ETHE1 is a mitochondrial matrix persulfide dioxygenase that uses molecular oxygen to convert glutathione persulfide to sulfite and glutathione. Its characterized human catalytic site contains one iron ion per protomer within a metallo-beta-lactamase fold. The reaction removes sulfane sulfur from a glutathione conjugate and supplies the persulfide-oxidation step of mitochondrial sulfide catabolism. Biallelic loss-of-function variants cause ethylmalonic encephalopathy, in which impaired sulfide clearance contributes to toxic sulfide accumulation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005506 iron ion binding | IDA PMID:23144459 Characterization of patient mutations in human persulfide di... | ACCEPT | Summary: Human ETHE1 binds an iron cofactor. Reason: PMID:23144459 directly measures 0.82 mol iron per mol wild-type recombinant human ETHE1 by plasma emission spectroscopy (Experimental Procedures; Table 1). Independent human crystallography resolves one iron coordinated by His79, His135 and Asp154 per protomer (PMID:25596185). The former assay uses a reported N-terminal 11-residue deletion and the latter a distinct engineered deletion; neither establishes the metal content of every natural product. UniProt CC:COFACTOR corroborates one Fe(2+) ion per subunit. Iron ion binding is retained as a mechanistic facet of the single sulfur-dioxygenase core, not a separate catalytic activity. |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | KEEP AS NON CORE | Summary: The screened ETHE1 association with Q3LHN2 is supported but is not a defined core activity. Reason: Archived HuRI PSI records pair human ETHE1 ORF 2869 with partner ORF 100014381 in screen(s) 9, with array, pooling and validated two-hybrid records. These human ORFs were assayed in yeast. The positive interaction is retained under the campaign supported-binding policy; the source does not establish a specific adaptor or enzymatic role for this pair. Orthogonal validation of a study-wide subset is not attributed to this individual pair, and equivalence to every current natural product is not assumed. Supporting Evidence: |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | KEEP AS NON CORE | Summary: The screened ETHE1 association with Q7Z3C6-3 is supported but is not a defined core activity. Reason: Archived HuRI PSI records pair human ETHE1 ORF 2869 with partner ORF 12318 in screen(s) 4 and 6, with array, pooling and validated two-hybrid records. These human ORFs were assayed in yeast. The positive interaction is retained under the campaign supported-binding policy; the source does not establish a specific adaptor or enzymatic role for this pair. Orthogonal validation of a study-wide subset is not attributed to this individual pair, and equivalence to every current natural product is not assumed. Supporting Evidence: |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | KEEP AS NON CORE | Summary: The screened ETHE1 association with Q99757 is supported but is not a defined core activity. Reason: Archived HuRI PSI records pair human ETHE1 ORF 2869 with partner ORF 2398 in screen(s) 5 and 6, with array, pooling and validated two-hybrid records. These human ORFs were assayed in yeast. The positive interaction is retained under the campaign supported-binding policy; the source does not establish a specific adaptor or enzymatic role for this pair. Orthogonal validation of a study-wide subset is not attributed to this individual pair, and equivalence to every current natural product is not assumed. Supporting Evidence: |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | KEEP AS NON CORE | Summary: The screened ETHE1 association with Q9H8Y8 is supported but is not a defined core activity. Reason: Archived HuRI PSI records pair human ETHE1 ORF 2869 with partner ORF 4973 in screen(s) 7, with array, pooling and validated two-hybrid records. These human ORFs were assayed in yeast. The positive interaction is retained under the campaign supported-binding policy; the source does not establish a specific adaptor or enzymatic role for this pair. Orthogonal validation of a study-wide subset is not attributed to this individual pair, and equivalence to every current natural product is not assumed. Supporting Evidence: |
