PDI1 encodes the essential protein disulfide isomerase of the ER lumen, a multifunctional oxidoreductase required for formation and isomerization of disulfide bonds in secretory and cell-surface proteins. Pdi1p catalyzes both the oxidation of free thiols and the reduction/rearrangement of non-native disulfide bonds, ensuring correct folding of ER client proteins. It forms a complex with the exomannosidase Mnl1p to recognize misfolded glycoproteins, process Man8GlcNAc2 oligosaccharides to Man7GlcNAc2, and reduce disulfide bonds of demannosylated substrates to generate unfolded polypeptides for retrotranslocation as part of ER-associated degradation (ERAD). Pdi1p also maintains Mnl1p solubility in the ER lumen and activates the oxidase Ero1p, which regenerates oxidized Pdi1p. Its closest human counterpart is PDIA1/P4HB, the canonical, general-substrate protein disulfide-isomerase of the mammalian ER.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: Manual review: endoplasmic reticulum is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0006457 protein folding | IBA GO_REF:0000033 | ACCEPT | Summary: Protein folding (oxidative folding of secretory clients) is a core biological process for Pdi1p. Oxidizing equivalents flow Ero1p->Pdi1p->substrate, and a principal experimental client is carboxypeptidase Y (CPY), whose maturation requires Pdi1p disulfide formation and isomerization. Reason: Retained as supported or plausible for this gene and evidence context. Supporting Evidence: file:yeast/PDI1/PDI1-deep-research-falcon.md A widely supported model is that oxidizing equivalents flow from **Ero1p β Pdi1p β substrates**. Ero1p is essential for ER thiol oxidation |
| GO:0034976 response to endoplasmic reticulum stress | IBA GO_REF:0000033 | ACCEPT | Summary: Manual review: response to endoplasmic reticulum stress is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0003756 protein disulfide isomerase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Protein disulfide isomerase activity is the core molecular function of Pdi1p, well supported by biochemical and genetic evidence in yeast. Pdi1p both introduces disulfides (oxidase) and rearranges incorrect disulfides (isomerase), with the active sites partially reduced (~32%) in vivo to support isomerization. Reason: Retained as supported or plausible for this gene and evidence context. Supporting Evidence: file:yeast/PDI1/PDI1-deep-research-falcon.md active-site cysteines are oxidized (forming a disulfide), it can oxidize client proteins; when reduced (dithiol), it can reduce or isomerize incorrect disulfides |
| GO:0003756 protein disulfide isomerase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Manual review: protein disulfide isomerase activity is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0005788 endoplasmic reticulum lumen | IEA GO_REF:0000044 | ACCEPT | Summary: Manual review: endoplasmic reticulum lumen is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0006457 protein folding | IEA GO_REF:0000117 | ACCEPT | Summary: Manual review: protein folding is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0015035 protein-disulfide reductase activity | IEA GO_REF:0000117 | ACCEPT | Summary: Protein-disulfide reductase activity is supported by the reductive branch of Pdi1p chemistry: when its active sites are reduced, Pdi1p reduces/rearranges incorrect disulfides, and in the Htm1/Mnl1-Pdi1 ERAD complex Pdi1 can be switched toward acting as a disulfide reductase on misfolded glycoproteins. Reason: Retained as supported or plausible for this gene and evidence context. Supporting Evidence: file:yeast/PDI1/PDI1-deep-research-falcon.md the **Htm1/Mnl1βPdi1** complex proposes that association with the mannosidase can **block canonical oxidative function** of Pdi1 and enable it to operate as a **disulfide reductase** for misfolded glycoproteins |
| GO:0016853 isomerase activity | IEA GO_REF:0000043 | ACCEPT | Summary: Manual review: isomerase activity is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0051082 unfolded protein binding | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: Manual review: unfolded protein binding is too generic or over-extended for PDI1. Reason: Marked over-annotated because more specific terms capture the biology more accurately. |
| GO:0005515 protein binding | IPI PMID:16368681 Domain architecture of protein-disulfide isomerase facilitat... | MARK AS OVER ANNOTATED | Summary: Manual review: protein binding is too generic or over-extended for PDI1. Reason: Marked over-annotated because more specific terms capture the biology more accurately. |
| GO:0005515 protein binding | IPI PMID:16429126 Proteome survey reveals modularity of the yeast cell machine... | MARK AS OVER ANNOTATED | Summary: Manual review: protein binding is too generic or over-extended for PDI1. Reason: Marked over-annotated because more specific terms capture the biology more accurately. |
| GO:0005515 protein binding | IPI PMID:16554755 Global landscape of protein complexes in the yeast Saccharom... | MARK AS OVER ANNOTATED | Summary: Manual review: protein binding is too generic or over-extended for PDI1. Reason: Marked over-annotated because more specific terms capture the biology more accurately. |
| GO:0005515 protein binding | IPI PMID:19124653 Htm1 protein generates the N-glycan signal for glycoprotein ... | MARK AS OVER ANNOTATED | Summary: Manual review: protein binding is too generic or over-extended for PDI1. Reason: Marked over-annotated because more specific terms capture the biology more accurately. |
