id: Q9P0I2
gene_symbol: EMC3
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: EMC3 (ER membrane protein complex subunit 3; also TMEM111) is a 261-residue polytopic ER membrane protein with three transmembrane helices and a lumenal N-terminus, and is the catalytic insertase subunit of the ER membrane protein complex (EMC), a conserved nine- to ten-subunit transmembrane-domain insertase and membrane-protein chaperone of the endoplasmic reticulum. EMC3 belongs to the Oxa1/YidC/Get1 insertase superfamily and is a distant homolog of the tail-anchored-protein insertase Get1; together with the small subunit EMC6 it forms the membrane-embedded hydrophilic vestibule through which substrate transmembrane domains are inserted. A methionine-rich cytosolic loop of EMC3 is required for substrate engagement, and structure-guided mutations of EMC3 residues lining the vestibule (e.g. Arg-31, the Met-rich loop, Arg-180) reduce client insertion without disrupting complex assembly, demonstrating that EMC3 provides the substrate-conducting active site. As part of the EMC, EMC3 enables the energy-independent insertion of newly synthesized membrane proteins into the ER membrane, with a preference for transmembrane domains that are weakly hydrophobic or carry destabilizing charged or aromatic residues. It mediates post-translational insertion of tail-anchored proteins and cotranslational insertion and N-exo topogenesis of multipass membrane proteins, including the first transmembrane domain of G protein-coupled receptors, in cooperation with the Sec61 translocon. EMC3 is broadly expressed and resides in the ER membrane.
alternative_products:
- name: '1'
  id: Q9P0I2-1
- name: '2'
  id: Q9P0I2-2
  sequence_note: VSP_014886
existing_annotations:
- term:
    id: GO:0032977
    label: membrane insertase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: contributes_to
  review:
    summary: Phylogenetic (PAN-GO) assignment of membrane insertase activity across the EMC3/Oxa1-YidC family. EMC3 forms the substrate-conducting catalytic vestibule of the EMC with EMC6, so membrane insertase activity is the core molecular function; the contributes_to qualifier reflects that EMC3 acts within the multi-subunit complex.
    action: ACCEPT
    reason: Core molecular function; EMC3 is the catalytic insertase subunit (YidC/Oxa1/Get1 superfamily) and provides the membrane vestibule, with mutagenesis separating its insertion role from complex assembly.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: No effect on EMC assembly but decreased
- term:
    id: GO:0071816
    label: tail-anchored membrane protein insertion into ER membrane
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: Phylogenetic propagation of the EMC's tail-anchored protein insertion role across the EMC3 family, consistent with direct experimental and structural evidence. Core EMC process executed at the EMC3/EMC6 vestibule.
    action: ACCEPT
    reason: Core EMC-mediated process; the EMC post-translationally inserts tail-anchored proteins through the EMC3-containing vestibule.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: post-translational insertion of tail-anchored/TA proteins in
- term:
    id: GO:0072546
    label: EMC complex
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: part_of
  review:
    summary: Phylogenetic assignment of EMC complex membership across the EMC3 family, matching direct experimental and structural evidence. Core structural identity of EMC3.
    action: ACCEPT
    reason: EMC complex membership is a core cellular-component identity of EMC3 and is supported by IDA, cryo-EM structures, and the conserved EMC3 family.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: Component of the ER membrane protein complex (EMC).
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Electronic transfer of the ER membrane subcellular location from UniProt; the correct and core compartment for the multipass ER membrane subunit EMC3.
    action: ACCEPT
    reason: Correct core location; redundant with experimental EXP/IDA evidence.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
    id: GO:0016020
    label: membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: located_in
  review:
    summary: InterPro-based generic membrane assignment, a parent of the specific ER membrane localization.
    action: KEEP_AS_NON_CORE
    reason: Correct but generic; the specific ER membrane term captures the informative localization.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: Multi-pass membrane protein
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:26496610
  qualifier: enables
  review:
    summary: Quantitative interactome capture of EMC3 with the EMC cytosolic scaffold EMC2 (Q15006). A bona fide intra-complex partnership, but bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Genuine EMC subunit interaction (EMC2); bare protein binding is uninformative and not core.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: 'Q9P0I2; Q15006: EMC2'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  qualifier: enables
  review:
    summary: High-throughput binary (HuRI) interactome capture of EMC3 with a non-EMC partner (Q13126). Bare protein binding is uninformative and the partner is most plausibly an incidental high-throughput hit or a membrane-protein client.
    action: KEEP_AS_NON_CORE
    reason: High-throughput binary interaction; bare protein binding is uninformative and not core.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: Component of the ER membrane protein complex (EMC).
