21969381
2011 TIM23-mediated membrane insertion of transmembrane alpha-helices into the mitochondrial inner membrane depends strongly on hydrophobicity and position of polar/aromatic residues, paralleling the ER system, but shows striking differences in the effect of flanking charged residues compared to the ER translocon. Systematic mutagenesis of model transmembrane segments, in vitro import assays in yeast mitochondria The EMBO journal Medium 21326212
2013 High-resolution fluorescence mapping of TMS2 of Tim23 in energized versus depolarized membranes showed that TMS2 forms a continuous alpha-helix inaccessible to the IMS aqueous phase in energized membranes. Upon depolarization, helical periodicity is disrupted and the channel becomes exposed to the IMS. Kinetic measurements confirmed that TMS2 conformational changes coincide with depolarization. Site-directed fluorescence labeling in intact yeast membranes, multiple spectroscopic methods, kinetic measurements Nature structural & molecular biology High 23832274
2012 Sym1 (yeast ortholog of MPV17), a multispanning inner membrane protein, is imported via TIM23 in a presequence-independent manner using internal targeting signals, rather than via TIM22 as expected for carrier-type proteins. This defines a novel transport mechanism for a polytopic inner membrane protein through TIM23. Import assays with TIM23/TIM22 depletion, translocation intermediate trapping, protease protection Molecular and cellular biology Medium 23045398
2014 Molecular basis of TIM23 architecture: Tim23 loop 1 (between TM1 and TM2, matrix-exposed) cross-links to Tim44; alterations in this loop destabilize Tim44 interaction with the translocon. Tim17 loop 1 cross-links to Pam17; alterations destabilize Pam17-translocon interaction. This positions Tim44 and Pam17 as regulatory subunits at distinct translocon interaction sites. Site-specific in vivo photocross-linking, co-immunoprecipitation, genetic analysis The Journal of biological chemistry High 25157107
2014 The IMS domain of Tim23 tightly associates with both inner and outer mitochondrial membrane-like membranes through a hydrophobic anchor at its N-terminus. The membrane-bound Tim23 IMS domain remains highly dynamic. Cardiolipin enhances Tim23 membrane attachment, suggesting cardiolipin influences preprotein import. NMR spectroscopy with membrane model systems, cardiolipin-containing liposomes The Journal of biological chemistry Medium 25349212
2014 NMR characterization of the dynamic interaction network within the TIM23 IMS: Tim23 IMS domain contains multiple sites for interaction with Tim21 IMS domain, and also interacts with Tim50 and Tom22. The atomic details of the Tim23IMS-Tim21IMS complex were determined, establishing Tim23 IMS as a hub for TIM23 complex organization. NMR spectroscopy, chemical shift perturbation mapping at single-residue level Structure High 25263020
2015 GxxxG motifs in transmembrane segments 1 and 2 of Tim23 are necessary for structural integrity of the TIM23 complex. Mutations of specific glycines in TM1 and TM2 caused lethal or temperature-sensitive phenotypes correlated with TIM23 complex destabilization, without impairing Tim23 import or membrane integration itself. Systematic mutagenesis of GxxxG motifs, yeast growth assays, blue native gel electrophoresis The FEBS journal Medium 25765297
2016 Tim17 contains a pair of highly conserved cysteine residues forming a structural disulfide bond exposed to the IMS. This disulfide bond is critical for efficient protein translocation through TIM23 and for dynamic gating of the preprotein-conducting channel. The disulfide is formed during Tim17 insertion, dependent on Mia40 binding but not its oxidoreductase activity; direct oxidation by Erv1 is suggested. Cysteine mutagenesis, electrophysiology (channel gating assays), import assays, redox biochemistry The Journal of cell biology High 27502485