| GO:0005634 nucleus | EXP PMID:12398897 A novel protein overexpressed in hepatoma accelerates export... | KEEP AS NON CORE | Summary: Retain context-dependent nuclear localization with independent human-cell support. Reason: The original PMID:12398897 Methods and Results remain inaccessible; its abstract reports nuclearβcytoplasmic shuttling, which has not been independently verified here. HPA029029 provides a separate positive human immunofluorescence observation of nucleoplasm and mitochondria in A-431, U-251MG and U2OS, including the inspected U2OS image. This antibody is rated supported, whereas two enhanced antibodies show mitochondrial localization; the gene-level HPA summary retains mitochondria. Its antigen is shared by all compared ETHE1 products, so the signal is not product-specific. This limited nuclear evidence warrants non-core retention, alongside the mitochondrial-only experiments reported in PMID:14732903; it does not verify shuttling or the earlier assay design. GO_REF:0000052 supplies the imported mitochondrion annotation; the separate positive nuclear evidence is the antibody-level HPA029029 portal record, not a nuclear assertion in that GO_REF mapping (https://www.proteinatlas.org/ENSG00000105755-ETHE1/subcellular). |
| GO:0005634 nucleus | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: Nuclear localization has independent, antibody-dependent human evidence and remains a secondary context. Reason: The UniProt SL-0191 mapping is mechanically correct but traces to PMID:12398897, whose operative original remains unavailable. Independently, current HPA029029 immunofluorescence reports nucleoplasm and mitochondria in A-431, U-251MG and U2OS; the inspected selected U2OS image contains diffuse central/nuclear green signal alongside stronger extranuclear structures, without a visible blue overlay. Selected images alone do not establish quantitative localization or antibody specificity. This is supported antibody-level evidence, whereas two enhanced antibodies and the gene-level HPA summary emphasize mitochondria. PMID:14732903 Discussion reports failure to detect nuclear localization under its conditions. Preserve this cross-assay uncertainty rather than declaring the older result an artifact. The HPA029029 antigen is shared by all captured RefSeq products, so the nuclear signal cannot be assigned to canonical ETHE1 or a particular alternative. Retain broad nucleus as a non-core context; neither universal nuclear residence nor a nuclear biochemical function is established. GO_REF:0000052 supplies the imported mitochondrion annotation; the separate positive nuclear evidence is the antibody-level HPA029029 portal record, not a nuclear assertion in that GO_REF mapping (https://www.proteinatlas.org/ENSG00000105755-ETHE1/subcellular). Propagation Review Root cause: NO FAILURE NON CORE Sources checked: UniProtKB-SubCell:SL-0191 SUPPORTS TRANSFER Exact nucleus mapping; independent HPA antibody-level nuclear signal supports a bounded non-core localization, with conflicting assays and unresolved product specificity. |
| GO:0005737 cytoplasm | EXP PMID:12398897 A novel protein overexpressed in hepatoma accelerates export... | KEEP AS NON CORE | Summary: Retain the historical cytoplasmic observation as a bounded non-core context. Reason: PMID:12398897 reports nuclearβcytoplasmic shuttling in its verified abstract, and UniProt separately curates its cytoplasmic and nuclear observations. The original Methods and Results remain unavailable, so the precise diffuse-localization, construct and shuttling conditions are not independently verified. Retain this experimental cytoplasmic assertion without replacing its possible extra-mitochondrial context by matrix. Native human matrix localization in PMID:14732903 is independently well supported and is used for the separate broad gene-level location refinements; it neither reproduces nor negates the older cytoplasmic experiment. No expression-artifact or wrong-product inference is made. |
