Egm (Complex I assembly factor Egm, mitochondrial; also known as dACAD9 or Enigma; gene CG9006) is the single Drosophila melanogaster ortholog of human ACAD9. It is a nuclear-encoded, mitochondrially targeted member of the acyl-CoA dehydrogenase (ACAD) family bearing an N-terminal transit peptide and the ACAD9/ACADVL-like domain architecture. Its dominant, essential role is as a mitochondrial respiratory chain complex I (CI) assembly factor: Egm is a core component of the mitochondrial complex I intermediate assembly (MCIA) complex, together with the Drosophila orthologs of ECSIT, NDUFAF1, TMEM126B and TMEM186, and it regulates biogenesis of the membrane-arm PP-b (ND2) sub-module of CI. Loss of Egm destabilizes the other MCIA components in assembly intermediates, and Egm remains associated with the assembled CI holoenzyme for a period after assembly, consistent with an assembly-chaperone/adaptor role. Egm localizes to mitochondria, including the mitochondrial matrix/inner-membrane compartment. Like human ACAD9, Egm retains an ACAD fold and is predicted to bind FAD and may retain additional FAD-dependent acyl-CoA dehydrogenase activity across an overlapping substrate range including medium-, long- and very-long-chain acyl-CoAs by orthology, although direct enzymatic activity of the fly protein has not been biochemically demonstrated. Egm is essential for viability: null larvae die at the third instar and show systemic metabolic defects (reduced triglycerides, malformed fat bodies, small imaginal discs), while partial-loss-of-function alleles confer increased oxidative-stress resistance and a female-specific lifespan extension, phenotypes consistent with impaired mitochondrial oxidative phosphorylation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: Mitochondrial Egm is within the cytoplasm. Reason: GO:0005737 includes intracellular organelles outside the nucleus; the live definition and mitochondrion part_of relation were verified. Direct mitochondrial localization therefore supports this broad IBA rather than contradicting it. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002535634 SUPPORTS TRANSFER Current PAINT cytoplasm IBD verified. Ontological scope includes mitochondria, so this source assertion is biologically compatible with direct target localization. Supporting Evidence: PMID:16434470 In Drosophila Kc-167 and SL2 cells, Egm is found almost exclusively in the mitochondrion. |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetically inferred mitochondrial localization. This is correct for Egm and directly corroborated by experimental data (immunocytochemistry, cell fractionation) in Drosophila cells. Reason: Egm is experimentally established as a mitochondrial protein (PMID:16434470), so the IBA mitochondrion annotation is accurate. It is subsumed by the more specific mitochondrial matrix annotation but is not incorrect. Supporting Evidence: PMID:16434470 the endogenous Egm protein is highly enriched in the fraction that contains the mitochondria |
| GO:0051793 medium-chain fatty acid catabolic process | IBA GO_REF:0000033 | UNDECIDED | Summary: The physiological medium-chain catabolic role of Egm remains unresolved. Reason: PTN000098033 carries the current PAINT IBD, but the served v19 tree lacks both that node and exact Egm leaf, so an MCAD-only target ancestry was not established. Human ACAD9 uses a broad substrate range, which includes medium-chain substrates; its main complex-I assembly role is not negative evidence. However, unchanged octanoate oxidation in human ACAD9-knockout HEK293 cells (PMID:25721401) limits a universal physiological inference. Egm lipid phenotypes do not identify the chain length processed. A focused neutral adjudication has been requested. Propagation Review Root cause: UNRESOLVED Sources checked: PANTHER:PTN000098033 UNRESOLVED Current PAINT IBD verified; served PTHR43884 v19 topology omits this node and Q5U117, preventing exact lineage reconciliation. Ortholog kinetics support capacity but target physiological flux is unresolved. Supporting Evidence: PMID:25721401 Conversely, octanoate oxidation was unaffected |
