{"gene":"ERO1B","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":1998,"finding":"Ero1p (yeast ortholog of ERO1B) is an essential ER-resident protein required for oxidative protein folding; loss-of-function causes ER retention of disulfide-stabilized proteins in a reduced, non-native form, while disulfide-free protein maturation is unaffected, demonstrating a specific role in disulfide bond formation.","method":"Genetic loss-of-function (DTT-sensitivity screen), overexpression (DTT resistance), protein maturation assays in yeast","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic loss-of-function with specific molecular phenotype, replicated by overexpression complementation, foundational paper","pmids":["9659914"],"is_preprint":false},{"year":2010,"finding":"ERO1β is the predominant ERO1 isoform in insulin-producing pancreatic β-cells; homozygous disruption of Ero1lb selectively impairs oxidative folding of proinsulin and causes glucose intolerance in mice, demonstrating a cell-type-specific role for ERO1β in insulin biogenesis.","method":"Ero1lb knockout mouse model, proinsulin folding and secretion assays, glucose tolerance tests, genetic epistasis with Ero1l double knockout","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo knockout with specific molecular (proinsulin folding) and physiological (glucose intolerance) phenotypes, epistasis with double knockout","pmids":["20308425"],"is_preprint":false},{"year":2004,"finding":"ERO1α and ERO1β oxidize PDI in the ER lumen, which in turn transfers oxidative equivalents to cargo proteins; cytosolic reduced glutathione (GSH) opposes Ero1-driven PDI oxidation, establishing a redox balance across compartments.","method":"Semipermeable cell assays, PDI redox state measurements, overexpression of Ero1α, GSH addition experiments","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical assay in semipermeable cells with multiple conditions, single lab","pmids":["15161913"],"is_preprint":false},{"year":2005,"finding":"ERO1β forms homodimers and mixed heterodimers with ERO1α, and ERO1β–PDI heterodimers; dimerization requires the ERO active site. ERO1β is constitutively expressed in pancreatic islets and gastric chief cells in a cell-type-specific manner.","method":"Co-immunoprecipitation, in vivo dimerization assays, active-site mutagenesis, immunohistochemistry of tissue sections","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with mutagenesis in a single lab, multiple orthogonal methods","pmids":["16012172"],"is_preprint":false},{"year":2006,"finding":"ERO1β is retained in the ER through dynamic covalent interactions with PDI and ERp44; overexpressed ERO1β is secreted unless co-expressed with PDI or ERp44 (KDEL/RDEL-dependent), and ERp44–ERO1 covalent interactions are essential for retention. PDI lacking active-site cysteines still partially retains ERO1β, and PDI and ERp44 compete for ERO1 binding.","method":"Co-expression/secretion assays in HeLa transfectants, co-immunoprecipitation, KDEL/RDEL-dependent retention assays, cysteine mutagenesis of PDI","journal":"Antioxidants & redox signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional secretion assay with mutagenesis, single lab with multiple orthogonal approaches","pmids":["16677073"],"is_preprint":false},{"year":2006,"finding":"Mutations in the FAD binding domain of ERO1β (Gly-to-Ser and His-to-Tyr, modeled on yeast ero1-1 and ero1-2 mutations) do not prevent ERO1β dimerization or non-covalent PDI interaction, but the Gly-to-Ser mutation abolishes disulfide-dependent PDI–ERO1β heterodimers; both mutations cause ERO1β misoxidation and aggregation under temperature or redox stress.","method":"Site-directed mutagenesis, Co-immunoprecipitation, redox/temperature stress assays, dimerization assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — active-site mutagenesis with biochemical functional assays, single lab","pmids":["16822866"],"is_preprint":false},{"year":2011,"finding":"Recombinant human ERO1β is approximately twice as enzymatically active as ERO1α in oxidizing PDI; ERO1β preferentially drives oxidative folding through the a' active site of PDI. ERO1β activity is regulated by long-range disulfide bonds, with Cys130 playing a critical role in feedback regulation, but overall regulation is loose compared to ERO1α.","method":"In vitro enzymatic assays with recombinant proteins, PDI family member oxidation assays, disulfide mutant analysis","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins and mutagenesis, single lab with multiple orthogonal