| GO:0005737 cytoplasm | IDA GO_REF:0000054 | MODIFY | Summary: The broad cytoplasmic location can be refined to the independently demonstrated mitochondrial matrix. Reason: GO:0005737 includes organelles and does not mean cytosol alone. GO_REF:0000054 describes LIFEdb GFP-fusion imaging, not HPA; the current resource link redirects to a general proteomics page, so the exact historical ETHE1 clone and images were not recovered. Independent native human fibroblast protease protection and soluble mitochondrial fractionation establish matrix localization (PMID:14732903, Figure 6cβd); the source guide distinguishes these measurements from engineered import constructs. Refine the broad gene-level location using this independent evidence. This does not claim that the original fusion assay resolved the matrix, invalidate its cytoplasmic signal, or establish that every alternative product is imported. Proposed replacements: mitochondrial matrix Supporting Evidence: |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | MODIFY | Summary: The cytoplasm mapping is compatible with the established, more precise matrix location. Reason: The target UniProt record carries SL-0086 from PMID:12398897, whose full experiment remains unread. The current GO cytoplasm definition includes mitochondria; this is not a cytosol-specific assertion. Independent native human fibroblast protease protection and soluble mitochondrial fractionation establish matrix localization (PMID:14732903, Figure 6cβd); the source guide distinguishes these measurements from engineered import constructs. Use matrix as the independently supported refinement while keeping the historical diffuse-cytoplasmic claim separately unresolved. No expression-artifact or wrong-product conclusion follows from this refinement. Propagation Review Root cause: TERM SCOPING PROBLEM Sources checked: UniProtKB-SubCell:SL-0086 SUPPORTS TRANSFER Correct broad cytoplasm mapping; independent native human fractionation supports matrix specificity without verifying the older diffuse-localization assay. Proposed replacements: mitochondrial matrix Supporting Evidence: |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | MODIFY | Summary: Specify the mitochondrial matrix using independent native-human localization evidence. Reason: MitoCoP directly identifies the ETHE1 protein group in mitochondrial subtractive and spatial proteomics and TOMM40 importomics (Supplementary Tables S1βS3). The group contains O95571, M0QXB5, M0QY80 and M0QX80; it does not resolve every product separately. Its carbonate/sonication classification is peripheral membrane-associated, not an assay of soluble matrix location. The finer matrix assignment comes independently from native human fibroblast protease protection and submitochondrial fractionation in PMID:14732903, Figure 6cβd. These preparation-specific measurements are kept distinct. Proposed replacements: mitochondrial matrix |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | MODIFY | Summary: PAINT correctly supports mitochondrial ancestry; human evidence supports matrix specificity. Reason: Human O95571 leaf PTN002534467 descends from the actual mitochondrial IBD at PTN000940093 in PTHR43084. Its ungapped MSA sequence exactly matches the 254-residue canonical protein. Three positive IBDs and no NOT occur on the target path. The human self-WITH and Arabidopsis AT1G53580 donor are valid evidence sources, not circularity or weak donor-count support; current plant source records were traced but the plant originals were not re-read. Independent native human fibroblast protease protection and soluble mitochondrial fractionation establish matrix localization (PMID:14732903, Figure 6cβd); the source guide distinguishes these measurements from engineered import constructs. The matrix refinement is based on human compartment evidence and does not reject the ancestral placement or assign all RefSeq forms the same targeting. Propagation Review Root cause: TERM SCOPING PROBLEM Sources checked: PANTHER:PTN000940093 SUPPORTS TRANSFER Actual ancestral mitochondrial IBD lies on the exact human target path; human evidence supports matrix refinement. UniProtKB:O95571 SUPPORTS TRANSFER Target experimental localization is legitimate descendant grounding. AGI_LocusCode:AT1G53580 SUPPORTS TRANSFER Q9C8L4 identity/tree placement and experimental mitochondrial source records were traced; plant originals not independently re-read. Proposed replacements: mitochondrial matrix |
