{"gene":"PF3D7_1031000","run_date":"2026-09-08T12:51:28","timeline":{"discoveries":[{"year":2001,"finding":"P25 (Pbs25) of Plasmodium berghei is required for protection of ookinetes against lethal factors (including protease attack) in the mosquito midgut, and for efficient traversal of the midgut epithelium and transformation into oocysts. Single knockout of P25 causes only mild reduction in ookinete/oocyst development, while double knockout of P25 and P28 causes severe impairment, demonstrating that P25 and P28 are partially redundant in these functions.","method":"Single and double gene knockout in P. berghei, mosquito infection assays, phenotypic analysis of ookinete/oocyst development","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic knockouts with defined cellular phenotypes, replicated across single and double KO conditions in a rigorous study","pmids":["11483501"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2001,"finding":"P25 (Pbs25) of Plasmodium berghei physically interacts with Anopheles gambiae laminin gamma 1 polypeptide, as demonstrated by yeast two-hybrid and confirmed by in vitro binding of purified fusion proteins, suggesting a receptor/ligand function during parasite development in the mosquito midgut. Laminin gamma 1 also interacts with P28, but more weakly.","method":"Yeast two-hybrid system; in vitro binding assay with purified fusion proteins","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (yeast two-hybrid and in vitro pulldown), single lab","pmids":["11223130"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2000,"finding":"P25 (Pbs25) of Plasmodium berghei is capable of homodimerisation and of forming heterodimers with Pbs21 (P28), as demonstrated by yeast two-hybrid. In vitro co-culture experiments show that double knockout ookinetes lacking both Pbs21 and Pbs25 have substantially reduced transformation into oocysts, while motility and cell entry are normal.","method":"Yeast two-hybrid; in vitro co-culture of ookinetes with insect cell lines","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid for dimerisation, in vitro functional assay for oocyst transformation, single lab","pmids":["10984433"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2000,"finding":"P25 (Pbs25) of Plasmodium berghei is anchored to the parasite surface via a GPI anchor, as determined by biochemical analysis of the protein.","method":"Biochemical analysis (GPI anchor detection)","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical demonstration of GPI anchor, single lab single method","pmids":["10989152"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2005,"finding":"The crystal structure of P25 from Plasmodium vivax (Pvs25) reveals a triangular prism shape composed of four EGF-like domains, and a cocrystal with a transmission-blocking antibody shows the antibody uses only its heavy chain to bind Pvs25 at a vertex of the triangle. The residues forming the triangle are conserved in P25 and P28 across all Plasmodium species, suggesting this geometry is relevant for surface tiling.","method":"X-ray crystallography; cocrystal structure with transmission-blocking antibody","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure with functional antibody cocrystal, rigorous structural validation","pmids":["16327807"],"is_preprint":false,"attribution":[{"species":"Plasmodium vivax","strain":""}]},{"year":2017,"finding":"Six crystal structures of P25 (Pfs25) from Plasmodium falciparum in complex with inhibitory antibodies reveal two distinct immunogenic sites on Pfs25; antibodies targeting these non-overlapping sites can additively increase parasite inhibition. Structural data also inform on the natural disposition of Pfs25 on the ookinete surface.","method":"X-ray crystallography of Pfs25–antibody complexes; functional transmission-blocking assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple crystal structures with functional validation, multiple orthogonal methods in a single rigorous study","pmids":["29146922"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"P25 (Pvs25) of Plasmodium vivax interacts specifically with calreticulin on the apical surface of Anopheles albimanus midgut microvilli, as demonstrated by blot overlay assay (Pvs25 but not Pvs28 bound the 50 kDa protein), mass spectrometry identification, immunofluorescence localization of calreticulin, cDNA cloning, and co-immunoprecipitation of recombinant proteins.","method":"Blot overlay assay, LC-MS identification, immunofluorescence, cDNA cloning, co-immunoprecipitation","journal":"Molecular and biochemical parasitology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (overlay, MS, IF, co-IP) in a single study demonstrating specific P25–calreticulin interaction","pmids":["17442413"],"is_preprint":false,"attribution":[{"species":"Plasmodium vivax","strain":""}]},{"year":2006,"finding":"3' gene-flanking sequences of Pfs25 (P25) from Plasmodium falciparum are required for protein expression; transient transfection deletion experiments show that elements necessary for expression