UQCRC1

---
id: P31930
gene_symbol: UQCRC1
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  UQCRC1 encodes Cytochrome b-c1 complex subunit 1 (Core protein I), one of
  two large structural/core subunits of mitochondrial Complex III (cytochrome
  bc1 complex, CIII2). It resides on the matrix side of the inner
  mitochondrial membrane, forming part of the obligate CIII dimer interface
  and contributing to matrix-side contacts with Complex I in respiratory
  supercomplexes (PMID:28844695). UQCRC1 belongs to the peptidase M16 family
  and is homologous to beta-MPP (the catalytic subunit of mitochondrial
  processing peptidase), but in mammals the catalytic residues required for
  metallopeptidase activity are not conserved and UQCRC1 has no demonstrated
  intrinsic peptidase activity (PMID:8407948, Kohler et al. 2023 EMBO Rep).
  In yeast, the homologous Cor1/Mas1 retains MPP processing activity within
  Complex III, but this function is less established in mammals where a
  separate MPP complex exists. UniProt notes the processing of UQCRFS1 as
  "probable" based on similarity. UQCRC1 does not participate directly in
  Q-cycle redox chemistry; its role is structural, stabilizing the CIII2 dimer
  and supporting supercomplex/respirasome formation. Mutations in UQCRC1 cause
  autosomal dominant parkinsonism with polyneuropathy (PKNPY, OMIM:619279)
  (PMID:33141179). The deep research review (UQCRC1-deep-research-falcon.md)
  confirms UQCRC1 as a non-catalytic structural core protein of CIII2.
existing_annotations:
# ============================================================
# IBA ANNOTATIONS (phylogenetically inferred)
# ============================================================
  - term:
      id: GO:0017087
      label: mitochondrial processing peptidase complex
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: >-
        IBA annotation placing UQCRC1 as part_of the mitochondrial processing
        peptidase (MPP) complex. This is phylogenetically inferred based on
        homology to beta-MPP across the M16 peptidase family (PANTHER
        PTN000220169). In yeast, the Complex III core proteins Cor1 (UQCRC1
        homolog) and Cor2 (UQCRC2 homolog) have been shown to retain MPP-like
        processing activity within the assembled complex. However, in mammals,
        UQCRC1 and UQCRC2 have diverged from their MPP ancestors and there is
        no direct experimental evidence that mammalian UQCRC1 is part of an MPP
        complex or retains peptidase activity (PMID:8407948). UniProt describes
        this function as "Probable" based on similarity to yeast. Reactome
        R-HSA-9906017 notes that the peptidase responsible for cleaving UQCRFS1
        in humans is "unknown" with UQCRC1/UQCRC2 listed only as "possible
        candidates." The IBA inference from yeast is phylogenetically reasonable
        but likely does not accurately reflect mammalian biology.
      action: REMOVE
      reason: >-
        In mammals, UQCRC1 is best supported as a non-catalytic structural core
        subunit of Complex III rather than a component of a dedicated
        mitochondrial processing peptidase complex. The peptidase that cleaves
        human UQCRFS1 remains unresolved in Reactome, with UQCRC1 listed only as
        a possible candidate. Given the lack of direct mammalian evidence for
        UQCRC1 membership in an MPP complex, this annotation is removed from the
        core review set.
      additional_reference_ids: ["Reactome:R-HSA-9906017"]
      supported_by:
        - reference_id: PMID:8407948
          supporting_text: >-
            The predicted human protein shows significant homology with core I
            protein from Saccharomyces cerevisiae, rather high homology (64%
            similarity, 46% identity) with the processing enhancing protein, which
            functions as core I protein in Neurospora crassa, and, surprisingly,
            highest homology with the small subunit of the mitochondrial processing
            peptidase of rat (74% similarity, 55% identity).
        - reference_id: Reactome:R-HSA-9906017
          supporting_text: >-
            An unknown peptidase cleaves the N-terminal 78 amino acids of UQCRFS1
            ...Possible candidates for the peptidase are the UQCRC1 and UQCRC2
            subunits (as hinted at in the cattle model) or the SPY complex

# ============================================================
# IEA ANNOTATIONS (electronic/computational)
# ============================================================
  - term:
      id: GO:1902600
      label: proton transmembrane transport
    evidence_type: IEA
    original_reference_id: GO_REF:0000108
    review:
      summary: >-
        IEA annotation inferred from the quinol-cytochrome-c reductase activity
        (GO:0008121) annotation via logical inter-ontology links. Complex III
        couples electron transfer to proton translocation across the inner
        mitochondrial membrane during the Q-cycle. As a structural core subunit
        of Complex III, UQCRC1 contributes to maintaining the integrity of the
        complex that performs proton transmembrane transport (PMID:28844695).
        While UQCRC1 does not itself directly translocate protons, it is a
        necessary structural component of the complex that does.
      action: ACCEPT
      reason: >-
        This is a valid biological process annotation for UQCRC1 as a subunit
        of Complex III, which couples electron transfer to proton translocation.
        The IEA inference from GO:0008121 is logically sound. The term is at an
        appropriate level of specificity for a structural subunit.
  - term:
      id: GO:0005743
      label: mitochondrial inner membrane
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    review:
      summary: >-
        IEA annotation for mitochondrial inner membrane localization,
        transferred from mouse ortholog (UniProtKB:Q9CZ13). UQCRC1 is a
        peripheral membrane protein on the matrix side of the inner
        mitochondrial membrane, confirmed by cryo-EM structures (PMID:28844695,
        PDB:5XTE) and UniProt subcellular localization annotation.
      action: ACCEPT
      reason: >-
        Correct localization. UQCRC1 is part of Complex III which is embedded
        in the inner mitochondrial membrane. Cryo-EM structural data directly
        confirms this (PMID:28844695). This IEA is consistent with multiple
        higher-confidence annotations for the same term.
  - term:
      id: GO:0016020
      label: membrane
    evidence_type: IEA
    original_reference_id: GO_REF:0000117
    review:
      summary: >-
        IEA annotation for generic membrane localization via ARBA machine
        learning. UQCRC1 is indeed associated with the inner mitochondrial
        membrane as part of Complex III. However, this term is very general
        and is fully subsumed by the more specific GO:0005743 (mitochondrial
        inner membrane) annotations already present from multiple evidence
        sources.
      action: ACCEPT
      reason: >-
        While very broad, this annotation is not incorrect. UQCRC1 is a
        peripheral membrane protein associated with the inner mitochondrial
        membrane. More specific annotations (GO:0005743) are also present.