methods","pmids":["21091435"],"is_preprint":false},{"year":2014,"finding":"ERO1β expression is paradoxically decreased in β-cells of diabetic model mice despite increased ER stress; overexpression of ERO1β in β-cells causes ER stress (UPR gene upregulation, enlarged ER lumen) and decreases insulin content, impairing glucose-stimulated insulin secretion, demonstrating that fine-tuned ERO1β activity is required for normal β-cell function.","method":"Mouse diabetic models, ERO1β overexpression in β-cells, UPR gene expression analysis, electron microscopy (ER lumen), insulin secretion assays","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and cell-based overexpression with specific molecular and physiological readouts, single lab","pmids":["24469402"],"is_preprint":false},{"year":2014,"finding":"The regulatory disulfide bonds in ERO1β are Cys90-Cys130 and Cys95-Cys100 (conserved with ERO1α), not an isoform-specific Cys262-Cys100 bond; Cys262 is buried and reduced in the ER of living cells. Mutation of Cys100 (not Cys262) renders ERO1β hyperactive, inducing UPR and oxidative perturbation of ER redox state.","method":"Site-directed mutagenesis of Cys residues, alkylation protection assays in living cells, UPR reporter assays, molecular modeling of ERO1β structure","journal":"Bioscience reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with functional cell-based readouts and structural modeling, single lab","pmids":["27919037"],"is_preprint":false}],"current_model":"ERO1B (ERO1β) is an ER-resident FAD-dependent sulfhydryl oxidase that oxidizes PDI preferentially via its a' active site, driving disulfide bond formation in secretory proteins; it is constitutively and selectively expressed in professional secretory cells (especially pancreatic β-cells and gastric chief cells), is retained in the ER through dynamic covalent interactions with PDI and ERp44, is regulated by intramolecular disulfide bonds (Cys90-Cys130 and Cys95-Cys100) but is more loosely regulated and approximately twice as active as ERO1α, and plays an essential, cell-type-specific role in proinsulin oxidative folding and glucose homeostasis in vivo."},"narrative":{"mechanistic_narrative":"ERO1B (ERO1β) is an ER-resident FAD-dependent sulfhydryl oxidase that drives oxidative protein folding in the secretory pathway, conserved from the essential yeast Ero1p, whose loss causes ER retention of disulfide-stabilized proteins in a reduced, non-native form while leaving disulfide-free maturation intact [PMID:9659914]. Mechanistically, ERO1β oxidizes protein disulfide isomerase (PDI) in the ER lumen, which then relays oxidative equivalents to cargo proteins, a flux opposed by cytosolic reduced glutathione to set ER redox balance [PMID:15161913]; recombinant ERO1β is roughly twice as active as ERO1α and preferentially engages the a' active site of PDI [PMID:21091435]. Its catalytic output is restrained by regulatory disulfide bonds Cys90-Cys130 and Cys95-Cys100, with Cys130 critical to feedback control, and disruption of Cys100 yields a hyperactive enzyme that perturbs ER redox state and induces the UPR [PMID:21091435, PMID:27919037]. ERO1β functions as homodimers and as heterodimers with ERO1α and PDI through its active site [PMID:16012172], and is retained in the ER via dynamic covalent interactions with PDI and ERp44, which compete for binding [PMID:16677073]. ERO1β is constitutively and selectively expressed in professional secretory cells, notably pancreatic β-cells and gastric chief cells [PMID:16012172], where it serves a cell-type-specific, essential role in proinsulin oxidative folding and glucose homeostasis; its dosage must be fine-tuned, as both loss and overexpression impair insulin biogenesis and β-cell function in vivo [PMID:20308425, PMID:24469402].","teleology":[{"year":1998,"claim":"Established that the ERO1 family is an essential, dedicated catalyst of ER disulfide bond formation rather than a general folding factor, by showing loss specifically blocks maturation of disulfide-containing proteins.","evidence":"Genetic loss-of-function and overexpression complementation with protein maturation assays in yeast","pmids":["9659914"],"confidence":"High","gaps":["Yeast ortholog only; does not address human ERO1β isoform specialization","Direct enzymatic mechanism (FAD chemistry, PDI as proximal substrate) not resolved here"]},{"year":2004,"claim":"Defined the catalytic relay by showing ERO1 oxidizes PDI, which passes oxidizing equivalents to cargo, and that cytosolic GSH counterbalances this flux across