alg3 (SPAC7D4.06c; UniProt Q9Y7I4) encodes the Dol-P-Man:Man5GlcNAc2-PP-Dol alpha-1,3-mannosyltransferase Alg3, which adds the first lumenal mannose after the Man5 intermediate is flipped. alg3 deletion in an och1 background produces truncated N-glycans, a strain used for humanised glycoprotein production. In the lumenal phase of dolichol-linked oligosaccharide (Glc3Man9GlcNAc2-PP-Dol) assembly on the ER membrane, it adds the next sugar to the growing precursor that oligosaccharyltransferase transfers to nascent glycoproteins. Function is assigned by orthology to the S. cerevisiae ALG enzymes.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000030 mannosyltransferase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: Generic mannosyltransferase; the specific activity is annotated. Reason: True but entailed by GO:0052925 (Dol-P-Man:Man(5)GlcNAc(2)-PP-Dol alpha-1,3-mannosyltransferase activity), accepted elsewhere in this review. The specific step is assigned by similarity to S. cerevisiae ALG3 (UniProt FUNCTION, ECO:0000250|UniProtKB:P38179) and is consistent with the S. pombe alg3 deletion, whose N-glycans are truncated to Man5-based M5B structures (PMID:20854854). Supporting Evidence: file:SCHPO/alg3/alg3-uniprot.txt adds the first dolichyl beta-D-mannosyl phosphate derived mannose in an alpha-1,3 linkage to Man(5)GlcNAc(2)-PP-dolichol PMID:20854854 These analyses revealed that the N-linked oligosaccharides of S. pombe alg3Ξoch1Ξ cells mainly consisted of two or three Ξ±-galactose-capped M5B structures. |
| GO:0005783 endoplasmic reticulum | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: ORFeome screen: ER. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference. Reason: The ER claim holds: UniProt places alg3 in the endoplasmic reticulum membrane by similarity to S. cerevisiae Alg3 (ECO:0000250|UniProtKB:P38179), with predicted multi-pass transmembrane helices (ECO:0000255); the ORFeome HDA row independently localizes it to the ER. The organelle term is kept alongside the ER-membrane rows. Supporting Evidence: file:SCHPO/alg3/alg3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane file:SCHPO/alg3/alg3-uniprot.txt Multi-pass membrane protein |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: ER membrane: LLO assembly takes place on the ER membrane. Reason: UniProt places alg3 in the endoplasmic reticulum membrane by similarity to S. cerevisiae Alg3 (ECO:0000250|UniProtKB:P38179) as a multi-pass membrane protein (predicted transmembrane helices, ECO:0000255), consistent with lumenal-face LLO assembly. Supporting Evidence: file:SCHPO/alg3/alg3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane file:SCHPO/alg3/alg3-uniprot.txt Multi-pass membrane protein |
| GO:0005789 endoplasmic reticulum membrane | ISS GO_REF:0000024 | ACCEPT | Summary: ER membrane: LLO assembly takes place on the ER membrane. Reason: UniProt places alg3 in the endoplasmic reticulum membrane by similarity to S. cerevisiae Alg3 (ECO:0000250|UniProtKB:P38179) as a multi-pass membrane protein (predicted transmembrane helices, ECO:0000255), consistent with lumenal-face LLO assembly. Supporting Evidence: file:SCHPO/alg3/alg3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane file:SCHPO/alg3/alg3-uniprot.txt Multi-pass membrane protein |
| GO:0006487 protein N-linked glycosylation | IMP PMID:20854854 Production of heterologous glycoproteins by a glycosylation-... | ACCEPT | Summary: alg3 deletion alters N-glycan structures in och1 cells. Supporting Evidence: PMID:20854854 In this study, we deleted the alg3(+) gene in the och1Ξ mutant and analyzed the detailed oligosaccharide structures in alg3Ξoch1Ξ double mutant. |
| GO:0006488 dolichol-linked oligosaccharide biosynthetic process | IMP PMID:20854854 Production of heterologous glycoproteins by a glycosylation-... | ACCEPT | Summary: alg3 deletion blocks the first lumenal mannose addition. Supporting Evidence: PMID:20854854 In this study, we deleted the alg3(+) gene in the och1Ξ mutant and analyzed the detailed oligosaccharide structures in alg3Ξoch1Ξ double mutant. |
| GO:0009101 glycoprotein biosynthetic process | IBA GO_REF:0000033 | TOO GENERAL | Summary: Broad parent of the protein N-linked glycosylation annotated in this review. Reason: True but entailed by GO:0006487 (protein N-linked glycosylation), accepted elsewhere in this review on S. pombe mutant evidence. The alg3 deletion alters the N-linked oligosaccharides of S. pombe glycoproteins (PMID:20854854), and by similarity to S. cerevisiae ALG3 the enzyme builds the dolichol-linked precursor used in protein N-glycosylation. Supporting Evidence: PMID:20854854 These analyses revealed that the N-linked oligosaccharides of S. pombe alg3Ξoch1Ξ cells mainly consisted of two or three Ξ±-galactose-capped M5B structures. file:SCHPO/alg3/alg3-uniprot.txt mannosyltransferase that operates in the biosynthetic pathway of dolichol-linked oligosaccharides, the glycan precursors employed in protein asparagine (N)-glycosylation. |
