{"gene":"PF3D7_1439500","run_date":"2026-09-08T14:19:07","timeline":{"discoveries":[{"year":2016,"finding":"ORP2 (PF3D7_1439500) contains a histone-fold domain (HFD) that promotes heterodimer formation with ORP1 at the oocyst capsule at the time of rupture; loss of either protein prevents oocyst rupture, and mutational analysis confirmed the HFD is essential for ORP2 function; heterodimer formation was verified in vitro.","method":"Genetic knockout (loss-of-function), mutational analysis of HFD, in vitro heterodimer reconstitution","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution of heterodimer, HFD mutagenesis, and genetic KO with defined rupture phenotype in a single rigorous study","pmids":["27982038"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2018,"finding":"Domain deletion analysis of ORP2 in P. berghei showed that the N-terminal HFD of ORP2 is required for sporozoite egress from the oocyst, while progressive C-terminal deletions caused absent or significantly impaired sporozoite egress, demonstrating that different regions of ORP2 play independent roles in sporozoite egress.","method":"Deletion mutant analysis, monitoring oocyst formation/rupture and salivary gland sporozoite counts in P. berghei","journal":"International journal for parasitology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple deletion constructs with defined phenotypic readouts in a single focused study; replicates and extends the KO phenotype from the 2016 paper","pmids":["30391497"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2026,"finding":"X-ray crystal structure of the ORP1/ORP2 HFD heterodimer was solved at 3.1 Å resolution, revealing the oligomerization interface; six cyclic peptides identified by a GAL4-based yeast two-hybrid combinatorial library inhibit ORP1/ORP2 dimerization in vitro, with molecular docking confirming binding at the dimer interface.","method":"X-ray crystallography (3.1 Å), GAL4-based Y2H combinatorial cyclic-peptide library screen, in vitro dimerization inhibition assay, molecular docking","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure plus orthogonal in vitro inhibition assay and docking, single lab but multiple methods in one study","pmids":["41506730"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2026,"finding":"ORP2 (together with ORP1) forms a trimeric NF-Y-like complex with a third protein ORP3 at the oocyst capsule; the ORP1/ORP2 dimer recruits ORP3 via its conserved NF-YA helix A1, forming a trimer confirmed in vitro by Yeast-3-hybrid; the trimeric complex is required for oocyst excystation and sporozoite egress.","method":"Genetic KO of orp3 with phenotypic analysis, Yeast-3-hybrid in vitro trimerization assay, localization of ORP3 to oocyst periphery","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro trimeric complex reconstitution (Y3H), genetic KO phenotype, and ORP3 localization data; extends ORP2's role into a defined trimeric assembly","pmids":["42045549"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]}],"current_model":"ORP2 (PF3D7_1439500) is a histone-fold domain-containing protein that localizes to the Plasmodium oocyst capsule, where its HFD heterodimerizes with ORP1 and the resulting dimer recruits a third subunit, ORP3, to form a trimeric NF-Y-like complex; this trimeric assembly is essential for oocyst capsule opening and sporozoite egress, as loss of ORP2 or disruption of its HFD blocks excystation, and the heterodimer interface has been structurally resolved by X-ray crystallography at 3.1 Å."},"narrative":{"mechanistic_narrative":"ORP2 (PF3D7_1439500) is a histone-fold domain (HFD)-containing protein that acts at the Plasmodium oocyst capsule to enable oocyst rupture and sporozoite egress [PMID:27982038]. Its N-terminal HFD mediates heterodimerization with the partner protein ORP1 at the capsule at the time of rupture, and this HFD is essential for ORP2 function, since its disruption or loss of either partner blocks oocyst rupture [PMID:27982038]. Distinct regions of ORP2 contribute independently to egress: the HFD is required for sporozoite egress, and progressive C-terminal deletions also abolish or severely impair egress [PMID:30391497]. The ORP1/ORP2 heterodimer nucleates assembly of a trimeric NF-Y-like complex by recruiting a third subunit, ORP3, through ORP3's conserved NF-YA helix A1, and this trimeric assembly at the oocyst periphery is required for excystation and sporozoite egress [PMID:42045549]. The ORP1/ORP2 HFD heterodimer interface has been resolved by X-ray crystallography at 3.1 Å, and cyclic peptides that bind this interface inhibit dimerization in vitro, defining the oligomerization surface as a druggable target [PMID:41506730]. All characterization of ORP2 derives from Plasmodium