compartments.","evidence":"Semipermeable cell assays with PDI redox-state measurements, ERO1α overexpression and GSH addition","pmids":["15161913"],"confidence":"Medium","gaps":["Largely centered on ERO1α; ERO1β-specific contribution not separately quantified","Single lab biochemical system"]},{"year":2005,"claim":"Showed ERO1β assembles into active-site-dependent homo- and heterodimers and is expressed in a cell-type-restricted pattern, linking the enzyme to professional secretory cells.","evidence":"Reciprocal Co-IP, active-site mutagenesis, dimerization assays, and tissue immunohistochemistry","pmids":["16012172"],"confidence":"Medium","gaps":["Functional consequence of dimerization for catalysis not established","Single-lab Co-IP evidence"]},{"year":2006,"claim":"Identified the ER-retention mechanism for ERO1β through covalent interactions with PDI and ERp44, with ERp44 covalent binding essential and PDI/ERp44 competing for ERO1.","evidence":"Co-expression/secretion assays in HeLa cells, Co-IP, KDEL/RDEL retention assays, PDI cysteine mutagenesis","pmids":["16677073"],"confidence":"Medium","gaps":["Relative in vivo contribution of PDI versus ERp44 to retention unresolved","Based on overexpression in non-secretory HeLa cells"]},{"year":2006,"claim":"Mapped FAD-binding-domain residues required for catalytic integrity, separating dimerization/non-covalent PDI binding from disulfide-dependent PDI engagement and revealing misoxidation/aggregation under stress.","evidence":"Site-directed mutagenesis modeled on yeast ero1-1/ero1-2, Co-IP, redox/temperature stress and dimerization assays","pmids":["16822866"],"confidence":"Medium","gaps":["No structural model of the FAD domain in human ERO1β","Single-lab mutagenesis"]},{"year":2010,"claim":"Demonstrated a non-redundant, cell-type-specific physiological role by showing ERO1β is the predominant β-cell isoform whose loss impairs proinsulin oxidative folding and causes glucose intolerance.","evidence":"Ero1lb knockout mice, proinsulin folding/secretion assays, glucose tolerance tests, epistasis with Ero1l double knockout","pmids":["20308425"],"confidence":"High","gaps":["Molecular basis for β-cell selectivity of ERO1β not explained","Residual oxidative folding capacity in knockout implies redundancy not fully defined"]},{"year":2011,"claim":"Quantified ERO1β as ~2-fold more active than ERO1α with preference for the PDI a' site, and showed its activity is regulated by long-range disulfides but more loosely than ERO1α.","evidence":"In vitro enzymatic assays with recombinant proteins, PDI-family oxidation assays, disulfide mutant analysis","pmids":["21091435"],"confidence":"High","gaps":["Physiological consequence of loose regulation in β-cells not directly tested here","Single-lab reconstitution"]},{"year":2014,"claim":"Established that ERO1β dosage must be fine-tuned, since both reduced expression in diabetic models and forced overexpression impair β-cell function via ER stress and reduced insulin content.","evidence":"Diabetic mouse models, β-cell ERO1β overexpression, UPR gene analysis, EM of ER, insulin secretion assays","pmids":["24469402"],"confidence":"Medium","gaps":["Mechanism coupling ERO1β overactivity to UPR induction not fully resolved","Cause of paradoxical downregulation in diabetes unknown"]},{"year":2014,"claim":"Resolved the identity of the regulatory disulfides (Cys90-Cys130, Cys95-Cys100) and showed Cys100 mutation, not the previously proposed Cys262 bond, drives hyperactivity and ER redox perturbation.","evidence":"Cys mutagenesis, alkylation protection in living cells, UPR reporters, molecular modeling","pmids":["27919037"],"confidence":"Medium","gaps":["No experimental structure of the regulated and hyperactive states","Single-lab modeling-based interpretation"]},{"year":null,"claim":"How ERO1β's loose redox regulation is tuned in vivo to the high secretory burden of β-cells, and what determines its cell-type-restricted expression, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experimental structure of human ERO1β","Transcriptional/regulatory basis of β-cell and chief-cell selectivity unknown","Quantitative contribution of PDI versus ERp44 to retention in native secretory cells undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[0,2,6]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,6]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[6]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,2,4]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[7,8]}],"complexes":[],"partners":["P4HB","ERP44","ERO1A"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q86YB8","full_name":"ERO1-like