2017 Both domains of Tim44 interact with the major matrix-exposed loop of Tim23: the C-terminal domain (CTD) anchors Tim44 to the translocon (also binding Tim17), while the N-terminal domain (NTD) is intrinsically disordered and dynamically interacts with presequences near the region important for Hsp70 and Tim23 interaction. Site-specific in vivo crosslinking, genetic analysis, in vitro binding assays eLife High 28440746
2017 Cardiolipin directly modulates interactions between the Tim50 soluble receptor domain and the Tim23 channel. The Tim50 receptor domain interacts with membranes and with specific sites on Tim23 in a cardiolipin-dependent manner. SAXS-based structure of the full soluble Tim50 receptor was determined. Molecular dynamics simulations confirmed cardiolipin-driven Tim50 association with lipid bilayers with concomitant structural changes. SAXS structure determination, molecular dynamics simulations, biophysical measurements in liposomes, in vivo and isolated mitochondria assays Science advances High 28879236
2017 Cation selectivity of the Tim23 channel is essential for protein import. Structure-based mutations of highly conserved pore-lining amino acids reduce selectivity, reduce protein import capacity, and render the Tim23 channel insensitive to substrates, demonstrating that cation selectivity is a key feature for substrate recognition. Structure-based mutagenesis, electrophysiology (cation selectivity measurements), in vitro import assays eLife High 28857742
2018 The import motor J-protein Pam18 controls lateral protein release into the lipid bilayer through the TIM23 lateral gate. Constitutively translocase-associated Pam18 obstructs lateral precursor transport and displaces Mgr2 from the translocase, demonstrating that during motor-dependent matrix import, the Pam18 transmembrane segment closes the lateral gate to promote anterograde translocation. Genetic and biochemical analysis, import assays of matrix-targeted vs stop-transfer substrates, co-immunoprecipitation Nature communications Medium 30279421
2019 Mutant huntingtin (mHTT) specifically binds the TIM23 subunit (of the four TIM23 complex proteins) and resides in the mitochondrial intermembrane space. mHTT binding inhibits mitochondrial protein import specifically through TIM23, reducing levels of TIM23-imported soluble matrix proteins in mHTT-expressing cells and HD patient brain tissue. Co-immunoprecipitation, mitochondrial fractionation, quantitative proteomics, quantitative immunoblotting in cell lines and human HD brain tissue Proceedings of the National Academy of Sciences of the United States of America High 31346086
2019 In the IMS, the Tim23-Tim50 interaction surface is larger than previously thought; an unexpected interaction of Tim23 with Pam17 in the IMS was identified. Mutations of two conserved negatively charged residues of Tim23 near the inner membrane prevented Tim23 dimerization and increased Tim23 surface exposure, while membrane potential dissipation decreased surface exposure. In vivo mutagenesis, crosslinking, dimerization assays, surface accessibility experiments Journal of molecular biology Medium 32277989
2021 Chemical cross-linking combined with mass spectrometry of a stalled TOM-TIM23 supercomplex mapped protein-protein interactions at the IMS interface between TOM and TIM23 at amino acid resolution, including contacts involving Tim23 and Tim50. The import motor interactions were also mapped in this context. Chemical cross-linking with mass spectrometric analysis, structural modeling, purification of stalled translocation intermediate Nature communications High 34588454
2023 Cryo-EM structure of the core TIM23 complex (Tim17-Tim23-Tim44 heterotrimer) from S. cerevisiae was determined. Contrary to the prevailing model, Tim23 and Tim17 do not form a shared water-filled channel; instead, they have separate lipid-exposed concave cavities facing opposite directions. The cavity of Tim17 (not Tim23) forms the protein translocation path; Tim23 has primarily a structural role. Mgr2 seals the lateral opening of the Tim17 cavity to facilitate translocation. Cryo-electron microscopy structure determination, biochemical validation Nature High 37344598