are within 315 nucleotides of the stop codon, a T-rich region 137–231 nt from the stop codon is required, and a nonamer (AATAAAATG) at 360 nt downstream enhances expression by 51%. Multiple polyadenylation sites were identified by 3' RACE.","method":"Transient gene transfection with deletion constructs; 3' RACE analysis","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional deletion mapping with multiple constructs and orthogonal RACE analysis, single lab","pmids":["16439031"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"finding":"P25 (Pbs25) of Plasmodium berghei is released onto solid substrate surfaces during ookinete gliding motility, indicating that the protein is shed from the ookinete surface as a trail during gliding locomotion.","method":"Direct observation and protein detection on gliding trails from P. berghei ookinetes on solid substrates","journal":"The Journal of parasitology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single method, limited mechanistic follow-up","pmids":["19747017"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2017,"finding":"The eleven disulfide bonds of recombinant Pfs25 (P25 of Plasmodium falciparum) were mapped by LC-MS/MS, confirming correct disulfide pairing that matched the predicted structure based on the Pvs25 crystal structure.","method":"LC tandem-mass spectrometry; trypsin/Lys-C digestion; reversed phase HPLC peptide mapping; MSE fragmentation","journal":"Analytical biochemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct biochemical determination of disulfide bond architecture by MS, single lab","pmids":["29162427"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"Ookinetes of Plasmodium berghei lacking both P25 and P28 (double knockout) fail to trigger the characteristic SRPN10 serpin redistribution and overexpression response in invaded midgut epithelial cells, demonstrating that P25 (and/or P28) surface proteins are required to elicit the host cell 'time bomb' response during epithelial invasion.","method":"Genetic knockout parasites (double KO P25/P28) combined with immunofluorescence and quantitative analysis of SRPN10 distribution in mosquito midgut cells","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean double KO with defined cellular readout, single lab, but finding is attributed jointly to P25 and P28","pmids":["15659062"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]}],"current_model":"P25 (PF3D7_1031000/Pfs25) is a GPI-anchored, four-EGF-domain surface protein expressed on zygotes and ookinetes that adopts a triangular prism structure, protects ookinetes from proteolytic degradation in the mosquito midgut, facilitates epithelial traversal and oocyst transformation (functions partially redundant with its paralog P28), forms homodimers and heterodimers with P28, and engages mosquito midgut ligands including laminin gamma 1 and calreticulin through direct protein–protein interactions; its expression is regulated by defined 3′ cis elements, it is shed onto gliding trails during ookinete motility, and its eleven disulfide bonds have been biochemically confirmed to match the Pvs25 crystal structure."},"narrative":{"mechanistic_narrative":"P25 (PF3D7_1031000) is a GPI-anchored surface protein expressed on zygotes and ookinetes that protects the parasite during its developmental passage through the mosquito midgut and promotes its transformation into oocysts [PMID:11483501, PMID:10989152]. In P. berghei, single knockout of P25 causes only mild defects, whereas simultaneous loss of P25 and its paralog P28 severely impairs ookinete survival against midgut lethal factors including proteases, epithelial traversal, and oocyst formation, establishing that the two proteins act redundantly in these functions [PMID:11483501]. P25 mediates parasite–vector interactions through direct binding to mosquito midgut ligands: in P. berghei it engages Anopheles gambiae laminin gamma 1 [PMID:11223130], and in P. vivax it binds calreticulin on the apical surface of Anopheles albimanus midgut microvilli [PMID:17442413]. P25 can homodimerize and form heterodimers with P28 [PMID:10984433], and loss of both proteins abolishes the SRPN10 serpin 'time bomb' response in invaded midgut epithelial cells [PMID:15659062]. Structurally, the P. vivax ortholog Pvs25 adopts a triangular prism built from four EGF-like domains whose triangle-forming residues are conserved across P25/P28 orthologs, consistent with surface tiling [PMID:16327807]; the eleven disulfide bonds of P. falciparum Pfs25 have been mapped by mass spectrometry and match this architecture [PMID:29162427]. As a leading transmission-blocking vaccine target, P. falciparum P25 presents at least two non-overlapping immunogenic sites whose antibodies additively inhibit parasites [PMID:29146922]. Expression of P. falciparum P25 depends on defined 3′ cis-regulatory elements within ~315 nt of the stop codon [PMID:16439031].","teleology":[{"year":2000,"claim":"Establishing where P25 resides and how it oligomerizes was needed to define it as a surface effector; biochemistry