ALG1 is an endoplasmic reticulum beta-1,4-mannosyltransferase that catalyzes the first mannose addition during dolichol-linked oligosaccharide assembly. It uses GDP-mannose to convert GlcNAc2-PP-dolichol to Man1GlcNAc2-PP-dolichol on the cytoplasmic face of the ER membrane, producing the substrate for ALG2. This catalytic step builds the glycan precursor subsequently transferred to proteins during N-linked glycosylation. Biallelic pathogenic variants cause ALG1-CDG, an autosomal recessive disorder with variable multisystem and neurodevelopmental manifestations, including severe early-lethal presentations.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT places ALG1 in the endoplasmic reticulum. Reason: ER localization is consistent with the conserved membrane-associated first mannosylation reaction, the curated human UniProt record and the human ALG1 reporter in PMID:35136180. The original PAINT alignment and placement of PTN000315506 were not reconstructed; the retained broad location is supported independently at the human target. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN000315506 UNRESOLVED Seeded ancestral assertion retained with curator deference and independent human ER evidence. The original tree/MSA and exact IBD placement were not independently reconstructed. UNRESOLVED is limited to exact ancestral placement, not donor identity, donor count or lack of support for the independently established human function. AGI_LocusCode:AT1G16570 UNRESOLVED Ensembl Plants confirms the Arabidopsis locus identity and glycosyltransferase annotation. The particular experimental descendant annotation and placement used by PAINT were not independently reconstructed; no negative inference is made from that access limit. SGD:S000000314 SUPPORTS TRANSFER NCBI Gene 852407 identifies SGD:S000000314 as S. cerevisiae ALG1/YBR110W and records ER location, beta-1,4-mannosyltransferase activity and LLO biosynthesis. This agrees with the P16661 ISS donor and human rescue evidence. This source assessment does not claim to reconstruct its precise PAINT IBD placement. UniProtKB:Q388S6 UNRESOLVED This exact accession is present in the original WITH/FROM list. Its primary entry and source-specific experimental assertion were not retrieved in this follow-up; no species, assay or functional loss is inferred from the unavailable record. Supporting Evidence: file:human/ALG1/ALG1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane PMID:35136180 In contrast, untreated FLAG-Suc2A-hAlg1 migrated with a larger molecular weight than the PNGase treated sample, indicating it had undergone N-glycan modification |
| GO:0009101 glycoprotein biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: ALG1 catalyzes a step in the assembly of the glycan precursor used to make glycoproteins. Reason: The first mannose transfer is direct biosynthetic work, not merely a consequence of loss of glycoproteins. Human enzyme assays and restoration of CPY glycosylation by human ALG1 in yeast support this broader process. PTN000315506 includes human experimental grounding; the target appearing among descendant evidence is legitimate, not circular. No target-specific functional loss is established. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN000315506 UNRESOLVED Target activity and human-transgene rescue support the inherited process. Human Q9BT22 in the seeded descendant evidence is valid experimental grounding; exact ancestral placement remains unreviewed. UNRESOLVED is limited to exact ancestral placement, not donor identity, donor count or lack of support for the independently established human function. AGI_LocusCode:AT1G16570 UNRESOLVED Ensembl Plants confirms the Arabidopsis locus identity and glycosyltransferase annotation. The particular experimental descendant annotation and placement used by PAINT were not independently reconstructed; no negative inference is made from that access limit. SGD:S000000314 SUPPORTS TRANSFER NCBI Gene 852407 identifies SGD:S000000314 as S. cerevisiae ALG1/YBR110W and records ER location, beta-1,4-mannosyltransferase activity and LLO biosynthesis. This agrees with the P16661 ISS donor and human rescue evidence. This source assessment does not claim to reconstruct its precise PAINT IBD placement. UniProtKB:Q9BT22 SUPPORTS TRANSFER Human ALG1 is the target itself. Its experimental mannosyltransferase and glycosylation evidence legitimately grounds the ancestral assertion; this is not circular propagation. Supporting Evidence: PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. PMID:26931382 while wild-type hALG1 cDNA fully restored both normal growth and full CPY glycosylation |