berghei.","teleology":[{"year":2016,"claim":"Established that ORP2 is a histone-fold protein whose function at the oocyst capsule is required for oocyst rupture, answering what molecular activity underlies its role in the parasite life cycle.","evidence":"Genetic knockout, HFD mutational analysis, and in vitro heterodimer reconstitution with ORP1 in P. berghei","pmids":["27982038"],"confidence":"High","gaps":["Structural basis of the ORP1/ORP2 HFD interface not resolved at this stage","How the heterodimer physically drives capsule opening was not defined","No identification of additional complex members"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2018,"claim":"Dissected the modular contribution of ORP2 regions, showing that both the N-terminal HFD and C-terminal segments are independently needed for sporozoite egress rather than the HFD alone.","evidence":"Deletion-mutant analysis with oocyst rupture and salivary gland sporozoite counts in P. berghei","pmids":["30391497"],"confidence":"High","gaps":["Molecular partners or activities of the C-terminal regions unidentified","Mechanism by which C-terminal deletions impair egress not defined"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2026,"claim":"Resolved the ORP1/ORP2 HFD heterodimer interface at atomic resolution and demonstrated it can be pharmacologically targeted, establishing the oligomerization surface as essential and druggable.","evidence":"X-ray crystallography at 3.1 Å, GAL4-based yeast two-hybrid cyclic-peptide screen, in vitro dimerization inhibition, and molecular docking in P. berghei","pmids":["41506730"],"confidence":"High","gaps":["In vivo efficacy of the inhibitory cyclic peptides not demonstrated","Structure of the higher-order (trimeric) assembly not resolved"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2026,"claim":"Extended the ORP2 mechanism from a dimer to a trimeric NF-Y-like complex, showing the ORP1/ORP2 dimer recruits ORP3 to form the functional unit required for excystation.","evidence":"Genetic KO of orp3, yeast-3-hybrid trimerization assay, and ORP3 localization to the oocyst periphery in P. berghei","pmids":["42045549"],"confidence":"High","gaps":["Biochemical mechanism by which the trimer effects capsule opening remains unknown","Whether additional subunits or regulators join the complex is undetermined"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":null,"claim":"The physical mechanism by which the ORP1/ORP2/ORP3 trimeric complex triggers oocyst capsule opening and sporozoite egress remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No effector activity linking the complex to capsule disassembly identified","Function of ORP2 in human-infective Plasmodium species not established","No structure of the full trimeric assembly"],"attribution":[{"species":"Plasmodium berghei","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["ORP1/ORP2 HFD heterodimer","ORP1/ORP2/ORP3 trimeric NF-Y-like complex"],"partners":["ORP1","ORP3"],"other_free_text":["N-terminal histone-fold domain of ORP2 mediates heterodimerization with ORP1 and is essential for function [#0, #1]","C-terminal regions of ORP2 independently required for sporozoite egress [#1]","ORP1/ORP2 HFD heterodimer interface solved by X-ray crystallography at 3.1 Å; cyclic peptides inhibit dimerization at the interface [#2]","ORP1/ORP2 dimer recruits ORP3 via ORP3's conserved NF-YA helix A1 to form a trimer required for oocyst excystation [#3]","All findings established in Plasmodium berghei"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"27982038","id":"PMC_27982038","title":"Release of Plasmodium sporozoites requires proteins with histone-fold dimerization domains.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/27982038","citation_count":15,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ORP2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30391497","id":"PMC_30391497","title":"Identification of Plasmodium berghei Oocyst Rupture Protein 2 (ORP2) domains involved in sporozoite egress from the oocyst.","date":"2018","source":"International journal for parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/30391497","citation_count":10,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ORP2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"41506730","id":"PMC_41506730","title":"Targeting the histone-fold dimerization interface of oocyst rupture proteins from Plasmodium berghei for antimalarial inhibitor discovery.","date":"2026","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/41506730","citation_count":1,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ORP2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"42045549","id":"PMC_42045549","title":"Sporozoite egress from Plasmodium oocysts requires a trimeric