showed GPI anchoring and yeast two-hybrid revealed homo- and heterodimerization with P28, linking the two paralogs physically.","evidence":"GPI anchor biochemical analysis and yeast two-hybrid dimerization assays with in vitro ookinete co-culture in P. berghei","pmids":["10989152","10984433"],"confidence":"Medium","gaps":["Dimerization shown only by yeast two-hybrid, not confirmed on the native ookinete surface","Functional consequence of dimerization not dissected"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2001,"claim":"Whether P25 has a genetically defined role in mosquito-stage development, and whether it acts alone, was resolved by single and double knockouts showing partial redundancy with P28 in protecting ookinetes and enabling midgut traversal and oocyst formation.","evidence":"Single and double gene knockout in P. berghei with mosquito infection and ookinete/oocyst phenotyping","pmids":["11483501"],"confidence":"High","gaps":["Molecular basis of protection against midgut proteases not defined","Individual contribution of P25 versus P28 not separable due to redundancy"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2001,"claim":"To assign a receptor/ligand role, P25 was tested against mosquito proteins, revealing a specific interaction with Anopheles gambiae laminin gamma 1 stronger than that of P28.","evidence":"Yeast two-hybrid and in vitro binding of purified fusion proteins in P. berghei","pmids":["11223130"],"confidence":"Medium","gaps":["In vivo relevance of the laminin interaction to midgut traversal not demonstrated","Binding interface not mapped"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2005,"claim":"The link between P25/P28 surface proteins and the host midgut defensive response was addressed by showing double-knockout ookinetes fail to trigger SRPN10 serpin redistribution, connecting the parasite surface to epithelial 'time bomb' signaling.","evidence":"Double KO P25/P28 parasites with immunofluorescence and quantitation of SRPN10 in P. berghei midgut cells","pmids":["15659062"],"confidence":"Medium","gaps":["Response attributed jointly to P25 and P28, not to P25 alone","Mechanism linking surface protein to serpin induction unknown"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2005,"claim":"The three-dimensional architecture underlying P25 function and antibody recognition was defined by the Pvs25 crystal structure, revealing a four-EGF triangular prism with conserved triangle residues and a heavy-chain-only antibody contact at a vertex.","evidence":"X-ray crystallography of Pvs25 alone and cocrystal with a transmission-blocking antibody in P. vivax","pmids":["16327807"],"confidence":"High","gaps":["Proposed surface tiling not directly observed on ookinetes","Structure is of the P. vivax ortholog, not PF3D7_1031000 itself"],"attribution":[{"species":"Plasmodium vivax","strain":""}]},{"year":2006,"claim":"How P25 expression is controlled at the mRNA level was mapped, identifying 3′ cis elements within ~315 nt of the stop codon, a required T-rich region, and an enhancing nonamer.","evidence":"Transient transfection deletion constructs and 3′ RACE in P. falciparum","pmids":["16439031"],"confidence":"Medium","gaps":["Trans-acting factors binding these elements not identified","Stage-specificity of regulation not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"claim":"A second midgut ligand for P25 was identified, showing Pvs25 specifically binds calreticulin on Anopheles albimanus microvillar surfaces, distinguishing it from P28.","evidence":"Blot overlay, LC-MS identification, immunofluorescence, cDNA cloning, and co-IP of recombinant proteins in P. vivax","pmids":["17442413"],"confidence":"High","gaps":["Functional role of calreticulin binding in traversal or oocyst formation not tested","Interaction demonstrated for the P. vivax ortholog"],"attribution":[{"species":"Plasmodium vivax","strain":""}]},{"year":2010,"claim":"Whether P25 is retained or shed during motility was addressed by detecting the protein on gliding trails, indicating it is deposited onto substrates during ookinete locomotion.","evidence":"Protein detection on gliding trails of P. berghei ookinetes on solid substrates","pmids":["19747017"],"confidence":"Low","gaps":["Single lab, single method with limited mechanistic follow-up","Whether shedding is functionally required for motility not tested"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2017,"claim":"For P. falciparum P25 as a vaccine antigen, the number and location of protective epitopes were defined, revealing two non-overlapping immunogenic sites whose antibodies additively inhibit transmission, and confirming the correct disulfide architecture of recombinant Pfs25.","evidence":"Six crystal structures of Pfs25–antibody complexes with transmission-blocking assays, and LC-MS/MS mapping of eleven disulfide bonds in P. falciparum","pmids":["29146922","29162427"],"confidence":"High","gaps":["Native surface disposition inferred rather than directly imaged","Relationship of epitope sites to endogenous