| GO:0005515 protein binding | IPI PMID:27107014 An inter-species protein-protein interaction network across ... | MARK AS OVER ANNOTATED | Summary: Manual review: protein binding is too generic or over-extended for PDI1. Reason: Marked over-annotated because more specific terms capture the biology more accurately. |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | MARK AS OVER ANNOTATED | Summary: Manual review: protein binding is too generic or over-extended for PDI1. Reason: Marked over-annotated because more specific terms capture the biology more accurately. |
| GO:0005788 endoplasmic reticulum lumen | IDA PMID:21700223 A complex of Pdi1p and the mannosidase Htm1p initiates clear... | ACCEPT | Summary: Endoplasmic reticulum lumen is the established site of Pdi1p function. Pdi1p is a soluble ER luminal resident with a C-terminal AIHDEL/HDEL retrieval motif that mediates ER-Golgi retrieval cycling, keeping it in the ER lumen. Reason: Retained as supported or plausible for this gene and evidence context. Supporting Evidence: file:yeast/PDI1/PDI1-deep-research-falcon.md Pdi1p is an **ER luminal resident** protein. A systematic yeast ER-resident analysis reports its C-terminal ER retrieval motif as **AIHDEL** |
| GO:1900103 positive regulation of endoplasmic reticulum unfolded protein response | IDA PMID:21700223 A complex of Pdi1p and the mannosidase Htm1p initiates clear... | ACCEPT | Summary: Manual review: positive regulation of endoplasmic reticulum unfolded protein response is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0005783 endoplasmic reticulum | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | ACCEPT | Summary: Manual review: endoplasmic reticulum is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0036508 protein alpha-1,2-demannosylation | IDA PMID:21700223 A complex of Pdi1p and the mannosidase Htm1p initiates clear... | ACCEPT | Summary: Manual review: protein alpha-1,2-demannosylation is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:1904382 mannose trimming involved in glycoprotein ERAD pathway | IDA PMID:21700223 A complex of Pdi1p and the mannosidase Htm1p initiates clear... | ACCEPT | Summary: Pdi1p participates in glycoprotein ERAD as part of a complex with the mannosidase Htm1/Mnl1; within this complex Pdi1 can be switched from oxidative folding toward disulfide reduction of misfolded glycoproteins destined for retrotranslocation. Reason: Retained as supported or plausible for this gene and evidence context. Supporting Evidence: file:yeast/PDI1/PDI1-deep-research-falcon.md the **Htm1/Mnl1βPdi1** complex proposes that association with the mannosidase can **block canonical oxidative function** of Pdi1 and enable it to operate as a **disulfide reductase** for misfolded glycoproteins |
| GO:1904382 mannose trimming involved in glycoprotein ERAD pathway | IMP PMID:21700223 A complex of Pdi1p and the mannosidase Htm1p initiates clear... | ACCEPT | Summary: Manual review: mannose trimming involved in glycoprotein ERAD pathway is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:1904382 mannose trimming involved in glycoprotein ERAD pathway | IGI PMID:21700223 A complex of Pdi1p and the mannosidase Htm1p initiates clear... | ACCEPT | Summary: Manual review: mannose trimming involved in glycoprotein ERAD pathway is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:1904382 mannose trimming involved in glycoprotein ERAD pathway | IDA PMID:27053108 A Complex of Htm1 and the Oxidoreductase Pdi1 Accelerates De... | ACCEPT | Summary: Manual review: mannose trimming involved in glycoprotein ERAD pathway is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0005515 protein binding | IPI PMID:16002399 Interactions among yeast protein-disulfide isomerase protein... | MARK AS OVER ANNOTATED | Summary: Manual review: protein binding is too generic or over-extended for PDI1. Reason: Marked over-annotated because more specific terms capture the biology more accurately. |
| GO:0051082 unfolded protein binding | IDA PMID:16002399 Interactions among yeast protein-disulfide isomerase protein... | MARK AS OVER ANNOTATED | Summary: Manual review: unfolded protein binding is too generic or over-extended for PDI1. Reason: Marked over-annotated because more specific terms capture the biology more accurately. |
| GO:0003756 protein disulfide isomerase activity | IMP PMID:11157982 Functional differences in yeast protein disulfide isomerases... | ACCEPT | Summary: Manual review: protein disulfide isomerase activity is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0003756 protein disulfide isomerase activity | IDA PMID:16002399 Interactions among yeast protein-disulfide isomerase protein... | ACCEPT | Summary: Manual review: protein disulfide isomerase activity is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0003756 protein disulfide isomerase activity | IDA PMID:16413482 The crystal structure of yeast protein disulfide isomerase s... | ACCEPT | Summary: Manual review: protein disulfide isomerase activity is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0005788 endoplasmic reticulum lumen | IDA PMID:1761554 The Saccharomyces cerevisiae TRG1 gene is essential for grow... | ACCEPT | Summary: Manual review: endoplasmic reticulum lumen is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0006457 protein folding | IMP PMID:11157982 Functional differences in yeast protein disulfide isomerases... | ACCEPT | Summary: Manual review: protein folding is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
| GO:0015035 protein-disulfide reductase activity | IDA PMID:16002399 Interactions among yeast protein-disulfide isomerase protein... | ACCEPT | Summary: Manual review: protein-disulfide reductase activity is consistent with known biology of PDI1. Reason: Retained as supported or plausible for this gene and evidence context. |
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