protein beta","aliases":["Endoplasmic reticulum oxidoreductase beta","Endoplasmic reticulum oxidoreductin-1-like protein B","Oxidoreductin-1-L-beta"],"length_aa":467,"mass_kda":53.5,"function":"Oxidoreductase involved in disulfide bond formation in the endoplasmic reticulum. Efficiently reoxidizes P4HB/PDI, the enzyme catalyzing protein disulfide formation, in order to allow P4HB to sustain additional rounds of disulfide formation. Other protein disulfide isomerase family members can also be reoxidized, but at lower rates compared to P4HB, including PDIA2 (50% of P4HB reoxidation rate), as well as PDIA3, PDIA4, PDIA6 and NXNDC12 (<10%). Following P4HB reoxidation, passes its electrons to molecular oxygen via FAD, leading to the production of reactive oxygen species (ROS) in the cell. May be involved in oxidative proinsulin folding in pancreatic cells, hence may play a role in glucose homeostasis","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/Q86YB8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ERO1B","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ERO1B","total_profiled":1310},"omim":[],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"pancreas","ntpm":172.5}],"url":"https://www.proteinatlas.org/search/ERO1B"},"hgnc":{"alias_symbol":["ERO1-L(beta)","Ero1beta"],"prev_symbol":["ERO1LB"]},"alphafold":{"accession":"Q86YB8","domains":[{"cath_id":"-","chopping":"32-94_137-192_245-467","consensus_level":"high","plddt":83.8752,"start":32,"end":467}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86YB8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q86YB8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q86YB8-F1-predicted_aligned_error_v6.png","plddt_mean":75.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ERO1B","jax_strain_url":"https://www.jax.org/strain/search?query=ERO1B"},"sequence":{"accession":"Q86YB8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q86YB8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q86YB8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86YB8"}},"corpus_meta":[{"pmid":"9659914","id":"PMC_9659914","title":"Ero1p: a novel and ubiquitous protein with an essential role in oxidative protein folding in the endoplasmic reticulum.","date":"1998","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/9659914","citation_count":380,"is_preprint":false},{"pmid":"20308425","id":"PMC_20308425","title":"ERO1-beta, a pancreas-specific disulfide oxidase, promotes insulin biogenesis and glucose homeostasis.","date":"2010","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/20308425","citation_count":218,"is_preprint":false},{"pmid":"15161913","id":"PMC_15161913","title":"Glutathione limits Ero1-dependent oxidation in the endoplasmic reticulum.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15161913","citation_count":128,"is_preprint":false},{"pmid":"16677073","id":"PMC_16677073","title":"Dynamic retention of Ero1alpha and Ero1beta in the endoplasmic reticulum by interactions with PDI and ERp44.","date":"2006","source":"Antioxidants & redox signaling","url":"https://pubmed.ncbi.nlm.nih.gov/16677073","citation_count":90,"is_preprint":false},{"pmid":"16012172","id":"PMC_16012172","title":"Tissue-specific expression and dimerization of the endoplasmic reticulum oxidoreductase Ero1beta.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16012172","citation_count":78,"is_preprint":false},{"pmid":"21398518","id":"PMC_21398518","title":"Molecular bases of cyclic and specific disulfide interchange between human ERO1alpha protein and protein-disulfide isomerase (PDI).","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21398518","citation_count":71,"is_preprint":false},{"pmid":"21091435","id":"PMC_21091435","title":"The endoplasmic reticulum sulfhydryl oxidase Ero1β drives efficient oxidative protein folding with loose regulation.","date":"2011","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/21091435","citation_count":54,"is_preprint":false},{"pmid":"25122773","id":"PMC_25122773","title":"Inhibition of the functional interplay between endoplasmic reticulum (ER) oxidoreduclin-1α (Ero1α) and protein-disulfide isomerase (PDI) by the endocrine disruptor bisphenol A.","date":"2014","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25122773","citation_count":44,"is_preprint":false},{"pmid":"20562109","id":"PMC_20562109","title":"Ero1alpha is expressed on blood platelets in association with protein-disulfide isomerase and contributes to redox-controlled