mosquito-ligand binding not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"The precise molecular mechanism by which P25 binding to laminin gamma 1 and calreticulin drives midgut traversal, protease protection, and oocyst transformation—and how these functions are partitioned from the redundant paralog P28—remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of P25 bound to a mosquito ligand","Individual, non-redundant function of P25 versus P28 not separated","Causal link between ligand binding and specific developmental phenotypes untested"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["P25 homodimer","P25-P28 heterodimer"],"partners":["P28 (PARALOG; HETERODIMER PARTNER AND REDUNDANT PARTNER)","ANOPHELES GAMBIAE LAMININ GAMMA 1","ANOPHELES ALBIMANUS CALRETICULIN (P. VIVAX ORTHOLOG)"],"other_free_text":["GPI-anchored ookinete/zygote surface protein composed of four EGF-like domains forming a triangular prism (ortholog structure)","Eleven disulfide bonds mapped in recombinant P. falciparum Pfs25, matching the Pvs25 crystal structure","Loss of P25 together with P28 abolishes SRPN10 serpin redistribution in invaded mosquito midgut epithelial cells","Expression depends on 3' cis-regulatory elements within ~315 nt of the stop codon, including a required T-rich region and an enhancing nonamer","Leading transmission-blocking vaccine target with two non-overlapping immunogenic sites","Shed onto gliding trails during ookinete motility (Low confidence)"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"18612426","id":"PMC_18612426","title":"Phase 1 trial of malaria transmission blocking vaccine candidates Pfs25 and Pvs25 formulated with montanide ISA 51.","date":"2008","source":"PloS 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modeling","url":"https://pubmed.ncbi.nlm.nih.gov/19057932","citation_count":3,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["P25"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":22411,"output_tokens":2935,"usd":0.055629,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8604,"output_tokens":3870,"usd":0.069885,"stage2_stop_reason":"end_turn"},"total_usd":0.125514,"stage1_batch_id":"msgbatch_01DisAaTypwmC8QwdMBuePHo","stage2_batch_id":"msgbatch_0184zxZTqxiEfdYYfPMfkqjb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"P25 (Pbs25) of Plasmodium berghei is required for protection of ookinetes against lethal factors (including protease attack) in the mosquito midgut, and for efficient traversal of the midgut epithelium and transformation into oocysts. Single knockout of P25 causes only mild reduction in ookinete/oocyst development, while double knockout of P25 and P28 causes severe impairment, demonstrating that P25 and P28 are partially redundant in these functions.\",\n      \"method\": \"Single and double gene knockout in P. berghei, mosquito infection assays, phenotypic analysis of ookinete/oocyst development\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic knockouts with defined cellular phenotypes, replicated across single and double KO conditions in a rigorous study\",\n      \"pmids\": [\"11483501\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"P25 (Pbs25) of Plasmodium berghei physically interacts with Anopheles gambiae laminin gamma 1 polypeptide, as demonstrated by yeast two-hybrid and confirmed by in vitro binding of purified fusion proteins, suggesting a receptor/ligand function during parasite development in the mosquito midgut. Laminin gamma 1 also interacts with P28, but more weakly.\",\n      \"method\": \"Yeast two-hybrid system; in vitro binding assay with purified fusion proteins\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (yeast two-hybrid and in vitro pulldown), single lab\",\n      \"pmids\": [\"11223130\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"P25 (Pbs25) of Plasmodium berghei is capable of homodimerisation and of forming heterodimers with Pbs21 (P28), as demonstrated by yeast two-hybrid. In vitro co-culture experiments show that double knockout ookinetes lacking both Pbs21 and Pbs25 have substantially reduced transformation into oocysts, while motility and cell entry are normal.\",\n      \"method\": \"Yeast two-hybrid; in vitro co-culture of ookinetes with insect cell lines\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid for dimerisation, in vitro functional assay for oocyst transformation, single lab\",\n      \"pmids\": [\"10984433\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"P25 (Pbs25) of Plasmodium berghei is anchored to the parasite surface via a GPI anchor, as determined by biochemical analysis of the protein.\",\n      \"method\": \"Biochemical analysis (GPI anchor detection)\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical demonstration of GPI anchor, single lab single method\",\n      \"pmids\": [\"10989152\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The crystal structure of P25 from Plasmodium vivax (Pvs25) reveals a triangular prism shape composed of four EGF-like domains, and a cocrystal with a transmission-blocking antibody shows the antibody uses only its heavy chain to bind Pvs25 at a vertex of the triangle. The residues forming the triangle are conserved in P25 and P28 across all Plasmodium species, suggesting this geometry is relevant for surface tiling.