Probable 3-methyl-2-oxobutanoate hydroxymethyltransferase (ketopantoate hydroxymethyltransferase, PanB; EC 2.1.2.11) of fission yeast, encoded by SPAC5H10.09c adjacent to pan6. It is predicted to transfer a hydroxymethyl group from 5,10-methylenetetrahydrofolate to 3-methyl-2-oxobutanoate (alpha-ketoisovalerate) to form 2-dehydropantoate, the first committed step of pantoate and hence pantothenate (vitamin B5) synthesis. The S. pombe protein localises to mitochondria in a genome-wide YFP-fusion screen, as does its S. cerevisiae ortholog Ecm31, whose deletion causes pantothenate auxotrophy. No S. pombe-specific biochemical or genetic data are available.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000287 magnesium ion binding | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: PAINT IBA (PTN000466854) from E. coli and M. tuberculosis PanB, which require Mg2+ for catalysis. PanB-family enzymes bind a divalent metal in the active site, so this is plausible for ecm31. Reason: Cofactor binding that is part of the catalytic mechanism rather than a separate function; kept as non-core as in the S. cerevisiae ECM31 review. Supporting Evidence: file:SCHPO/ecm31/ecm31-uniprot.txt SIMILARITY: Belongs to the PanB family. |
| GO:0003864 3-methyl-2-oxobutanoate hydroxymethyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN000466854 (donors include E. coli PanB, S. cerevisiae Ecm31). ecm31 is a canonical PanB family member. Reason: Core activity by phylogenetic inference; consistent with UniProt and with the S. cerevisiae ortholog's auxotrophy. Supporting Evidence: file:SCHPO/ecm31/ecm31-uniprot.txt Reaction=(6R)-5,10-methylene-5,6,7,8-tetrahydrofolate + 3-methyl-2- file:SCHPO/ecm31/ecm31-uniprot.txt SIMILARITY: Belongs to the PanB family. PMID:19266201 we show that deletion of ECM31 and PAN6 results in mutants requiring pantothenate while loss of PAN5 (related to panE from E. coli) still allows prototrophic growth |
| GO:0003864 3-methyl-2-oxobutanoate hydroxymethyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: UniProt combined IEA (InterPro IPR003700, RHEA:11824, EC 2.1.2.11). Correct. Reason: Agrees with phylogenetic inference. Supporting Evidence: file:SCHPO/ecm31/ecm31-uniprot.txt Reaction=(6R)-5,10-methylene-5,6,7,8-tetrahydrofolate + 3-methyl-2- file:SCHPO/ecm31/ecm31-uniprot.txt SIMILARITY: Belongs to the PanB family. |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | MODIFY | Summary: IBA for cytoplasm from PTN000466876, seeded only by E. coli PanB (a bacterial cytoplasmic enzyme). S. pombe ecm31 was localised to mitochondria (HDA), as was S. cerevisiae Ecm31; the PomBase pantothenate GO-CAM also places ecm31 in the mitochondrion. Reason: Bacterial cytoplasmic location does not transfer to the fungal enzyme, which is mitochondrial in both yeasts. Propagation Review Root cause: PROPAGATION BAD Failure modes: COMPARTMENT OR COMPLEX MISMATCH Sources checked: UniProtKB:P31057 · E. coli PanB SUPPORTS SOURCE BUT NOT TARGET Bacterial cytoplasmic enzyme; the fungal orthologs are mitochondrial. Proposed replacements: mitochondrion Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins, corresponding to approximately 90% of the fission yeast proteome, by tagging each ORF with the yellow fluorescent protein |
| GO:0005739 mitochondrion | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: Genome-wide YFP-fusion screen placed ecm31 in mitochondria; matches the mitochondrial location of S. cerevisiae Ecm31. Reason: S. pombe-specific localisation evidence. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins, corresponding to approximately 90% of the fission yeast proteome, by tagging each ORF with the yellow fluorescent protein |
| GO:0015940 pantothenate biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA (PTN000466854) for pantothenate biosynthesis; ketopantoate formation is the first committed step. Reason: Core process. Supporting Evidence: file:SCHPO/ecm31/ecm31-uniprot.txt PATHWAY: Cofactor biosynthesis; (R)-pantothenate biosynthesis; (R)- PMID:19266201 we show that deletion of ECM31 and PAN6 results in mutants requiring pantothenate while loss of PAN5 (related to panE from E. coli) still allows prototrophic growth |
| GO:0015940 pantothenate biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: UniProt combined IEA (InterPro IPR003700, UniPathway UPA00028). Correct. Reason: Agrees with phylogenetic inference. Supporting Evidence: file:SCHPO/ecm31/ecm31-uniprot.txt PATHWAY: Cofactor biosynthesis; (R)-pantothenate biosynthesis; (R)- |
| GO:0072330 monocarboxylic acid biosynthetic process | IEA GO_REF:0000117 | MODIFY | Summary: ARBA rule mapping to 'monocarboxylic acid biosynthetic process', a generic parent of pantothenate biosynthesis. Reason: Too general; pantothenate biosynthetic process (a child term) is the informative annotation, as in the S. cerevisiae ECM31 review. Proposed replacements: pantothenate biosynthetic process Supporting Evidence: file:SCHPO/ecm31/ecm31-uniprot.txt PATHWAY: Cofactor biosynthesis; (R)-pantothenate biosynthesis; (R)- |
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Download this section (compressed HTML)Q: Is S. pombe ecm31 required for pantothenate prototrophy (as for pan6), and how is 2-dehydropantoate exported from mitochondria to the cytosolic pan5/pan6 steps?
Experiment: Test growth of an S. pombe ecm31 deletion (in a liz1 background) on pantothenate-free medium with and without uracil or beta-alanine, mirroring the pan6 analysis.
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