{"gene":"PF3D7_1464600","run_date":"2026-09-08T14:19:07","timeline":{"discoveries":[{"year":2016,"finding":"UIS2 (PF3D7_1464600) is a PP2C/PPM-family serine/threonine phosphatase that dephosphorylates eukaryotic initiation factor 2α phosphoserine-59 (eIF2α-P) in Plasmodium sporozoites. Conditional knockout of uis2 led to highly elevated eIF2α phosphorylation and loss of sporozoite infectivity, establishing UIS2 as the eIF2α-P phosphatase required for sporozoite-to-liver-stage transformation. Unlike mammalian cells where PP1 performs this function, malaria sporozoites rely on this PP2C-family enzyme.","method":"Conditional genetic knockout parasites; measurement of eIF2α phosphorylation levels; infectivity assays of mutant sporozoites","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean conditional KO with defined cellular phenotype (eIF2α-P accumulation and infectivity loss), supported by epistasis with UIS1, with mechanistic pathway placement","pmids":["26735921"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"UIS2 stably binds phosphorylated eIF2α, unlike most eukaryotic phosphatases that interact transiently with their substrates, indicating a stable phosphatase–substrate complex.","method":"Biochemical binding/co-immunoprecipitation assay demonstrating stable complex between UIS2 and eIF2α-P","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — described as stable binding observed experimentally but abstract does not detail orthogonal methods; single study","pmids":["26735921"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"UIS2 expression is translationally repressed by the Pumilio protein Puf2 in salivary gland sporozoites. This repression is relieved when sporozoites develop into liver stage parasites, thereby allowing UIS2-mediated dephosphorylation of eIF2α-P and resumption of translation.","method":"Genetic analysis of uis2 expression in wild-type vs. puf2 mutant sporozoites and liver stages; transcriptional and translational assays","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis and expression analysis in multiple mutant backgrounds, single lab study","pmids":["26735921","28357358"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"finding":"UIS2 (the P. falciparum orthologue, PF3D7_1464600) localises to the parasitophorous vacuole (PV) in blood stage parasites, and GFP knock-in validation and targeted gene disruption attempts strongly suggest it is essential for parasite growth. This is contrary to a previous proposal that UIS2 regulates translation in the parasite cytoplasm.","method":"BioID proximity biotinylation; GFP knock-in localisation; selectable targeted gene disruption (inability to obtain disruptants indicating essentiality)","journal":"International journal of medical microbiology : IJMM","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — BioID combined with GFP knock-in localisation and failed gene disruption (essentiality inference), single lab","pmids":["28784333"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"The P. berghei orthologue of UIS2 (PBANKA_1328000) localises to the parasitophorous vacuole membrane (PVM) in blood and liver stage parasites, identified as a novel PVM protein.","method":"BioID with BirA*-fused PVM marker (EXP1), affinity purification, LC-MS/MS, and follow-up localisation validation in P. berghei","journal":"mSphere","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — BioID plus direct localisation validation in P. berghei; single lab, two orthogonal methods","pmids":["29404413"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2024,"finding":"UIS2 contains a bona fide PEXEL motif in its N-terminus that is cleaved by the aspartic protease Plasmepsin V (PMV) in the P. falciparum blood stage, making UIS2 a non-exported protein that nonetheless undergoes canonical PEXEL proteolytic processing. The UIS2 PEXEL has an unusual aspartic acid (Asp) at the P1' position following cleavage (RIL↓DE); Asp at P1' is permissive for PMV cleavage but abrogates export. Mutation of this Asp to Ala enables export of a reporter, demonstrating that the mature N-terminus residue identity (not PEXEL cleavage per se) controls export.","method":"Chimeric reporter fusion constructs; N-terminal sequence analysis; Plasmepsin V cleavage assays; mutagenesis of PEXEL fourth-position residue; export assays in P. falciparum blood stages","journal":"mSphere","confidence":"High","confidence_rationale":"Tier 1 / Strong — biochemical processing assay with mutagenesis and chimeric reporter fusions; peer-reviewed with multiple orthogonal approaches in single rigorous study","pmids":["38334391"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"Structure-based