erg5 (SPAC19A8.04; cyp61) encodes the cytochrome P450 sterol C-22 desaturase (CYP61) of Schizosaccharomyces pombe. Using O2 and NADPH-derived electrons from P450 reductase it introduces the C22=C23 double bond into the side chain of 5-dehydroepisterol (ergosta-5,7,24(28)-trienol), giving ergosta-5,7,22,24(28)-tetraen-3beta-ol, the substrate of the final reductase erg4 (EC 1.14.19.41). erg5 deletion mutants are viable but lack ergosterol and grow even when lanosterol and ergosterol are depleted further by terbinafine. Erg5 binds the heme protein Dap1 (PGRMC1 homolog), which is required for full activity of the two sterol P450s Erg11 and Erg5. erg5 is induced by Sre1 under low oxygen.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000249 C-22 sterol desaturase (NADPH) activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined automated annotation from the UniProt EC 1.14.19.41 / Rhea:33467 assignment (5-dehydroepisterol + NADPH + O2 -> ergosta-5,7,22,24(28)-tetraenol), which is the GO:0000249 definition. Correct core MF. Supporting Evidence: file:SCHPO/erg5/erg5-uniprot.txt Reaction=5-dehydroepisterol + NADPH + O2 + H(+) = |
| GO:0000249 C-22 sterol desaturase (NADPH) activity | ISO GO_REF:0000024 | ACCEPT | Summary: PomBase ISO from S. cerevisiae ERG5/CYP61, whose recombinant enzyme performs sterol Delta22 desaturation; erg5 is the single CYP61 ortholog in S. pombe and its deletion abolishes ergosterol. Supporting Evidence: file:SCHPO/erg5/erg5-uniprot.txt Reaction=5-dehydroepisterol + NADPH + O2 + H(+) = file:SCHPO/erg5/erg5-uniprot.txt DISRUPTION PHENOTYPE: Abolishes the production of ergosterol |
| GO:0004497 monooxygenase activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO monooxygenase activity from the cytochrome P450 signature. Erg5 is an O2-dependent P450, but its reaction is a desaturation, and GO:0000249 is not classified under monooxygenase activity; the specific term is the informative one. Reason: Generic P450 mapping; use the specific C-22 desaturase. Proposed replacements: C-22 sterol desaturase (NADPH) activity Supporting Evidence: file:SCHPO/erg5/erg5-uniprot.txt Reaction=5-dehydroepisterol + NADPH + O2 + H(+) = |
| GO:0005506 iron ion binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro2GO iron ion binding from the P450 domain; the iron is the heme iron (UniProt cofactor heme). Correct cofactor-level statement, not the function. Reason: Heme-iron cofactor; non-core. Supporting Evidence: file:SCHPO/erg5/erg5-uniprot.txt Name=heme; Xref=ChEBI:CHEBI:30413; |
| GO:0005515 protein binding | IPI PMID:17276356 Dap1/PGRMC1 binds and regulates cytochrome P450 enzymes. | REMOVE | Summary: IPI with Dap1 (Hughes et al. 2007): Dap1 is a hemoprotein that binds Erg5 (Cyp61) and Erg11 (Cyp51) and is required for their activity. The interaction is real and functionally relevant, but 'protein binding' does not describe Erg5's activity; the regulatory relationship is captured on Dap1 (enzyme activator activity in the PomBase GO-CAM). Same decision as for erg11. Reason: Uninformative protein binding term; the Dap1 interaction itself is not disputed. Supporting Evidence: PMID:17276356 We show that S. pombe Dap1 is a hemoprotein that binds and positively regulates Cyp51A1 and Cyp61A1, two P450s required for sterol biosynthesis. |
| GO:0005783 endoplasmic reticulum | ISO GO_REF:0000024 | ACCEPT | Summary: ISO ER from S. cerevisiae Erg5, a microsomal P450. PomBase places erg5 activity in the ER in its GO-CAM. Correct; ER membrane would be more precise for this anchored P450. Supporting Evidence: file:SCHPO/erg5/erg5-uniprot.txt bond in the sterol side chain (By similarity). The third module or late |
| GO:0006696 ergosterol biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA ergosterol biosynthetic process from the CYP61 clade; confirmed by S. pombe deletion data. Supporting Evidence: PMID:18310029 Disruption mutants of these genes were unable to synthesize ergosterol |