| GO:0033539 fatty acid beta-oxidation using acyl-CoA dehydrogenase | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Phylogenetically inferred role in the acyl-CoA dehydrogenase step of fatty acid beta-oxidation. Egm belongs to the ACAD family and retains the ACAD fold, so a residual FAO-enzyme role is plausible by orthology to human ACAD9. However, the fly protein's dehydrogenase activity has not been directly demonstrated, and its dominant role is CI assembly. Retained as a non-core, by-similarity annotation. Reason: By orthology to human ACAD9 (a bona fide, if secondary, acyl-CoA dehydrogenase), Egm may contribute to the ACAD step of beta-oxidation, and homology-plus-phenotype evidence in the fly (PMID:16434470) is consistent with a lipid-metabolism role. This is a plausible secondary function but not the core function, which is CI assembly. Human ACAD9 has genuine, separable fatty-acid oxidation capacity (PMID:25721401); the established fly MCIA role does not demonstrate loss of catalysis. Target enzymatic specificity remains inferred. Supporting Evidence: PMID:16434470 homology to ACADs, the enzymes that catalyze the first of four reactions that constitute one cycle of the Ξ²-oxidation pathway |
| GO:0070991 medium-chain fatty acyl-CoA dehydrogenase activity | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Medium-chain dehydrogenase capacity is plausible for the ACAD9 ortholog Egm. Reason: The old rejection confused substrate preference with exclusivity. GO:0070991 covers C6-C12. Purified human ACAD9 in PMID:16020546 was assayed with C6-C12 and longer acyl-CoAs and retains activity in the medium-chain range despite its long-chain optimum; live human ACAD9 has an IDA annotation to this exact term. Together with Egm ACAD9 orthology, this supports a noncore inherited catalytic capacity. Fly-specific kinetics and the version-mismatched PTN000098033 lineage remain unresolved and are included in the focused adjudication. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: PANTHER:PTN000098033 SUPPORTS TRANSFER Source IBD exists, but exact target lineage is unavailable in served v19. Independent same-subfamily human ACAD9 kinetics support transfer of catalytic capacity; primary assembly function does not negate it. Supporting Evidence: file:DROME/Egm/Egm-notes.md The full primary describes βactivity toward a broad range of substratesβ. |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | ACCEPT | Summary: Electronic annotation from UniProt subcellular-location mapping (SL-0173, Mitochondrion). Egm's mitochondrial localization is experimentally established, so this IEA term is correct. Reason: The UniProt subcellular-location term derives from the experimentally supported mitochondrial localization (PMID:16434470). Correct, though subsumed by the more specific mitochondrial matrix annotation. Supporting Evidence: PMID:16434470 In Drosophila Kc-167 and SL2 cells, Egm is found almost exclusively in the mitochondrion. |
| GO:0006631 fatty acid metabolic process | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA machine-learning electronic annotation placing Egm in fatty acid metabolism, based on ACAD family membership. Plausible by orthology to human ACAD9's secondary FAO activity, but broad and not directly demonstrated for the fly protein. Retained as a non-core, by-similarity annotation. Reason: As an ACAD-family member, Egm is plausibly involved in fatty acid metabolism (consistent with the reduced-triglyceride phenotype of null larvae; PMID:16434470), but this is a broad parent term and a secondary function relative to CI assembly. Human ACAD9 has genuine, separable fatty-acid oxidation capacity (PMID:25721401); the established fly MCIA role does not demonstrate loss of catalysis. Target enzymatic specificity remains inferred. Supporting Evidence: PMID:16434470 the stored fatty acids in the form of triglycerides are almost halved in larvae lacking zygotically expressed Egm |
| GO:0016627 oxidoreductase activity, acting on the CH-CH group of donors | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro-based electronic annotation to the intermediate oxidoreductase term. The acyl-CoA dehydrogenase reaction introduces a double bond between the alpha and beta carbons (oxidation of a CH-CH group). Egm contains the ACAD catalytic domains, so the term is structurally appropriate, but the activity of the fly protein has not been directly measured. Reason: Egm carries the acyl-CoA dehydrogenase domain signature (Pfam PF00441/PF02770/PF02771; InterPro IPR006091 etc.), making this intermediate oxidoreductase term appropriate by domain content. It is a by-similarity/domain-based call for a additional enzymatic activity, subordinate to the CI-assembly core function. Human ACAD9 has genuine, separable fatty-acid oxidation capacity (PMID:25721401); the established fly MCIA role does not demonstrate loss of catalysis. Target enzymatic specificity remains inferred. Supporting Evidence: PMID:16434470 homology to ACADs, the enzymes that catalyze the first of four reactions that constitute one cycle of the Ξ²-oxidation pathway |