\",\n      \"method\": \"X-ray crystallography; cocrystal structure with transmission-blocking antibody\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure with functional antibody cocrystal, rigorous structural validation\",\n      \"pmids\": [\"16327807\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium vivax\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Six crystal structures of P25 (Pfs25) from Plasmodium falciparum in complex with inhibitory antibodies reveal two distinct immunogenic sites on Pfs25; antibodies targeting these non-overlapping sites can additively increase parasite inhibition. Structural data also inform on the natural disposition of Pfs25 on the ookinete surface.\",\n      \"method\": \"X-ray crystallography of Pfs25–antibody complexes; functional transmission-blocking assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple crystal structures with functional validation, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"29146922\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"P25 (Pvs25) of Plasmodium vivax interacts specifically with calreticulin on the apical surface of Anopheles albimanus midgut microvilli, as demonstrated by blot overlay assay (Pvs25 but not Pvs28 bound the 50 kDa protein), mass spectrometry identification, immunofluorescence localization of calreticulin, cDNA cloning, and co-immunoprecipitation of recombinant proteins.\",\n      \"method\": \"Blot overlay assay, LC-MS identification, immunofluorescence, cDNA cloning, co-immunoprecipitation\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (overlay, MS, IF, co-IP) in a single study demonstrating specific P25–calreticulin interaction\",\n      \"pmids\": [\"17442413\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium vivax\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"3' gene-flanking sequences of Pfs25 (P25) from Plasmodium falciparum are required for protein expression; transient transfection deletion experiments show that elements necessary for expression are within 315 nucleotides of the stop codon, a T-rich region 137–231 nt from the stop codon is required, and a nonamer (AATAAAATG) at 360 nt downstream enhances expression by 51%. Multiple polyadenylation sites were identified by 3' RACE.\",\n      \"method\": \"Transient gene transfection with deletion constructs; 3' RACE analysis\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional deletion mapping with multiple constructs and orthogonal RACE analysis, single lab\",\n      \"pmids\": [\"16439031\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"P25 (Pbs25) of Plasmodium berghei is released onto solid substrate surfaces during ookinete gliding motility, indicating that the protein is shed from the ookinete surface as a trail during gliding locomotion.\",\n      \"method\": \"Direct observation and protein detection on gliding trails from P. berghei ookinetes on solid substrates\",\n      \"journal\": \"The Journal of parasitology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single method, limited mechanistic follow-up\",\n      \"pmids\": [\"19747017\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The eleven disulfide bonds of recombinant Pfs25 (P25 of Plasmodium falciparum) were mapped by LC-MS/MS, confirming correct disulfide pairing that matched the predicted structure based on the Pvs25 crystal structure.\",\n      \"method\": \"LC tandem-mass spectrometry; trypsin/Lys-C digestion; reversed phase HPLC peptide mapping; MSE fragmentation\",\n      \"journal\": \"Analytical biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct biochemical determination of disulfide bond architecture by MS, single lab\",\n      \"pmids\": [\"29162427\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Ookinetes of Plasmodium berghei lacking both P25 and P28 (double knockout) fail to trigger the characteristic SRPN10 serpin redistribution and overexpression response in invaded midgut epithelial cells, demonstrating that P25 (and/or P28) surface proteins are required to elicit the host cell 'time bomb' response during epithelial invasion.\",\n      \"method\": \"Genetic knockout parasites (double KO P25/P28) combined with immunofluorescence and quantitative analysis of SRPN10 distribution in mosquito midgut cells\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean double KO with defined cellular readout, single lab, but finding is attributed jointly to P25 and P28\",\n      \"pmids\": [\"15659062\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"P25 (PF3D7_1031000/Pfs25) is a GPI-anchored, four-EGF-domain surface protein expressed on zygotes and ookinetes that adopts a triangular prism structure, protects ookinetes from proteolytic degradation in the mosquito midgut, facilitates epithelial traversal and oocyst transformation (functions partially redundant with its paralog P28), forms homodimers and heterodimers with P28, and engages mosquito midgut ligands including laminin gamma 1 and calreticulin through direct protein–protein interactions; its expression is regulated by defined 3′ cis elements, it is shed onto gliding trails during ookinete motility, and its eleven disulfide bonds have been biochemically confirmed to match the Pvs25 crystal structure.