| GO:0006696 ergosterol biosynthetic process | IMP PMID:18310029 Multiple functions of ergosterol in the fission yeast Schizo... | ACCEPT | Summary: Iwaki et al. 2008: erg5 disruptants cannot synthesise ergosterol. Direct support. Supporting Evidence: PMID:18310029 Disruption mutants of these genes were unable to synthesize ergosterol file:SCHPO/erg5/erg5-uniprot.txt DISRUPTION PHENOTYPE: Abolishes the production of ergosterol |
| GO:0006696 ergosterol biosynthetic process | IMP PMID:23145048 A genetic and pharmacological analysis of isoprenoid pathway... | ACCEPT | Summary: Nakamura et al. 2012: ergosterol levels were extremely low in erg5-deleted cells by LC-MS/MS. Direct support. Supporting Evidence: PMID:23145048 On the other hand, in Ξerg6 cells, Ξerg31Ξerg32 cells, and Ξerg5 cells, the ergosterol levels were extremely lower than that in wild-type cells |
| GO:0016126 sterol biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: UniPathway ergosterol biosynthesis mapping to sterol biosynthetic process; correct parent of GO:0006696. Supporting Evidence: file:SCHPO/erg5/erg5-uniprot.txt PATHWAY: Steroid metabolism; ergosterol biosynthesis. |
| GO:0016491 oxidoreductase activity | IBA GO_REF:0000033 | MODIFY | Summary: IBA oxidoreductase activity from the P450 family node; correct but the most generic MF parent of the specific C-22 sterol desaturase activity (which is annotated by IEA/ISO). Reason: Too general; GO:0000249 is the specific activity of this CYP61 ortholog. Propagation Review Root cause: TERM SCOPING PROBLEM Sources checked: PANTHER:PTN001209376 Β· PTN001209376 SUPPORTS TRANSFER Deep cytochrome P450 node seeded by many plant, animal and fungal P450s; oxidoreductase activity is correct for every descendant but is only a grouping term for CYP61. Proposed replacements: C-22 sterol desaturase (NADPH) activity Supporting Evidence: file:SCHPO/erg5/erg5-uniprot.txt Reaction=5-dehydroepisterol + NADPH + O2 + H(+) = |
| GO:0016705 oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO oxidoreductase activity acting on paired donors with incorporation/reduction of O2, from the P450 signature; GO:0000249 is a descendant of this term, so it is correct but less specific. Reason: Generic parent of GO:0000249. Proposed replacements: C-22 sterol desaturase (NADPH) activity Supporting Evidence: file:SCHPO/erg5/erg5-uniprot.txt Reaction=5-dehydroepisterol + NADPH + O2 + H(+) = |
| GO:0020037 heme binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro2GO heme binding from the P450 domain; Erg5 is a heme-thiolate P450 (UniProt cofactor heme). Correct cofactor binding, supporting but not describing the function. Reason: Cofactor binding; non-core. Supporting Evidence: file:SCHPO/erg5/erg5-uniprot.txt Name=heme; Xref=ChEBI:CHEBI:30413; |
| GO:0020037 heme binding | TAS PMID:17276356 Dap1/PGRMC1 binds and regulates cytochrome P450 enzymes. | KEEP AS NON CORE | Summary: TAS (Hughes et al. 2007): the paper treats Cyp61A1/Erg5 as a heme-dependent P450 regulated by the heme protein Dap1. Correct cofactor statement. Reason: Cofactor binding; non-core. Supporting Evidence: PMID:17276356 Cytochrome P450 enzymes are heme-dependent monoxygenases PMID:17276356 We show that S. pombe Dap1 is a hemoprotein that binds and positively regulates Cyp51A1 and Cyp61A1, two P450s required for sterol biosynthesis. |
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Download this section (compressed HTML)Q: Does Dap1 act on Erg5 as a heme chaperone, an electron-transfer partner, or a structural activator, and is ccr1 (P450 reductase) the sole reductant for S. pombe Erg5?
Q: Is S. pombe Erg5 inhibited by azoles as S. cerevisiae CYP61 is, and does erg5 deletion alter azole sensitivity?
Experiment: Measure Erg5 heme content, CO-difference spectrum and C-22 desaturase activity in microsomes from wild-type and dap1-deleted S. pombe.
Hypothesis: Dap1 binding is required for heme incorporation or stability of Erg5.
Type: biochemistry
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