remodeling of alphaIIbbeta3.","date":"2010","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20562109","citation_count":40,"is_preprint":false},{"pmid":"24469402","id":"PMC_24469402","title":"Deregulation of pancreas-specific oxidoreductin ERO1β in the pathogenesis of diabetes mellitus.","date":"2014","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/24469402","citation_count":38,"is_preprint":false},{"pmid":"24022479","id":"PMC_24022479","title":"Endoplasmic reticulum oxidoreductin-1α (Ero1α) improves folding and secretion of mutant proinsulin and limits mutant proinsulin-induced endoplasmic reticulum stress.","date":"2013","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24022479","citation_count":38,"is_preprint":false},{"pmid":"30076651","id":"PMC_30076651","title":"ERO1L promotes pancreatic cancer cell progression through activating the Wnt/catenin pathway.","date":"2018","source":"Journal of cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30076651","citation_count":23,"is_preprint":false},{"pmid":"25739021","id":"PMC_25739021","title":"Activation of the unfolded protein response in aged human lenses.","date":"2015","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/25739021","citation_count":16,"is_preprint":false},{"pmid":"33559868","id":"PMC_33559868","title":"ERO1α mediates endoplasmic reticulum stress-induced apoptosis via microRNA-101/EZH2 axis in colon cancer RKO and HT-29 cells.","date":"2021","source":"Human cell","url":"https://pubmed.ncbi.nlm.nih.gov/33559868","citation_count":14,"is_preprint":false},{"pmid":"35785492","id":"PMC_35785492","title":"ERO1L promotes the proliferation and metastasis of lung adenocarcinoma via the Wnt2/β-catenin signaling pathway.","date":"2022","source":"Molecular carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/35785492","citation_count":11,"is_preprint":false},{"pmid":"24084034","id":"PMC_24084034","title":"Ixeris dentata-induced regulation of amylase synthesis and secretion in glucose-treated human salivary gland cells.","date":"2013","source":"Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association","url":"https://pubmed.ncbi.nlm.nih.gov/24084034","citation_count":11,"is_preprint":false},{"pmid":"16822866","id":"PMC_16822866","title":"Mutations in the FAD binding domain cause stress-induced misoxidation of the endoplasmic reticulum oxidoreductase Ero1beta.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16822866","citation_count":9,"is_preprint":false},{"pmid":"27919037","id":"PMC_27919037","title":"Biochemical evidence that regulation of Ero1β activity in human cells does not involve the isoform-specific cysteine 262.","date":"2014","source":"Bioscience reports","url":"https://pubmed.ncbi.nlm.nih.gov/27919037","citation_count":8,"is_preprint":false},{"pmid":"37014092","id":"PMC_37014092","title":"Knockdown of ERO1L attenuates tumor growth, migration and invasion in lung adenocarcinoma through Wnt/β‑catenin pathway.","date":"2023","source":"Biotechnology & genetic engineering reviews","url":"https://pubmed.ncbi.nlm.nih.gov/37014092","citation_count":2,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.03.31.25324887","title":"Comprehensive profiling of the mutational landscape of hidradenoma papilliferum validates key role of alterations in the PI3K/AKT pathway alterations","date":"2025-04-01","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.31.25324887","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11935,"output_tokens":2337,"usd":0.03543,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9564,"output_tokens":3227,"usd":0.064247,"stage2_stop_reason":"end_turn"},"total_usd":0.099677,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"Ero1p (yeast ortholog of ERO1B) is an essential ER-resident protein required for oxidative protein folding; loss-of-function causes ER retention of disulfide-stabilized proteins in a reduced, non-native form, while disulfide-free protein maturation is unaffected, demonstrating a specific role in disulfide bond formation.\",\n      \"method\": \"Genetic loss-of-function (DTT-sensitivity screen), overexpression (DTT resistance), protein maturation assays in yeast\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic loss-of-function with specific molecular phenotype, replicated by overexpression complementation, foundational paper\",\n      \"pmids\": [\"9659914\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"ERO1β is the predominant ERO1 isoform in insulin-producing pancreatic β-cells; homozygous disruption of Ero1lb selectively impairs oxidative folding of proinsulin and causes glucose intolerance in mice, demonstrating a cell-type-specific role for ERO1β in insulin biogenesis.