spo9 (SPBC36.06c; UniProt O59703) encodes an FPS-like prenyltransferase that has no detectable activity on its own and is not a functional farnesyl diphosphate synthase. Instead it partners with the true FPS, Fps1, to form a heteromeric complex with geranylgeranyl diphosphate synthase activity, which stands in for the dedicated GGPP synthase that S. pombe lacks. spo9 deletion abolishes cellular GGPP but leaves FPP unchanged. It impairs membrane attachment of geranylgeranylated proteins such as ypt7 and rhb1, causes temperature-sensitive growth, and blocks forespore membrane expansion during sporulation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004311 geranylgeranyl diphosphate synthase activity | IDA PMID:17596513 Geranylgeranyl diphosphate synthase in fission yeast is a he... | ACCEPT | Summary: Spo9 alone lacks GGPS activity but forms an active GGPS complex with Fps1; GGPS activity is reduced in the spo9 mutant. Supporting Evidence: PMID:17596513 the two proteins together form a complex with GGPS activity PMID:17596513 the GGPS activity is significantly reduced in the spo9 |
| GO:0004311 geranylgeranyl diphosphate synthase activity | IEA GO_REF:0000120 | ACCEPT | Summary: EC/RHEA mapping of GGPS activity. The term is right; Spo9 works as part of the Fps1-Spo9 heteromer (see the contributes_to IDA). Supporting Evidence: PMID:17596513 the two proteins together form a complex with GGPS activity |
| GO:0004337 (2E,6E)-farnesyl diphosphate synthase activity | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: PAINT places spo9 under the FPS node. spo9, unlike fps1, does not rescue S. cerevisiae FPS deficiency, and FPP levels are normal in spo9 deletion cells. spo9 has diverged from FPS function towards its role as a GGPS subunit. Reason: Target-specific evidence of functional divergence from the FPS node. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000162949 SUPPORTS SOURCE BUT NOT TARGET Node donors are bona fide FPSs; spo9 is a divergent FPS-like paralog that fails to complement FPS deficiency and whose loss leaves FPP unchanged. Supporting Evidence: PMID:17596513 Expression of fps1(+), but not spo9(+), suppresses the lethality of a PMID:23145048 Results showed that FPP level in Ξspo9 cells was almost equal to that in wild-type cells, however, GGPP was not detected in Ξspo9 cells (Figure 1B). |
| GO:0004337 (2E,6E)-farnesyl diphosphate synthase activity | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: EC/RHEA mapping of FPS activity; as for the IBA. Reason: Target-specific evidence argues against FPS activity. Supporting Evidence: PMID:17596513 Expression of fps1(+), but not spo9(+), suppresses the lethality of a PMID:23145048 Results showed that FPP level in Ξspo9 cells was almost equal to that in wild-type cells, however, GGPP was not detected in Ξspo9 cells (Figure 1B). |
| GO:0004659 prenyltransferase activity | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Generic prenyltransferase family mapping; correct at family level. Supporting Evidence: PMID:17596513 the two proteins together form a complex with GGPS activity |
| GO:0005634 nucleus | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | KEEP AS NON CORE | Summary: ORFeome YFP screen recorded nuclear signal for spo9. Soluble metabolic enzymes often show diffuse nucleocytoplasmic signal in this screen; no nuclear role is known. Reason: Experimental HDA kept, but not part of the core function. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0005634 nucleus | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt location mapping of the nuclear screen signal; no nuclear role known. Reason: Not part of the core function. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (cytoplasm), derived from the localisation screen. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0005783 endoplasmic reticulum | ISO GO_REF:0000024 | KEEP AS NON CORE | Summary: Transfer of ER location from S. cerevisiae ERG20; not tested for spo9. Reason: Not part of the core function. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0005829 cytosol | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: ORFeome YFP screen placed spo9 in the cytosol, consistent with a soluble metabolic enzyme. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0005829 cytosol | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic inference of location; agrees with the localisation screen. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0008299 isoprenoid biosynthetic process | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Correct but broad parent of GGPP biosynthesis, which is also annotated. Supporting Evidence: PMID:17596513 the two proteins together form a complex with GGPS activity |
| GO:0016765 transferase activity, transferring alkyl or aryl (other than methyl) groups | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Generic family-level transferase mapping. Supporting Evidence: PMID:17596513 the two proteins together form a complex with GGPS activity |
| GO:0033384 geranyl diphosphate biosynthetic process | IEA GO_REF:0000041 | MARK AS OVER ANNOTATED | Summary: UniPathway GPP biosynthesis follows from the FPS assignment, which the data do not support for spo9. Reason: Derived from the FPS mapping. Supporting Evidence: PMID:17596513 Expression of fps1(+), but not spo9(+), suppresses the lethality of a |
| GO:0033386 geranylgeranyl diphosphate biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: UniPathway mapping to GGPP biosynthesis; supported by the deletion phenotype. Supporting Evidence: PMID:23145048 Results showed that FPP level in Ξspo9 cells was almost equal to that in wild-type cells, however, GGPP was not detected in Ξspo9 cells (Figure 1B). |
| GO:0033386 geranylgeranyl diphosphate biosynthetic process | IMP PMID:23145048 A genetic and pharmacological analysis of isoprenoid pathway... | ACCEPT | Summary: GGPP is undetectable in spo9 deletion cells while FPP is normal. Supporting Evidence: PMID:23145048 Results showed that FPP level in Ξspo9 cells was almost equal to that in wild-type cells, however, GGPP was not detected in Ξspo9 cells (Figure 1B). |
| GO:0045337 trans, trans-farnesyl diphosphate biosynthetic process | EXP PMID:17596513 Geranylgeranyl diphosphate synthase in fission yeast is a he... | MARK AS OVER ANNOTATED | Summary: EXP assertion of FPP biosynthesis. The same paper shows spo9 cannot replace FPS, and later metabolite measurements show FPP is unaffected by spo9 deletion. GGPP synthesis is the supported role. The curator may have recorded the FPP-utilising step of GGPP formation. Reason: spo9 is dispensable for FPP synthesis. Supporting Evidence: PMID:17596513 Expression of fps1(+), but not spo9(+), suppresses the lethality of a PMID:23145048 Results showed that FPP level in Ξspo9 cells was almost equal to that in wild-type cells, however, GGPP was not detected in Ξspo9 cells (Figure 1B). |
| GO:0045337 trans, trans-farnesyl diphosphate biosynthetic process | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: PAINT FPP-biosynthesis inference; spo9 has diverged. Reason: As above. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000162949 SUPPORTS SOURCE BUT NOT TARGET Node donors are bona fide FPSs; spo9 is a divergent FPS-like paralog that fails to complement FPS deficiency and whose loss leaves FPP unchanged. Supporting Evidence: PMID:17596513 Expression of fps1(+), but not spo9(+), suppresses the lethality of a PMID:23145048 Results showed that FPP level in Ξspo9 cells was almost equal to that in wild-type cells, however, GGPP was not detected in Ξspo9 cells (Figure 1B). |
| GO:0045337 trans, trans-farnesyl diphosphate biosynthetic process | IEA GO_REF:0000041 | MARK AS OVER ANNOTATED | Summary: UniPathway mapping; as above. Reason: As above. Supporting Evidence: PMID:17596513 Expression of fps1(+), but not spo9(+), suppresses the lethality of a PMID:23145048 Results showed that FPP level in Ξspo9 cells was almost equal to that in wild-type cells, however, GGPP was not detected in Ξspo9 cells (Figure 1B). |
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