ERG6 notes (O74198, CAALFM_C302150CA)

• PANTHER family context: ERG6 is a PTHR44068:SF1 member with S. cerevisiae ERG6 (P25087), S. pombe erg6 (O14321), C. albicans ERG6 (O74198), Aspergillus fumigatus erg6 (Q4W9V1), and N. crassa erg-4 (Q9P3R1). The PTHR44068 PAINT table places GO:0003838 sterol 24-C-methyltransferase activity, GO:0005783 endoplasmic reticulum, and the parent GO:0016126 sterol biosynthetic process on PTN002226525; the more specific fungal ergosterol biosynthesis call GO:0006696 is on PTN000802684, seeded by CGD:CAL0000189580, PomBase:SPBC16E9.05, and SGD:S000004467.
• Direct Candida activity: Ganapathy et al. purified native Candida 24-SMT and found zymosterol is the optimal substrate and fecosterol is the product PMID:20946868. Liu et al. 2023 and later inhibitor papers also treat CaERG6 as a directly assayed sterol 24-C-methyltransferase PMID:37005772; the 2023 Cell Chemical Biology H55 paper and 2024 JMC H55-derivative paper were found in the PubMed search beyond the GOA set and cached.
• Original genetics: Jensen-Pergakes et al. cloned C. albicans ERG6 by complementing S. cerevisiae erg6 PMID:9593144 and disrupted both Candida alleles, producing sterol-pathway drug phenotypes.
• Local IBA comparison: the completed S. cerevisiae ERG6 review accepts GO:0003838, ER localization, lipid droplet localization, and ergosterol biosynthesis; the completed S. pombe erg6 review accepts GO:0003838, ER, and ergosterol biosynthesis and raises the unresolved question of whether pombe Erg6 also acts on lipid droplets. For Candida, I kept ER as the only core location because the lipid-droplet row is an Ensembl transfer from yeast rather than direct Candida evidence.
• PMID:19824013 plasma-membrane localization: the cached paper is abstract-only and reports a broad plasma-membrane proteomics workflow, not the Erg6 peptide evidence. I left GO:0005886 UNDECIDED rather than removing a CGD experimental row without the full text/supplement.
• PMID:17604452 xenobiotic response: the CaFT study shows altered ERG6 strain fitness in response to fluconazole and other compounds, but this is a membrane-sterol/drug-susceptibility phenotype rather than an Erg6 execution step in a xenobiotic response, so GO:0071466 is marked over-annotated.
• Deep research: UV_PROJECT_ENVIRONMENT=/srv/home/cmungall/orca/workspaces/ai-gene-review/aigr-ros-yeast/.venv just deep-research-falcon CANAL ERG6 was attempted twice on 2026-10-21. The first attempt exposed missing sparse-checkout support files (scripts/deep_research_wrapper.py, then templates/gene_research_go_focused.md); after adding those cones, Falcon failed because agentapi was unavailable and no OpenAI, Edison, Asta, or Perplexity API keys were configured. No ERG6-deep-research-falcon.md file was fabricated.
• 2026-11-06 PTHR44068 re-review: refreshed the UniProt flat file from entry
  version 126 to 127; the only substantive-visible differences were NCBI
  taxonomy line wording and the OMA xref, with no functional, catalytic,
  pathway, GO, PANTHER or feature changes. Web searches for newer Candida ERG6
  papers found 2025-2026 work using ERG6 as an ergosterol-pathway context gene,
  low-quality in-silico inhibitor docking, and a 2025 bioRxiv expression and
  crystallization preprint, but no newer peer-reviewed direct function paper
  stronger than the already cited 2025 zymosterol paper (PMID:40698822) or the
  direct CaErg6 inhibitor papers already in the review.