cho1 encodes the phosphatidyl-N-methylethanolamine N-methyltransferase of Schizosaccharomyces pombe (EC 2.1.1.71), a small multi-pass ER membrane protein of the PEMT/Opi3 family. It catalyses the second and third S-adenosylmethionine-dependent methylations, phosphatidyl-N-monomethylethanolamine to phosphatidyl-N,N-dimethylethanolamine and then to phosphatidylcholine, after cho2 has made the first methylation of phosphatidylethanolamine. cho1 mutants are choline auxotrophs, and S. cerevisiae OPI3 and rat PEMT complement them. Despite the shared name, S. pombe cho1 is the ortholog of S. cerevisiae OPI3, not of S. cerevisiae CHO1 (phosphatidylserine synthase, whose S. pombe ortholog is pps1).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PANTHER IBA from PTN000397368 (PEMT/Opi3 family node with S. cerevisiae Opi3, Arabidopsis PLMT and cho1 itself). Reason: Phylogenetic inference consistent with OPI3/rat PEMT complementation of cho1 mutants. Supporting Evidence: PMID:9755189 Phospholipid methyltransferases encoded by a rat liver cDNA and the S. cerevisiae OPI3 gene are both able to complement the choline auxotrophy of the S. pombe cho1 mutants. |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA from HAMAP UniRule UR000345849, RHEA:32735/32739 and EC 2.1.1.71. Reason: Correct assignment of the second and third methylations. Supporting Evidence: file:SCHPO/cho1/cho1-uniprot.txt Reaction=a 1,2-diacyl-sn-glycero-3-phospho-N-methylethanolamine + S- |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | IMP PMID:9755189 The Schizosaccharomyces pombe cho1+ gene encodes a phospholi... | ACCEPT | Summary: cho1 disruption mutants are choline auxotrophs defective in PE methylation, and the defect is complemented by S. cerevisiae OPI3 and rat PEMT. Reason: Core activity; abstract-only, but the complementation by Opi3-type enzymes strongly supports the PMME/PDME N-methyltransferase activity. Supporting Evidence: PMID:9755189 These mutants are choline auxotrophs and fall into two unlinked complementation groups, cho1 and cho2. PMID:9755189 Phospholipid methyltransferases encoded by a rat liver cDNA and the S. cerevisiae OPI3 gene are both able to complement the choline auxotrophy of the S. pombe cho1 mutants. |
| GO:0005741 mitochondrial outer membrane | ISO GO_REF:0000024 | REMOVE | Summary: PomBase ortholog transfer of mitochondrial outer membrane with/from UniProtKB:P08456, which is S. cerevisiae Cho1, the phosphatidylserine synthase. S. pombe cho1 is not the ortholog of S. cerevisiae CHO1: it is the OPI3 ortholog (PEMT family), whereas the S. cerevisiae Cho1 ortholog in S. pombe is pps1. Reason: The transfer source is a non-orthologous protein that shares only the gene name (CHO1), so the inference is invalid for this protein. No S. pombe evidence places cho1 in the mitochondrial outer membrane. Propagation Review Root cause: PROPAGATION BAD Failure modes: WRONG ORTHOLOG OR PARALOG Sources checked: UniProtKB:P08456 · CHO1 (S. cerevisiae phosphatidylserine synthase) SUPPORTS SOURCE BUT NOT TARGET Mitochondrial outer membrane may be valid for S. cerevisiae Cho1, but Cho1 is a CDP-alcohol phosphatidyltransferase unrelated to the PEMT/Opi3-family S. pombe cho1; the source was apparently chosen by gene-name identity. The S. pombe ortholog of P08456 is pps1 (O94584). Supporting Evidence: PMID:9755189 Sequence analysis of the cho1+ gene indicates that it encodes a protein closely related to phospholipid methyltransferases from Saccharomyces cerevisiae and rat. PMID:9755189 Phospholipid methyltransferases encoded by a rat liver cDNA and the S. cerevisiae OPI3 gene are both able to complement the choline auxotrophy of the S. pombe cho1 mutants. |
| GO:0005783 endoplasmic reticulum | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: ORFeome-wide YFP localization placed cho1 in the ER; UniProt cites this study for the ER membrane location. Reason: Core location. Supporting Evidence: file:SCHPO/cho1/cho1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: PANTHER IBA (PTN000397368) to ER, with S. cerevisiae Opi3 and human PEMT among the sources. Reason: Correct. Supporting Evidence: file:SCHPO/cho1/cho1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005789 endoplasmic reticulum membrane | EXP PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: PomBase EXP location from the ORFeome survey. Reason: Core location; matches the S. cerevisiae OPI3 review. Supporting Evidence: file:SCHPO/cho1/cho1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000120 | ACCEPT | Summary: UniProt SubCell SL-0097 and HAMAP UniRule UR000345849. Reason: Correct. Supporting Evidence: file:SCHPO/cho1/cho1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0006656 phosphatidylcholine biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PANTHER IBA (PTN000397368) to PC biosynthetic process. Reason: Core process. Supporting Evidence: PMID:1324908 We examined expression of these enzymes in cho2 and cho1 mutants, which are blocked in the methylation pathway for synthesis of PC. |
| GO:0006656 phosphatidylcholine biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: InterPro IPR024960, HAMAP UniRule and UniPathway UPA00753. Reason: Correct. Supporting Evidence: PMID:1324908 We examined expression of these enzymes in cho2 and cho1 mutants, which are blocked in the methylation pathway for synthesis of PC. |
| GO:0006656 phosphatidylcholine biosynthetic process | IMP PMID:9755189 The Schizosaccharomyces pombe cho1+ gene encodes a phospholi... | ACCEPT | Summary: cho1 mutants are choline auxotrophs blocked in PC synthesis by the methylation route. Reason: Core process; S. pombe genetic evidence. Supporting Evidence: PMID:9755189 These mutants are choline auxotrophs and fall into two unlinked complementation groups, cho1 and cho2. PMID:1324908 We examined expression of these enzymes in cho2 and cho1 mutants, which are blocked in the methylation pathway for synthesis of PC. |
| GO:0008757 S-adenosylmethionine-dependent methyltransferase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro IPR024960 (PEMT/PEM2 methyltransferase) mapping to S-adenosylmethionine-dependent methyltransferase activity. Reason: Correct but a less specific parent-level description of GO:0000773. |
| GO:0031966 mitochondrial membrane | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: UniProt SubCell SL-0171 and HAMAP UniRule UR000345849 (mitochondrion membrane), a family-level location consistent with the experimental mitochondrial-membrane annotation of S. cerevisiae Opi3. Reason: Rule-based, without S. pombe evidence; treated as a secondary location as in the S. cerevisiae OPI3 review. Unlike the mitochondrial outer membrane ISO row, this rule comes from the correct (Opi3) family. Supporting Evidence: file:SCHPO/cho1/cho1-uniprot.txt Mitochondrion |
Loading supporting content…
Download this section (compressed HTML)Q: Does S. pombe cho1, like S. cerevisiae Opi3 and mammalian PEMT, also catalyse the first PE methylation at a low rate, giving partial redundancy with cho2?
Experiment: Measure PE, PMME and PDME methyltransferase activities in microsomes from cho1, cho2 and cho1 cho2 deletion strains to define the substrate range of each enzyme.
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)