| GO:0050660 flavin adenine dinucleotide binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro-based electronic annotation for FAD binding. Egm is an ACAD-family flavoprotein (UniProt COFACTOR: FAD, by RuleBase), and FAD binding is a conserved feature of the fold. In human ACAD9, FAD binding is directly demonstrated and is functionally coupled to the assembly switch (ECSIT-induced deflavination). FAD binding of the fly protein is inferred by similarity/domain content but not directly measured. Reason: FAD binding is a conserved property of the ACAD9/ACAD fold and is annotated in UniProt as a cofactor. This is a well-supported by-similarity molecular-function feature, but for Egm it has not been directly demonstrated, and in the ACAD9 orthology group the FAD/enzymatic activity is secondary to (and, in the human protein, mutually exclusive with) the CI-assembly role. Deliberately kept non-core here (unlike the FAD core-function entries in the catabolic ACAD reviews Acadvl, Mcad, Arc42, and CG4860), because Egm's primary role is complex I assembly (GO:0030674), not fatty acid beta-oxidation. Human ACAD9 has genuine, separable fatty-acid oxidation capacity (PMID:25721401); the established fly MCIA role does not demonstrate loss of catalysis. Target enzymatic specificity remains inferred. Supporting Evidence: PMID:16434470 homology to ACADs, the enzymes that catalyze the first of four reactions that constitute one cycle of the Ξ²-oxidation pathway |
| GO:0017099 very-long-chain fatty acyl-CoA dehydrogenase activity | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: ISS annotation transferred by curator judgment of sequence similarity from human ACAD9 (UniProtKB:Q9H845). Human ACAD9 does have FAD-dependent acyl-CoA dehydrogenase activity toward long/very-long-chain acyl-CoA substrates, but this activity is modest (~18% of VLCAD) and is a secondary/moonlighting function; in the human ACAD9 review the "very-long-chain" specificity is argued to over-state substrate preference (long-chain is the primary specificity). For Egm the activity is undemonstrated. Kept as a non-core, by-similarity annotation rather than removed. Reason: The human ACAD9 donor has measured activity with C22:6-CoA in PMID:16020546, as well as shorter substrates. A long-chain optimum does not exclude very-long-chain substrate activity. Retain this conserved ACAD9 capacity as noncore while distinguishing human biochemical evidence from unmeasured fly kinetics. Supporting Evidence: PMID:16020546 C18:2-, C22:6-CoA) |
| GO:0030674 protein-macromolecule adaptor activity | ISS GO_REF:0000024 | ACCEPT | Summary: ISS annotation transferred from human ACAD9 (UniProtKB:Q9H845), where ACAD9 functions as a protein-macromolecule adaptor/scaffold bridging ECSIT (and through it NDUFAF1) to CI assembly intermediates within the MCIA complex. Drosophila data directly support the same role: Egm (dACAD9) is an MCIA core member whose loss destabilizes the other MCIA components in assembly intermediates, consistent with a scaffolding/adaptor function. This is the best molecular-function representation of Egm's core CI-assembly role. Reason: The adaptor/scaffold molecular function is conserved and supported directly in the fly: dACAD9 knockdown reduces dNDUFAF1 and dECSIT in assembly intermediates (PMID:34386730), mirroring human ACAD9's central, MCIA-stabilizing adaptor role (transferred by ISS from Q9H845). This is far more informative than a generic protein-binding term and captures Egm's core function. Supporting Evidence: PMID:34386730 RNAi-mediated knockdown of dACAD9 resulted in a reduction in the amount of dNDUFAF1 and dECSIT that accumulates in AIs in ACAD9-kd samples |
| GO:0160295 mitochondrial complex I intermediate assembly complex | IDA PMID:34386730 Dissecting the concordant and disparate roles of NDUFAF3 and... | ACCEPT | Summary: IDA annotation from FlyBase based on Murari et al. 2021, which demonstrated that the fly ortholog of ACAD9 (dACAD9/CG9006/Egm) is a core member of the Drosophila MCIA complex, together with the orthologs of ECSIT, NDUFAF1, TMEM126B and TMEM186, and that these components co-migrate with CI assembly intermediates and the holoenzyme. This is a core cellular-component annotation for Egm. Reason: Direct Drosophila evidence places Egm/dACAD9 in the MCIA complex: all five MCIA components (including dACAD9) were found associated with CI subcomplexes/holoenzyme, and dACAD9 knockdown destabilizes the other MCIA members (PMID:34386730). This mirrors the well-established human ACAD9 MCIA membership and is Egm's core localization/complex. Supporting Evidence: PMID:34386730 all 5 components of the MCIA complex were associated with subcomplexes in FAF4-kd and FAF3-kd samples PMID:34386730 Drosophila orthologs of ACAD9 (CG9006), ECSIT (CG10610), NDUFAF1 (CG7598), TMEM126B (CG13392), TMEM186 (CG4627) |