modelling reveals that UIS2 dephosphorylates eIF2α-P through both its N-terminal domain and phosphatase domain, each independently binding the eIF2α phosphoserine-59 loop via electrostatic interactions. The phosphatase domain contains a defined binding pocket with six cooperative electrostatic binding patches that stabilise the phosphopeptide near the active site; this pocket geometry is distinct from human PP1α, suggesting parasite selectivity. The inhibitor Salubrinal competes with eIF2α-P for this pocket by engaging three of the six binding patches through hydrophobic and hydrogen-bonding interactions.","method":"AlphaFold structural modelling; molecular dynamics simulations; metadynamics simulations; molecular docking; free energy perturbation analyses","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 4 / Weak — entirely computational (AlphaFold + MD/metadynamics); no in vitro biochemical or mutagenesis validation reported in abstract; preprint","pmids":["40463039"],"is_preprint":true,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"Bioinformatic analysis classified UIS2 (PF3D7_1464600) as a member of the PP2C/PPM phosphatase family within the P. falciparum phosphatome; P. falciparum contains a cluster of 7 closely related PP2C/PPM members.","method":"Bioinformatics: database mining (PlasmoDB), sequence analysis, and phylogenetic tree construction","journal":"BMC genomics","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational/bioinformatic classification only; no experimental validation","pmids":["18793411"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"UIS2 (PF3D7_1464600) is a PP2C/PPM-family serine/threonine phosphatase that dephosphorylates eIF2α at phosphoserine-59, forming a stable complex with its substrate; its expression is translationally repressed by Puf2 in dormant sporozoites and de-repressed upon liver-stage entry, enabling resumption of translation. In blood-stage parasites UIS2 localises to the parasitophorous vacuole (membrane) rather than the cytoplasm, is apparently essential for parasite growth, and contains a PEXEL motif that is cleaved by Plasmepsin V but whose unusual Asp residue at the P1' position prevents export into the host erythrocyte."},"narrative":{"mechanistic_narrative":"UIS2 (PF3D7_1464600) is a PP2C/PPM-family serine/threonine protein phosphatase that controls Plasmodium translational status by dephosphorylating eukaryotic initiation factor 2α at phosphoserine-59, the eIF2α-P that suppresses translation [PMID:26735921]. Conditional knockout in sporozoites causes accumulation of eIF2α-P and loss of infectivity, establishing UIS2 as the eIF2α-P phosphatase required for the sporozoite-to-liver-stage transition—a role played by PP1 in mammalian cells but delegated to this PP2C-family enzyme in the parasite [PMID:26735921]. UIS2 forms an unusually stable phosphatase–substrate complex with phosphorylated eIF2α rather than the transient association typical of eukaryotic phosphatases [PMID:26735921], and its activity is gated developmentally: the Pumilio protein Puf2 translationally represses UIS2 in salivary-gland sporozoites, with de-repression on liver-stage entry permitting eIF2α-P dephosphorylation and resumption of translation [PMID:26735921, PMID:28357358]. In blood-stage parasites UIS2 localises to the parasitophorous vacuole/PV membrane rather than the cytoplasm and appears essential for growth [PMID:28784333], with the P. berghei orthologue independently identified as a PV membrane protein [PMID:29404413]. UIS2 carries a bona fide PEXEL motif cleaved by Plasmepsin V, but an atypical aspartate at the P1' position (RIL↓DE) permits cleavage while blocking export, so that mature N-terminal residue identity—not PEXEL processing itself—dictates its non-exported fate [PMID:38334391].","teleology":[{"year":2008,"claim":"Before any function was known, UIS2 needed to be placed within the parasite enzyme repertoire to predict its catalytic class.","evidence":"Bioinformatic phosphatome analysis of P. falciparum (PlasmoDB mining, phylogenetics)","pmids":["18793411"],"confidence":"Low","gaps":["Purely computational classification with no biochemical validation","Does not distinguish UIS2 from the six other closely related PP2C/PPM members","No substrate or cellular role implied"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"The central question of what UIS2 does was answered by identifying eIF2α-P as its substrate and showing it is required for the sporozoite-to-liver-stage transition, defining a PP2C-based route to translational recovery distinct from the mammalian PP1 system.","evidence":"Conditional knockout parasites, eIF2α phosphorylation measurement, sporozoite