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"P25 (PF3D7_1031000) is a GPI-anchored surface protein expressed on zygotes and ookinetes that protects the parasite during its developmental passage through the mosquito midgut and promotes its transformation into oocysts [#0, #3]. In P. berghei, single knockout of P25 causes only mild defects, whereas simultaneous loss of P25 and its paralog P28 severely impairs ookinete survival against midgut lethal factors including proteases, epithelial traversal, and oocyst formation, establishing that the two proteins act redundantly in these functions [#0]. P25 mediates parasite–vector interactions through direct binding to mosquito midgut ligands: in P. berghei it engages Anopheles gambiae laminin gamma 1 [#1], and in P. vivax it binds calreticulin on the apical surface of Anopheles albimanus midgut microvilli [#6]. P25 can homodimerize and form heterodimers with P28 [#2], and loss of both proteins abolishes the SRPN10 serpin 'time bomb' response in invaded midgut epithelial cells [#10]. Structurally, the P. vivax ortholog Pvs25 adopts a triangular prism built from four EGF-like domains whose triangle-forming residues are conserved across P25/P28 orthologs, consistent with surface tiling [#4]; the eleven disulfide bonds of P. falciparum Pfs25 have been mapped by mass spectrometry and match this architecture [#9]. As a leading transmission-blocking vaccine target, P. falciparum P25 presents at least two non-overlapping immunogenic sites whose antibodies additively inhibit parasites [#5]. Expression of P. falciparum P25 depends on defined 3′ cis-regulatory elements within ~315 nt of the stop codon [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing where P25 resides and how it oligomerizes was needed to define it as a surface effector; biochemistry showed GPI anchoring and yeast two-hybrid revealed homo- and heterodimerization with P28, linking the two paralogs physically.\",\n      \"evidence\": \"GPI anchor biochemical analysis and yeast two-hybrid dimerization assays with in vitro ookinete co-culture in P. berghei\",\n      \"pmids\": [\"10989152\", \"10984433\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Dimerization shown only by yeast two-hybrid, not confirmed on the native ookinete surface\", \"Functional consequence of dimerization not dissected\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Whether P25 has a genetically defined role in mosquito-stage development, and whether it acts alone, was resolved by single and double knockouts showing partial redundancy with P28 in protecting ookinetes and enabling midgut traversal and oocyst formation.\",\n      \"evidence\": \"Single and double gene knockout in P. berghei with mosquito infection and ookinete/oocyst phenotyping\",\n      \"pmids\": [\"11483501\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of protection against midgut proteases not defined\", \"Individual contribution of P25 versus P28 not separable due to redundancy\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"To assign a receptor/ligand role, P25 was tested against mosquito proteins, revealing a specific interaction with Anopheles gambiae laminin gamma 1 stronger than that of P28.\",\n      \"evidence\": \"Yeast two-hybrid and in vitro binding of purified fusion proteins in P. berghei\",\n      \"pmids\": [\"11223130\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of the laminin interaction to midgut traversal not demonstrated\", \"Binding interface not mapped\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"The link between P25/P28 surface proteins and the host midgut defensive response was addressed by showing double-knockout ookinetes fail to trigger SRPN10 serpin redistribution, connecting the parasite surface to epithelial 'time bomb' signaling.\",\n      \"evidence\": \"Double KO P25/P28 parasites with immunofluorescence and quantitation of SRPN10 in P. berghei midgut cells\",\n      \"pmids\": [\"15659062\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Response attributed jointly to P25 and P28, not to P25 alone\", \"Mechanism linking surface protein to serpin induction unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"The three-dimensional architecture underlying P25 function and antibody recognition was defined by the Pvs25 crystal structure, revealing a four-EGF triangular prism with conserved triangle residues and a heavy-chain-only antibody contact at a vertex.