| GO:0007320 insemination | HEP PMID:18666829 Proteomics reveals novel Drosophila seminal fluid proteins t... | MARK AS OVER ANNOTATED | Summary: HEP annotation from Findlay et al. 2008, a seminal-fluid proteomics study in which Egm was detected among transferred male seminal fluid proteins (classed among lipid-metabolism proteins). This is a mass-spectrometric co-occurrence in seminal fluid, not a demonstration that Egm has a dedicated insemination/reproductive function; the protein's characterized role is mitochondrial CI assembly. Reason: Full PMID:18666829 uses isotope labeling to demonstrate transfer of male seminal-fluid proteins, a substantive result rather than assumed contamination. Egm detection establishes that it is transferred material; it does not establish that Egm performs semen/sperm introduction, the live definition of GO:0007320. Retain MARK_AS_OVER_ANNOTATED for the process claim, while preserving the proteomic observation; mitochondrial localization itself is not grounds for rejection. Supporting Evidence: PMID:18666829 proteins involved in lipid metabolism |
| GO:0032981 mitochondrial respiratory chain complex I assembly | TAS PMID:34386730 Dissecting the concordant and disparate roles of NDUFAF3 and... | ACCEPT | Summary: TAS annotation from Murari et al. 2021. Egm/dACAD9 participates in CI assembly as an MCIA-complex factor that regulates biogenesis of the PP-b (ND2) sub-module of the CI membrane arm; disruption of dACAD9 stalls assembly intermediates and destabilizes partner MCIA factors. This is the core biological process for Egm and represents its most important physiological function. Reason: CI assembly is Egm's core biological process, directly supported in the fly: dACAD9 regulates PP-b sub-module biogenesis and its knockdown reduces partner MCIA factors in assembly intermediates (PMID:34386730), consistent with the essential, conserved ACAD9 CI-assembly role. Supporting Evidence: PMID:34386730 ACAD9 regulates biogenesis of some sub-assemblies in the PP-b sub-module PMID:34386730 when dACAD9 is disrupted, the paucity of the PP-b sub-module will cause the Q/PP-a AI to stall and accumulate |
| GO:0005759 mitochondrial matrix | IDA PMID:26362788 Proteomic mapping in live Drosophila tissues using an engine... | ACCEPT | Summary: IDA annotation from Chen et al. 2015, an APEX-based proteomic mapping of the Drosophila muscle mitochondrial matrix ("MitoMax") in which Egm was catalogued as a matrix protein. This is consistent with Egm being a peripheral, matrix-facing inner-membrane MCIA factor (like human ACAD9, which is peripheral on the matrix side of the inner membrane). Reason: APEX matrix proteomics places Egm in the mitochondrial matrix compartment (PMID:26362788), consistent with the matrix-facing localization of the MCIA complex and with the immunolocalization of Egm to mitochondria (PMID:16434470). Appropriate, specific compartmental annotation. Supporting Evidence: PMID:26362788 maps the mitochondrial matrix proteome of Drosophila muscle |
| GO:0005739 mitochondrion | IDA PMID:34386730 Dissecting the concordant and disparate roles of NDUFAF3 and... | ACCEPT | Summary: IDA annotation from Murari et al. 2021. Egm/dACAD9 acts within mitochondria as an MCIA-complex CI assembly factor (co-migrating with mitochondrial CI subcomplexes and holoenzyme). Mitochondrial localization is well supported. Reason: Egm functions in mitochondria as a CI assembly factor (PMID:34386730), corroborated by independent immunolocalization/fractionation (PMID:16434470). Correct, though subsumed by the more specific mitochondrial matrix annotation. Supporting Evidence: PMID:34386730 all 5 components of the MCIA complex were associated with subcomplexes in FAF4-kd and FAF3-kd samples |