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  qualifier: enables
  review:
    summary: BioPlex affinity-MS interactome capture of EMC3 with the EMC scaffold EMC2 (Q15006). Genuine EMC partner but bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Genuine EMC subunit interaction (EMC2); bare protein binding is uninformative and not core.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: 'Q9P0I2; Q15006: EMC2'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:35271311
  qualifier: enables
  review:
    summary: OpenCell endogenous-tagging interactome capture of EMC3 with the EMC scaffold EMC2 (Q15006). Genuine EMC partner but bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Genuine EMC subunit interaction (EMC2); bare protein binding is uninformative and not core.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: 'Q9P0I2; Q15006: EMC2'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:40205054
  qualifier: enables
  review:
    summary: Multimodal cell-map interactome capture of EMC3 with the EMC scaffold EMC2 (Q15006). Genuine EMC partner but bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Genuine EMC subunit interaction (EMC2); bare protein binding is uninformative and not core.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: 'Q9P0I2; Q15006: EMC2'
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: EXP
  original_reference_id: PMID:22119785
  qualifier: located_in
  review:
    summary: Experimental ER membrane localization from the foundational ERAD-network mapping study that first identified the EMC. Core compartment.
    action: ACCEPT
    reason: Experimentally supported core location.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: NAS
  original_reference_id: PMID:29242231
  qualifier: located_in
  review:
    summary: ComplexPortal NAS annotation of ER membrane localization for the EMC, consistent with the experimental evidence and core compartment of EMC3.
    action: ACCEPT
    reason: Correct core location; consistent with EXP/IDA evidence.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
    id: GO:0045050
    label: protein insertion into ER membrane by stop-transfer membrane-anchor sequence
  evidence_type: IDA
  original_reference_id: PMID:29242231
  qualifier: involved_in
  review:
    summary: The EMC inserts transmembrane domains, including stop-transfer membrane-anchor sequences of multipass clients; EMC3 forms the insertase vestibule. Core EMC process.
    action: ACCEPT
    reason: Core EMC-mediated process; EMC3 provides the substrate-conducting active site of the insertase.
    supported_by:
    - reference_id: PMID:29242231
      supporting_text: transmembrane domain insertase
- term:
    id: GO:0071816
    label: tail-anchored membrane protein insertion into ER membrane
  evidence_type: IDA
  original_reference_id: PMID:29242231
  qualifier: involved_in
  review:
    summary: The EMC mediates post-translational insertion of tail-anchored proteins with moderately hydrophobic TMDs, demonstrated directly in this study; insertion occurs at the EMC3/EMC6 vestibule. Core EMC process.
    action: ACCEPT
    reason: Core EMC-mediated process; directly demonstrated, executed at the EMC3-containing vestibule.
    supported_by:
    - reference_id: PMID:29242231
      supporting_text: tail-anchored membrane proteins with moderately hydrophobic transmembrane
- term:
    id: GO:0072546
    label: EMC complex
  evidence_type: IPI
  original_reference_id: PMID:32439656
  qualifier: part_of
  review:
    summary: ComplexPortal IPI assignment of EMC complex membership based on the cryo-EM structure of the human EMC, which places EMC3 at the catalytic insertion vestibule. Core structural identity.
    action: ACCEPT
    reason: Structurally demonstrated core EMC membership.
    supported_by:
    - reference_id: PMID:32439656
      supporting_text: formed by the subunits EMC3 and EMC6
- term:
    id: GO:0032977
    label: membrane insertase activity
  evidence_type: IMP
  original_reference_id: PMID:29809151
  qualifier: contributes_to
  review:
    summary: IMP evidence (cotranslational multipass biogenesis study) that the EMC has membrane insertase activity; EMC3 provides the catalytic vestibule. Core MF.
