AP4E1 encodes the epsilon large subunit of the heterotetrameric AP-4 adaptor complex. AP-4 forms a nonclathrin coat on the cytoplasmic face of the trans-Golgi network and sorts membrane proteins into transport carriers. The epsilon N-terminal trunk contributes to the complex core and binds activated ARF1 for membrane recruitment, while its C-terminal ear binds the accessory protein tepsin. These interactions support coat assembly and cargo transport in coordination with the mu4 cargo-recognition subunit.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:26496610 A human interactome in three quantitative dimensions organiz... | UNDECIDED | Summary: The original TEPSIN screen experiment remains unadjudicated. Reason: The exact pair-specific supplementary entry, constructs and controls in this source were not independently inspected. Separate human epsilonβtepsin binding and recruitment experiments establish the partnership but do not adjudicate this particular screen record. Preserve the original assertion as uncertain without denying the interaction or transferring a different paperβs mechanistic evidence into its source fields. |
| GO:0005515 protein binding | IPI PMID:26542808 Bivalent Motif-Ear Interactions Mediate the Association of t... | MODIFY | Summary: The epsilon appendage recruits tepsin to the AP-4 machinery. Reason: Human epsilon ear binding to a defined tepsin peptide is supported by ITC, motif perturbation and reduced cellular recruitment. Epsilon incorporation into AP-4 supplies the second side of the bridge, so accessory-factor recruitment supports protein-macromolecule adaptor activity. AP-4 crosslinking is a proposed model. This refinement does not assign direct cargo-motif recognition or HOOK binding to epsilon. The parent adaptor term here describes epsilon-mediated accessory recruitment tested in this paper, whereas the inherited cargo-adaptor term describes the assembled heterotetramer with mu4 cargo recognition. These are distinct interfaces; no new ancestor annotation is added. Proposed replacements: protein-macromolecule adaptor activity Supporting Evidence: PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. PMID:10066790 beta4 is a component of a multisubunit complex (AP-4) that also contains the sigma4 polypeptide and two additional adaptor subunit homologs named mu4 (mu-ARP2) and epsilon. file:human/AP4E1/AP4E1-notes.md |
| GO:0005515 protein binding | IPI PMID:32073997 The FTS-Hook-FHIP (FHF) complex interacts with AP-4 to media... | KEEP AS NON CORE | Summary: The human epsilonβtepsin Y2H positive control supports the partner interaction. Reason: The original Results and Figure 3 include an inspected human epsilonβtepsin Y2H positive control. Retain that observed partner interaction as non-core. This pair assay does not itself demonstrate an adaptor bridge, and the separate recruitment experiments in PMID:26542808 are not substituted for it. Genericity alone does not establish that an experimentally observed interaction is incorrect. Direct HOOK binding elsewhere in the study belongs to mu4 and is not assigned to epsilon. The original-body result and public locator are recorded in notes; the normal cache remains abstract-only. Supporting Evidence: file:human/AP4E1/AP4E1-notes.md Control experiments showed interactions of tepsin with AP-4 Ξ΅ and AP-4 Ξ²4 |
| GO:0005515 protein binding | IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling... | UNDECIDED | Summary: The original TEPSIN screen experiment remains unadjudicated. Reason: The exact pair-specific supplementary entry, constructs and controls in this source were not independently inspected. Separate human epsilonβtepsin binding and recruitment experiments establish the partnership but do not adjudicate this particular screen record. Preserve the original assertion as uncertain without denying the interaction or transferring a different paperβs mechanistic evidence into its source fields. |
| GO:0005768 endosome | IEA GO_REF:0000117 | UNDECIDED | Summary: A distinct endosomal pool is not resolved by the available target evidence. Reason: AP-4 is enriched on the cytoplasmic face of the TGN. This does not exclude a transient endosomal pool. The actual ARBA00028568 inference chain has not been inspected, and delivery of APP cargo to endosomes does not by itself establish adaptor residence there. The broad endosome assertion therefore remains uncertain; the enclosed-lumen topology objection is a separate issue. Supporting Evidence: PMID:11707398 localizes to the cytoplasmic face of the trans-Golgi network (TGN). file:human/AP4E1/AP4E1-notes.md |
| GO:0005794 Golgi apparatus | IEA GO_REF:0000044 | MODIFY | Summary: Refine the broad Golgi/TGN compartment to its membrane-associated AP-4 pool. Reason: Human biochemical evidence places AP-4 on the cytoplasmic face of the TGN, where ARF1 recruits the epsilon-containing complex. The peripheral membrane pool is more precise than the broad compartment; this does not imply epsilon spans the bilayer. Proposed replacements: trans-Golgi network membrane Supporting Evidence: PMID:11707398 localizes to the cytoplasmic face of the trans-Golgi network (TGN). PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. |
