erg1 (SPBC713.12, UniProt Q9C1W3) notes

Module: ergosterol_biosynthesis (squalene epoxidase); S. cerevisiae ortholog ERG1 (P32476). Fetch verified: Q9C1W3.

Evidence

• Reaction squalene + O2 + reduced CPR -> (S)-2,3-epoxysqualene; FAD cofactor [UniProt:Q9C1W3 "Reaction=squalene + reduced [NADPH--hemoprotein reductase] + O2 = (S)-"].
• Inhibition of Erg1 (terbinafine) causes squalene accumulation PMID:33223513; UniProt disruption phenotype: squalene accumulation.
• Takami et al. quantified fission-yeast squalene and ergosterol by LC-MS/MS after terbinafine treatment, directly tying Erg1 inhibition to squalene accumulation and ergosterol-pathway flux PMID:23145048.
• Anaerobic induction is Sre1-independent PMID:16537923 - contradicts UniProt INDUCTION text ("up-regulated via ... sre1").

2026-11-06 re-review

• Re-fetched SCHPO/erg1; GOA still has 13 rows and the existing review covers them all. The Q9C1W3 UniProt record advanced from entry version 137 to 138, changing only the OMA cross-reference among cached lines used here.
• Tried the default just deep-research-falcon SCHPO erg1 provider, but falcon was not available in this environment, so no provider-authored deep-research file was generated.
• Searched for newer direct fission-yeast Erg1/squalene monooxygenase literature with "erg1" "Schizosaccharomyces pombe" terbinafine fission yeast, "Tif302" "erg1" terbinafine fission yeast Erg1, and "Schizosaccharomyces pombe" "squalene epoxidase" "LC-MS/MS". No newer paper directly assaying S. pombe Erg1 after PMID:33223513 was found; a 2025 Schizosaccharomyces japonicus hopanoid study only used S. pombe as a terbinafine-sensitive comparator.

Curation decisions

• vacuolar membrane (IEA SubCell, deriving from ORFeome HTP) MARK_AS_OVER_ANNOTATED.
• cytoplasm HDA marked TOO_GENERAL; membrane IEA and sterol metabolic process ARBA modified to specific terms.
• Consistent with yeast ERG1 core function.