infectivity assays, plus a stable-binding co-IP with eIF2α-P","pmids":["26735921"],"confidence":"High","gaps":["Stable phosphatase–substrate binding shown but not resolved to the residue level at this stage","Catalytic residues/mechanism not defined biochemically","Substrate specificity beyond eIF2α not tested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"How UIS2 activity is timed across the life cycle was addressed by showing Puf2 translationally represses UIS2 in dormant sporozoites and releases it upon liver-stage entry.","evidence":"Genetic analysis of uis2 expression in wild-type versus puf2 mutant sporozoites and liver stages","pmids":["26735921","28357358"],"confidence":"Medium","gaps":["Direct binding of Puf2 to uis2 mRNA not detailed here","Other regulators of UIS2 timing not excluded","Single-lab expression analysis"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"claim":"The assumed cytoplasmic site of UIS2 action was overturned by localising it to the parasitophorous vacuole in blood-stage parasites and inferring essentiality from failed disruption.","evidence":"BioID proximity biotinylation, GFP knock-in localisation, and unsuccessful targeted gene disruption in P. falciparum","pmids":["28784333"],"confidence":"Medium","gaps":["Essentiality inferred from failure to disrupt rather than conditional depletion","How a PV-localised phosphatase reaches cytoplasmic eIF2α is unresolved","Reconciliation with the eIF2α-P role not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"The PV localisation was corroborated in a second species by identifying the P. berghei orthologue as a PV membrane protein across blood and liver stages.","evidence":"BioID with a BirA*-EXP1 PVM marker, affinity purification, LC-MS/MS, and localisation validation in P. berghei","pmids":["29404413"],"confidence":"Medium","gaps":["Functional consequences of PVM residence not tested in P. berghei","Membrane topology not defined","Link to eIF2α dephosphorylation not addressed in this system"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2024,"claim":"The trafficking logic was clarified by showing UIS2 has a PEXEL motif cleaved by Plasmepsin V yet is not exported, because an atypical P1' aspartate permits cleavage while blocking export.","evidence":"Chimeric reporter fusions, Plasmepsin V cleavage assays, and P1' Asp-to-Ala mutagenesis with export assays in P. falciparum blood stages","pmids":["38334391"],"confidence":"High","gaps":["Physiological role of PEXEL processing for UIS2 function not established","How the cleaved N-terminus relates to PV/PVM targeting not defined","Does not address the eIF2α catalytic mechanism"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"claim":"A structural rationale for parasite-selective eIF2α-P recognition was modelled, proposing dual-domain engagement of the phosphoserine-59 loop and a six-patch electrostatic pocket exploited by the inhibitor Salubrinal.","evidence":"AlphaFold modelling, molecular dynamics/metadynamics, docking, and free-energy perturbation (preprint)","pmids":["40463039"],"confidence":"Low","gaps":["Entirely computational with no in vitro or mutagenesis validation","Proposed binding patches not experimentally confirmed","Salubrinal selectivity not tested against parasites"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"It remains unresolved how a PV/PVM-localised phosphatase physically accesses and dephosphorylates cytoplasmic eIF2α, and whether UIS2 has substrates beyond eIF2α.","evidence":"","pmids":[],"confidence":"Low","gaps":["Topological reconciliation of PV localisation with cytoplasmic substrate","No experimentally validated active-site or catalytic mechanism","Substrate repertoire beyond eIF2α unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Stable UIS2–phosphorylated eIF2α phosphatase–substrate complex [#1]"],"partners":["EIF2Α (PHOSPHOSERINE-59 SUBSTRATE) [#0, #1, #6]","PUF2 (TRANSLATIONAL REPRESSOR OF UIS2 MRNA) [#2]","PLASMEPSIN V (PEXEL-CLEAVING PROTEASE ACTING ON UIS2 N-TERMINUS) [#5]"],"other_free_text":["PP2C/PPM-family serine/threonine phosphatase; one of a cluster of 7 closely related PP2C members in P. falciparum [#7]","Functionally substitutes for the PP1 role used by mammalian cells in eIF2α-P dephosphorylation [#0]","Required for sporozoite-to-liver-stage transformation; conditional KO abolishes sporozoite infectivity [#0]","Appears essential for blood-stage growth (failed gene disruption) [#3]","Carries a PEXEL motif (RIL↓DE) cleaved by Plasmepsin V; atypical P1' Asp permits cleavage but blocks export, so UIS2 is non-exported [#5]","Computationally modelled six-patch electrostatic binding pocket distinct from human PP1α, targeted