NF-Y-like complex.","date":"2026","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/42045549","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ORP2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":4711,"output_tokens":1291,"usd":0.016749,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":6159,"output_tokens":2303,"usd":0.044185,"stage2_stop_reason":"end_turn"},"total_usd":0.060934,"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\": \"ORP2 (PF3D7_1439500) contains a histone-fold domain (HFD) that promotes heterodimer formation with ORP1 at the oocyst capsule at the time of rupture; loss of either protein prevents oocyst rupture, and mutational analysis confirmed the HFD is essential for ORP2 function; heterodimer formation was verified in vitro.\",\n      \"method\": \"Genetic knockout (loss-of-function), mutational analysis of HFD, in vitro heterodimer reconstitution\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution of heterodimer, HFD mutagenesis, and genetic KO with defined rupture phenotype in a single rigorous study\",\n      \"pmids\": [\"27982038\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Domain deletion analysis of ORP2 in P. berghei showed that the N-terminal HFD of ORP2 is required for sporozoite egress from the oocyst, while progressive C-terminal deletions caused absent or significantly impaired sporozoite egress, demonstrating that different regions of ORP2 play independent roles in sporozoite egress.\",\n      \"method\": \"Deletion mutant analysis, monitoring oocyst formation/rupture and salivary gland sporozoite counts in P. berghei\",\n      \"journal\": \"International journal for parasitology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple deletion constructs with defined phenotypic readouts in a single focused study; replicates and extends the KO phenotype from the 2016 paper\",\n      \"pmids\": [\"30391497\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"X-ray crystal structure of the ORP1/ORP2 HFD heterodimer was solved at 3.1 Å resolution, revealing the oligomerization interface; six cyclic peptides identified by a GAL4-based yeast two-hybrid combinatorial library inhibit ORP1/ORP2 dimerization in vitro, with molecular docking confirming binding at the dimer interface.\",\n      \"method\": \"X-ray crystallography (3.1 Å), GAL4-based Y2H combinatorial cyclic-peptide library screen, in vitro dimerization inhibition assay, molecular docking\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure plus orthogonal in vitro inhibition assay and docking, single lab but multiple methods in one study\",\n      \"pmids\": [\"41506730\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"ORP2 (together with ORP1) forms a trimeric NF-Y-like complex with a third protein ORP3 at the oocyst capsule; the ORP1/ORP2 dimer recruits ORP3 via its conserved NF-YA helix A1, forming a trimer confirmed in vitro by Yeast-3-hybrid; the trimeric complex is required for oocyst excystation and sporozoite egress.\",\n      \"method\": \"Genetic KO of orp3 with phenotypic analysis, Yeast-3-hybrid in vitro trimerization assay, localization of ORP3 to oocyst periphery\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro trimeric complex reconstitution (Y3H), genetic KO phenotype, and ORP3 localization data; extends ORP2's role into a defined trimeric assembly\",\n      \"pmids\": [\"42045549\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"ORP2 (PF3D7_1439500) is a histone-fold domain-containing protein that localizes to the Plasmodium oocyst capsule, where its HFD heterodimerizes with ORP1 and the resulting dimer recruits a third subunit, ORP3, to form a trimeric NF-Y-like complex; this trimeric assembly is essential for oocyst capsule opening and sporozoite egress, as loss of ORP2 or disruption of its HFD blocks excystation, and the heterodimer interface has been structurally resolved by X-ray crystallography at 3.1 Å.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ORP2 (PF3D7_1439500) is a histone-fold domain (HFD)-containing protein that acts at the Plasmodium oocyst capsule to enable oocyst rupture and sporozoite egress [#0]. Its N-terminal HFD mediates heterodimerization with the partner protein ORP1 at the capsule at the time of rupture, and this HFD is essential for ORP2 function, since its disruption or loss of either partner blocks oocyst rupture [#0]. Distinct regions of ORP2 contribute independently to egress: the HFD is required for sporozoite egress, and progressive C-terminal deletions also abolish or severely impair egress [#1]. The ORP1/ORP2 heterodimer nucleates assembly of a trimeric NF-Y-like complex by recruiting a third subunit, ORP3, through ORP3's conserved NF-YA helix A1, and this trimeric assembly at the oocyst periphery is required for excystation and sporozoite egress [#3]. The ORP1/ORP2 HFD heterodimer interface has been resolved by X-ray crystallography at 3.1 Å, and cyclic peptides that bind this interface inhibit dimerization in vitro, defining the oligomerization surface as a druggable target [#2]. All characterization of ORP2 derives from Plasmodium berghei.