2023 Cryo-EM structures of the active TOM-TIM23 supercomplex with translocating substrate revealed that TIM23 contains a heterotrimer of Tim23, Tim17, and Mgr2. Polypeptide substrates are shielded from lipids by Mgr2 and Tim17, with a translocation pathway characterized by a negatively charged entrance and central hydrophobic region. In TOM, the substrate passes through the center of Tom40. Cryo-electron microscopy of active supercomplex with translocating substrate, biochemical analysis Nature structural & molecular biology High 37696957
2023 TIM23 interacts with PINK1 and facilitates PINK1 accumulation upon mitochondrial depolarization by protecting PINK1 from degradation by the OMA1 protease. TIM23 knockdown decreases PINK1 levels and delays autophosphorylation; OMA1 inactivation rescues PINK1 levels when TIM23 is depleted. Pathogenic PINK1 mutants that fail to interact with TIM23 have deficiencies partially restored by OMA1 inactivation. Mass spectrometric identification of PINK1 co-immunoprecipitates, co-immunoprecipitation, TIM23 knockdown, OMA1 inactivation, PINK1 autophosphorylation assays Cell reports High 37160114
2024 PINK1 forms a high-molecular-weight PINK1-TOM-TIM23 supercomplex upon mitochondrial stress in human cultured cell lines, dopamine neurons, and midbrain organoids. PINK1 is required to stably tether TOM to TIM23 complexes in response to stress. This tethering depends on an interaction between the PINK1 N-terminal C-terminal extension module and the cytosolic domain of Tom20; disruption by designer or PD-associated PINK1 mutations inhibits downstream mitophagy. Co-immunoprecipitation, blue native gel electrophoresis, PINK1 mutagenesis, mitophagy assays in multiple cell models including organoids Proceedings of the National Academy of Sciences of the United States of America High 38416681
2024 OCIAD1 and the prohibitin complex regulate the stability of the human TIM23 translocase. Prohibitins stabilize both TIMM17A- and TIMM17B-containing TIM23 variants. OCIAD1 assembles with the prohibitin complex to specifically protect the TIMM17A variant from degradation by the YME1L protease. OCIAD1 expression is regulated by TIM23 complex status. Co-immunoprecipitation, protease inhibition, siRNA knockdown, quantitative proteomics Cell reports Medium 39630581
2024 TIMM50 pathogenic variants reduce levels and activity of the TIM23 complex, and proteomic analysis reveals that laterally released substrates imported via the TIM23SORT pathway are most sensitive to TIMM50 loss. Proteins involved in OXPHOS and mitochondrial ultrastructure are enriched in the TIM23SORT substrate pool, providing a biochemical mechanism for TIMM50-associated disease. Quantitative proteomics of patient fibroblasts and HEK293 cell model, import assays, blue native gel electrophoresis Molecular and cellular biology Medium 38828998
2025 Cryo-EM structures of the active TOM-TIM23 supercomplex captured with translocating substrate show that the Tim17-Mgr2 pathway creates the translocation channel with a central restriction formed by four conserved hydrophobic residues. Substrate hydrophobicity modulates Mgr2 association with Tim17, enabling dynamic regulation of protein sorting toward matrix or membrane. Cryo-electron microscopy of active translocating supercomplex, biochemical validation Nature structural & molecular biology High 40877479
2020 Tim23 knockdown in mouse muscle (40% reduction) caused a 32% decrease in matrix-destined protein import and activated the CHOP branch of the UPRmt (increased ClpP and cpn10) without activating the ATF5 arm, demonstrating that reduced TIM23 import capacity triggers a specific branch of the mitochondrial unfolded protein response. In vivo antisense oligonucleotide knockdown, import assays, UPRmt marker measurements American journal of physiology. Cell physiology Medium 29949403