| GO:0005739 mitochondrion | IDA GO_REF:0000052 | MODIFY | Summary: HPA supports mitochondria; separate native-human assays resolve the matrix. Reason: Actual HPA XML and three selected images were inspected. Enhanced HPA028360 and HPA029028 support mitochondrial patterns in A-431, U-251MG and U2OS, while supported HPA029029 also reports nucleoplasm. The gene-level HPA summary is mitochondrial. None of these images resolves the mitochondrial matrix or distinguishes all natural products. Independent native human fibroblast protease protection and soluble mitochondrial fractionation establish matrix localization (PMID:14732903, Figure 6cβd); the source guide distinguishes these measurements from engineered import constructs. Use that independent evidence for the finer location; do not relabel immunofluorescence as suborganellar fractionation. Proposed replacements: mitochondrial matrix |
| GO:0005739 mitochondrion | IEA GO_REF:0000117 | MODIFY | Summary: The mitochondrial ARBA rule genuinely matches ETHE1; human fractionation supports a finer location. Reason: Current ARBA00026962 condition set 370 of 380 (zero-based) matches the target FunFam 3.60.15.10:FF:000013 and Eukaryota taxonomy and assigns mitochondrion. This is a valid current rule application, not a historical-rule identity assumption. Independent native human fibroblast protease protection and soluble mitochondrial fractionation establish matrix localization (PMID:14732903, Figure 6cβd); the source guide distinguishes these measurements from engineered import constructs. Refine to matrix on independent human evidence without extending targeting to untested RefSeq alternatives. Propagation Review Root cause: TERM SCOPING PROBLEM Sources checked: ARBA:ARBA00026962 SUPPORTS TRANSFER Current target-matching FunFam/taxon conjunction supports mitochondria; matrix specificity is independently measured. Proposed replacements: mitochondrial matrix Supporting Evidence: |
| GO:0005759 mitochondrial matrix | EXP PMID:14732903 Ethylmalonic encephalopathy is caused by mutations in ETHE1,... | ACCEPT | Summary: ETHE1 is established in the mitochondrial matrix of human cells. Reason: PMID:14732903 combines native human fibroblast fractionation, protease protection and soluble-versus-membrane separation with human ETHE1-HA imaging and import assays. Figure 6cβd and the corresponding Results support matrix localization directly. The full-cDNA and engineered P21-start constructs are distinct, and the cleavage experiment only bounded the leader to fewer than 20 residues; it did not itself identify the later Arg7βVal8 processing site or establish localization of all shorter transcripts. Supporting Evidence: |
| GO:0005759 mitochondrial matrix | IEA GO_REF:0000044 | ACCEPT | Summary: ETHE1 has a directly supported human mitochondrial-matrix location. Reason: The current UniProt SL-0170 mapping is explicitly GO:0005759 and the target record cites PMID:14732903. Independent native human fibroblast protease protection and soluble mitochondrial fractionation establish matrix localization (PMID:14732903, Figure 6cβd); the source guide distinguishes these measurements from engineered import constructs. The separate Reactome target entity 1614628 also has its own matrix compartment and modeled residues 8β254. Those coordinates are a processing representation, not evidence that the engineered Ξ20 protein or the distinct shorter RefSeq records are interchangeable. Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB-SubCell:SL-0170 SUPPORTS TRANSFER Exact matrix mapping supported by operative native-human localization assays. |
| GO:0005759 mitochondrial matrix | TAS Reactome:R-HSA-1614605 | ACCEPT | Summary: The actual human ETHE1 participant is assigned to matrix, independently of a cofactor-composition problem. Reason: The explicit chain is R-HSA-1614605 β catalystActivity 1614523 β complex 1614521 β protein 1614628 β O95571 reference entity. ETHE1 itself is human, residues 8β254, with its own GO:0005759 compartment. Independent native human fibroblast protease protection and soluble mitochondrial fractionation establish matrix localization (PMID:14732903, Figure 6cβd); the source guide distinguishes these measurements from engineered import constructs. The complex separately contains two Zn2+ entities, which conflicts with measured single-iron human enzyme preparations in PMID:23144459 and PMID:25596185. That composition discrepancy is proposed as a separate source query; it does not invalidate the participant location or convert ETHE1 into a zinc-dependent hydrolase. Supporting Evidence: Reactome:R-HSA-1614605 file:human/ETHE1/ETHE1-uniprot.txt |
