Neurospora crassa erg-1 encodes a late ergosterol-biosynthetic sterol C-8 isomerase that acts at the endoplasmic-reticulum membrane. The protein is the filamentous-fungal ERG2 ortholog and contributes to fungal membrane sterol composition by promoting formation of the sterol B-ring C-7 double bond needed for progression from zymosterol toward ergosterol; loss of erg-1 blocks ergosterol biosynthesis and causes accumulation of C-8/C-9-unsaturated sterol intermediates that perturb vegetative germling fusion and development.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000247 C-8 sterol isomerase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Core C-8 sterol isomerase activity propagated from the fungal ERG2 PAINT node. Reason: PTN001280219 is the fungal ERG2 node in PTHR10868, carries the C-8 sterol isomerase activity assertion from Candida and budding-yeast ERG2 experimental annotations, and is separate from the animal Sigma-receptor nodes in the same family. The transfer matches the Neurospora UniProt function summary and Weichert et al.'s direct characterization of erg-1 as the Neurospora homolog of S. cerevisiae ERG2. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN001280219 SUPPORTS TRANSFER Fungal ERG2 PAINT node carrying C-8 sterol isomerase activity and ergosterol biosynthesis; it supports transfer to N. crassa erg-1. Supporting Evidence: file:interpro/panther/PTHR10868/PTHR10868-paint.tsv PTHR10868 PTN001280219 GO:0000247 F IBD false CGD:CAL0000177093|SGD:S000004815 taxon:451864 20251127 file:NEUCR/erg-1/erg-1-uniprot.txt Catalyzes the reaction which results in unsaturation at C-7 PMID:33046504 erg-1 (NCU04156), which encodes a sterol C-8 isomerase homologous to Erg2 of S. cerevisiae |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: Broad eukaryotic ERG2/SIGMAR1-family PAINT transfer to the endoplasmic reticulum is valid for the Neurospora C-8 sterol isomerase. Reason: PTN001328958 is broader than the fungal ERG2 node and is seeded by animal SIGMAR1 as well as fungal ERG2 entries, but the propagated assertion is only the shared endoplasmic-reticulum compartment. The animal-specific Sigma-receptor signaling and postsynaptic-density rows in PTHR10868 are confined to different PTN descendants and did not propagate to erg-1, and UniProt's by-similarity ER-membrane placement is consistent with this homology transfer but is not target-local experimental localization for N. crassa ERG-1. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN001328958 SUPPORTS TRANSFER Eukaryotic ERG2/SIGMAR1-family ER-localization node; the shared ER compartment transfers to erg-1 without importing animal-specific Sigma-receptor functions. Supporting Evidence: file:interpro/panther/PTHR10868/PTHR10868-paint.tsv PTHR10868 PTN001328958 GO:0005783 C IBD false MGI:MGI:1195268|RGD:68364|SGD:S000004815|UniProtKB:Q99720 taxon:2759 20260528 file:NEUCR/erg-1/erg-1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location transfer by similarity places erg-1 at the endoplasmic reticulum membrane. Reason: UniProt annotates the Neurospora C-8 sterol isomerase as an endoplasmic reticulum single-pass membrane protein by similarity, matching the expected location for a late ergosterol-biosynthetic enzyme but leaving ER localization untested in N. crassa. Supporting Evidence: file:NEUCR/erg-1/erg-1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0006696 ergosterol biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: Fungal ERG2 PAINT transfer correctly assigns erg-1 to ergosterol biosynthesis. Reason: PTN001280219 carries ergosterol-biosynthesis from PomBase and SGD ERG2 seeds, and the target is a fungal C-8 sterol isomerase in the same inherited clade. Neurospora erg-1 directly participates in the pathway by catalyzing the late sterol B-ring isomerization step; its loss blocks ergosterol accumulation and causes buildup of intermediates with a double bond between C-8 and C-9. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN001280219 SUPPORTS TRANSFER Fungal ERG2 PAINT node carrying C-8 sterol isomerase activity and ergosterol biosynthesis; it supports transfer to N. crassa erg-1. Supporting Evidence: file:interpro/panther/PTHR10868/PTHR10868-paint.tsv PTHR10868 PTN001280219 GO:0006696 P IBD false PomBase:SPAC20G8.07c|SGD:S000004815 taxon:451864 20170228 file:NEUCR/erg-1/erg-1-uniprot.txt Steroid metabolism; ergosterol biosynthesis PMID:33046504 not only confirmed a block in ergosterol biosynthesis, but also the accumulation of mainly three sterol intermediates |
| GO:0016126 sterol biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: UniPathway transfer to sterol biosynthesis is a true parent of the ergosterol-specific pathway row. Reason: The UniPathway mapping is broader than the fungal PAINT ergosterol row, but it is not misleading: ergosterol is the major fungal sterol, and erg-1 catalyzes a late sterol-ring isomerization required to proceed from zymosterol toward ergosterol. Supporting Evidence: file:NEUCR/erg-1/erg-1-uniprot.txt Steroid metabolism; ergosterol biosynthesis |
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Download this section (compressed HTML)Q: Which membrane-associated step between cell-to-cell contact recognition and fusion-machinery engagement is sensitive to the C-8/C-9-unsaturated sterol intermediates that accumulate in N. crassa erg-1 mutants?
Experiment: Express a functional ERG-1-GFP fusion from the native locus and test colocalization with an endoplasmic reticulum marker under vegetative growth conditions.
Hypothesis: ERG-1 localizes to the endoplasmic reticulum membrane in N. crassa.
Type: fluorescence colocalization assay
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