| GO:0009101 glycoprotein biosynthetic process | IMP PMID:34851357 A novel fission yeast platform to model N-glycosylation and ... | TOO GENERAL | Summary: Broad parent; platform mutants alter glycoprotein N-glycans, captured more specifically by LLO biosynthesis. Supporting Evidence: PMID:34851357 We constructed a platform of 16 Schizosaccharomyces pombe strains that synthesize all possible theoretical combinations of LLOs containing three to zero glucose (Glc) residues and nine to five mannose (Man) residues. |
| GO:0016757 glycosyltransferase activity | IMP PMID:34851357 A novel fission yeast platform to model N-glycosylation and ... | TOO GENERAL | Summary: Generic glycosyltransferase; the platform deletion defines the specific step. Supporting Evidence: PMID:34851357 We constructed a platform of 16 Schizosaccharomyces pombe strains that synthesize all possible theoretical combinations of LLOs containing three to zero glucose (Glc) residues and nine to five mannose (Man) residues. |
| GO:0052925 dol-P-Man:Man(5)GlcNAc(2)-PP-Dol alpha-1,3-mannosyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference. Reason: Curated UniProt FUNCTION text, by similarity to S. cerevisiae Alg3 (ECO:0000250|UniProtKB:P38179), assigns alpha-1,3 transfer of the first Dol-P-Man-derived mannose onto Man5GlcNAc2-PP-Dol. In S. pombe, deletion of alg3 in an och1 background leaves glycoproteins carrying M5B-based N-glycans (PMID:20854854), the structure expected when this step is missing; that is phenotypic support, not an enzyme assay. Supporting Evidence: file:SCHPO/alg3/alg3-uniprot.txt adds the first dolichyl beta-D-mannosyl phosphate derived mannose in an file:SCHPO/alg3/alg3-uniprot.txt alpha-1,3 linkage to Man(5)GlcNAc(2)-PP-dolichol to produce PMID:20854854 N-linked oligosaccharides of S. pombe alg3Ξoch1Ξ cells mainly consisted of two or three Ξ±-galactose-capped M5B structures |
| GO:0052925 dol-P-Man:Man(5)GlcNAc(2)-PP-Dol alpha-1,3-mannosyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Mapping. Reason: Curated UniProt FUNCTION text, by similarity to S. cerevisiae Alg3 (ECO:0000250|UniProtKB:P38179), assigns alpha-1,3 transfer of the first Dol-P-Man-derived mannose onto Man5GlcNAc2-PP-Dol. In S. pombe, deletion of alg3 in an och1 background leaves glycoproteins carrying M5B-based N-glycans (PMID:20854854), the structure expected when this step is missing; that is phenotypic support, not an enzyme assay. Supporting Evidence: file:SCHPO/alg3/alg3-uniprot.txt adds the first dolichyl beta-D-mannosyl phosphate derived mannose in an file:SCHPO/alg3/alg3-uniprot.txt alpha-1,3 linkage to Man(5)GlcNAc(2)-PP-dolichol to produce PMID:20854854 N-linked oligosaccharides of S. pombe alg3Ξoch1Ξ cells mainly consisted of two or three Ξ±-galactose-capped M5B structures |
| GO:0052925 dol-P-Man:Man(5)GlcNAc(2)-PP-Dol alpha-1,3-mannosyltransferase activity | IMP PMID:20854854 Production of heterologous glycoproteins by a glycosylation-... | ACCEPT | Summary: alg3 deletion leads to truncated Man5-based structures. Supporting Evidence: PMID:20854854 In this study, we deleted the alg3(+) gene in the och1Ξ mutant and analyzed the detailed oligosaccharide structures in alg3Ξoch1Ξ double mutant. |
| GO:0052925 dol-P-Man:Man(5)GlcNAc(2)-PP-Dol alpha-1,3-mannosyltransferase activity | ISS GO_REF:0000024 | ACCEPT | Summary: Similarity. Reason: Curated UniProt FUNCTION text, by similarity to S. cerevisiae Alg3 (ECO:0000250|UniProtKB:P38179), assigns alpha-1,3 transfer of the first Dol-P-Man-derived mannose onto Man5GlcNAc2-PP-Dol. In S. pombe, deletion of alg3 in an och1 background leaves glycoproteins carrying M5B-based N-glycans (PMID:20854854), the structure expected when this step is missing; that is phenotypic support, not an enzyme assay. Supporting Evidence: file:SCHPO/alg3/alg3-uniprot.txt adds the first dolichyl beta-D-mannosyl phosphate derived mannose in an file:SCHPO/alg3/alg3-uniprot.txt alpha-1,3 linkage to Man(5)GlcNAc(2)-PP-dolichol to produce PMID:20854854 N-linked oligosaccharides of S. pombe alg3Ξoch1Ξ cells mainly consisted of two or three Ξ±-galactose-capped M5B structures |
| GO:0098553 lumenal side of endoplasmic reticulum membrane | TAS PMID:9878760 The dolichol pathway of N-linked glycosylation. | ACCEPT | Summary: Lumenal-face LLO assembly steps (after flipping), using Dol-P-Man/Dol-P-Glc donors. Supporting Evidence: PMID:9878760 The oligosaccharide substrate for the N-linked protein glycosylation is assembled at the membrane of the endoplasmic reticulum. |
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