| GO:0006749 glutathione metabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: ETHE1 directly performs a glutathione-persulfide metabolic reaction. Reason: The actual glutathione-metabolism IBD is at root PTN002454072 on the human target path, grounded by experimental O95571 evidence; human self-WITH is expected. Independent human Ξ11 and Ξ20 preparations support GSSH-dependent oxygen consumption, with enzyme-dependent sulfite HPLC detection in PMID:23144459 and corroborating activity in PMID:25596185. Full construct, control, structural-docking and data-not-shown MS boundaries are retained in the source guide and reference assessments. Oxidation of a glutathione conjugate and regeneration of glutathione constitute chemical participation in this process, not merely a secondary change in antioxidant levels. This does not assert glutathione synthesis, glutathione reductase activity, or equivalent function of all alternative products. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002454072 SUPPORTS TRANSFER Actual root IBD, exact human descent and target biochemical evidence agree. UniProtKB:O95571 SUPPORTS TRANSFER Experimental human persulfide turnover grounds the self-donor assertion; not circular. |
| GO:0006749 glutathione metabolic process | IDA PMID:23144459 Characterization of patient mutations in human persulfide di... | ACCEPT | Summary: ETHE1 directly catalyzes a glutathione-persulfide metabolic reaction. Reason: Purified recombinant human ETHE1 consumes oxygen with glutathione persulfide and produces sulfite (PMID:23144459, Experimental Procedures, Tables 1β2 and Figure 5). The enzyme performs the conversion of S-sulfanylglutathione to sulfite and glutathione; participation is catalytic, not inferred merely from substrate necessity. GSH alone was not a substrate in the tested assay, and the paper leaves the physiological persulfide-carrier question open. Supporting Evidence: |
| GO:0006749 glutathione metabolic process | IEA GO_REF:0000002 | ACCEPT | Summary: The persulfide-dioxygenase domain mapping agrees with direct human glutathione-conjugate turnover. Reason: The target has an actual IPR044528 match; its current domain record maps both sulfur dioxygenase activity and glutathione metabolism. It is the persulfide-dioxygenase-like MBL domain, not a generic assertion that every MBL-fold protein is a dioxygenase or a glyoxalase. Independent human Ξ11 and Ξ20 preparations support GSSH-dependent oxygen consumption, with enzyme-dependent sulfite HPLC detection in PMID:23144459 and corroborating activity in PMID:25596185. Full construct, control, structural-docking and data-not-shown MS boundaries are retained in the source guide and reference assessments. The direct reaction on a glutathione conjugate supports the process; no additional general antioxidant function or biosynthetic role is inferred. Propagation Review Root cause: NO FAILURE CORE Sources checked: InterPro:IPR044528 SUPPORTS TRANSFER Actual target domain match and current mapping are corroborated by human GSSH oxidation assays. |
| GO:0019418 sulfide oxidation | IDA PMID:23144459 Characterization of patient mutations in human persulfide di... | ACCEPT | Summary: ETHE1 executes the persulfide-oxidation step of sulfide oxidation. Reason: GO:0019418 covers conversion of sulfide to sulfite or sulfate. The human enzyme directly oxidizes the sulfane sulfur of glutathione persulfide to sulfite, demonstrated by oxygen consumption and product analysis in PMID:23144459. This is an executed pathway step; ETHE1 is not being assigned the upstream initial oxidation of free H2S or every downstream sulfur-conversion reaction. Supporting Evidence: |