    action: ACCEPT
    reason: Core MF; EMC3 is the catalytic insertase subunit, with activity separable from assembly by mutagenesis.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: No effect on EMC assembly but decreased
- term:
    id: GO:0032977
    label: membrane insertase activity
  evidence_type: IMP
  original_reference_id: PMID:30415835
  qualifier: contributes_to
  review:
    summary: IMP evidence (topogenesis study) supporting the EMC's membrane insertase activity; EMC3 forms the substrate-conducting vestibule. Core MF.
    action: ACCEPT
    reason: Core MF; EMC3 provides the catalytic insertase active site.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: No effect on EMC assembly but decreased
- term:
    id: GO:0045050
    label: protein insertion into ER membrane by stop-transfer membrane-anchor sequence
  evidence_type: IMP
  original_reference_id: PMID:29809151
  qualifier: involved_in
  review:
    summary: The EMC is required for cotranslational insertion of multipass proteins in which stop-transfer membrane-anchor sequences become membrane-spanning helices; EMC3 is the catalytic subunit. Core EMC process.
    action: ACCEPT
    reason: Core EMC-mediated process; supported by IMP of EMC subunits.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: stop-transfer membrane-anchor sequences become ER membrane spanning
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: IDA
  original_reference_id: PMID:32439656
  qualifier: located_in
  review:
    summary: Direct (cryo-EM structural) evidence placing EMC3 in the ER membrane as a multipass subunit at the insertase vestibule. Core compartment.
    action: ACCEPT
    reason: Experimentally supported core location.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
    id: GO:0045050
    label: protein insertion into ER membrane by stop-transfer membrane-anchor sequence
  evidence_type: IMP
  original_reference_id: PMID:30415835
  qualifier: involved_in
  review:
    summary: IMP evidence (topogenesis study) that the EMC inserts stop-transfer membrane-anchor sequences and sets the N-exo topology of multipass clients such as GPCRs; EMC3 is the catalytic subunit. Core EMC process.
    action: ACCEPT
    reason: Core EMC-mediated process.
    supported_by:
    - reference_id: PMID:30415835
      supporting_text: G protein-coupled receptors
- term:
    id: GO:0016020
    label: membrane
  evidence_type: IDA
  original_reference_id: PMID:22119785
  qualifier: located_in
  review:
    summary: Direct generic membrane localization from the EMC-discovery study; a parent of the specific ER membrane term.
    action: KEEP_AS_NON_CORE
    reason: Correct but generic; the ER membrane term captures the informative localization.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
    id: GO:0072546
    label: EMC complex
  evidence_type: IDA
  original_reference_id: PMID:22119785
  qualifier: part_of
  review:
    summary: Direct experimental identification of EMC3 in the EMC by the foundational ERAD-network mapping study. Core structural identity.
    action: ACCEPT
    reason: Core EMC membership; directly demonstrated.
    supported_by:
    - reference_id: file:human/EMC3/EMC3-uniprot.txt
      supporting_text: Component of the ER membrane protein complex (EMC).
core_functions:
- description: Catalytic insertase subunit of the EMC (Oxa1/YidC/Get1 superfamily); together with EMC6 forms the membrane-embedded hydrophilic vestibule that provides the substrate-conducting active site for energy-independent insertion of transmembrane domains into the ER membrane.
  molecular_function:
    id: GO:0032977
    label: membrane insertase activity
  in_complex:
    id: GO:0072546
    label: EMC complex
  locations:
  - id: GO:0005789
    label: endoplasmic reticulum membrane
  supported_by:
  - reference_id: file:human/EMC3/EMC3-uniprot.txt
    supporting_text: No effect on EMC assembly but decreased
  - reference_id: PMID:32439656
    supporting_text: formed by the subunits EMC3 and EMC6
  - reference_id: PMID:37199759
    supporting_text: Positively charged residues at the entrance to the vestibule function as a selectivity filter
- description: As the catalytic core of the EMC, mediates post-translational insertion of tail-anchored proteins and cotranslational insertion and N-exo topogenesis of multipass membrane proteins (including GPCRs) at the ER membrane.