\",\n      \"method\": \"Ero1lb knockout mouse model, proinsulin folding and secretion assays, glucose tolerance tests, genetic epistasis with Ero1l double knockout\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo knockout with specific molecular (proinsulin folding) and physiological (glucose intolerance) phenotypes, epistasis with double knockout\",\n      \"pmids\": [\"20308425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"ERO1α and ERO1β oxidize PDI in the ER lumen, which in turn transfers oxidative equivalents to cargo proteins; cytosolic reduced glutathione (GSH) opposes Ero1-driven PDI oxidation, establishing a redox balance across compartments.\",\n      \"method\": \"Semipermeable cell assays, PDI redox state measurements, overexpression of Ero1α, GSH addition experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical assay in semipermeable cells with multiple conditions, single lab\",\n      \"pmids\": [\"15161913\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"ERO1β forms homodimers and mixed heterodimers with ERO1α, and ERO1β–PDI heterodimers; dimerization requires the ERO active site. ERO1β is constitutively expressed in pancreatic islets and gastric chief cells in a cell-type-specific manner.\",\n      \"method\": \"Co-immunoprecipitation, in vivo dimerization assays, active-site mutagenesis, immunohistochemistry of tissue sections\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with mutagenesis in a single lab, multiple orthogonal methods\",\n      \"pmids\": [\"16012172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ERO1β is retained in the ER through dynamic covalent interactions with PDI and ERp44; overexpressed ERO1β is secreted unless co-expressed with PDI or ERp44 (KDEL/RDEL-dependent), and ERp44–ERO1 covalent interactions are essential for retention. PDI lacking active-site cysteines still partially retains ERO1β, and PDI and ERp44 compete for ERO1 binding.\",\n      \"method\": \"Co-expression/secretion assays in HeLa transfectants, co-immunoprecipitation, KDEL/RDEL-dependent retention assays, cysteine mutagenesis of PDI\",\n      \"journal\": \"Antioxidants & redox signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional secretion assay with mutagenesis, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"16677073\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Mutations in the FAD binding domain of ERO1β (Gly-to-Ser and His-to-Tyr, modeled on yeast ero1-1 and ero1-2 mutations) do not prevent ERO1β dimerization or non-covalent PDI interaction, but the Gly-to-Ser mutation abolishes disulfide-dependent PDI–ERO1β heterodimers; both mutations cause ERO1β misoxidation and aggregation under temperature or redox stress.\",\n      \"method\": \"Site-directed mutagenesis, Co-immunoprecipitation, redox/temperature stress assays, dimerization assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — active-site mutagenesis with biochemical functional assays, single lab\",\n      \"pmids\": [\"16822866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Recombinant human ERO1β is approximately twice as enzymatically active as ERO1α in oxidizing PDI; ERO1β preferentially drives oxidative folding through the a' active site of PDI. ERO1β activity is regulated by long-range disulfide bonds, with Cys130 playing a critical role in feedback regulation, but overall regulation is loose compared to ERO1α.\",\n      \"method\": \"In vitro enzymatic assays with recombinant proteins, PDI family member oxidation assays, disulfide mutant analysis\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins and mutagenesis, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"21091435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ERO1β expression is paradoxically decreased in β-cells of diabetic model mice despite increased ER stress; overexpression of ERO1β in β-cells causes ER stress (UPR gene upregulation, enlarged ER lumen) and decreases insulin content, impairing glucose-stimulated insulin secretion, demonstrating that fine-tuned ERO1β activity is required for normal β-cell function.