by Salubrinal (preprint) [#6]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"18793411","id":"PMC_18793411","title":"The protein-phosphatome of the human malaria parasite Plasmodium falciparum.","date":"2008","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/18793411","citation_count":57,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"28784333","id":"PMC_28784333","title":"Identification of novel parasitophorous vacuole proteins in P. falciparum parasites using BioID.","date":"2017","source":"International journal of medical microbiology : IJMM","url":"https://pubmed.ncbi.nlm.nih.gov/28784333","citation_count":47,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["UIS2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"26735921","id":"PMC_26735921","title":"UIS2: A Unique Phosphatase Required for the Development of Plasmodium Liver Stages.","date":"2016","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/26735921","citation_count":38,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["UIS2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"29404413","id":"PMC_29404413","title":"BioID Reveals Novel Proteins of the Plasmodium Parasitophorous Vacuole Membrane.","date":"2018","source":"mSphere","url":"https://pubmed.ncbi.nlm.nih.gov/29404413","citation_count":33,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["UIS2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"28357358","id":"PMC_28357358","title":"Translational Repression in Malaria Sporozoites.","date":"2016","source":"Microbial cell (Graz, Austria)","url":"https://pubmed.ncbi.nlm.nih.gov/28357358","citation_count":8,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["UIS2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"38334391","id":"PMC_38334391","title":"PEXEL is a proteolytic maturation site for both exported and non-exported Plasmodium proteins.","date":"2024","source":"mSphere","url":"https://pubmed.ncbi.nlm.nih.gov/38334391","citation_count":8,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["UIS2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37503245","id":"PMC_37503245","title":"PEXEL is a proteolytic maturation site for both exported and non-exported Plasmodium proteins.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/37503245","citation_count":2,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["UIS2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"40463039","id":"PMC_40463039","title":"Mechanistic Insights into the Plasmodium Phosphatase UIS2 in eIF2α Dephosphorylation via Integrated Structure-Based Modeling.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40463039","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["UIS2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7280,"output_tokens":2421,"usd":0.029077,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7887,"output_tokens":3675,"usd":0.065655,"stage2_stop_reason":"end_turn"},"total_usd":0.094732,"stage1_batch_id":"msgbatch_011BPjN2BL33F8cJXD1r7V7T","stage2_batch_id":"msgbatch_01Qwg6vP7qxkpL6Gsc7tajsb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"UIS2 (PF3D7_1464600) is a PP2C/PPM-family serine/threonine phosphatase that dephosphorylates eukaryotic initiation factor 2α phosphoserine-59 (eIF2α-P) in Plasmodium sporozoites. Conditional knockout of uis2 led to highly elevated eIF2α phosphorylation and loss of sporozoite infectivity, establishing UIS2 as the eIF2α-P phosphatase required for sporozoite-to-liver-stage transformation. Unlike mammalian cells where PP1 performs this function, malaria sporozoites rely on this PP2C-family enzyme.\",\n      \"method\": \"Conditional genetic knockout parasites; measurement of eIF2α phosphorylation levels; infectivity assays of mutant sporozoites\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean conditional KO with defined cellular phenotype (eIF2α-P accumulation and infectivity loss), supported by epistasis with UIS1, with mechanistic pathway placement\",\n      \"pmids\": [\"26735921\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"UIS2 stably binds phosphorylated eIF2α, unlike most eukaryotic phosphatases that interact transiently with their substrates, indicating a stable phosphatase–substrate complex.\",\n      \"method\": \"Biochemical binding/co-immunoprecipitation assay demonstrating stable complex between UIS2 and eIF2α-P\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — described as stable binding observed experimentally but abstract does not detail orthogonal methods; single study\",\n      \"pmids\": [\"26735921\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"UIS2 expression is translationally repressed by the Pumilio protein Puf2 in salivary gland sporozoites. This repression is relieved when sporozoites develop into liver stage parasites, thereby allowing UIS2-mediated dephosphorylation of eIF2α-P and resumption of translation.