| GO:0000030 mannosyltransferase activity | IBA GO_REF:0000033 | MODIFY | Summary: The conserved mannosyltransferase activity can be resolved to ALG1's measured substrate and linkage. Reason: PMID:14973778 measures the GDP-mannose-dependent elongation of GlcNAc2-PP-dolichol and links its deficiency to human ALG1 by complementation. GO:0004578 captures this reaction more precisely than mannosyltransferase activity. This is a target-level refinement based on human evidence, not a claim that every descendant of the PAINT node has been shown to carry the exact substrate specificity. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000315506 UNRESOLVED The general ancestral mannosyltransferase assertion is biologically compatible with ALG1. Its full tree/MSA was not inspected; the specific replacement is independently supported for the human target. UNRESOLVED is limited to exact ancestral placement, not donor identity, donor count or lack of support for the independently established human function. SGD:S000000314 SUPPORTS TRANSFER NCBI Gene 852407 identifies SGD:S000000314 as S. cerevisiae ALG1/YBR110W and records ER location, beta-1,4-mannosyltransferase activity and LLO biosynthesis. This agrees with the P16661 ISS donor and human rescue evidence. This source assessment does not claim to reconstruct its precise PAINT IBD placement. UniProtKB:Q388S6 UNRESOLVED This exact accession is present in the original WITH/FROM list. Its primary entry and source-specific experimental assertion were not retrieved in this follow-up; no species, assay or functional loss is inferred from the unavailable record. UniProtKB:Q9BT22 SUPPORTS TRANSFER Human ALG1 is the target itself. Its experimental mannosyltransferase and glycosylation evidence legitimately grounds the ancestral assertion; this is not circular propagation. Proposed replacements: chitobiosyldiphosphodolichol beta-mannosyltransferase activity Supporting Evidence: PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. PMID:14973778 The disease-causing nature of the hALG1 mutation for the glycosylation defect was verified by a retroviral complementation approach in patient-derived primary fibroblasts |
| GO:0000030 mannosyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: The ALG1-like InterPro family mapping supports a more specific catalytic assignment. Reason: The seeded IPR026051 mapping identifies the ALG1-like family in the human UniProt record. The broad mannosyltransferase term is correct, but direct human biochemical and complementation evidence supports GO:0004578. Family membership alone is not used to infer the exact assay outcome. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: InterPro:IPR026051 SUPPORTS TRANSFER ALG1-like family occurrence verified in the immutable human UniProt record; target enzymology supplies the specificity missing from the broad mapping. Proposed replacements: chitobiosyldiphosphodolichol beta-mannosyltransferase activity Supporting Evidence: PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. PMID:14973778 The disease-causing nature of the hALG1 mutation for the glycosylation defect was verified by a retroviral complementation approach in patient-derived primary fibroblasts |
| GO:0004578 chitobiosyldiphosphodolichol beta-mannosyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Rhea and EC mappings identify the specific first mannose-transfer reaction. Reason: RHEA:13865 and EC:2.4.1.142 in the human UniProt catalytic record match GO:0004578, whose live definition transfers GDP-mannose onto GlcNAc2-PP-dolichol with a beta-1,4 linkage. Human cell-extract enzymology and complementation independently support this reaction. Propagation Review Root cause: NO FAILURE CORE Sources checked: RHEA:13865 SUPPORTS TRANSFER Exact reaction is recorded for human ALG1 and matches the live GO definition and experimental substrate/product assignment. EC:2.4.1.142 SUPPORTS TRANSFER The EC mapping names the experimentally supported ALG1 reaction. Supporting Evidence: PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. file:human/ALG1/ALG1-uniprot.txt ChEBI:CHEBI:58189, ChEBI:CHEBI:58472; EC=2.4.1.142; |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: The UniProt location mapping correctly places ALG1 in the ER membrane. Reason: The seeded SL-0097 mapping reproduces the curated ER membrane location. Human N-terminal glycosylation-reporter data provide compatible experimental evidence for ER-spanning topology, while the biochemical reaction occurs on the cytoplasmic face. The mapping itself is not a new direct topology assay. Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB-SubCell:SL-0097 SUPPORTS TRANSFER ER membrane vocabulary mapping agrees with the human curated location and independent human reporter evidence. Supporting Evidence: file:human/ALG1/ALG1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane PMID:35136180 In contrast, untreated FLAG-Suc2A-hAlg1 migrated with a larger molecular weight than the PNGase treated sample, indicating it had undergone N-glycan modification |