\",\n      \"method\": \"Mouse diabetic models, ERO1β overexpression in β-cells, UPR gene expression analysis, electron microscopy (ER lumen), insulin secretion assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and cell-based overexpression with specific molecular and physiological readouts, single lab\",\n      \"pmids\": [\"24469402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The regulatory disulfide bonds in ERO1β are Cys90-Cys130 and Cys95-Cys100 (conserved with ERO1α), not an isoform-specific Cys262-Cys100 bond; Cys262 is buried and reduced in the ER of living cells. Mutation of Cys100 (not Cys262) renders ERO1β hyperactive, inducing UPR and oxidative perturbation of ER redox state.\",\n      \"method\": \"Site-directed mutagenesis of Cys residues, alkylation protection assays in living cells, UPR reporter assays, molecular modeling of ERO1β structure\",\n      \"journal\": \"Bioscience reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with functional cell-based readouts and structural modeling, single lab\",\n      \"pmids\": [\"27919037\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ERO1B (ERO1β) is an ER-resident FAD-dependent sulfhydryl oxidase that oxidizes PDI preferentially via its a' active site, driving disulfide bond formation in secretory proteins; it is constitutively and selectively expressed in professional secretory cells (especially pancreatic β-cells and gastric chief cells), is retained in the ER through dynamic covalent interactions with PDI and ERp44, is regulated by intramolecular disulfide bonds (Cys90-Cys130 and Cys95-Cys100) but is more loosely regulated and approximately twice as active as ERO1α, and plays an essential, cell-type-specific role in proinsulin oxidative folding and glucose homeostasis in vivo.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ERO1B (ERO1β) is an ER-resident FAD-dependent sulfhydryl oxidase that drives oxidative protein folding in the secretory pathway, conserved from the essential yeast Ero1p, whose loss causes ER retention of disulfide-stabilized proteins in a reduced, non-native form while leaving disulfide-free maturation intact [#0]. Mechanistically, ERO1β oxidizes protein disulfide isomerase (PDI) in the ER lumen, which then relays oxidative equivalents to cargo proteins, a flux opposed by cytosolic reduced glutathione to set ER redox balance [#2]; recombinant ERO1β is roughly twice as active as ERO1α and preferentially engages the a' active site of PDI [#6]. Its catalytic output is restrained by regulatory disulfide bonds Cys90-Cys130 and Cys95-Cys100, with Cys130 critical to feedback control, and disruption of Cys100 yields a hyperactive enzyme that perturbs ER redox state and induces the UPR [#6, #8]. ERO1β functions as homodimers and as heterodimers with ERO1α and PDI through its active site [#3], and is retained in the ER via dynamic covalent interactions with PDI and ERp44, which compete for binding [#4]. ERO1β is constitutively and selectively expressed in professional secretory cells, notably pancreatic β-cells and gastric chief cells [#3], where it serves a cell-type-specific, essential role in proinsulin oxidative folding and glucose homeostasis; its dosage must be fine-tuned, as both loss and overexpression impair insulin biogenesis and β-cell function in vivo [#1, #7].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that the ERO1 family is an essential, dedicated catalyst of ER disulfide bond formation rather than a general folding factor, by showing loss specifically blocks maturation of disulfide-containing proteins.\",\n      \"evidence\": \"Genetic loss-of-function and overexpression complementation with protein maturation assays in yeast\",\n      \"pmids\": [\"9659914\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Yeast ortholog only; does not address human ERO1β isoform specialization\",\n        \"Direct enzymatic mechanism (FAD chemistry, PDI as proximal substrate) not resolved here\"\n      ]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined the catalytic relay by showing ERO1 oxidizes PDI, which passes oxidizing equivalents to cargo, and that cytosolic GSH counterbalances this flux across compartments.\",\n      \"evidence\": \"Semipermeable cell assays with PDI redox-state measurements, ERO1α overexpression and GSH addition\",\n      \"pmids\": [\"15161913\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Largely centered on ERO1α; ERO1β-specific contribution not separately quantified\",\n        \"Single lab biochemical system\"\n      ]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showed ERO1β assembles into active-site-dependent homo- and heterodimers and is expressed in a cell-type-restricted pattern, linking the enzyme to professional secretory cells.