2008 Tim23 undergoes intra-mitochondrial proteolytic degradation following mitochondrial outer membrane permeabilization (MOMP) in a caspase-independent but Bax/Bak-dependent manner. This degradation is mitochondrion-autonomous (occurs in isolated mitochondria undergoing permeability transition), selective for Tim23, and depletion of Tim23 by siRNA inhibits cell proliferation and prevents long-term survival. Caspase inhibition, Bax/Bak knockout, isolated mitochondria assays, siRNA knockdown, Tim23-GFP complementation Cell death and differentiation Medium 18174902
2023 NOX4 localizes to the mitochondrial matrix following asbestos exposure in lung macrophages via direct interaction with TIM23. TIM23 augments NOX4-induced mitochondrial ROS and metabolic reprogramming to oxidative phosphorylation. Silencing TIM23 decreased mitochondrial ROS and oxidative phosphorylation. The interaction was localized to the proximal transmembrane region of NOX4. Co-immunoprecipitation, TIM23 silencing, mitochondrial fractionation, ROS measurement, OXPHOS analysis The Journal of biological chemistry Medium 37044213
2020 Mitochondrial ROS induces rapid translocation of APE1 from the IMS into the matrix through the TIM23/PAM machinery complex. The IMS serves as a storage site for APE1 under basal conditions. Mitochondrial fractionation, import assays, TIM23 knockdown, oxidative stress induction Journal of molecular biology Medium 33197464
2013 TM1 of Tim23 is required for homodimerization; TM1 and TM2 together are involved in preprotein binding within the channel, and TM2 recruits Tim21 and the PAM subcomplex to Tim23. The matrix-exposed loop L1 generates specificity in PAM subcomplex association. The C-terminal sequence of Tim23 functions as an inhibitor of Tim21 binding. Mutagenesis, co-immunoprecipitation, genetic complementation, import assays in yeast Molecular and cellular biology Medium 24061477
2019 Deletion of Mgr2 decreases normal TIM23 channel gating frequency and produces a residual channel activity lacking gating transitions but remaining sensitive to import signal peptides. A G145L mutation in Tim23 displaces Mgr2 from the complex leading to the same gating impairment, establishing that Mgr2 regulates TIM23 channel gating behavior. Patch clamp electrophysiology of yeast inner membranes, Mgr2 deletion and Tim23 point mutation Frontiers in physiology Medium 30697167
2019 Mgr2 controls the threshold hydrophobicity and flanking charge requirements for TIM23-mediated membrane insertion via the stop-transfer mechanism. Deletion of Mgr2 reduces the hydrophobicity threshold required for membrane insertion and reduces the requirement for matrix-facing positive charges, establishing Mgr2 as a lateral gatekeeper that discriminates stop-transfer signal features. Systematic mutagenesis of model transmembrane segments, membrane insertion assays in Mgr2-deletion and overexpression yeast strains FEBS letters Medium 31764998
2026 PGC-1α promotes binding of NRF1 to the Tim23 promoter, upregulating Tim23 expression, which in turn reduces DRP1 transcription and ACSL4 mitochondrial translocation, thereby inhibiting ferroptosis and MASH. This establishes a PGC-1α-Tim23-DRP1-ACSL4 axis in hepatocyte ferroptosis. Western blot, RT-qPCR, immunofluorescence, luciferase reporter assays, co-immunoprecipitation, mouse MASH models Cell death & disease Medium 41724762
2025 In the absence of TIM23, PINK1 is stabilized in the TOM complex. The MMP (not the PAM import motor) is the primary driving force for PINK1 import through TIM23. Loss of TIM23 is sufficient to activate Parkin, establishing TIM23 as the essential inner membrane translocase that separates PINK1 from TOM as the key damage-sensing switch in the PINK1-Parkin mitophagy pathway. Genome-wide screens, PINK1 import assays, TIM23 knockout, Parkin activation assays, membrane potential manipulation bioRxivpreprint Medium