        Acceptable as a broader IEA that is consistent with the more specific
        annotations.
  - term:
      id: GO:0022904
      label: respiratory electron transport chain
    evidence_type: IEA
    original_reference_id: GO_REF:0000043
    review:
      summary: >-
        IEA annotation from UniProtKB keyword mapping (KW:Electron transport).
        UQCRC1 is a structural subunit of Complex III which is part of the
        respiratory electron transport chain. While UQCRC1 does not itself
        perform electron transfer chemistry, it is an integral structural
        component of the complex that does. This is a broader parent of the
        more specific GO:0006122 (mitochondrial electron transport, ubiquinol
        to cytochrome c) which is also annotated.
      action: ACCEPT
      reason: >-
        Valid biological process annotation. As a structural core subunit of
        Complex III, UQCRC1 is involved in the respiratory electron transport
        chain, even though it does not directly participate in redox chemistry.
        The broader term is acceptable alongside the more specific GO:0006122.
  - term:
      id: GO:0046872
      label: metal ion binding
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    review:
      summary: >-
        IEA annotation from InterPro domain mapping (IPR011249,
        Metalloenz_LuxS/M16). The M16 peptidase family to which UQCRC1 belongs
        is characterized by a zinc-binding metallopeptidase active site.
        However, in mammalian UQCRC1, the catalytic zinc-binding residues are
        not conserved and there is no evidence that human UQCRC1 actually binds
        metal ions. The InterPro domain annotation reflects the evolutionary
        origin of the fold rather than the current function of the human protein.
        UniProt does not annotate any metal binding sites for UQCRC1, and the
        cryo-EM structures (PDB:5XTE) do not show bound metal ions at the
        ancestral active site.
      action: REMOVE
      reason: >-
        This annotation is based on the M16 peptidase domain architecture, but
        mammalian UQCRC1 has lost the catalytic metal-binding residues that
        define active M16 family peptidases. There is no experimental evidence
        for metal ion binding by human UQCRC1, and UniProt does not annotate
        any metal binding sites. This represents a case where domain-based
        inference incorrectly transfers an ancestral function that has been
        lost in the mammalian lineage.
      supported_by:
        - reference_id: file:human/UQCRC1/UQCRC1-deep-research-falcon.md
          supporting_text: >-
            UQCRC1 has no demonstrated enzymatic activity within Complex III. It
            is a structural core protein; catalytic chemistry (Q cycle) is executed
            by cytochrome b, Rieske (UQCRFS1), and cytochrome c1 (CYC1).
  - term:
      id: GO:0098803
      label: respiratory chain complex
    evidence_type: IEA
    original_reference_id: GO_REF:0000117
    review:
      summary: >-
        IEA annotation for respiratory chain complex localization via ARBA
        machine learning. UQCRC1 is indeed a component of respiratory chain
        complex III. This is a parent of the more specific GO:0045275
        (respiratory chain complex III) also annotated via IEA. Acceptable but
        less informative than the more specific term.
      action: ACCEPT
      reason: >-
        Correct but broad. UQCRC1 is unambiguously a component of respiratory
        chain complex III. The more specific GO:0045275 is also present. This
        broader IEA annotation is consistent.

# ============================================================
# PROTEIN BINDING ANNOTATIONS (IPI)
# ============================================================
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:17353931
    review:
      summary: >-
        IPI annotation for protein binding based on large-scale mass
        spectrometry interactome mapping (Ewing et al. 2007). The WITH/FROM
        column indicates UQCRC2 (P22695) as the interacting partner. UQCRC1
        and UQCRC2 are the two core subunits of Complex III and directly
        interact within the complex (PMID:28844695). However, "protein binding"
        is an uninformative term that does not convey the nature of the
        interaction.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        The interaction between UQCRC1 and UQCRC2 within Complex III is well
        established, but "protein binding" is uninformative. This interaction
        is better captured by the CC annotation GO:0045275 (respiratory chain
        complex III), which implies subunit-subunit interactions. Per curation
        guidelines, generic "protein binding" annotations should be avoided.
      supported_by:
        - reference_id: PMID:17353931
          supporting_text: >-
            Large-scale immunoprecipitation of Flag-tagged versions of these proteins
            followed by LC-ESI-MS/MS analysis resulted in the identification of
            24,540 potential protein interactions.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:19688755
    review:
      summary: >-
        IPI annotation for protein binding based on BN-PAGE/LC-MS/MS analysis
        of OXPHOS complexes (Wessels et al. 2009). WITH/FROM indicates UQCRC2
        (P22695). This study used blue native gel analysis combined with
        LC-MS/MS to characterize protein complexes in the mitochondrial
        fraction. The UQCRC1-UQCRC2 interaction within Complex III is
        well-established.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        Same as above: the UQCRC1-UQCRC2 interaction is real but better
        captured by complex membership annotations (GO:0045275). "Protein
        binding" is uninformative per curation guidelines.
      supported_by:
        - reference_id: PMID:19688755
          supporting_text: >-
            We demonstrate the feasibility of this approach by considering the
            oxidative phosphorylation complexes I-V in the native human embryonic
            kidney 293 mitochondrial fraction
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:32814053
    review:
      summary: >-
        IPI annotation for protein binding based on interactome mapping of
        neurodegenerative disease proteins (Haenig et al. 2020). This study
        identified numerous interaction partners for UQCRC1 in a large-scale
        Y2H screen. The WITH/FROM column lists many interactors (NPHP1,
        PRMT5, SULT1B1, BECN1, ARHGDIB, etc.), most of which are not known
        Complex III subunits and likely represent non-specific or indirect
        interactions from a high-throughput screen. These interactions have
        not been validated by targeted studies.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        High-throughput interactome screen results. Most of the listed
        interactors are not known mitochondrial proteins or Complex III
        components. "Protein binding" is uninformative and these are likely
        non-specific high-throughput hits. Per curation guidelines, generic
        "protein binding" should be avoided.
      supported_by:
        - reference_id: PMID:32814053
          supporting_text: >-
            Interactome Mapping Provides a Network of Neurodegenerative Disease
            Proteins and Uncovers Widespread Protein Aggregation in Affected Brains.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:33961781
    review:
      summary: >-
        IPI annotation for protein binding from the BioPlex 3.0 proteome-scale
        interactome (Huttlin et al. 2021). WITH/FROM indicates UQCRC2
        (P22695). The UQCRC1-UQCRC2 interaction within Complex III is
        well-established from structural data (PMID:28844695, PDB:5XTE).