\",\n      \"evidence\": \"X-ray crystallography of Pvs25 alone and cocrystal with a transmission-blocking antibody in P. vivax\",\n      \"pmids\": [\"16327807\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Proposed surface tiling not directly observed on ookinetes\", \"Structure is of the P. vivax ortholog, not PF3D7_1031000 itself\"],\n      \"attribution\": [{\"species\": \"Plasmodium vivax\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"How P25 expression is controlled at the mRNA level was mapped, identifying 3′ cis elements within ~315 nt of the stop codon, a required T-rich region, and an enhancing nonamer.\",\n      \"evidence\": \"Transient transfection deletion constructs and 3′ RACE in P. falciparum\",\n      \"pmids\": [\"16439031\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trans-acting factors binding these elements not identified\", \"Stage-specificity of regulation not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"A second midgut ligand for P25 was identified, showing Pvs25 specifically binds calreticulin on Anopheles albimanus microvillar surfaces, distinguishing it from P28.\",\n      \"evidence\": \"Blot overlay, LC-MS identification, immunofluorescence, cDNA cloning, and co-IP of recombinant proteins in P. vivax\",\n      \"pmids\": [\"17442413\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role of calreticulin binding in traversal or oocyst formation not tested\", \"Interaction demonstrated for the P. vivax ortholog\"],\n      \"attribution\": [{\"species\": \"Plasmodium vivax\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Whether P25 is retained or shed during motility was addressed by detecting the protein on gliding trails, indicating it is deposited onto substrates during ookinete locomotion.\",\n      \"evidence\": \"Protein detection on gliding trails of P. berghei ookinetes on solid substrates\",\n      \"pmids\": [\"19747017\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single lab, single method with limited mechanistic follow-up\", \"Whether shedding is functionally required for motility not tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"For P. falciparum P25 as a vaccine antigen, the number and location of protective epitopes were defined, revealing two non-overlapping immunogenic sites whose antibodies additively inhibit transmission, and confirming the correct disulfide architecture of recombinant Pfs25.\",\n      \"evidence\": \"Six crystal structures of Pfs25–antibody complexes with transmission-blocking assays, and LC-MS/MS mapping of eleven disulfide bonds in P. falciparum\",\n      \"pmids\": [\"29146922\", \"29162427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Native surface disposition inferred rather than directly imaged\", \"Relationship of epitope sites to endogenous mosquito-ligand binding not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The precise molecular mechanism by which P25 binding to laminin gamma 1 and calreticulin drives midgut traversal, protease protection, and oocyst transformation—and how these functions are partitioned from the redundant paralog P28—remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structure of P25 bound to a mosquito ligand\", \"Individual, non-redundant function of P25 versus P28 not separated\", \"Causal link between ligand binding and specific developmental phenotypes untested\"],\n      \"attribution\": []\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005102\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"GO:0042803\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0009986\", \"supporting_discovery_ids\": [3, 8]},\n      {\"term_id\": \"GO:0046658\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0020035\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [0, 10]}\n    ],\n    \"complexes\": [\n      \"P25 homodimer\",\n      \"P25-P28 heterodimer\"\n    ],\n    \"partners\": [\n      \"P28 (paralog; heterodimer partner and redundant partner)\",\n      \"Anopheles gambiae laminin gamma 1\",\n      \"Anopheles albimanus calreticulin (P. vivax ortholog)\"\n    ],\n    \"other_free_text\": [\n      \"GPI-anchored ookinete/zygote surface protein composed of four EGF-like domains forming a triangular prism (ortholog structure)\",\n      \"Eleven disulfide bonds mapped in recombinant P. falciparum Pfs25, matching the Pvs25 crystal structure\",\n      \"Loss of P25 together with P28 abolishes SRPN10 serpin redistribution in invaded mosquito midgut epithelial cells\",\n      \"Expression depends on 3' cis-regulatory elements within ~315 nt of the stop codon, including a required T-rich region and an enhancing nonamer\",\n      \"Leading transmission-blocking vaccine target with two non-overlapping immunogenic sites\",\n      \"Shed onto gliding trails during ookinete motility (Low confidence)\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1031000","name":null,"product":"ookinete surface protein P25","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0515000","name":null,"product":"ookinete surface protein P25","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0615700","name":null,"product":"ookinete surface protein P25, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"P25","evaluation":null}