2025 OMA1-mediated degradation of DNAJC15 reduces protein import of OXPHOS-related proteins via the TIMM23-TIMM17A translocase under mitochondrial stress, limiting OXPHOS biogenesis. Loss of DNAJC15 specifically reduces TIMM17A-containing TIM23 complex-dependent import. Proteomic analysis, import assays, OMA1 and DNAJC15 genetic perturbations, blue native gel electrophoresis bioRxivpreprint Medium

Source papers

Stage 0 corpus · 80 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1996 Role of Tim23 as voltage sensor and presequence receptor in protein import into mitochondria. Cell 249 8858146
2002 Tim50 is a subunit of the TIM23 complex that links protein translocation across the outer and inner mitochondrial membranes. Cell 211 12437925
2003 Tim14, a novel key component of the import motor of the TIM23 protein translocase of mitochondria. The EMBO journal 168 14517234
2000 Tim23 links the inner and outer mitochondrial membranes. Cell 142 10830167
2004 The J domain-related cochaperone Tim16 is a constituent of the mitochondrial TIM23 preprotein translocase. Nature structural & molecular biology 133 14981506
2000 The role of the TIM8-13 complex in the import of Tim23 into mitochondria. The EMBO journal 131 11101512
2009 Tim23-Tim50 pair coordinates functions of translocators and motor proteins in mitochondrial protein import. The Journal of cell biology 117 19139266
1997 Tim23, a protein import component of the mitochondrial inner membrane, is required for normal activity of the multiple conductance channel, MCC. The Journal of cell biology 101 9128249
2006 Tim17p regulates the twin pore structure and voltage gating of the mitochondrial protein import complex TIM23. The Journal of biological chemistry 98 17148445
2002 Protein import into and across the mitochondrial inner membrane: role of the TIM23 and TIM22 translocons. Biochimica et biophysica acta 95 12191765
2008 Fluorescence mapping of mitochondrial TIM23 complex reveals a water-facing, substrate-interacting helix surface. Cell 88 18692467
2006 Identification of Tam41 maintaining integrity of the TIM23 protein translocator complex in mitochondria. The Journal of cell biology 87 16943180
2008 The yeast Aac2 protein exists in physical association with the cytochrome bc1-COX supercomplex and the TIM23 machinery. Molecular biology of the cell 86 18614795
2019 Mutant huntingtin disrupts mitochondrial proteostasis by interacting with TIM23. Proceedings of the National Academy of Sciences of the United States of America 85 31346086
2011 Tim50's presequence receptor domain is essential for signal driven transport across the TIM23 complex. The Journal of cell biology 79 22065641
2023 Structural basis of mitochondrial protein import by the TIM23 complex. Nature 72 37344598
1998 Biogenesis of Tim23 and Tim17, integral components of the TIM machinery for matrix-targeted preproteins. The EMBO journal 65 9501078
2024 Tom20 gates PINK1 activity and mediates its tethering of the TOM and TIM23 translocases upon mitochondrial stress. Proceedings of the National Academy of Sciences of the United States of America 63 38416681
2013 Structural changes in the mitochondrial Tim23 channel are coupled to the proton-motive force. Nature structural & molecular biology 63 23832274
2008 The Tim8-Tim13 complex has multiple substrate binding sites and binds cooperatively to Tim23. Journal of molecular biology 63 18706423
2004 Conserved N-terminal negative charges in the Tim17 subunit of the TIM23 translocase play a critical role in the import of preproteins into mitochondria. The Journal of biological chemistry 62 15618217
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
2016 A disulfide bond in the TIM23 complex is crucial for voltage gating and mitochondrial protein import. The Journal of cell biology 54 27502485
2021 Mapping protein interactions in the active TOM-TIM23 supercomplex. Nature communications 53 34588454
2003 Human poly(ADP-ribose) glycohydrolase (PARG) gene and the common promoter sequence it shares with inner mitochondrial membrane translocase 23 (TIM23). Gene 53 14527731