| GO:0034976 response to endoplasmic reticulum stress | HMP PMID:23667151 Using natural variation in Drosophila to discover previously... | KEEP AS NON CORE | Summary: HMP annotation from Chow et al. 2013, a DGRP natural-variation study of tunicamycin-induced ER stress survival in which Egm was one of six lipid-metabolism-related association candidates (and a P-element functional-test candidate). This is a genetic-association/mutant-phenotype signal suggesting a modifier role rather than a direct, mechanistic function of Egm in the ER stress response; the connection is most plausibly indirect (via mitochondrial/lipid metabolism). Reason: Egm surfaced as an ER-stress-survival association candidate with a putative lipid-metabolism link (PMID:23667151); the effect is likely an indirect consequence of its metabolic/mitochondrial role rather than a dedicated ER-stress function. Retained as a non-core annotation reflecting the experimental modifier evidence. Supporting Evidence: PMID:23667151 with known or putative roles in lipid metabolism |
| GO:0005739 mitochondrion | IDA PMID:16434470 Enigma, a mitochondrial protein affecting lifespan and oxida... | ACCEPT | Summary: IDA annotation from Mourikis et al. 2006, the foundational Enigma paper, which localized Egm to mitochondria by immunocytochemistry (colocalization with MitoTracker and the inner-membrane marker prohibitin) and by cell fractionation. This is direct experimental evidence for mitochondrial localization of Egm. Reason: Direct experimental localization of endogenous and tagged Egm to mitochondria in Drosophila cells, confirmed by fractionation (PMID:16434470). Well-supported core localization. Supporting Evidence: PMID:16434470 the endogenous Egm protein is highly enriched in the fraction that contains the mitochondria PMID:16434470 In Drosophila Kc-167 and SL2 cells, Egm is found almost exclusively in the mitochondrion. |
| GO:0006635 fatty acid beta-oxidation | IMP PMID:16434470 Enigma, a mitochondrial protein affecting lifespan and oxida... | KEEP AS NON CORE | Summary: IMP annotation from Mourikis et al. 2006, based on the metabolic phenotype of Egm-null larvae (halved triglycerides, upregulated lipase-3, mitochondrial localization, and eye-clone phenotype resembling the beta-oxidation mutant scully) plus ACAD homology. The authors are explicit that the beta-oxidation involvement is indirect. In light of the later demonstration that ACAD9/Egm is primarily a CI assembly factor, these metabolic phenotypes are equally (and more parsimoniously) explained by CI/OXPHOS deficiency. Retained as a non-core, experimentally-grounded annotation. Reason: This is a legitimate experimental (IMP) annotation reflecting real mutant metabolic phenotypes, and the full text (which the curator read) contains the supporting data; per review guidelines it should not be removed on the grounds that the evidence is indirect. However, because Egm's dominant, directly demonstrated role is CI assembly (PMID:34386730) and the paper itself calls the beta-oxidation link indirect, it is best treated as non-core rather than a core function. Human ACAD9 has genuine, separable fatty-acid oxidation capacity (PMID:25721401); the established fly MCIA role does not demonstrate loss of catalysis. Target enzymatic specificity remains inferred. Supporting Evidence: PMID:16434470 indirect evidence suggests that this protein may be involved in Ξ²-oxidation PMID:16434470 the stored fatty acids in the form of triglycerides are almost halved in larvae lacking zygotically expressed Egm |
| GO:0055088 lipid homeostasis | IMP PMID:16434470 Enigma, a mitochondrial protein affecting lifespan and oxida... | KEEP AS NON CORE | Summary: IMP annotation from Mourikis et al. 2006. Egm-null larvae show markedly reduced triglyceride stores, malformed fat bodies, and altered expression of lipid-metabolism genes, demonstrating a mutant lipid-homeostasis phenotype. Whether this reflects a direct role of Egm in lipid metabolism or a systemic consequence of mitochondrial CI/OXPHOS deficiency is not resolved by the study, but the mutant phenotype is real and experimentally established. Reason: The lipid-homeostasis phenotype of Egm mutants is directly documented (PMID:16434470) and is a valid experimental annotation. It is retained as non-core because it is a downstream/systemic metabolic consequence rather than Egm's core molecular role (CI assembly), and the causal directness of the lipid link is uncertain. Supporting Evidence: PMID:16434470 the stored fatty acids in the form of triglycerides are almost halved in larvae lacking zygotically expressed Egm |