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        The UQCRC1-UQCRC2 interaction is real but "protein binding" is
        uninformative. This interaction is already captured by complex
        membership annotations. Per curation guidelines, generic "protein
        binding" should be avoided.
      supported_by:
        - reference_id: PMID:33961781
          supporting_text: >-
            Through affinity-purification mass spectrometry, we have created
            two proteome-scale, cell-line-specific interaction networks.

# ============================================================
# LOCALIZATION ANNOTATIONS
# ============================================================
  - term:
      id: GO:0005739
      label: mitochondrion
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    review:
      summary: >-
        IEA annotation for mitochondrial localization, combined automated
        annotation from multiple sources including mouse ortholog
        (UniProtKB:Q9CZ13) and ARBA. UQCRC1 is a well-established
        mitochondrial protein. This is consistent with multiple
        higher-confidence annotations.
      action: ACCEPT
      reason: >-
        Correct localization. UQCRC1 is unambiguously a mitochondrial protein.
        Confirmed by IDA, HDA, and HTP annotations from independent sources.
  - term:
      id: GO:0014823
      label: response to activity
    evidence_type: IEA
    original_reference_id: GO_REF:0000107
    review:
      summary: >-
        IEA annotation transferred from rat ortholog (UniProtKB:Q68FY0) via
        Ensembl Compara. This likely reflects expression changes in UQCRC1
        observed in response to physical exercise or similar activity stimuli
        in rat studies. While mitochondrial OXPHOS proteins can be upregulated
        in response to exercise, this annotation represents a secondary
        downstream response rather than a core function of UQCRC1.
      action: KEEP_AS_NON_CORE
      reason: >-
        This annotation likely reflects expression-level changes of UQCRC1 in
        response to activity/exercise. While plausible for a mitochondrial
        OXPHOS protein, this is not a core function and represents a
        pleiotropic response. Keeping as non-core.
  - term:
      id: GO:0043279
      label: response to alkaloid
    evidence_type: IEA
    original_reference_id: GO_REF:0000107
    review:
      summary: >-
        IEA annotation transferred from rat ortholog (UniProtKB:Q68FY0) via
        Ensembl Compara. This likely reflects expression changes in response
        to alkaloid treatment in rat studies. Not a core function of UQCRC1.
        Many mitochondrial proteins show expression changes in response to
        various chemical stimuli without those being core functions.
      action: KEEP_AS_NON_CORE
      reason: >-
        Pleiotropic response annotation. While UQCRC1 expression may change
        in response to alkaloids (many of which affect mitochondrial
        function), this is not a core evolved function. Keeping as non-core.
  - term:
      id: GO:0044877
      label: protein-containing complex binding
    evidence_type: IEA
    original_reference_id: GO_REF:0000107
    review:
      summary: >-
        IEA annotation transferred from rat ortholog (UniProtKB:Q68FY0) via
        Ensembl Compara. UQCRC1 does participate in protein complexes
        (Complex III, supercomplexes), but "protein-containing complex
        binding" is vague. The actual function is being a structural subunit
        of Complex III, which is captured by CC annotations. This MF term
        does not add informative annotation beyond what is already captured
        by the complex membership terms.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        While UQCRC1 is a subunit of Complex III and participates in
        supercomplexes, "protein-containing complex binding" is an
        uninformative MF term. The structural role within Complex III is
        better described by the CC term GO:0045275 (respiratory chain
        complex III). This term does not convey the specific nature of
        UQCRC1's participation in protein complexes.
  - term:
      id: GO:0045275
      label: respiratory chain complex III
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    review:
      summary: >-
        IEA annotation for respiratory chain complex III membership, transferred
        from ortholog data. UQCRC1 is one of the two core structural subunits
        of Complex III (along with UQCRC2). This is confirmed by cryo-EM
        structures of the human respiratory megacomplex (PMID:28844695,
        PDB:5XTE) and extensive biochemical evidence. Complex III is an
        obligatory dimer (CIII2) and UQCRC1 is present in both copies.
      action: ACCEPT
      reason: >-
        Core annotation. UQCRC1 is unambiguously a component of respiratory
        chain complex III. This is confirmed by structural data (PMID:28844695),
        UniProt annotation, and ComplexPortal (CPX-560). This is one of the
        most important annotations for this protein.
      supported_by:
        - reference_id: PMID:28844695
          supporting_text: >-
            The MCI2III2IV2 forms a circular structure with the dimeric CIII
            located in the center, where it is surrounded by two copies each of
            CI and CIV.

# ============================================================
# EXPERIMENTAL LOCALIZATION ANNOTATIONS
# ============================================================
  - term:
      id: GO:0005739
      label: mitochondrion
    evidence_type: IDA
    original_reference_id: GO_REF:0000052
    review:
      summary: >-
        IDA annotation for mitochondrial localization from HPA
        immunofluorescence data (GO_REF:0000052). UQCRC1 is a well-established
        mitochondrial protein, and immunofluorescence confirmation is consistent
        with all other evidence.
      action: ACCEPT
      reason: >-
        Direct experimental evidence confirming mitochondrial localization of
        UQCRC1 via immunofluorescence. Consistent with all other localization
        annotations and the known biology of this Complex III subunit.
  - term:
      id: GO:0005743
      label: mitochondrial inner membrane
    evidence_type: IDA
    original_reference_id: PMID:28844695
    review:
      summary: >-
        IDA annotation for mitochondrial inner membrane localization from
        ComplexPortal, citing the cryo-EM structure of the human respiratory
        megacomplex (Guo et al. 2017). The structure (PDB:5XTE) directly shows
        UQCRC1 as a peripheral protein on the matrix side of the inner
        mitochondrial membrane within Complex III.
      action: ACCEPT
      reason: >-
        Direct structural evidence from cryo-EM at 3.4 Angstrom resolution
        places UQCRC1 on the matrix side of the mitochondrial inner membrane
        as part of Complex III. This is high-quality direct evidence.
      supported_by:
        - reference_id: PMID:28844695
          supporting_text: >-
            The structure not only reveals the precise assignment of individual
            subunits of human CI and CIII, but also enables future in-depth
            analysis of the electron transport chain as a whole.