| GO:0005802 trans-Golgi network | IEA GO_REF:0000117 | MODIFY | Summary: Refine the broad Golgi/TGN compartment to its membrane-associated AP-4 pool. Reason: Human biochemical evidence places AP-4 on the cytoplasmic face of the TGN, where ARF1 recruits the epsilon-containing complex. The peripheral membrane pool is more precise than the broad compartment; this does not imply epsilon spans the bilayer. Proposed replacements: trans-Golgi network membrane Supporting Evidence: PMID:11707398 localizes to the cytoplasmic face of the trans-Golgi network (TGN). PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. |
| GO:0005802 trans-Golgi network | NAS PMID:10436028 Characterization of a fourth adaptor-related protein complex... | MODIFY | Summary: Refine the broad Golgi/TGN compartment to its membrane-associated AP-4 pool. Reason: Human biochemical evidence places AP-4 on the cytoplasmic face of the TGN, where ARF1 recruits the epsilon-containing complex. The peripheral membrane pool is more precise than the broad compartment; this does not imply epsilon spans the bilayer. Proposed replacements: trans-Golgi network membrane Supporting Evidence: PMID:11707398 localizes to the cytoplasmic face of the trans-Golgi network (TGN). PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. |
| GO:0006605 protein targeting | IC PMID:10066790 AP-4, a novel protein complex related to clathrin adaptors. | ACCEPT | Summary: AP-4 coat assembly and cargo sorting support this protein-transport or localization assertion. Reason: Epsilon is part of the AP-4 machinery that sorts membrane-protein cargo into carriers at the TGN. This supports the existing protein-specific targeting, localization or transport term. The original annotation remains valid even though vesicle-mediated transport describes a complementary mechanistic aspect. Replacing it with that already-present term would discard protein-cargo information and add no coverage. No downstream cargo chemistry is assigned to epsilon. Supporting Evidence: PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. |
| GO:0006886 intracellular protein transport | IEA GO_REF:0000002 | ACCEPT | Summary: AP-4 coat assembly and cargo sorting support this protein-transport or localization assertion. Reason: Epsilon is part of the AP-4 machinery that sorts membrane-protein cargo into carriers at the TGN. This supports the existing protein-specific targeting, localization or transport term. The original annotation remains valid even though vesicle-mediated transport describes a complementary mechanistic aspect. Replacing it with that already-present term would discard protein-cargo information and add no coverage. No downstream cargo chemistry is assigned to epsilon. Supporting Evidence: PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. |
| GO:0008104 intracellular protein localization | IC PMID:10066790 AP-4, a novel protein complex related to clathrin adaptors. | ACCEPT | Summary: AP-4 coat assembly and cargo sorting support this protein-transport or localization assertion. Reason: Epsilon is part of the AP-4 machinery that sorts membrane-protein cargo into carriers at the TGN. This supports the existing protein-specific targeting, localization or transport term. The original annotation remains valid even though vesicle-mediated transport describes a complementary mechanistic aspect. Replacing it with that already-present term would discard protein-cargo information and add no coverage. No downstream cargo chemistry is assigned to epsilon. Supporting Evidence: PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. |
| GO:0008104 intracellular protein localization | IEA GO_REF:0000117 | ACCEPT | Summary: AP-4 coat assembly and cargo sorting support this protein-transport or localization assertion. Reason: Epsilon is part of the AP-4 machinery that sorts membrane-protein cargo into carriers at the TGN. This supports the existing protein-specific targeting, localization or transport term. The original annotation remains valid even though vesicle-mediated transport describes a complementary mechanistic aspect. Replacing it with that already-present term would discard protein-cargo information and add no coverage. No downstream cargo chemistry is assigned to epsilon. Supporting Evidence: PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. |
| GO:0015031 protein transport | IEA GO_REF:0000002 | ACCEPT | Summary: AP-4 coat assembly and cargo sorting support this protein-transport or localization assertion. Reason: Epsilon is part of the AP-4 machinery that sorts membrane-protein cargo into carriers at the TGN. This supports the existing protein-specific targeting, localization or transport term. The original annotation remains valid even though vesicle-mediated transport describes a complementary mechanistic aspect. Replacing it with that already-present term would discard protein-cargo information and add no coverage. No downstream cargo chemistry is assigned to epsilon. Supporting Evidence: PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. |