2023 Molecular pathway of mitochondrial preprotein import through the TOM-TIM23 supercomplex. Nature structural & molecular biology 52 37696957
2008 The F1F0-ATP synthase complex influences the assembly state of the cytochrome bc1-cytochrome oxidase supercomplex and its association with the TIM23 machinery. The Journal of biological chemistry 52 18187422
2014 A novel import route for an N-anchor mitochondrial outer membrane protein aided by the TIM23 complex. EMBO reports 51 24781694
2007 Quaternary structure of the mitochondrial TIM23 complex reveals dynamic association between Tim23p and other subunits. Molecular biology of the cell 51 17959826
2020 From TOM to the TIM23 complex - handing over of a precursor. Biological chemistry 50 32074073
2014 Cooperation of TOM and TIM23 complexes during translocation of proteins into mitochondria. Journal of molecular biology 50 25083920
2011 Direct interaction of mitochondrial targeting presequences with purified components of the TIM23 protein complex. The Journal of biological chemistry 48 21969381
2011 TIM23-mediated insertion of transmembrane α-helices into the mitochondrial inner membrane. The EMBO journal 42 21326212
2023 TIM23 facilitates PINK1 activation by safeguarding against OMA1-mediated degradation in damaged mitochondria. Cell reports 40 37160114
2017 Dual interaction of scaffold protein Tim44 of mitochondrial import motor with channel-forming translocase subunit Tim23. eLife 40 28440746
2016 The TIM23 mitochondrial protein import complex: function and dysfunction. Cell and tissue research 40 27590886
2007 Association of the Tim14.Tim16 subcomplex with the TIM23 translocase is crucial for function of the mitochondrial protein import motor. The Journal of biological chemistry 38 17452317
2012 The channel-forming Sym1 protein is transported by the TIM23 complex in a presequence-independent manner. Molecular and cellular biology 37 23045398
2010 The intermembrane space domain of Tim23 is intrinsically disordered with a distinct binding region for presequences. Protein science : a publication of the Protein Society 37 20718036
2001 Modular structure of the TIM23 preprotein translocase of mitochondria. The Journal of biological chemistry 37 11344168
2018 Motor recruitment to the TIM23 channel's lateral gate restricts polypeptide release into the inner membrane. Nature communications 33 30279421
2015 GxxxG motifs hold the TIM23 complex together. The FEBS journal 33 25765297
2017 Cation selectivity of the presequence translocase channel Tim23 is crucial for efficient protein import. eLife 31 28857742
2014 Architecture of the TIM23 inner mitochondrial translocon and interactions with the matrix import motor. The Journal of biological chemistry 31 25157107
2008 Neurological phenotype and reduced lifespan in heterozygous Tim23 knockout mice, the first mouse model of defective mitochondrial import. Biochimica et biophysica acta 30 19111522
2005 The import motor of the yeast mitochondrial TIM23 preprotein translocase contains two different J proteins, Tim14 and Mdj2. The Journal of biological chemistry 30 16027163
2022 Towards a molecular mechanism underlying mitochondrial protein import through the TOM and TIM23 complexes. eLife 29 35674314
2017 Stendomycin selectively inhibits TIM23-dependent mitochondrial protein import. Nature chemical biology 28 28991239
2018 Effect of Tim23 knockdown in vivo on mitochondrial protein import and retrograde signaling to the UPRmt in muscle. American journal of physiology. Cell physiology 27 29949403
2008 Intra-mitochondrial degradation of Tim23 curtails the survival of cells rescued from apoptosis by caspase inhibitors. Cell death and differentiation 24 18174902
2014 Molecular basis of the dynamic structure of the TIM23 complex in the mitochondrial intermembrane space. Structure (London, England : 1993) 23 25263020
2019 Metformin restores the mitochondrial membrane potentials in association with a reduction in TIMM23 and NDUFS3 in MPP+-induced neurotoxicity in SH-SY5Y cells. EXCLI journal 22 31645842