\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Established that ORP2 is a histone-fold protein whose function at the oocyst capsule is required for oocyst rupture, answering what molecular activity underlies its role in the parasite life cycle.\",\n      \"evidence\": \"Genetic knockout, HFD mutational analysis, and in vitro heterodimer reconstitution with ORP1 in P. berghei\",\n      \"pmids\": [\"27982038\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the ORP1/ORP2 HFD interface not resolved at this stage\",\n        \"How the heterodimer physically drives capsule opening was not defined\",\n        \"No identification of additional complex members\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Dissected the modular contribution of ORP2 regions, showing that both the N-terminal HFD and C-terminal segments are independently needed for sporozoite egress rather than the HFD alone.\",\n      \"evidence\": \"Deletion-mutant analysis with oocyst rupture and salivary gland sporozoite counts in P. berghei\",\n      \"pmids\": [\"30391497\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular partners or activities of the C-terminal regions unidentified\",\n        \"Mechanism by which C-terminal deletions impair egress not defined\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Resolved the ORP1/ORP2 HFD heterodimer interface at atomic resolution and demonstrated it can be pharmacologically targeted, establishing the oligomerization surface as essential and druggable.\",\n      \"evidence\": \"X-ray crystallography at 3.1 Å, GAL4-based yeast two-hybrid cyclic-peptide screen, in vitro dimerization inhibition, and molecular docking in P. berghei\",\n      \"pmids\": [\"41506730\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"In vivo efficacy of the inhibitory cyclic peptides not demonstrated\",\n        \"Structure of the higher-order (trimeric) assembly not resolved\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended the ORP2 mechanism from a dimer to a trimeric NF-Y-like complex, showing the ORP1/ORP2 dimer recruits ORP3 to form the functional unit required for excystation.\",\n      \"evidence\": \"Genetic KO of orp3, yeast-3-hybrid trimerization assay, and ORP3 localization to the oocyst periphery in P. berghei\",\n      \"pmids\": [\"42045549\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Biochemical mechanism by which the trimer effects capsule opening remains unknown\",\n        \"Whether additional subunits or regulators join the complex is undetermined\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The physical mechanism by which the ORP1/ORP2/ORP3 trimeric complex triggers oocyst capsule opening and sporozoite egress remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No effector activity linking the complex to capsule disassembly identified\",\n        \"Function of ORP2 in human-infective Plasmodium species not established\",\n        \"No structure of the full trimeric assembly\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0046982\", \"supporting_discovery_ids\": [0, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0106364\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0030436\", \"supporting_discovery_ids\": [0, 1, 3]}\n    ],\n    \"complexes\": [\n      \"ORP1/ORP2 HFD heterodimer\",\n      \"ORP1/ORP2/ORP3 trimeric NF-Y-like complex\"\n    ],\n    \"partners\": [\n      \"ORP1\",\n      \"ORP3\"\n    ],\n    \"other_free_text\": [\n      \"N-terminal histone-fold domain of ORP2 mediates heterodimerization with ORP1 and is essential for function [#0, #1]\",\n      \"C-terminal regions of ORP2 independently required for sporozoite egress [#1]\",\n      \"ORP1/ORP2 HFD heterodimer interface solved by X-ray crystallography at 3.1 Å; cyclic peptides inhibit dimerization at the interface [#2]\",\n      \"ORP1/ORP2 dimer recruits ORP3 via ORP3's conserved NF-YA helix A1 to form a trimer required for oocyst excystation [#3]\",\n      \"All findings established in Plasmodium berghei\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1439500","name":null,"product":"oocyst rupture protein 2, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1303400","name":null,"product":"oocyst rupture protein 2","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1242800","name":null,"product":"oocyst rupture protein 2, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"ORP2","evaluation":null}