| GO:0016192 vesicle-mediated transport | IEA GO_REF:0000002 | ACCEPT | Summary: AP4E1 participates in vesicle-mediated transport as an AP-4 coat subunit. Reason: AP-4 is a nonclathrin carrier coat. Epsilon contributes the structural core, ARF1-dependent membrane recruitment and an accessory-protein-binding ear. These are direct roles in transport machinery, rather than an inference from a downstream cargo phenotype. Supporting Evidence: PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. |
| GO:0016192 vesicle-mediated transport | NAS PMID:10436028 Characterization of a fourth adaptor-related protein complex... | ACCEPT | Summary: AP4E1 participates in vesicle-mediated transport as an AP-4 coat subunit. Reason: AP-4 is a nonclathrin carrier coat. Epsilon contributes the structural core, ARF1-dependent membrane recruitment and an accessory-protein-binding ear. These are direct roles in transport machinery, rather than an inference from a downstream cargo phenotype. Supporting Evidence: PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. |
| GO:0030117 membrane coat | IEA GO_REF:0000002 | MODIFY | Summary: The membrane-coat assignment can be specified as AP-4. Reason: Epsilon is an experimentally established component of the heterotetrameric AP-4 coat. Use this specific complex instead of the broad coat parent; clathrin binding is not assigned. Proposed replacements: AP-4 adaptor complex Supporting Evidence: PMID:10066790 beta4 is a component of a multisubunit complex (AP-4) that also contains the sigma4 polypeptide and two additional adaptor subunit homologs named mu4 (mu-ARP2) and epsilon. PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. |
| GO:0030124 AP-4 adaptor complex | IBA GO_REF:0000033 | ACCEPT | Summary: Epsilon is a structural subunit of the AP-4 heterotetramer. Reason: Human-cell biochemical complex characterization and purified human AP-4 structural work support epsilon membership with beta4, mu4 and sigma4. The PAINT node and all donors are retained. Target self-inclusion is legitimate descendant evidence, not circularity; the exact ancestral placement has not been independently reconstructed. Supporting Evidence: PMID:10066790 beta4 is a component of a multisubunit complex (AP-4) that also contains the sigma4 polypeptide and two additional adaptor subunit homologs named mu4 (mu-ARP2) and epsilon. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. |
| GO:0030124 AP-4 adaptor complex | IDA PMID:10066790 AP-4, a novel protein complex related to clathrin adaptors. | ACCEPT | Summary: Epsilon is a structural subunit of the AP-4 heterotetramer. Reason: Human-cell biochemical complex characterization and purified human AP-4 structural work support epsilon membership with beta4, mu4 and sigma4. Supporting Evidence: PMID:10066790 beta4 is a component of a multisubunit complex (AP-4) that also contains the sigma4 polypeptide and two additional adaptor subunit homologs named mu4 (mu-ARP2) and epsilon. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. |
| GO:0030124 AP-4 adaptor complex | IEA GO_REF:0000002 | ACCEPT | Summary: Epsilon is a structural subunit of the AP-4 heterotetramer. Reason: Human-cell biochemical complex characterization and purified human AP-4 structural work support epsilon membership with beta4, mu4 and sigma4. Supporting Evidence: PMID:10066790 beta4 is a component of a multisubunit complex (AP-4) that also contains the sigma4 polypeptide and two additional adaptor subunit homologs named mu4 (mu-ARP2) and epsilon. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. |
| GO:0030124 AP-4 adaptor complex | NAS PMID:10436028 Characterization of a fourth adaptor-related protein complex... | ACCEPT | Summary: Epsilon is a structural subunit of the AP-4 heterotetramer. Reason: Human-cell biochemical complex characterization and purified human AP-4 structural work support epsilon membership with beta4, mu4 and sigma4. Supporting Evidence: PMID:10066790 beta4 is a component of a multisubunit complex (AP-4) that also contains the sigma4 polypeptide and two additional adaptor subunit homologs named mu4 (mu-ARP2) and epsilon. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. |
| GO:0031904 endosome lumen | TAS Reactome:R-HSA-5229111 | REMOVE | Summary: The cargo destination in the Reactome event does not place epsilon inside the endosome lumen. Reason: The cited event describes APP delivery and recognition of its cytoplasmic tail by mu4. GO0031904 is the enclosed endosomal volume. AP-4 instead forms a cytoplasm-facing coat recruited through epsilonβARF1 contacts. Assigning that coat subunit to the cargo destination lumen conflicts with this topology. This is a source-specific TAS compartment correction; it does not claim a wrong experimental paper or exclude every endosome-associated pool. Supporting Evidence: PMID:11707398 localizes to the cytoplasmic face of the trans-Golgi network (TGN). PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. file:human/AP4E1/AP4E1-notes.md Reactome:R-HSA-5229111 |
