PHO86 encodes an endoplasmic-reticulum resident membrane chaperone required for ER exit of the high-affinity phosphate transporter Pho84. Pho86 is not itself the phosphate transporter; instead, it prevents aggregation or misfolding of its cognate polytopic client and enables Pho84 packaging into COPII vesicles. Its core function is ER-localized chaperone-mediated regulation of phosphate transport and ER-to-Golgi traffic, not direct phosphate ion transport or generic protein binding.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006817 phosphate ion transport | IEA GO_REF:0000043 | MODIFY | Summary: PHO86 affects phosphate uptake, but the direct transport activity belongs to Pho84 rather than Pho86. Reason: Pho86 is required for Pho84 ER export and therefore regulates phosphate transport indirectly; the existing term overstates Pho86 as the transporter. Proposed replacements: regulation of phosphate transport Supporting Evidence: PMID:10655492 Pho84p is localized to the endoplasmic reticulum (ER) and fails to be targeted to the plasma membrane in the absence of Pho86p |
| GO:0016020 membrane | IEA GO_REF:0000044 | MODIFY | Summary: Membrane localization is true but too broad for Pho86. Reason: Direct evidence and functional context place Pho86 as an ER-resident membrane protein, making endoplasmic reticulum membrane more specific than the broad membrane term. Proposed replacements: endoplasmic reticulum membrane Supporting Evidence: PMID:10655492 Pho86p, an endoplasmic reticulum (ER) resident protein |
| GO:0005515 protein binding | IPI PMID:16429126 Proteome survey reveals modularity of the yeast cell machine... | MARK AS OVER ANNOTATED | Summary: The high-throughput interaction annotation is too generic for PHO86 function. Reason: Pho86's interpretable role is a client-specific ER chaperone for Pho84 export, not generic protein binding. Supporting Evidence: PMID:15623581 Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER |
| GO:0005515 protein binding | IPI PMID:18467557 An in vivo map of the yeast protein interactome. | MARK AS OVER ANNOTATED | Summary: Interactome evidence does not provide a useful standalone molecular-function annotation. Reason: Generic protein binding should not be accepted when the literature supports a more specific chaperone/export role. Supporting Evidence: PMID:10655492 Pho86p is required for packaging of Pho84p into COPII vesicles |
| GO:0005515 protein binding | IPI PMID:27107014 An inter-species protein-protein interaction network across ... | MARK AS OVER ANNOTATED | Summary: Cross-species interaction data are too broad for accepting protein binding as PHO86's function. Reason: The curated function should emphasize Pho84-specific ER chaperone activity and regulated phosphate transport. Supporting Evidence: file:yeast/PHO86/PHO86-deep-research-falcon.md ER-resident membrane protein required for ER exit of the high-affinity phosphate transporter Pho84 |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | MARK AS OVER ANNOTATED | Summary: Social-interactome protein binding is not informative enough for PHO86 curation. Reason: Protein binding is a broad physical interaction bucket and should not obscure the direct ER chaperone/export phenotype. Supporting Evidence: PMID:15623581 prevent aggregation of polytopic proteins in the ER |
| GO:0005783 endoplasmic reticulum | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | ACCEPT | Summary: High-throughput ER localization is consistent with direct PHO86 evidence. Reason: Pho86 is an ER-resident membrane protein required before Pho84 exits the ER. Supporting Evidence: PMID:10655492 endoplasmic reticulum (ER) resident protein |
| GO:0005783 endoplasmic reticulum | IDA PMID:10655492 Pho86p, an endoplasmic reticulum (ER) resident protein in Sa... | ACCEPT | Summary: Direct ER localization is well supported and central to function. Reason: Pho86 acts in the ER to permit Pho84 folding/export and does not travel with Pho84 to the plasma membrane. Supporting Evidence: PMID:10655492 Pho86p, an endoplasmic reticulum (ER) resident protein |
| GO:0006457 protein folding | IMP PMID:15623581 Specialized membrane-localized chaperones prevent aggregatio... | ACCEPT | Summary: Protein folding is a defensible process annotation for Pho86's specialized ER chaperone role. Reason: Pho86 prevents aggregation or misfolding of a cognate polytopic membrane client in the ER. Supporting Evidence: PMID:15623581 Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER |
| GO:0006888 endoplasmic reticulum to Golgi vesicle-mediated transport | IMP PMID:10655492 Pho86p, an endoplasmic reticulum (ER) resident protein in Sa... | ACCEPT | Summary: Pho86 is required for ER exit of Pho84, so ER-to-Golgi vesicle-mediated transport is supported. Reason: The phenotype specifically involves failure to package Pho84 into COPII vesicles. Supporting Evidence: PMID:10655492 Pho86p is required for packaging of Pho84p into COPII vesicles |
| GO:0010966 regulation of phosphate transport | IMP PMID:10655492 Pho86p, an endoplasmic reticulum (ER) resident protein in Sa... | ACCEPT | Summary: Regulation of phosphate transport accurately captures the indirect transport phenotype. Reason: Pho86 controls delivery of the high-affinity phosphate transporter Pho84, thereby regulating phosphate uptake capacity without being the transporter. Supporting Evidence: PMID:10655492 Pho84p is localized to the endoplasmic reticulum (ER) and fails to be targeted to the plasma membrane in the absence of Pho86p |
| GO:0051082 unfolded protein binding | IMP PMID:15623581 Specialized membrane-localized chaperones prevent aggregatio... | MODIFY | Summary: The evidence supports a specialized ER chaperone role rather than generic unfolded protein binding. Reason: Pho86 is one of the specialized membrane-localized chaperones that prevent aggregation of cognate polytopic membrane proteins in the ER; protein folding chaperone is the more informative term. Proposed replacements: protein folding chaperone Supporting Evidence: PMID:15623581 Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER |
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Download this section (compressed HTML)Q: What is the direct physical interface between Pho86 and Pho84, and which Pho84 folding state does Pho86 recognize?
Suggested experts: ER membrane-protein biogenesis experts, yeast phosphate-homeostasis researchers
Q: Does Pho86 act only on Pho84, or does it have a broader client range among phosphate- or nutrient-transporter family members?
Suggested experts: yeast transporter biologists
Experiment: Mutate conserved Pho86 transmembrane and loop residues, then assay Pho84 binding, Pho84 aggregation, and Pho84 ER export under phosphate starvation.
Hypothesis: A defined Pho86 membrane interface recognizes Pho84 and is required for transporter export without affecting general COPII function.
Type: site-directed mutagenesis and co-immunoprecipitation
Experiment: Reconstitute Pho84 packaging from ER membranes with wild-type or chaperone-defective Pho86 alleles and quantify Pho84 incorporation into COPII vesicles.
Hypothesis: Pho86 promotes a COPII-competent Pho84 state rather than acting downstream of vesicle formation.
Type: in vitro COPII budding assay
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Download this section (compressed HTML)The YAML description field was revised to keep it as a standalone biological summary. Project-specific curation framing moved here instead.
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