  - term:
      id: GO:0006122
      label: mitochondrial electron transport, ubiquinol to cytochrome c
    evidence_type: NAS
    original_reference_id: PMID:28844695
    review:
      summary: >-
        NAS annotation from ComplexPortal for the core biological process of
        Complex III, citing Guo et al. 2017. Complex III catalyzes electron
        transfer from ubiquinol to cytochrome c via the Q-cycle mechanism.
        UQCRC1 is a structural core subunit that does not directly participate
        in redox chemistry but is required for complex integrity and therefore
        contributes to this process. The ComplexPortal annotation is at the
        complex level (CPX-560).
      action: ACCEPT
      reason: >-
        Valid biological process annotation. While UQCRC1 is not catalytically
        active in the Q-cycle, it is an essential structural subunit of the
        complex that performs this electron transport. The NAS evidence code is
        appropriate as the publication describes the overall complex structure
        and function rather than specific biochemical activity of UQCRC1.
      supported_by:
        - reference_id: PMID:28844695
          supporting_text: >-
            The respiratory megacomplex represents the highest-order assembly of
            respiratory chain complexes, and it allows mitochondria to respond to
            energy-requiring conditions.
  - term:
      id: GO:0045333
      label: cellular respiration
    evidence_type: NAS
    original_reference_id: PMID:28844695
    review:
      summary: >-
        NAS annotation from ComplexPortal for cellular respiration. Complex III
        is a key component of the mitochondrial respiratory chain, and UQCRC1
        as a structural subunit contributes to this broader biological process.
        This is a parent process of the more specific GO:0006122 and
        GO:0009060 annotations also present.
      action: ACCEPT
      reason: >-
        Valid broader biological process annotation. UQCRC1 is a structural
        subunit of Complex III which is part of the respiratory chain driving
        cellular respiration. Consistent with the more specific electron
        transport annotations.
      supported_by:
        - reference_id: PMID:28844695
          supporting_text: >-
            The MCI2III2IV2 forms a circular structure with the dimeric CIII
            located in the center, where it is surrounded by two copies each of
            CI and CIV.

# ============================================================
# HTP LOCALIZATION
# ============================================================
  - term:
      id: GO:0005739
      label: mitochondrion
    evidence_type: HTP
    original_reference_id: PMID:34800366
    review:
      summary: >-
        HTP annotation for mitochondrial localization from the high-confidence
        human mitochondrial proteome study (Morgenstern et al. 2021). This
        quantitative proteomics study established a comprehensive inventory
        of the human mitochondrial proteome. UQCRC1 was identified as a
        high-confidence mitochondrial protein, consistent with its role as a
        Complex III core subunit.
      action: ACCEPT
      reason: >-
        High-throughput proteomics confirmation of mitochondrial localization.
        Consistent with all other localization evidence. The Morgenstern et al.
        study is a high-quality, quantitative mitochondrial proteome resource.
      supported_by:
        - reference_id: PMID:34800366
          supporting_text: >-
            Quantitative high-confidence human mitochondrial proteome and its
            dynamics in cellular context.

# ============================================================
# ADDITIONAL IPI ANNOTATIONS
# ============================================================
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:35101990
    review:
      summary: >-
        IPI annotation for protein binding from the mitolamban (Mtlbn) study
        (Makarewich et al. 2022). WITH/FROM indicates P0DP99 (STMP1/mitolamban).
        Mtlbn is a small inner mitochondrial membrane microprotein that
        interacts with Complex III subunits and regulates complex assembly.
        The interaction with UQCRC1 was detected by co-immunoprecipitation
        and mass spectrometry. This is a meaningful interaction relevant to
        Complex III assembly and regulation.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        While the UQCRC1-mitolamban interaction appears genuine and
        functionally relevant (mitolamban regulates Complex III assembly),
        "protein binding" is an uninformative term. A more appropriate
        annotation would capture the complex assembly context. Per curation
        guidelines, generic "protein binding" should be avoided.
      supported_by:
        - reference_id: PMID:35101990
          supporting_text: >-
            Mtlbn localizes specifically to the inner mitochondrial membrane
            where it interacts with subunits of complex III of the electron
            transport chain and with mitochondrial respiratory supercomplexes.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:32161263
    review:
      summary: >-
        IPI annotation for protein binding from the BRAWNIN/UQCC6 study
        (Zhang et al. 2020). WITH/FROM indicates Q69YU5 (UQCC6/BRAWNIN).
        UQCC6 is a mitochondrial peptide essential for Complex III assembly
        in vertebrates. The interaction with UQCRC1 is functionally relevant
        as UQCC6 is required for proper CIII2 assembly. UniProt also notes
        this interaction.
      action: MARK_AS_OVER_ANNOTATED
      reason: >-
        The UQCRC1-UQCC6 interaction is biologically meaningful for Complex
        III assembly, but "protein binding" is uninformative. The interaction
        is better described through complex assembly annotations. Per curation
        guidelines, generic "protein binding" should be avoided.
      supported_by:
        - reference_id: PMID:32161263
          supporting_text: >-
            Mitochondrial peptide BRAWNIN is essential for vertebrate respiratory
            complex III assembly.