| GO:0042802 identical protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | KEEP AS NON CORE | Summary: ETHE1 self-association is supported, without a universal oligomeric-state claim. Reason: HuRI records the ETHE1 ORF 2869 self-pair in screen 1 with validated two-hybrid evidence. Independently, the 2015 human preparation is predominantly dimeric by solution measurements and crystallography, whereas the 2012 preparation elutes as a monomer (PMIDs:25596185 and 23144459). These use different engineered constructs and conditions. The positive binding assertion is retained, but neither an obligate native dimer nor equivalent assembly of every natural product is inferred. UniProt CC:SUBUNIT preserves both preparation-dependent oligomer descriptions. |
| GO:0050313 sulfur dioxygenase activity | EXP PMID:19136963 Loss of ETHE1, a mitochondrial dioxygenase, causes fatal sul... | ACCEPT | Summary: The original study directly measures sulfur dioxygenase activity of human ETHE1. Reason: PMID:19136963 separates mouse knockout tissue, human HeLa overexpression and affinity-purified mature human ETHE1 expressed in E. coli. The human recombinant preparation consumes oxygen in the sulfur dioxygenase assay (Results and Figure 4c), so this source is not limited to mouse phenotype evidence. The main article does not fully specify the recombinant deletion boundary; it is not automatically equated to the processed native chain. Independent human GSSH kinetics and sulfite-product identification in PMID:23144459 corroborate the current reaction definition. |
| GO:0050313 sulfur dioxygenase activity | EXP PMID:25596185 Crystal structure of human persulfide dioxygenase: structura... | ACCEPT | Summary: The human structural preparation retains GSSH-dependent sulfur dioxygenase activity. Reason: PMID:25596185 measures oxygen consumption with GSSH and a substrate-omission control (Figure 3A and enzyme-activity Methods). Its deliberately truncated human construct is GPVD plus canonical residues 21β254 after tag cleavage, rather than the native chain beginning at residue 8. The crystal resolves a mono-iron site; GSSH was manually docked, not observed as a bound crystallographic ligand. The catalytic conclusion is supported by the actual activity assay, not docking alone. Supporting Evidence: |
| GO:0050313 sulfur dioxygenase activity | IBA GO_REF:0000033 | ACCEPT | Summary: The inherited sulfur-dioxygenase activity is directly established for human ETHE1. Reason: The GO:0050313 IBD at PTN002454072 is ancestral to the exact human sequence and is grounded by human and Arabidopsis experimental sources. No loss/NOT record occurs on this target path; donor count and self-WITH are not objections. Independent human Ξ11 and Ξ20 preparations support GSSH-dependent oxygen consumption, with enzyme-dependent sulfite HPLC detection in PMID:23144459 and corroborating activity in PMID:25596185. Full construct, control, structural-docking and data-not-shown MS boundaries are retained in the source guide and reference assessments. The current GO definition specifies S-sulfanylglutathione oxidation to sulfite and glutathione, matching the assayed chemistry. Plant original experiments were not re-read, and the engineered human constructs are not natural splice products. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002454072 SUPPORTS TRANSFER Actual ancestral activity IBD and exact target descent with direct human corroboration. UniProtKB:O95571 SUPPORTS TRANSFER Target-specific human biochemical evidence legitimately grounds the ancestral assertion. AGI_LocusCode:AT1G53580 SUPPORTS TRANSFER Actual Q9C8L4 donor identity and current IDA22786886 were traced; original plant paper not re-read. |
| GO:0050313 sulfur dioxygenase activity | IDA PMID:23144459 Characterization of patient mutations in human persulfide di... | ACCEPT | Summary: Human ETHE1 directly oxidizes glutathione persulfide to sulfite. Reason: PMID:23144459 measures GSSH-dependent oxygen consumption, substrate kinetics and a sulfite product that co-elutes with the derivatized standard by HPLC (Figure 5); the confirming mass-spectrometric measurement is reported as data not shown. This establishes GO:0050313 for the tested recombinant human preparation. Low activity with CoA persulfide and negative tested alternatives do not establish additional physiological substrates or all-product equivalence. Supporting Evidence: |