2013 Molecular insights revealing interaction of Tim23 and channel subunits of presequence translocase. Molecular and cellular biology 21 24061477
2024 Mitochondrial import stress and PINK1-mediated mitophagy: the role of the PINK1-TOMM-TIMM23 supercomplex. Autophagy 16 38597070
2020 Mitochondrial Oxidative Stress Induces Rapid Intermembrane Space/Matrix Translocation of Apurinic/Apyrimidinic Endonuclease 1 Protein through TIM23 Complex. Journal of molecular biology 16 33197464
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
2014 Interaction of the intermembrane space domain of Tim23 protein with mitochondrial membranes. The Journal of biological chemistry 15 25349212
2005 The phosphate carrier has an ability to be sorted to either the TIM22 pathway or the TIM23 pathway for its import into yeast mitochondria. The Journal of biological chemistry 15 15644337
2019 The Mgr2 subunit of the TIM23 complex regulates membrane insertion of marginal stop-transfer signals in the mitochondrial inner membrane. FEBS letters 14 31764998
2024 OCIAD1 and prohibitins regulate the stability of the TIM23 protein translocase. Cell reports 13 39630581
2020 InVivo Dissection of the Intrinsically Disordered Receptor Domain of Tim23. Journal of molecular biology 12 32277989
2024 Structure prediction analysis of human core TIM23 complex reveals conservation of the protein translocation mechanism. FEBS open bio 10 38837610
2005 A cryptic matrix targeting signal of the yeast ADP/ATP carrier normally inserted by the TIM22 complex is recognized by the TIM23 machinery. The Biochemical journal 9 15320873
2025 TIMM23 overexpression drives NSCLC cell growth and survival by enhancing mitochondrial function. Cell death & disease 8 40082395
2024 Reduced Protein Import via TIM23 SORT Drives Disease Pathology in TIMM50-Associated Mitochondrial Disease. Molecular and cellular biology 7 38828998
2023 NOX4-TIM23 interaction regulates NOX4 mitochondrial import and metabolic reprogramming. The Journal of biological chemistry 7 37044213
2022 Coordinated Translocation of Presequence-Containing Precursor Proteins Across Two Mitochondrial Membranes: Knowns and Unknowns of How TOM and TIM23 Complexes Cooperate With Each Other. Frontiers in physiology 7 35069261
2018 Expression of the human TIMM23 and TIMM23B genes is regulated by the GABP transcription factor. Biochimica et biophysica acta. Gene regulatory mechanisms 7 29413900
2019 Deletion of Mgr2p Affects the Gating Behavior of the TIM23 Complex. Frontiers in physiology 6 30697167
2019 Development of renal failure in PargParp-1 null and Timm23 hypomorphic mice. Biochemical pharmacology 6 31326434
2012 The structural characteristics of human preprotein translocase of the inner mitochondrial membrane Tim23: implications for its physiological activities. Protein expression and purification 5 22306744
2025 Dynamic TOM-TIM23 supercomplex directs mitochondrial protein translocation and sorting. Nature structural & molecular biology 4 40877479
2024 Moringa oleifera leaf extract suppresses TIMM23 and NDUFS3 expression and alleviates oxidative stress induced by Aβ1-42 in neuronal cells via activation of Akt. Research in pharmaceutical sciences 2 39006971
2025 Targeting TIMM23 to overcome osteosarcoma chemoresistance. Cell death & disease 1 41285805
2024 TOM-TIM23 supercomplex formation. Methods in enzymology 1 39488380
2024 Hotspots for Disease-Causing Mutations in the Mitochondrial TIM23 Import Complex. Genes 1 39766801
2016 Interaction of divalent metal ions with human translocase of inner membrane of mitochondria Tim23. Biochemical and biophysical research communications 1 27178215
2026 PGC-1α protects against MASH via Tim23-dependent inhibition of DRP1-mediated ferroptosis. Cell death & disease 0 41724762
2026 TIMM23-ERAL1 Axis: A novel regulator of mitochondrial apoptosis in hepatocellular carcinoma. Biochimica et biophysica acta. Molecular basis of disease 0 41912011

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