  molecular_function:
    id: GO:0032977
    label: membrane insertase activity
  locations:
  - id: GO:0005789
    label: endoplasmic reticulum membrane
  supported_by:
  - reference_id: file:human/EMC3/EMC3-uniprot.txt
    supporting_text: post-translational insertion of tail-anchored/TA proteins in
  - reference_id: PMID:37957425
    supporting_text: TMDs near the carboxyl terminus of mammalian multipass proteins are inserted post-translationally by the endoplasmic reticulum membrane protein complex (EMC)
  directly_involved_in:
  - id: GO:0071816
    label: tail-anchored membrane protein insertion into ER membrane
  - id: GO:0045050
    label: protein insertion into ER membrane by stop-transfer membrane-anchor sequence
proposed_new_terms: []
references:
- id: PMID:32459176
  title: The architecture of EMC reveals a path for membrane protein insertion.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: 'O''Donnell et al. 2020 (eLife). Cryo-EM architecture of the human EMC,
      establishing the overall complex organization and subunit topology relevant to
      EMC3 as a constitutive EMC subunit.'
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
  findings: []
- id: PMID:22119785
  title: Defining human ERAD networks through an integrative mapping strategy.
  findings:
  - statement: Affinity-MS ERAD-network mapping that first identified the EMC (including EMC3) in human cells and localized it to the ER membrane.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Foundational identification of the human EMC; source of EMC complex membership and ER membrane localization for EMC3.
- id: PMID:26496610
  title: A human interactome in three quantitative dimensions organized by stoichiometries and abundances.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Quantitative interactome; source of an IPI protein-binding annotation with the EMC scaffold EMC2.
- id: PMID:29242231
  title: The ER membrane protein complex is a transmembrane domain insertase.
  findings:
  - statement: EMC is a transmembrane domain insertase that post-translationally inserts tail-anchored membrane proteins; EMC3 is a distant homolog of the Get1 insertase.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Establishes the insertase function of the EMC and the YidC/Get1 ancestry of EMC3; basis for the insertion BP/MF annotations.
- id: PMID:29809151
  title: The ER membrane protein complex interacts cotranslationally to enable biogenesis of multipass membrane proteins.
  findings:
  - statement: The EMC engages multipass membrane protein clients cotranslationally to enable their biogenesis.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Cotranslational multipass biogenesis role of the EMC; basis for the IMP MF/BP annotations.
- id: PMID:30415835
  title: EMC Is Required to Initiate Accurate Membrane Protein Topogenesis.
  findings:
  - statement: The EMC sets the N-exo topology of the first TMD of GPCRs and other multipass proteins, initiating accurate topogenesis in cooperation with Sec61.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Topogenesis/orientation role of the EMC; GPCR clients; basis for IMP MF/BP annotations.
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: High-throughput HuRI binary interactome; source of an IPI protein-binding annotation with a non-EMC partner (likely incidental or a client).
- id: PMID:32439656
  title: Structural basis for membrane insertion by the human ER membrane protein complex.
  findings:
  - statement: Cryo-EM structure of the human EMC; substrate insertion occurs via an enclosed hydrophilic vestibule formed by the subunits EMC3 and EMC6 and requires a methionine-rich cytosolic loop.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Structural basis for the EMC3/EMC6 insertase vestibule; identifies EMC3 as the catalytic core. Abstract-only in cache.
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: BioPlex affinity-MS interactome; source of an IPI protein-binding annotation with the EMC scaffold EMC2.
- id: PMID:35271311
  title: 'OpenCell: Endogenous tagging for the cartography of human cellular organization.'
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: OpenCell endogenous-tagging interactome; source of an IPI protein-binding annotation with the EMC scaffold EMC2.
- id: PMID:40205054
  title: Multimodal cell maps as a foundation for structural and functional genomics.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Multimodal cell-map interactome; source of an IPI protein-binding annotation with the EMC scaffold EMC2.