| GO:0050313 sulfur dioxygenase activity | IEA GO_REF:0000120 | ACCEPT | Summary: The combined enzyme mappings agree with the measured human persulfide-dioxygenase reaction. Reason: ARBA00090275 actually matches the target FunFam 3.60.15.10:FF:000013 plus Eukaryota conjunction; IPR044528 actually matches and maps this activity. Official EC 1.13.11.18 and the UniProt RHEA:12981 cross-reference give S-sulfanylglutathione + O2 + H2O to sulfite + glutathione + 2 H+. Direct Rhea downloads returned HTTP403, so their contents are not claimed read. Independent human Ξ11 and Ξ20 preparations support GSSH-dependent oxygen consumption, with enzyme-dependent sulfite HPLC detection in PMID:23144459 and corroborating activity in PMID:25596185. Full construct, control, structural-docking and data-not-shown MS boundaries are retained in the source guide and reference assessments. The independent chemistry resolves the annotation without importing the conflicting two-zinc composition/model from Reactome or asserting sulfate production by ETHE1. Propagation Review Root cause: NO FAILURE CORE Sources checked: ARBA:ARBA00090275 SUPPORTS TRANSFER Current target-matching rule assigns sulfur dioxygenase activity. InterPro:IPR044528 SUPPORTS TRANSFER Actual target domain and current enzyme mapping agree. EC:1.13.11.18 SUPPORTS TRANSFER Official enzyme reaction matches actual human GSSH turnover. RHEA:12981 SUPPORTS TRANSFER Equation verified through official UniProt cross-reference and EC/GO; direct Rhea endpoint access was blocked, not independently read. |
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Download this section (compressed HTML)Q: Does endogenous human ETHE1 retain one iron ion per protomer across physiological metal and redox conditions, and what evidence underlies the two-zinc composition currently modeled in Reactome?
Q: Which shorter human RefSeq products are expressed, imported and processed in vivo, and do any retain glutathione-persulfide dioxygenase activity?
Q: Is the antibody-dependent nuclear signal attributable to ETHE1, and if so which product and cellular conditions produce it?
Q: Does endogenous human ETHE1 form a functional complex with TST, and does their association channel sulfur metabolites under physiological conditions? Tagged-protein co-immunoprecipitation and the UniProt-curated interaction establish association in a tested cellular context, but do not establish native substrate channeling.
Experiment: Isolate endogenous ETHE1 from human mitochondrial matrix under metal-controlled conditions, quantify metal occupancy by elemental analysis, and pair those measurements with GSSH-dependent oxygen consumption and sulfite HPLC assays. Compare with defined iron- and zinc-reconstituted recombinant controls while checking protein integrity, metal contamination and enzyme-free reactions.
Hypothesis: The active endogenous mitochondrial enzyme predominantly contains a single iron cofactor; any alternative metal occupancy is condition dependent.
Type: Metal analysis with matched enzyme kinetics and product detection
Experiment: Use transcript-junction and product-specific peptide measurements to establish which RefSeq products are expressed. Test detected products at matched abundance for mitochondrial import, protease protection, N-terminal processing and GSSH turnover, with the canonical precursor and the published engineered preparations as distinct controls.
Hypothesis: Natural internal-deletion products differ from engineered N-terminal deletions in abundance, mitochondrial import or catalytic competence.
Type: Product-resolved proteomics, import assays and enzymology
Experiment: Compare HPA029029 and independent ETHE1 reagents in matched wild-type, ETHE1-knockout and endogenous-tagged human cells using a nuclear counterstain. Confirm any nuclear signal with purified nuclear fractions, mitochondrial-contamination markers and product-informative peptide detection before testing a nuclear mechanism.
Hypothesis: The HPA029029 nuclear signal reflects either a conditional ETHE1 pool or antibody-dependent cross-reactivity rather than a uniformly nuclear protein.
Type: Genetic specificity controls, microscopy and subcellular proteomics
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