\",\n      \"evidence\": \"Reciprocal Co-IP, active-site mutagenesis, dimerization assays, and tissue immunohistochemistry\",\n      \"pmids\": [\"16012172\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional consequence of dimerization for catalysis not established\",\n        \"Single-lab Co-IP evidence\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identified the ER-retention mechanism for ERO1β through covalent interactions with PDI and ERp44, with ERp44 covalent binding essential and PDI/ERp44 competing for ERO1.\",\n      \"evidence\": \"Co-expression/secretion assays in HeLa cells, Co-IP, KDEL/RDEL retention assays, PDI cysteine mutagenesis\",\n      \"pmids\": [\"16677073\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Relative in vivo contribution of PDI versus ERp44 to retention unresolved\",\n        \"Based on overexpression in non-secretory HeLa cells\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Mapped FAD-binding-domain residues required for catalytic integrity, separating dimerization/non-covalent PDI binding from disulfide-dependent PDI engagement and revealing misoxidation/aggregation under stress.\",\n      \"evidence\": \"Site-directed mutagenesis modeled on yeast ero1-1/ero1-2, Co-IP, redox/temperature stress and dimerization assays\",\n      \"pmids\": [\"16822866\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structural model of the FAD domain in human ERO1β\",\n        \"Single-lab mutagenesis\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated a non-redundant, cell-type-specific physiological role by showing ERO1β is the predominant β-cell isoform whose loss impairs proinsulin oxidative folding and causes glucose intolerance.\",\n      \"evidence\": \"Ero1lb knockout mice, proinsulin folding/secretion assays, glucose tolerance tests, epistasis with Ero1l double knockout\",\n      \"pmids\": [\"20308425\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular basis for β-cell selectivity of ERO1β not explained\",\n        \"Residual oxidative folding capacity in knockout implies redundancy not fully defined\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Quantified ERO1β as ~2-fold more active than ERO1α with preference for the PDI a' site, and showed its activity is regulated by long-range disulfides but more loosely than ERO1α.\",\n      \"evidence\": \"In vitro enzymatic assays with recombinant proteins, PDI-family oxidation assays, disulfide mutant analysis\",\n      \"pmids\": [\"21091435\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Physiological consequence of loose regulation in β-cells not directly tested here\",\n        \"Single-lab reconstitution\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established that ERO1β dosage must be fine-tuned, since both reduced expression in diabetic models and forced overexpression impair β-cell function via ER stress and reduced insulin content.\",\n      \"evidence\": \"Diabetic mouse models, β-cell ERO1β overexpression, UPR gene analysis, EM of ER, insulin secretion assays\",\n      \"pmids\": [\"24469402\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism coupling ERO1β overactivity to UPR induction not fully resolved\",\n        \"Cause of paradoxical downregulation in diabetes unknown\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Resolved the identity of the regulatory disulfides (Cys90-Cys130, Cys95-Cys100) and showed Cys100 mutation, not the previously proposed Cys262 bond, drives hyperactivity and ER redox perturbation.\",\n      \"evidence\": \"Cys mutagenesis, alkylation protection in living cells, UPR reporters, molecular modeling\",\n      \"pmids\": [\"27919037\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No experimental structure of the regulated and hyperactive states\",\n        \"Single-lab modeling-based interpretation\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ERO1β's loose redox regulation is tuned in vivo to the high secretory burden of β-cells, and what determines its cell-type-restricted expression, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No experimental structure of human ERO1β\",\n        \"Transcriptional/regulatory basis of β-cell and chief-cell selectivity unknown\",\n        \"Quantitative contribution of PDI versus ERp44 to retention in native secretory cells undefined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [0, 2, 6]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 6]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [7, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"P4HB\",\n      \"ERP44\",\n      \"ERO1A\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}