- id: file:human/EMC3/EMC3-uniprot.txt
  title: UniProt entry Q9P0I2 (EMC3_HUMAN), ER membrane protein complex subunit 3
  findings:
  - statement: Multipass ER membrane catalytic insertase subunit of the EMC (YidC/Oxa1/Get1 superfamily); with EMC6 forms the insertase vestibule; EMC3 vestibule/Met-rich-loop mutations reduce client insertion without affecting assembly.
    reference_section_type: OTHER
- id: PMID:37199759
  title: A selectivity filter in the ER membrane protein complex limits protein misinsertion
    at the ER.
  findings:
  - statement: Two conserved positively charged EMC3 residues (R31 and R180) at the hydrophilic-vestibule entrance form a charge-repulsion selectivity filter that rejects mitochondrial tail-anchored proteins and enforces the positive-inside topology rule; introducing negative charge into the vestibule increases ER misinsertion, defining EMC3 as a fidelity determinant of insertion.
    reference_section_type: RESULTS
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified (J Cell Biol 2023, 222:e202212007). EMC3-specific mechanism (vestibule arginines R31/R180 as selectivity filter); advances EMC3 from insertase subunit to active client-discrimination/topology-fidelity determinant.
- id: PMID:37957425
  title: EMC rectifies the topology of multipass membrane proteins.
  findings:
  - statement: The EMC post-translationally inserts C-terminal transmembrane domains of multipass membrane proteins to rectify topology after ribosome release; the EMC cytosol-facing hydrophilic vestibule (formed by EMC3/EMC6) is adjacent to the pre-translocated C-terminal tail, and this mechanism may apply to ~250 diverse multipass proteins.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified (Nat Struct Mol Biol 2024, 31:32-41). Expands the EMC3/EMC6 vestibule's role to post-translational topology rectification of multipass clients; directly relevant to EMC3's catalytic insertase function.
- id: PMID:38517390
  title: Structural insights into human EMC and its interaction with VDAC.
  findings:
  - statement: Cryo-EM of human EMC in apo and VDAC-bound states identifies a gating plug within the EMC3/EMC6 hydrophilic vestibule (substrate-binding pocket); conformational changes of the gating plug between states suggest the EMC is not insertion-competent in the VDAC1-bound state, indicating state-dependent regulation of the insertase vestibule.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: PubMed-verified (Aging (Albany NY) 2024, 16:5501-5525). Identifies a gating plug regulating the EMC3-containing insertion vestibule; structural context directly relevant to EMC3's catalytic core.
- id: PMID:31263175
  title: ER complex proteins are required for rhodopsin biosynthesis and photoreceptor
    survival in Drosophila and mice.
  findings:
  - statement: Loss-of-function of emc3 (and emc5, emc6) in Drosophila causes defective phototransduction and photoreceptor degeneration with reduced rhodopsin, independent of ERAD; conditional Emc3 knockout in mice causes rhodopsin mislocalization and death of rod and cone photoreceptors, establishing a conserved in vivo requirement for EMC3 in rhodopsin (a multipass GPCR-like client) biogenesis.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified (Cell Death Differ 2020, 27:646-661). In vivo (fly and mouse) evidence that EMC3 is required for rhodopsin biosynthesis and photoreceptor survival; supports EMC3's physiological role in multipass membrane-protein biogenesis.
suggested_questions:
- question: What is the precise reaction trajectory of a substrate transmembrane domain through the EMC3/EMC6 hydrophilic vestibule, and how do the Met-rich cytosolic loop and the vestibule arginines (R31, R180) lower the energetic barrier to insertion?
- question: How does EMC3 discriminate moderately hydrophobic or charge-bearing client TMDs from highly hydrophobic TMDs that are instead handled by the Sec61 translocon?
suggested_experiments:
- description: Reconstitute insertion of model tail-anchored and multipass substrates into proteoliposomes containing wild-type versus vestibule-mutant EMC3 (R31A, Met-loop mutants, R180A) to quantify the residue-specific contribution of EMC3 to insertion efficiency independent of complex assembly.
- description: Use site-specific crosslinking or time-resolved cryo-EM to capture substrate TMDs engaged at the EMC3/EMC6 vestibule during insertion and define the path of the translocating segment.