  - term:
      id: GO:0031625
      label: ubiquitin protein ligase binding
    evidence_type: IPI
    original_reference_id: PMID:19725078
    review:
      summary: >-
        IPI annotation for ubiquitin protein ligase binding from a Parkin
        interactome study (Davison et al. 2009). WITH/FROM indicates O60260
        (Parkin/PRKN). The study used tandem affinity purification/MS in HEK293
        cells with inducible Parkin expression and identified UQCRC1 as one of
        14 potential Parkin interactants. Nine of these interactants were
        directly involved in mitochondrial energy metabolism. Parkin is an E3
        ubiquitin ligase involved in mitophagy, and its interaction with
        mitochondrial OXPHOS subunits including UQCRC1 is consistent with
        Parkin's role in mitochondrial quality control. This is relevant to
        the UQCRC1-associated parkinsonism phenotype (PMID:33141179).
      action: KEEP_AS_NON_CORE
      reason: >-
        The UQCRC1-Parkin interaction is plausible given Parkin's established
        role in mitophagy and mitochondrial quality control. UQCRC1 was
        identified as one of multiple mitochondrial proteins interacting with
        Parkin. While not a core molecular function of UQCRC1, this
        interaction is biologically relevant, especially given the association
        of UQCRC1 mutations with parkinsonism (PMID:33141179). The term
        "ubiquitin protein ligase binding" is more informative than generic
        "protein binding."
      supported_by:
        - reference_id: PMID:19725078
          supporting_text: >-
            Tandem affinity purification/MS revealed 14 potential interactants of
            Parkin; CKB, DBT, HSPD1, HSPA9, LRPPRC, NDUFS2, PRDX6, SLC25A5,
            TPI1, UCHL1, UQCRC1, VCL, YWHAZ, YWHAE. Nine of these are directly
            involved in mitochondrial energy metabolism

# ============================================================
# HDA LOCALIZATION
# ============================================================
  - term:
      id: GO:0005739
      label: mitochondrion
    evidence_type: HDA
    original_reference_id: PMID:20833797
    review:
      summary: >-
        HDA annotation for mitochondrial localization from a phosphoproteomics
        study of functional mitochondria isolated from human skeletal muscle
        (Zhao et al. 2011). UQCRC1 was identified by mass spectrometry in
        purified mitochondrial fractions. This study also identified
        phosphorylation sites on mitochondrial proteins including OXPHOS
        complex subunits.
      action: ACCEPT
      reason: >-
        High-throughput direct assay confirming mitochondrial localization of
        UQCRC1 via proteomics of isolated human muscle mitochondria. Consistent
        with all other localization evidence.
      supported_by:
        - reference_id: PMID:20833797
          supporting_text: >-
            We performed a phosphoproteomics study of functional mitochondria
            isolated from human muscle biopsies with the aim to obtain a
            comprehensive overview of mitochondrial phosphoproteins.

# ============================================================
# TAS ANNOTATIONS (Reactome and literature)
# ============================================================
  - term:
      id: GO:0005743
      label: mitochondrial inner membrane
    evidence_type: TAS
    original_reference_id: Reactome:R-HSA-164651
    review:
      summary: >-
        TAS annotation for mitochondrial inner membrane from Reactome pathway
        "Electron transfer from ubiquinol to cytochrome c of complex III"
        (R-HSA-164651). UQCRC1 is a subunit of Complex III which resides in
        the mitochondrial inner membrane, performing the Q-cycle.
      action: ACCEPT
      reason: >-
        Correct localization from a curated Reactome pathway. Consistent with
        structural and experimental evidence.
  - term:
      id: GO:0005743
      label: mitochondrial inner membrane
    evidence_type: TAS
    original_reference_id: Reactome:R-HSA-9906017
    review:
      summary: >-
        TAS annotation for mitochondrial inner membrane from Reactome pathway
        "Unknown peptidase cleaves UQCRFS1 subunit" (R-HSA-9906017). This
        Reactome entry describes the processing of the UQCRFS1 Rieske protein
        within Complex III. UQCRC1 is mentioned as a possible candidate for
        the unknown peptidase. The localization itself (inner membrane) is
        correct regardless of whether UQCRC1 has peptidase activity.
      action: ACCEPT
      reason: >-
        Correct localization. UQCRC1 is located in the mitochondrial inner
        membrane as part of Complex III, regardless of the specific Reactome
        reaction context.
  - term:
      id: GO:0005743
      label: mitochondrial inner membrane
    evidence_type: TAS
    original_reference_id: Reactome:R-HSA-9906042
    review:
      summary: >-
        TAS annotation for mitochondrial inner membrane from Reactome pathway
        "TTC19 clears UQCRFS1 fragments from Complex III" (R-HSA-9906042).
        The localization of UQCRC1 to the inner membrane is correct.
      action: ACCEPT
      reason: >-
        Correct localization from curated Reactome pathway. UQCRC1 is part of
        Complex III in the inner mitochondrial membrane.
  - term:
      id: GO:0006119
      label: oxidative phosphorylation
    evidence_type: TAS
    original_reference_id: PMID:8407948
    review:
      summary: >-
        TAS annotation for oxidative phosphorylation from the original gene
        cloning paper (Hoffman et al. 1993). The paper describes UQCRC1 as
        a nuclear-encoded component of the ubiquinol-cytochrome c reductase
        complex of the mitochondrial respiratory chain. Complex III is a key
        component of the electron transport chain that drives oxidative
        phosphorylation.
      action: ACCEPT
      reason: >-
        Valid biological process annotation. UQCRC1 is a structural subunit
        of Complex III, which is part of the OXPHOS pathway. The original
        cloning paper correctly places this protein in the respiratory chain
        context.
      supported_by:
        - reference_id: PMID:8407948
          supporting_text: >-
            Core I protein is a nuclear-encoded component of the
            ubiquinol-cytochrome c reductase complex of the mitochondrial
            respiratory chain.
  - term:
      id: GO:0008121
      label: quinol-cytochrome-c reductase activity
    evidence_type: TAS
    original_reference_id: PMID:8407948
    review:
      summary: >-
        TAS annotation for quinol-cytochrome-c reductase activity from the
        original gene cloning paper (Hoffman et al. 1993). This is the
        molecular function of Complex III as a whole. UQCRC1 is a structural
        core subunit that does not itself catalyze the Q-cycle reaction but
        is required for complex integrity. For OXPHOS complex subunits, the
        GO convention is to use "contributes_to" qualifier for the
        complex-level molecular function. The GOA TSV shows this with an
        "enables" qualifier, which may be too strong for a non-catalytic
        subunit.
      action: MODIFY
      reason: >-
        The quinol-cytochrome-c reductase activity (GO:0008121) is the
        molecular function of the entire Complex III. UQCRC1 is a
        non-catalytic structural core subunit that does not directly
        participate in the Q-cycle redox chemistry; the catalytic subunits
        are cytochrome b, UQCRFS1 (Rieske), and CYC1. For non-catalytic
        subunits of enzyme complexes, the appropriate qualifier should be
        "contributes_to" rather than "enables." The annotation itself is
        appropriate at the complex level but the qualifier should be changed
        to contributes_to if not already. Additionally, this annotation
        could be retained with that qualifier adjustment, recognizing that
        UQCRC1 contributes structurally to the activity without directly
        performing catalysis.
      proposed_replacement_terms:
        - id: GO:0008121
          label: quinol-cytochrome-c reductase activity
      supported_by:
        - reference_id: PMID:8407948
          supporting_text: >-
            Core I protein is a nuclear-encoded component of the
            ubiquinol-cytochrome c reductase complex of the mitochondrial
            respiratory chain.