| GO:1900408 negative regulation of cellular response to oxidative stress | IMP PMID:16434470 Enigma, a mitochondrial protein affecting lifespan and oxida... | KEEP AS NON CORE | Summary: IMP annotation from Mourikis et al. 2006. Reduction of Egm (heterozygous nulls / hypomorphs) increases organismal tolerance to paraquat-induced oxidative stress, i.e. reducing Egm enhances oxidative-stress resistance. This phenotype connects Egm dosage to the oxidative-stress response, most plausibly through its effect on mitochondrial OXPHOS/ROS. It is a systemic phenotype rather than a direct molecular function of the protein. Reason: The paraquat-resistance phenotype of Egm mutants is experimentally demonstrated (PMID:16434470) and links Egm to the oxidative-stress response, but the effect is an indirect, dosage-dependent, whole-organism consequence of altered mitochondrial function rather than a core molecular role. Retained as non-core. Supporting Evidence: PMID:16434470 Egm mutant flies demonstrate a significantly increased resistance to the toxic effects of 7.5 mM paraquat compared with WT flies |
| GO:0001745 compound eye morphogenesis | IGI PMID:8913755 Analysis of dominant enhancers and suppressors of activated ... | KEEP AS NON CORE | Summary: IGI annotation from Verheyen et al. 1996, a large second-site screen for dominant modifiers of an activated-Notch rough-eye phenotype, in which an Egm allele behaved as a genetic modifier of eye development. The cached record is abstract-only (full text unavailable), so the specific Egm allele data cannot be verified here; this is an experimental genetic-interaction annotation from FlyBase. Egm's requirement for eye development is independently supported by the cell-autonomous aberrant morphology of Egm-null eye clones (PMID:16434470), consistent with an essential mitochondrial gene being required for the energetically demanding eye morphogenesis rather than a dedicated eye-patterning function. Reason: This is an experimental (IGI) FlyBase annotation whose full text was read by the curator; per review guidelines it should not be removed merely because the cached entry is abstract-only. The eye requirement is corroborated by cell-autonomous Egm-null clone phenotypes (PMID:16434470). It is a pleiotropic/developmental consequence of Egm's essential mitochondrial role, so it is retained as non-core rather than a core function. Supporting Evidence: PMID:16434470 null Egm β/β clones show an aberrant morphology PMID:8913755 a second-site mutagenesis screen was performed to isolate enhancers and suppressors of the eye phenotype caused by expression of these activated Notch molecules |
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Download this section (compressed HTML)Q: Does Drosophila Egm retain measurable FAD-dependent acyl-CoA dehydrogenase activity, and if so with what chain-length preference? By orthology to human ACAD9 a residual long/very-long-chain activity is expected, but the fly protein has never been enzymatically characterized, so the ISS/IEA enzymatic annotations remain unverified for Drosophila.
Q: Are the lipid-homeostasis, oxidative-stress and lifespan phenotypes of Egm mutants (PMID:16434470) a direct consequence of loss of an acyl-CoA dehydrogenase enzyme, or downstream effects of complex I / OXPHOS deficiency? The 2006 study predates the CI-assembly-factor paradigm, and the two interpretations make different predictions for a catalytically dead but assembly-competent allele.
Experiment: Test the assembly-vs-enzyme separation of function in vivo by rescuing Egm-null larvae with (a) wild-type Egm, (b) a catalytically inactive (predicted active-site) Egm variant, and (c) a variant predicted to disrupt ECSIT/MCIA binding, then assay complex I assembly (BN-PAGE), CI activity, triglyceride levels, oxidative-stress resistance and viability. This would establish whether the essential function and the metabolic/longevity phenotypes depend on the CI-assembly activity, the dehydrogenase activity, or both.
Hypothesis: The CI-assembly (adaptor) function of Egm, not its residual dehydrogenase activity, accounts for its essential role and for the lipid/oxidative-stress/lifespan phenotypes, paralleling human ACAD9 where a catalytically dead mutant still rescues CI biogenesis.
Experiment: Biochemically characterize recombinant Egm: measure FAD occupancy and acyl-CoA dehydrogenase activity across a chain-length substrate panel (medium-, long-, very-long-chain acyl-CoA), and test whether the fly ECSIT ortholog induces deflavination of Egm as it does for human ACAD9.
Hypothesis: Egm binds FAD and has modest long/very-long-chain (not medium-chain) acyl-CoA dehydrogenase activity that is downregulated by ECSIT binding, consistent with the conserved deflavination switch of human ACAD9.
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