| GO:0016757 glycosyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: The broad glycosyltransferase assignment can be refined to the established ALG1 reaction. Reason: IPR001296 identifies a glycosyltransferase-family domain; this is compatible with ALG1 but lacks its known donor, acceptor and linkage specificity. Human functional assays support GO:0004578, a descendant of GO:0016757. The broad molecular function is true but too general, so a specific replacement is appropriate. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: InterPro:IPR001296 SUPPORTS TRANSFER The Glyco_trans_1 domain is present in the immutable UniProt record. Its family-level GO mapping is broader than the experimentally established human reaction. Proposed replacements: chitobiosyldiphosphodolichol beta-mannosyltransferase activity Supporting Evidence: PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. |
| GO:0006488 dolichol-linked oligosaccharide biosynthetic process | TAS Reactome:R-HSA-446193 | ACCEPT | Summary: ALG1 catalyzes the first mannosylation step of dolichol-linked oligosaccharide synthesis. Reason: Reactome R-HSA-446193 covers precursor assembly and subsequent transfer to protein. ALG1 performs the defined first mannose-transfer step, independently supported by human enzymology and complementation. The cached pathway summary has a sugar-list error (it calls the three terminal sugars GlcNAcs); the established precursor contains three glucoses. That textual error does not alter ALG1's pathway participation. Supporting Evidence: Reactome:R-HSA-446193 N-linked glycosylation commences with the 14-step synthesis of a dolichol lipid-linked oligosaccharide (LLO) PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. |
| GO:0004578 chitobiosyldiphosphodolichol beta-mannosyltransferase activity | TAS Reactome:R-HSA-446218 | ACCEPT | Summary: The normal Reactome ALG1 reaction matches its specific catalytic function. Reason: R-HSA-446218 explicitly identifies ALG1 as the catalyst adding the first mannose through a beta-1,4 linkage. The source reaction and human assays agree on GO:0004578. Supporting Evidence: Reactome:R-HSA-446218 A mannose is added to the N-glycan precursor via a beta-1,4 linkage. The reaction is catalyzed by ALG1 PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. |
| GO:0004578 chitobiosyldiphosphodolichol beta-mannosyltransferase activity | TAS Reactome:R-HSA-4549382 | ACCEPT | Summary: The disease reaction describes loss of the established wild-type ALG1 activity. Reason: R-HSA-4549382 describes defective ALG1 variants and explicitly contrasts them with the normal first mannose-transfer reaction. The gene-level activity is retained because normal human ALG1 catalysis is independently demonstrated in PMID:14973778; this does not assert that the defective forms catalyze the blocked reaction. Supporting Evidence: Reactome:R-HSA-4549382 ALG1) normally tranfers a mannose moiety to the lipid-linked oligosaccharide PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. |
| GO:0005789 endoplasmic reticulum membrane | ISS GO_REF:0000024 | ACCEPT | Summary: The yeast-derived ER membrane localization is compatible with human ALG1. Reason: The seeded donor P16661 is Saccharomyces cerevisiae ALG1. Human and yeast proteins perform the same early LLO reaction, and human ALG1 complements yeast alg1 deficiency. Human N-terminal reporter glycosylation independently supports ER topology. The exact historical donor localization experiment was not recovered, but this correct broad human location is retained with curator deference. Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB:P16661 SUPPORTS TRANSFER Verified as S. cerevisiae ALG1 in the primary UniProt/SGD records. Human functional complementation and human reporter evidence support conservation; the exact original donor localization assay was not independently recovered. Supporting Evidence: file:human/ALG1/ALG1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane PMID:35136180 In contrast, untreated FLAG-Suc2A-hAlg1 migrated with a larger molecular weight than the PNGase treated sample, indicating it had undergone N-glycan modification PMID:14973778 The disease-causing nature of the hALG1 mutation for the glycosylation defect was verified by a retroviral complementation approach in patient-derived primary fibroblasts |