\",\n      \"method\": \"Genetic analysis of uis2 expression in wild-type vs. puf2 mutant sporozoites and liver stages; transcriptional and translational assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis and expression analysis in multiple mutant backgrounds, single lab study\",\n      \"pmids\": [\"26735921\", \"28357358\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"UIS2 (the P. falciparum orthologue, PF3D7_1464600) localises to the parasitophorous vacuole (PV) in blood stage parasites, and GFP knock-in validation and targeted gene disruption attempts strongly suggest it is essential for parasite growth. This is contrary to a previous proposal that UIS2 regulates translation in the parasite cytoplasm.\",\n      \"method\": \"BioID proximity biotinylation; GFP knock-in localisation; selectable targeted gene disruption (inability to obtain disruptants indicating essentiality)\",\n      \"journal\": \"International journal of medical microbiology : IJMM\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — BioID combined with GFP knock-in localisation and failed gene disruption (essentiality inference), single lab\",\n      \"pmids\": [\"28784333\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The P. berghei orthologue of UIS2 (PBANKA_1328000) localises to the parasitophorous vacuole membrane (PVM) in blood and liver stage parasites, identified as a novel PVM protein.\",\n      \"method\": \"BioID with BirA*-fused PVM marker (EXP1), affinity purification, LC-MS/MS, and follow-up localisation validation in P. berghei\",\n      \"journal\": \"mSphere\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — BioID plus direct localisation validation in P. berghei; single lab, two orthogonal methods\",\n      \"pmids\": [\"29404413\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UIS2 contains a bona fide PEXEL motif in its N-terminus that is cleaved by the aspartic protease Plasmepsin V (PMV) in the P. falciparum blood stage, making UIS2 a non-exported protein that nonetheless undergoes canonical PEXEL proteolytic processing. The UIS2 PEXEL has an unusual aspartic acid (Asp) at the P1' position following cleavage (RIL↓DE); Asp at P1' is permissive for PMV cleavage but abrogates export. Mutation of this Asp to Ala enables export of a reporter, demonstrating that the mature N-terminus residue identity (not PEXEL cleavage per se) controls export.\",\n      \"method\": \"Chimeric reporter fusion constructs; N-terminal sequence analysis; Plasmepsin V cleavage assays; mutagenesis of PEXEL fourth-position residue; export assays in P. falciparum blood stages\",\n      \"journal\": \"mSphere\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — biochemical processing assay with mutagenesis and chimeric reporter fusions; peer-reviewed with multiple orthogonal approaches in single rigorous study\",\n      \"pmids\": [\"38334391\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Structure-based modelling reveals that UIS2 dephosphorylates eIF2α-P through both its N-terminal domain and phosphatase domain, each independently binding the eIF2α phosphoserine-59 loop via electrostatic interactions. The phosphatase domain contains a defined binding pocket with six cooperative electrostatic binding patches that stabilise the phosphopeptide near the active site; this pocket geometry is distinct from human PP1α, suggesting parasite selectivity. The inhibitor Salubrinal competes with eIF2α-P for this pocket by engaging three of the six binding patches through hydrophobic and hydrogen-bonding interactions.\",\n      \"method\": \"AlphaFold structural modelling; molecular dynamics simulations; metadynamics simulations; molecular docking; free energy perturbation analyses\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — entirely computational (AlphaFold + MD/metadynamics); no in vitro biochemical or mutagenesis validation reported in abstract; preprint\",\n      \"pmids\": [\"40463039\"],\n      \"is_preprint\": true,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Bioinformatic analysis classified UIS2 (PF3D7_1464600) as a member of the PP2C/PPM phosphatase family within the P. falciparum phosphatome; P. falciparum contains a cluster of 7 closely related PP2C/PPM members.