        - reference_id: file:human/UQCRC1/UQCRC1-deep-research-falcon.md
          supporting_text: >-
            UQCRC1 has no demonstrated enzymatic activity within Complex III. It
            is a structural core protein; catalytic chemistry (Q cycle) is
            executed by cytochrome b, Rieske (UQCRFS1), and cytochrome c1 (CYC1).
            Thus, there is no substrate specificity attributable to UQCRC1; its
            contribution is architectural and organizational.
  - term:
      id: GO:0009060
      label: aerobic respiration
    evidence_type: TAS
    original_reference_id: PMID:8407948
    review:
      summary: >-
        TAS annotation for aerobic respiration from the original gene cloning
        paper (Hoffman et al. 1993). Complex III is a key component of the
        aerobic respiratory chain. UQCRC1, as a structural subunit, contributes
        to this process.
      action: ACCEPT
      reason: >-
        Valid biological process annotation. UQCRC1 is a structural subunit
        of Complex III, which functions in aerobic respiration. This is a
        parent term of GO:0006122 and consistent with the overall functional
        context.
      supported_by:
        - reference_id: PMID:8407948
          supporting_text: >-
            Core I protein is a nuclear-encoded component of the ubiquinol-cytochrome
            c
            reductase complex of the mitochondrial respiratory chain.
  - term:
      id: GO:0098803
      label: respiratory chain complex
    evidence_type: TAS
    original_reference_id: PMID:8407948
    review:
      summary: >-
        TAS annotation for respiratory chain complex from the original gene
        cloning paper (Hoffman et al. 1993). UQCRC1 is a component of
        Complex III, which is a respiratory chain complex. This is consistent
        with the more specific GO:0045275 (respiratory chain complex III)
        annotation.
      action: ACCEPT
      reason: >-
        Correct but broad CC annotation. UQCRC1 is unambiguously part of a
        respiratory chain complex (Complex III). The more specific GO:0045275
        is also present. This TAS annotation from the original cloning paper
        is valid.
      supported_by:
        - reference_id: PMID:8407948
          supporting_text: >-
            Core I protein is a nuclear-encoded component of the
            ubiquinol-cytochrome c reductase complex of the mitochondrial
            respiratory chain.

references:
  - id: GO_REF:0000002
    title: Gene Ontology annotation through association of InterPro records with GO
      terms
    findings:
      - statement: InterPro2GO mapping from the M16 metallopeptidase fold
          (IPR011249) propagates an ancestral metal-ion-binding annotation to
          UQCRC1, although the catalytic residues are not conserved in mammalian
          UQCRC1.
  - id: GO_REF:0000033
    title: Annotation inferences using phylogenetic trees
    findings:
      - statement: PAINT/IBA phylogenetic propagation places UQCRC1 in the
          mitochondrial processing peptidase complex via PANTHER PTN000220169,
          based on yeast Cor1/beta-MPP ancestry rather than direct mammalian
          evidence.
  - id: GO_REF:0000043
    title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
    findings:
      - statement: UniProtKB keyword mapping (KW:Electron transport) propagates
          respiratory electron transport chain involvement to UQCRC1 as a
          Complex III core subunit.
  - id: GO_REF:0000052
    title: Gene Ontology annotation based on curation of immunofluorescence data
    findings:
      - statement: Curated immunofluorescence data (Human Protein Atlas) place
          UQCRC1 in mitochondria.
  - id: GO_REF:0000107
    title: Automatic transfer of experimentally verified manual GO annotation data
      to orthologs using Ensembl Compara
    findings:
      - statement: Ensembl Compara ortholog transfer from rodent UQCRC1
          (UniProtKB:Q68FY0, Q9CZ13) propagates response-to-activity,
          response-to-alkaloid, and protein-containing complex binding
          annotations to human UQCRC1.
  - id: GO_REF:0000108
    title: Automatic assignment of GO terms using logical inference, based on on inter-ontology
      links
    findings:
      - statement: Logical inference from quinol-cytochrome-c reductase activity
          (GO:0008121) propagates proton transmembrane transport (GO:1902600)
          to Complex III subunits including UQCRC1.
  - id: GO_REF:0000117
    title: Electronic Gene Ontology annotations created by ARBA machine learning models
    findings:
      - statement: ARBA machine-learning rules assign generic membrane and
          respiratory-chain-complex annotations to UQCRC1.
  - id: GO_REF:0000120
    title: Combined Automated Annotation using Multiple IEA Methods
    findings:
      - statement: Combined automated IEA methods propagate mitochondrial inner
          membrane localization, mitochondrion, and respiratory chain complex
          III membership to UQCRC1.
  - id: PMID:8407948
    title: Complete coding sequence, intron/exon organization, and chromosomal location
      of the gene for the core I protein of human ubiquinol-cytochrome c reductase.
    findings:
      - statement: >-
          Reports the complete coding sequence of human UQCRC1, showing 480
          amino acids with a 34-residue mitochondrial leader peptide. Shows
          highest homology with rat beta-MPP (74% similarity, 55% identity)
          and N. crassa processing enhancing protein (64% similarity).
        supporting_text: >-
          Core I protein is a nuclear-encoded component of the ubiquinol-cytochrome
          c
          reductase complex of the mitochondrial respiratory chain.
  - id: PMID:17353931
    title: Large-scale mapping of human protein-protein interactions by mass spectrometry.
    findings:
      - statement: >-
          Large-scale IP-MS interactome mapping of 338 bait proteins; detected
          UQCRC1-UQCRC2 interaction.
        supporting_text: >-
          Large-scale immunoprecipitation of Flag-tagged versions of these proteins
          followed by LC-ESI-MS/MS analysis resulted in the identification of
          24,540 potential protein interactions.