| GO:0006487 protein N-linked glycosylation | IDA PMID:26931382 ALG1-CDG: Clinical and Molecular Characterization of 39 Unre... | ACCEPT | Summary: Human ALG1 restores N-linked glycosylation in an alg1-deficient yeast assay. Reason: PMID:26931382 expresses the human reference cDNA and individual variants in a temperature-sensitive yeast alg1 strain. Wild-type human ALG1 restores CPY glycosylation, while tested variants incompletely rescue it. Together with the established mannose-transfer reaction, this supports direct participation in N-glycan precursor synthesis within protein N-linked glycosylation; it does not assign oligosaccharyltransferase chemistry to ALG1. Supporting Evidence: PMID:26931382 while wild-type hALG1 cDNA fully restored both normal growth and full CPY glycosylation PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. |
| GO:0098554 cytoplasmic side of endoplasmic reticulum membrane | ISS GO_REF:0000024 | ACCEPT | Summary: ALG1 performs its first mannose-transfer reaction on the cytoplasmic ER face. Reason: The ISS source is yeast ALG1 P16661, and the human reaction is explicitly assigned to the cytosolic ER side in PMID:14973778 and the curated UniProt function. The cached GO-CAM retains this same donor inference. The human N-terminal reporter in PMID:35136180 supports a luminal N terminus, consistent with the overall topology, but its ALG2 C-terminal protease-protection experiments are not evidence about ALG1. Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB:P16661 SUPPORTS TRANSFER Yeast ALG1 identity and conserved enzymology verified; the exact historical donor topology assay was not recovered. Independent human reaction context supports the cytoplasmic catalytic face. GO-CAM 65c57c3400000687 repeats this inference rather than providing an independent experiment. Supporting Evidence: PMID:14973778 elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. PMID:35136180 In contrast, untreated FLAG-Suc2A-hAlg1 migrated with a larger molecular weight than the PNGase treated sample, indicating it had undergone N-glycan modification |
| GO:0006487 protein N-linked glycosylation | IDA PMID:14973778 Deficiency of GDP-Man:GlcNAc2-PP-dolichol mannosyltransferas... | ACCEPT | Summary: Patient-cell enzymology and human ALG1 complementation support protein N-linked glycosylation. Reason: PMID:14973778 reports serum transferrin hypoglycosylation, accumulation of short dolichol-linked intermediates and loss of the first mannose-transfer reaction. Complementation with wild-type human ALG1 connects that catalytic step to precursor production and protein N-glycosylation. This is direct biosynthetic participation, not a disease phenotype alone. Supporting Evidence: PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. PMID:14973778 The disease-causing nature of the hALG1 mutation for the glycosylation defect was verified by a retroviral complementation approach in patient-derived primary fibroblasts PMID:14973782 could be restored by the human wild-type allele, whereas only slight restoration was observed after transformation with the patients' alleles. |
| GO:0004578 chitobiosyldiphosphodolichol beta-mannosyltransferase activity | IDA PMID:14973778 Deficiency of GDP-Man:GlcNAc2-PP-dolichol mannosyltransferas... | ACCEPT | Summary: Human ALG1 supplies the GDP-mannose-dependent first mannosylation reaction. Reason: Patient-cell extracts in PMID:14973778 show reduced GDP-mannose-dependent elongation of GlcNAc2-PP-dolichol, with human ALG1 rescue supporting attribution. The independent discovery studies support the same first mannosylation step. PMID:40328714 additionally measures recombinant human ALG1 expressed in E. coli by LC-MS using DPGn2; membrane addition partly restores activity lost during purification. These are distinct cell-extract, complementation and recombinant-protein experiments, not one kinetic dataset. Supporting Evidence: PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. PMID:14973778 The disease-causing nature of the hALG1 mutation for the glycosylation defect was verified by a retroviral complementation approach in patient-derived primary fibroblasts PMID:40328714 HsAlg1 had transglycosylation activity |