\",\n      \"method\": \"Bioinformatics: database mining (PlasmoDB), sequence analysis, and phylogenetic tree construction\",\n      \"journal\": \"BMC genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational/bioinformatic classification only; no experimental validation\",\n      \"pmids\": [\"18793411\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"UIS2 (PF3D7_1464600) is a PP2C/PPM-family serine/threonine phosphatase that dephosphorylates eIF2α at phosphoserine-59, forming a stable complex with its substrate; its expression is translationally repressed by Puf2 in dormant sporozoites and de-repressed upon liver-stage entry, enabling resumption of translation. In blood-stage parasites UIS2 localises to the parasitophorous vacuole (membrane) rather than the cytoplasm, is apparently essential for parasite growth, and contains a PEXEL motif that is cleaved by Plasmepsin V but whose unusual Asp residue at the P1' position prevents export into the host erythrocyte.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"UIS2 (PF3D7_1464600) is a PP2C/PPM-family serine/threonine protein phosphatase that controls Plasmodium translational status by dephosphorylating eukaryotic initiation factor 2\\u03b1 at phosphoserine-59, the eIF2\\u03b1-P that suppresses translation [#0]. Conditional knockout in sporozoites causes accumulation of eIF2\\u03b1-P and loss of infectivity, establishing UIS2 as the eIF2\\u03b1-P phosphatase required for the sporozoite-to-liver-stage transition\\u2014a role played by PP1 in mammalian cells but delegated to this PP2C-family enzyme in the parasite [#0]. UIS2 forms an unusually stable phosphatase\\u2013substrate complex with phosphorylated eIF2\\u03b1 rather than the transient association typical of eukaryotic phosphatases [#1], and its activity is gated developmentally: the Pumilio protein Puf2 translationally represses UIS2 in salivary-gland sporozoites, with de-repression on liver-stage entry permitting eIF2\\u03b1-P dephosphorylation and resumption of translation [#2]. In blood-stage parasites UIS2 localises to the parasitophorous vacuole/PV membrane rather than the cytoplasm and appears essential for growth [#3], with the P. berghei orthologue independently identified as a PV membrane protein [#4]. UIS2 carries a bona fide PEXEL motif cleaved by Plasmepsin V, but an atypical aspartate at the P1' position (RIL\\u2193DE) permits cleavage while blocking export, so that mature N-terminal residue identity\\u2014not PEXEL processing itself\\u2014dictates its non-exported fate [#5].\"\n  ,\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Before any function was known, UIS2 needed to be placed within the parasite enzyme repertoire to predict its catalytic class.\",\n      \"evidence\": \"Bioinformatic phosphatome analysis of P. falciparum (PlasmoDB mining, phylogenetics)\",\n      \"pmids\": [\"18793411\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Purely computational classification with no biochemical validation\", \"Does not distinguish UIS2 from the six other closely related PP2C/PPM members\", \"No substrate or cellular role implied\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The central question of what UIS2 does was answered by identifying eIF2\\u03b1-P as its substrate and showing it is required for the sporozoite-to-liver-stage transition, defining a PP2C-based route to translational recovery distinct from the mammalian PP1 system.\",\n      \"evidence\": \"Conditional knockout parasites, eIF2\\u03b1 phosphorylation measurement, sporozoite infectivity assays, plus a stable-binding co-IP with eIF2\\u03b1-P\",\n      \"pmids\": [\"26735921\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stable phosphatase\\u2013substrate binding shown but not resolved to the residue level at this stage\", \"Catalytic residues/mechanism not defined biochemically\", \"Substrate specificity beyond eIF2\\u03b1 not tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"How UIS2 activity is timed across the life cycle was addressed by showing Puf2 translationally represses UIS2 in dormant sporozoites and releases it upon liver-stage entry.\",\n      \"evidence\": \"Genetic analysis of uis2 expression in wild-type versus puf2 mutant sporozoites and liver stages\",\n      \"pmids\": [\"26735921\", \"28357358\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding of Puf2 to uis2 mRNA not detailed here\", \"Other regulators of UIS2 timing not excluded\", \"Single-lab expression analysis\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The assumed cytoplasmic site of UIS2 action was overturned by localising it to the parasitophorous vacuole in blood-stage parasites and inferring essentiality from failed disruption.