  - id: PMID:19688755
    title: LC-MS/MS as an alternative for SDS-PAGE in blue native analysis of protein
      complexes.
    findings:
      - statement: >-
          BN-PAGE/LC-MS/MS analysis of OXPHOS complexes confirming UQCRC1 as
          part of Complex III and its co-migration with UQCRC2.
        supporting_text: >-
          We demonstrate the feasibility of this approach by considering the
          oxidative phosphorylation complexes I-V in the native human embryonic
          kidney 293 mitochondrial fraction
  - id: PMID:19725078
    title: Proteomic analysis of increased Parkin expression and its interactants
      provides evidence for a role in modulation of mitochondrial function.
    findings:
      - statement: >-
          Identified UQCRC1 as one of 14 Parkin interactants by tandem affinity
          purification/MS, linking Parkin E3 ligase to mitochondrial OXPHOS
          components.
        supporting_text: >-
          Tandem affinity purification/MS revealed 14 potential interactants of
          Parkin; CKB, DBT, HSPD1, HSPA9, LRPPRC, NDUFS2, PRDX6, SLC25A5,
          TPI1, UCHL1, UQCRC1, VCL, YWHAZ, YWHAE.
  - id: PMID:20833797
    title: Phosphoproteome analysis of functional mitochondria isolated from resting
      human muscle reveals extensive phosphorylation of inner membrane protein complexes
      and enzymes.
    findings:
      - statement: >-
          Identified UQCRC1 in mitochondria purified from human skeletal muscle
          biopsies by phosphoproteomics.
        supporting_text: >-
          We performed a phosphoproteomics study of functional mitochondria
          isolated from human muscle biopsies
  - id: PMID:28844695
    title: Architecture of Human Mitochondrial Respiratory Megacomplex I(2)III(2)IV(2).
    findings:
      - statement: >-
          Cryo-EM structure of the human respiratory megacomplex at 3.4 Angstrom
          resolution directly resolves UQCRC1 (chains L/Y) within the CIII2 dimer
          at the center of the megacomplex I2III2IV2.
        supporting_text: >-
          The MCI2III2IV2 forms a circular structure with the dimeric CIII
          located in the center, where it is surrounded by two copies each of
          CI and CIV.
  - id: PMID:32161263
    title: Mitochondrial peptide BRAWNIN is essential for vertebrate respiratory complex
      III assembly.
    findings:
      - statement: >-
          Identified UQCC6/BRAWNIN as a mitochondrial peptide essential for CIII2
          assembly that interacts with UQCRC1.
        supporting_text: >-
          Mitochondrial peptide BRAWNIN is essential for vertebrate respiratory
          complex III assembly.
  - id: PMID:32814053
    title: Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins
      and Uncovers Widespread Protein Aggregation in Affected Brains.
    findings:
      - statement: >-
          Large-scale Y2H interactome mapping of neurodegenerative disease
          proteins identified numerous UQCRC1 interaction partners, most from
          high-throughput screening without targeted validation.
        supporting_text: >-
          Interactome Mapping Provides a Network of Neurodegenerative Disease
          Proteins and Uncovers Widespread Protein Aggregation in Affected Brains.
  - id: PMID:33961781
    title: Dual proteome-scale networks reveal cell-specific remodeling of the human
      interactome.
    findings:
      - statement: >-
          BioPlex 3.0 proteome-scale interactome detected UQCRC1-UQCRC2
          interaction in 293T cells.
        supporting_text: >-
          Through affinity-purification mass spectrometry, we have created
          two proteome-scale, cell-line-specific interaction networks.
  - id: PMID:34800366
    title: Quantitative high-confidence human mitochondrial proteome and its dynamics
      in cellular context.
    findings:
      - statement: >-
          Identified UQCRC1 as a high-confidence mitochondrial protein in the
          quantitative human mitochondrial proteome.
        supporting_text: >-
          Quantitative high-confidence human mitochondrial proteome and its
          dynamics in cellular context.
  - id: PMID:35101990
    title: The cardiac-enriched microprotein mitolamban regulates mitochondrial respiratory
      complex assembly and function in mice.
    findings:
      - statement: >-
          Identified mitolamban (Mtlbn/STMP1) as a microprotein that interacts
          with Complex III subunits including UQCRC1 and regulates complex
          assembly.
        supporting_text: >-
          Mtlbn localizes specifically to the inner mitochondrial membrane where
          it interacts with subunits of complex III of the electron transport
          chain and with mitochondrial respiratory supercomplexes.
  - id: PMID:33141179
    title: Mitochondrial UQCRC1 mutations cause autosomal dominant parkinsonism with
      polyneuropathy.
    findings:
      - statement: >-
          Identified UQCRC1 mutations (I311L, Y314S) as causing autosomal
          dominant parkinsonism with polyneuropathy (PKNPY). UQCRC1 plays an
          important role in maintenance of proper mitochondrial function in
          nigral dopaminergic neurons.
        supporting_text: >-
          Mitochondrial UQCRC1 mutations cause autosomal dominant parkinsonism
          with polyneuropathy.
  - id: Reactome:R-HSA-164651
    title: Electron transfer from ubiquinol to cytochrome c of complex III
    findings:
      - statement: >-
          Reactome pathway describing the Q-cycle mechanism by which Complex III
          transfers electrons from ubiquinol to cytochrome c with concomitant
          proton translocation.
        supporting_text: >-
          The protonmotive Q cycle is the mechanism by which complex III transfers
          electrons from ubiquinol to cytochrome c, linking this process to
          translocation of protons across the membrane.
  - id: Reactome:R-HSA-9906017
    title: Unknown peptidase cleaves UQCRFS1 subunit
    findings:
      - statement: >-
          Reactome notes that the peptidase that cleaves UQCRFS1 in humans is
          unknown, with UQCRC1 and UQCRC2 listed as possible candidates based
          on the cattle model.
        supporting_text: >-
          Possible candidates for the peptidase are the UQCRC1 and UQCRC2
          subunits (as hinted at in the cattle model) or the SPY complex
  - id: Reactome:R-HSA-9906042
    title: TTC19 clears UQCRFS1 fragments from Complex III
    findings:
      - statement: >-
          TTC19 clears N-terminal cleavage fragments of UQCRFS1 from Complex III
          to stabilize the final complex.
        supporting_text: >-
          N-terminal cleavage fragments of UQCRFS1 are cleared by TTC19,
          stabilizing the final complex.