| GO:0006488 dolichol-linked oligosaccharide biosynthetic process | IDA PMID:14973778 Deficiency of GDP-Man:GlcNAc2-PP-dolichol mannosyltransferas... | ACCEPT | Summary: ALG1 catalyzes a chemically defined step of LLO precursor biosynthesis. Reason: The source directly tests elongation of GlcNAc2-PP-dolichol and connects its impairment to human ALG1 by rescue. This establishes catalytic work in the process, beyond accumulation of a metabolite or a requirement inferred from disease alone. Supporting Evidence: PMID:14973778 Incubation of fibroblast extracts with [(14)C]GlcNAc(2)-PP-dolichol and GDP-mannose indicated a severely reduced activity of the beta 1,4-mannosyltransferase, elongating GlcNAc(2)-PP-dolichol to Man(1)GlcNAc(2)-PP-dolichol at the cytosolic side of the endoplasmic reticulum. PMID:14973778 The disease-causing nature of the hALG1 mutation for the glycosylation defect was verified by a retroviral complementation approach in patient-derived primary fibroblasts PMID:14709599 the ALG1 beta1,4 mannosyltransferase, which adds the first mannose residue to lipid-linked oligosaccharides. |
| GO:0005789 endoplasmic reticulum membrane | TAS Reactome:R-HSA-4549382 | ACCEPT | Summary: The disease-associated ALG1 reaction is assigned to the normal ER membrane context. Reason: R-HSA-4549382 concerns defective variants of an ER enzyme. The retained gene-level ER membrane location agrees with the curated human record and the human topology reporter. The cached disease summary does not separately demonstrate the trafficking or stability of every variant. Supporting Evidence: file:human/ALG1/ALG1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane PMID:35136180 In contrast, untreated FLAG-Suc2A-hAlg1 migrated with a larger molecular weight than the PNGase treated sample, indicating it had undergone N-glycan modification |
| GO:0005789 endoplasmic reticulum membrane | TAS Reactome:R-HSA-446218 | ACCEPT | Summary: The normal ALG1 reaction takes place at the ER membrane. Reason: R-HSA-446218 places the first mannose-addition reaction in LLO assembly. The human curated location and reporter data support the source-level ER membrane assertion; the more precise catalytic face is represented separately. Supporting Evidence: file:human/ALG1/ALG1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane PMID:35136180 In contrast, untreated FLAG-Suc2A-hAlg1 migrated with a larger molecular weight than the PNGase treated sample, indicating it had undergone N-glycan modification |
| GO:0016020 membrane | HDA PMID:19946888 Defining the membrane proteome of NK cells. | ACCEPT | Summary: The broad membrane assignment is compatible with ALG1's established ER membrane role. Reason: ALG1 is a membrane-associated enzyme whose established ER membrane location is part of its core catalytic mechanism. The broad membrane assertion therefore describes a core location at the source's resolution; breadth alone does not make that location non-core. Independent human reporter evidence supports ER membrane association. The original YTS proteomic identification is retained with curator deference, while its individual peptide assignment remains unverified; neither plasma-membrane residence nor an ALG1-specific survey percentage is inferred. Supporting Evidence: PMID:19946888 The present study was initiated to define the composition of the membrane proteome of the Natural Killer (NK) like cell line YTS. file:human/ALG1/ALG1-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane PMID:35136180 In contrast, untreated FLAG-Suc2A-hAlg1 migrated with a larger molecular weight than the PNGase treated sample, indicating it had undergone N-glycan modification |
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Download this section (compressed HTML)Q: Which native human ALG1 assemblies with ALG2 or ALG11 control reaction efficiency? Yeast interaction models and human heterologous rescue do not by themselves establish the composition or stoichiometry of a human complex.
Q: How do residual catalytic activity, membrane association and protein abundance jointly influence variant-specific ALG1-CDG severity? The 2016 yeast CPY assay did not rank patient clinical severity.
Experiment: Extend the recombinant human ALG1 membrane-dependence assay in PMID:40328714 to clinically relevant variants in matched membrane reconstitution assays, measuring first mannose transfer, protein abundance and membrane association. Test ALG2 and ALG11 addition separately to distinguish intrinsic catalytic defects from changes in assembly or substrate transfer.
Hypothesis: Some variants alter membrane-supported catalysis or assembly without producing the same quantitative defect in heterologous growth and CPY glycosylation assays.
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