\",\n      \"evidence\": \"BioID proximity biotinylation, GFP knock-in localisation, and unsuccessful targeted gene disruption in P. falciparum\",\n      \"pmids\": [\"28784333\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Essentiality inferred from failure to disrupt rather than conditional depletion\", \"How a PV-localised phosphatase reaches cytoplasmic eIF2\\u03b1 is unresolved\", \"Reconciliation with the eIF2\\u03b1-P role not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The PV localisation was corroborated in a second species by identifying the P. berghei orthologue as a PV membrane protein across blood and liver stages.\",\n      \"evidence\": \"BioID with a BirA*-EXP1 PVM marker, affinity purification, LC-MS/MS, and localisation validation in P. berghei\",\n      \"pmids\": [\"29404413\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequences of PVM residence not tested in P. berghei\", \"Membrane topology not defined\", \"Link to eIF2\\u03b1 dephosphorylation not addressed in this system\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The trafficking logic was clarified by showing UIS2 has a PEXEL motif cleaved by Plasmepsin V yet is not exported, because an atypical P1' aspartate permits cleavage while blocking export.\",\n      \"evidence\": \"Chimeric reporter fusions, Plasmepsin V cleavage assays, and P1' Asp-to-Ala mutagenesis with export assays in P. falciparum blood stages\",\n      \"pmids\": [\"38334391\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological role of PEXEL processing for UIS2 function not established\", \"How the cleaved N-terminus relates to PV/PVM targeting not defined\", \"Does not address the eIF2\\u03b1 catalytic mechanism\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A structural rationale for parasite-selective eIF2\\u03b1-P recognition was modelled, proposing dual-domain engagement of the phosphoserine-59 loop and a six-patch electrostatic pocket exploited by the inhibitor Salubrinal.\",\n      \"evidence\": \"AlphaFold modelling, molecular dynamics/metadynamics, docking, and free-energy perturbation (preprint)\",\n      \"pmids\": [\"40463039\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Entirely computational with no in vitro or mutagenesis validation\", \"Proposed binding patches not experimentally confirmed\", \"Salubrinal selectivity not tested against parasites\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how a PV/PVM-localised phosphatase physically accesses and dephosphorylates cytoplasmic eIF2\\u03b1, and whether UIS2 has substrates beyond eIF2\\u03b1.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Topological reconciliation of PV localisation with cytoplasmic substrate\", \"No experimentally validated active-site or catalytic mechanism\", \"Substrate repertoire beyond eIF2\\u03b1 unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004722\", \"supporting_discovery_ids\": [0, 6, 7]},\n      {\"term_id\": \"GO:0008287\", \"supporting_discovery_ids\": [0, 7]},\n      {\"term_id\": \"GO:0035304\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020003\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0020005\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006446\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0017148\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [\n      \"Stable UIS2\\u2013phosphorylated eIF2\\u03b1 phosphatase\\u2013substrate complex [#1]\"\n    ],\n    \"partners\": [\n      \"eIF2\\u03b1 (phosphoserine-59 substrate) [#0, #1, #6]\",\n      \"Puf2 (translational repressor of UIS2 mRNA) [#2]\",\n      \"Plasmepsin V (PEXEL-cleaving protease acting on UIS2 N-terminus) [#5]\"\n    ],\n    \"other_free_text\": [\n      \"PP2C/PPM-family serine/threonine phosphatase; one of a cluster of 7 closely related PP2C members in P. falciparum [#7]\",\n      \"Functionally substitutes for the PP1 role used by mammalian cells in eIF2\\u03b1-P dephosphorylation [#0]\",\n      \"Required for sporozoite-to-liver-stage transformation; conditional KO abolishes sporozoite infectivity [#0]\",\n      \"Appears essential for blood-stage growth (failed gene disruption) [#3]\",\n      \"Carries a PEXEL motif (RIL\\u2193DE) cleaved by Plasmepsin V; atypical P1' Asp permits cleavage but blocks export, so UIS2 is non-exported [#5]\",\n      \"Computationally modelled six-patch electrostatic binding pocket distinct from human PP1\\u03b1, targeted by Salubrinal (preprint) [#6]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1464600","name":null,"product":"serine/threonine protein phosphatase UIS2, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1328000","name":null,"product":"serine/threonine protein phosphatase UIS2","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1216900","name":null,"product":"serine/threonine protein phosphatase UIS2, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"UIS2","evaluation":null}