dfg10 (SPAC7D4.09c; UniProt O14264, still named "Uncharacterized protein C7D4.09c") is the fission yeast member of the Dfg10/SRD5A3 branch of the steroid 5-alpha reductase family, a multi-pass endoplasmic reticulum membrane protein. By orthology to budding-yeast Dfg10 and human SRD5A3 it is the NADPH-dependent polyprenal reductase that reduces the alpha-isoprene double bond of polyprenal to give dolichal, the middle step of the polyprenol to polyprenal to dolichal to dolichol route. The dolichol produced is phosphorylated by sec59 to dolichyl phosphate, the lipid carrier for N-glycan precursor assembly, Dol-P-mannose and Dol-P-glucose. A genome-wide screen localized it to the ER; no direct S. pombe biochemical or genetic study has been reported.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005783 endoplasmic reticulum | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: PomBase HDA from the ORFeome GFP screen (PMID:16823372); UniProt records ER membrane with this paper as experimental evidence. Consistent with the five predicted transmembrane helices and with ER-resident SRD5A3/Dfg10. Reason: Correct compartment from S. pombe high-throughput data. Supporting Evidence: file:SCHPO/dfg10/dfg10-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000379006 (donors human SRD5A3, rat, Arabidopsis) for endoplasmic reticulum. Matches S. pombe localization. Reason: Correct location. Supporting Evidence: file:SCHPO/dfg10/dfg10-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt SubCell mapping (SL-0097) of the experimentally supported ER membrane statement (multi-pass membrane protein). Most precise location. Reason: Correct, precise location. Supporting Evidence: file:SCHPO/dfg10/dfg10-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005789 endoplasmic reticulum membrane | NAS GO_REF:0000051 | ACCEPT | Summary: PomBase NAS (GO_REF:0000051) for ER membrane, also used as occurs_in for dfg10 polyprenal reductase activity in PomBase GO-CAM 671ae02600003548. Agrees with the GFP data and topology. Reason: Correct location. Supporting Evidence: file:SCHPO/dfg10/dfg10-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0006488 dolichol-linked oligosaccharide biosynthetic process | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA from PTN000379006 (donors mouse Srd5a3, S. cerevisiae DFG10) for dolichol-linked oligosaccharide biosynthetic process. The enzyme supplies dolichol for the Dol-P carrier on which the N-glycan precursor is built; it does not transfer sugars. Kept non-core as for DFG10. Reason: Upstream carrier-supply role; non-core. Supporting Evidence: PMID:38821050 We first measured polyisoprenoid levels from Dfg10-deficient yeast, and noted a 4-fold decrease in dolichol, accompanied by a 36-fold increase in polyprenol and a 45-fold increase in polyprenal |
| GO:0006629 lipid metabolic process | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO from IPR001104 (3-oxo-5-alpha-steroid 4-dehydrogenase C-terminal domain) to lipid metabolic process. True but very general; the specific process is dolichyl monophosphate biosynthesis. Reason: Replace with dolichyl monophosphate biosynthetic process (GO:0043048). Proposed replacements: dolichyl monophosphate biosynthetic process Supporting Evidence: file:SCHPO/dfg10/dfg10-uniprot.txt InterPro; IPR039698; Dfg10/SRD5A3. PMID:38821050 We first measured polyisoprenoid levels from Dfg10-deficient yeast, and noted a 4-fold decrease in dolichol, accompanied by a 36-fold increase in polyprenol and a 45-fold increase in polyprenal |
| GO:0016627 oxidoreductase activity, acting on the CH-CH group of donors | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO (IPR001104, IPR039698) to 'oxidoreductase activity, acting on the CH-CH group of donors'. Correct parent but the Dfg10/SRD5A3 subfamily activity is known: polyprenal reduction to dolichal (not polyprenol reduction, and not steroid 5-alpha reduction). Reason: Replace with polyprenal reductase activity (GO:0160198). Proposed replacements: polyprenal reductase activity Supporting Evidence: file:SCHPO/dfg10/dfg10-uniprot.txt InterPro; IPR039698; Dfg10/SRD5A3. PMID:38821050 The SRD5A3 yeast orthologue Dfg10 also shows activity on polyprenal but not on polyprenol. |
| GO:0043048 dolichyl monophosphate biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000379006 (donors S. cerevisiae DFG10, human SRD5A3) for dolichyl monophosphate biosynthetic process. Dfg10 and SRD5A3 loss lowers dolichol and accumulates polyprenol/polyprenal. Reason: Core process. Supporting Evidence: PMID:38821050 We first measured polyisoprenoid levels from Dfg10-deficient yeast, and noted a 4-fold decrease in dolichol, accompanied by a 36-fold increase in polyprenol and a 45-fold increase in polyprenal PMID:20637498 we detected a 70% decrease in dolichol in the dfg10–100 mutant compared to the wt yeast from the same background |
| GO:0043048 dolichyl monophosphate biosynthetic process | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO from IPR039698 (Dfg10/SRD5A3 family) to dolichyl monophosphate biosynthetic process. Correct, family-specific mapping. Reason: Correct electronic process. Supporting Evidence: file:SCHPO/dfg10/dfg10-uniprot.txt InterPro; IPR039698; Dfg10/SRD5A3. |
| GO:0043048 dolichyl monophosphate biosynthetic process | ISO GO_REF:0000024 | ACCEPT | Summary: PomBase ISO (GO_REF:0000024) from human SRD5A3 (Q9H8P0); same process used in PomBase GO-CAM 671ae02600003548. Reason: Correct ortholog transfer. Supporting Evidence: PMID:38821050 We first measured polyisoprenoid levels from Dfg10-deficient yeast, and noted a 4-fold decrease in dolichol, accompanied by a 36-fold increase in polyprenol and a 45-fold increase in polyprenal |
| GO:0160198 polyprenal reductase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000379006 (donors S. cerevisiae DFG10, human SRD5A3). The revised dolichol pathway shows SRD5A3 and yeast Dfg10 reduce polyprenal to dolichal and do not act on polyprenol. Reason: Core activity by well-supported phylogenetic inference. Supporting Evidence: PMID:38821050 The SRD5A3 yeast orthologue Dfg10 also shows activity on polyprenal but not on polyprenol. file:SCHPO/dfg10/dfg10-uniprot.txt InterPro; IPR039698; Dfg10/SRD5A3. |
| GO:0160198 polyprenal reductase activity | ISO GO_REF:0000024 | ACCEPT | Summary: PomBase ISO from human SRD5A3 (Q9H8P0); the activity asserted for SPAC7D4.09c in PomBase GO-CAM 671ae02600003548. Reason: Correct ortholog transfer of the core activity. Supporting Evidence: PMID:38821050 The SRD5A3 yeast orthologue Dfg10 also shows activity on polyprenal but not on polyprenol. |
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Download this section (compressed HTML)Q: Does S. pombe use the same DHRSX/TDA5-type dehydrogenase steps flanking dfg10 (polyprenol oxidation and dolichal reduction), and which S. pombe SDR performs them?
Experiment: Measure polyprenol, polyprenal and dolichol in an S. pombe dfg10 deletion and test complementation by human SRD5A3.
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