  - id: file:human/UQCRC1/UQCRC1-deep-research-falcon.md
    title: Deep research review of UQCRC1 (Falcon/Edison)
    findings:
      - statement: >-
          Comprehensive review confirms UQCRC1 as a non-catalytic structural
          core subunit of CIII2 with no intrinsic enzymatic activity. It
          stabilizes the CIII2 dimer and mediates matrix-side contacts with
          Complex I in supercomplexes via interactions with NDUFB4 and NDUFB9.
        supporting_text: >-
          UQCRC1 has no demonstrated enzymatic activity within Complex III.
          It is a structural core protein; catalytic chemistry (Q cycle) is
          executed by cytochrome b, Rieske (UQCRFS1), and cytochrome c1
          (CYC1). Thus, there is no substrate specificity attributable to
          UQCRC1; its contribution is architectural and organizational.
core_functions:
  - molecular_function:
      id: GO:0008121
      label: quinol-cytochrome-c reductase activity
    directly_involved_in:
      - id: GO:0006122
        label: mitochondrial electron transport, ubiquinol to cytochrome c
      - id: GO:1902600
        label: proton transmembrane transport
    locations:
      - id: GO:0005743
        label: mitochondrial inner membrane
    description: >-
      UQCRC1 (core protein 1) is a non-catalytic structural core subunit of the
      dimeric cytochrome bc1 complex (Complex III). It helps stabilize complex
      architecture and supports supercomplex organization, thereby enabling the
      complex-level electron-transfer and proton-coupled functions of Complex III
      without directly catalyzing Q-cycle redox chemistry.
    supported_by:
      - reference_id: PMID:28844695
        supporting_text: >-
          The MCI2III2IV2 forms a circular structure with the dimeric CIII located
          in the center, where it is surrounded by two copies each of CI and CIV.
      - reference_id: file:human/UQCRC1/UQCRC1-deep-research-falcon.md
        supporting_text: >-
          UQCRC1 has no demonstrated enzymatic activity within Complex III. It is
          a
          structural core protein; catalytic chemistry (Q cycle) is executed by
          cytochrome b, Rieske (UQCRFS1), and cytochrome c1 (CYC1). Thus, there is
          no
          substrate specificity attributable to UQCRC1; its contribution is
          architectural and organizational.
    in_complex:
      id: GO:0045275
      label: respiratory chain complex III
suggested_questions:
  - question: >-
      Does mammalian UQCRC1 retain any residual peptidase activity within Complex III,
      or are UQCRC1 / UQCRC2 the long-sought peptidase that cleaves UQCRFS1's N-terminal
      78 amino acids (Reactome:R-HSA-9906017)? Demonstrating either result would
      finalize the molecular-function annotation (currently structural only) and
      clarify whether the GO:0017087 / peptidase annotations are biologically valid in
      mammals rather than yeast-derived holdovers.
  - question: >-
      What is the molecular basis by which the PKNPY-causing variants I311L and Y314S
      (PMID:33141179) disrupt UQCRC1 function — do they primarily destabilize the CIII2
      dimer interface, perturb CI-CIII2 supercomplex contacts via NDUFB4/NDUFB9, or
      affect UQCRFS1 processing/maturation? Mapping the mechanism would justify either
      a "respirasome assembly" or a more specific "complex III dimer stabilization"
      annotation.
  - question: >-
      Why do UQCRC1 mutations preferentially affect nigral dopaminergic neurons and
      peripheral nerves (PKNPY phenotype) rather than producing a generalized OXPHOS
      deficiency? Is this tissue selectivity driven by the high dependence of these
      neurons on supercomplex-mediated efficient electron transfer, by altered ROS
      production, or by an unrecognized neuronal-specific UQCRC1 function?
suggested_experiments:
  - description: >-
      In vitro peptidase activity assay with purified human Complex III (wild-type vs.
      UQCRC1/UQCRC2 active-site reconstituted mutants) and recombinant pre-UQCRFS1
      substrate, with mass-spec mapping of cleavage products. Compare with isolated
      human MPP and with a UQCRC1/UQCRC2 double-KO HEK293 cell line tested for UQCRFS1
      processing in vivo.
    hypothesis: >-
      Mammalian UQCRC1 has lost direct peptidase activity, and UQCRFS1 processing in
      human cells is mediated by an as-yet-unidentified protease (e.g., the SPY/m-AAA
      complex) rather than by the Complex III core subunits.
    experiment_type: biochemistry / proteomics
  - description: >-
      CRISPR knock-in of UQCRC1 I311L and Y314S in dopaminergic iPSC-derived neurons
      vs. isogenic controls, followed by BN-PAGE supercomplex profiling, CI-CIII2
      cross-linking proteomics around NDUFB4/NDUFB9 contact sites, high-resolution
      respirometry, ROS measurements, and lysosomal/mitophagy assays. Pair with cryo-EM
      of patient-derived supercomplexes if material permits.
    hypothesis: >-
      I311L and Y314S destabilize the CI-CIII2 supercomplex interface (rather than the
      CIII2 dimer itself), elevating electron leakage and ROS specifically under the
      high OXPHOS load characteristic of dopaminergic neurons.
    experiment_type: structural biology / stem-cell neuroscience
  - description: >-
      Comparative metabolic vulnerability screen across iPSC-derived nigral
      dopaminergic neurons, peripheral sensory neurons, cortical neurons,
      cardiomyocytes, and hepatocytes from PKNPY patients vs. isogenic controls under
      varying galactose/glucose, hypoxia/normoxia, and pharmacological CIII inhibition
      (myxothiazol, antimycin). Quantify cell death, mitochondrial network morphology,
      and α-synuclein aggregation propensity in neurons.
    hypothesis: >-
      Dopaminergic neurons are uniquely vulnerable to partial CIII supercomplex
      dysfunction because their bioenergetic margin under physiological calcium load is
      narrowest, and partial UQCRC1 loss-of-function crosses this threshold while other
      cell types tolerate the defect.
    experiment_type: stem-cell biology / clinical model