| GO:0032588 trans-Golgi network membrane | TAS Reactome:R-HSA-5229111 | ACCEPT | Summary: AP-4 assembles at the trans-Golgi network membrane. Reason: Both Reactome APP events place the initial AP-4 cargo-recognition machinery at the TGN. Human biochemical and structural studies independently support a cytoplasmic peripheral-membrane coat, with epsilon directly engaging ARF1. Supporting Evidence: PMID:11707398 localizes to the cytoplasmic face of the trans-Golgi network (TGN). PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. Reactome:R-HSA-5229111 |
| GO:0032588 trans-Golgi network membrane | TAS Reactome:R-HSA-5229132 | ACCEPT | Summary: AP-4 assembles at the trans-Golgi network membrane. Reason: Both Reactome APP events place the initial AP-4 cargo-recognition machinery at the TGN. Human biochemical and structural studies independently support a cytoplasmic peripheral-membrane coat, with epsilon directly engaging ARF1. Supporting Evidence: PMID:11707398 localizes to the cytoplasmic face of the trans-Golgi network (TGN). PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. Reactome:R-HSA-5229132 |
| GO:0045184 establishment of protein localization | IEA GO_REF:0000117 | ACCEPT | Summary: AP-4 coat assembly and cargo sorting support this protein-transport or localization assertion. Reason: Epsilon is part of the AP-4 machinery that sorts membrane-protein cargo into carriers at the TGN. This supports the existing protein-specific targeting, localization or transport term. The original annotation remains valid even though vesicle-mediated transport describes a complementary mechanistic aspect. Replacing it with that already-present term would discard protein-cargo information and add no coverage. No downstream cargo chemistry is assigned to epsilon. Supporting Evidence: PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. |
| GO:0140312 cargo adaptor activity | IBA GO_REF:0000033 | ACCEPT | Summary: Epsilon contributes to AP-4 cargo-adaptor activity. Reason: The inherited adaptor-family function agrees with the demonstrated human AP-4 coat. Epsilon helps assemble and recruit the complex and its accessory factor; mu4 supplies the characterized cargo-motif binding site. The source enables qualifier and PAINT node are preserved, while the core synthesis describes the activity as contributed within the heterotetramer. Donor count alone is not a confidence test, and no new ancestral placement is asserted. Supporting Evidence: PMID:10436028 Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. PMID:26542808 Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. |
| GO:0031267 small GTPase binding | IPI PMID:11707398 Functional and physical interactions of the adaptor protein ... | NEW | Summary: Human epsilon directly binds activated ARF1 through its N-terminal trunk. Reason: The original human-epsilon experiments compare GTP-locked and GDP-preferring ARF1, epsilon truncations and switch-I/II mutants in Y2H and in-vitro-translated binding assays. A negative short epsilon fragment still binds sigma4, providing a functional control. Independent recombinant human AP-4 experiments map the ARF1 interface to epsilon and test interface mutations. This is a specific ARF1-effector interaction, separate from the TEPSIN partnerships in the existing generic-binding rows. It does not assign GTP hydrolysis, exchange activity or mu4 cargo recognition to epsilon. Supporting Evidence: PMID:11707398 epsilon binds only to ARF1-GTP and requires residues in the switch I and switch II regions of ARF1. PMID:11707398 ARF1Ξ17-Q71L-myc but not ARF1Ξ17-T31N-myc was found to co-precipitate with Ξ΅ 1β727 PMID:11707398 The cDNA for the Ξ΅ subunit of AP-4 was obtained by RTβPCR using gene-specific primers and total HeLa cell RNA. PMID:41565640 Collectively, our structural and biochemical data demonstrated direct interaction between the N-terminal region of Ξ΅ and ARF1 in the AP-4/ARF1 complex. |
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Download this section (compressed HTML)Q: Does endogenous human AP4E1 occupy a measurable endosomal membrane pool distinct from its TGN pool, and what evidence drives ARBA00028568?
Q: How does bivalent tepsin recruitment organize the AP-4 coat; does it bridge AP-4 complexes in a reconstituted human system?
Q: What contribution does epsilon ARF1 binding make to cargo selection beyond the mu4 recognition interface?
Experiment: Quantify endogenous epsilon localization using a validated knock-in tag, TGN and endosomal markers, and correlative imaging to distinguish transient membrane residence from cargo destination.
Experiment: Reconstitute full-length human AP-4 with ARF1, membrane cargo and tepsin, comparing epsilon ear and ARF1-interface mutants to test recruitment and coat organization directly.
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