{"gene":"PF3D7_0102600","run_date":"2026-09-07T10:55:51","timeline":{"discoveries":[{"year":2026,"finding":"FIKK1 (PF3D7_0102600) phosphorylates VAR2CSA in vitro, and this phosphorylation increases binding of recombinant VAR2CSA to the placental receptor chondroitin sulphate A (CSA). In vitro phosphorylation assays show FIKK1 phosphorylates recombinant DBL1-3 domains of VAR2CSA on several residues including S429 and T934, previously implicated in in vitro binding and infected erythrocyte cytoadhesion to CSA.","method":"In vitro phosphorylation assay with recombinant kinase and substrate; site-specific phosphorylation mapping","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro kinase assay with recombinant FIKK1 and VAR2CSA, site-specific phosphorylation identified, functional consequence (increased CSA binding) demonstrated, single lab but multiple orthogonal methods","pmids":["42525717"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"finding":"FIKK1 (PF3D7_0102600) localizes to punctuated foci within Maurer's clefts, co-localizing with VAR2CSA, as determined by immunofluorescence assay in an inducible transgenic parasite line expressing HA-tagged FIKK1.","method":"Immunofluorescence assay (IFA) with HA-tagged FIKK1 in transgenic P. falciparum","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct localization experiment with tagged protein in transgenic parasites, single lab, single method","pmids":["42525717"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"finding":"Rapamycin-induced knockout of FIKK1 (PF3D7_0102600) reduces infected erythrocyte cytoadhesion to CSA without affecting VAR2CSA surface levels, establishing that FIKK1 kinase activity (via VAR2CSA phosphorylation) is required for full cytoadhesion to the placental receptor.","method":"Inducible (rapamycin-mediated) conditional knockout of FIKK1 followed by cytoadhesion assay to CSA","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean conditional KO with defined cellular phenotype (reduced CSA cytoadhesion), combined with in vitro phosphorylation and localization data in same study, single lab","pmids":["42525717"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"FIKK1 (PF3D7_0102600) is an exported serine/threonine kinase that localizes to Maurer's clefts in infected erythrocytes, where it phosphorylates the PfEMP1 adhesin VAR2CSA at specific residues (including S429 and T934 of the DBL1-3 domains), thereby enhancing VAR2CSA binding to the placental receptor chondroitin sulphate A and promoting infected erythrocyte cytoadhesion relevant to placental malaria pathogenesis."},"narrative":{"mechanistic_narrative":"FIKK1 (PF3D7_0102600) is an exported serine/threonine kinase of the FIKK family that modifies the placental cytoadhesion machinery of P. falciparum-infected erythrocytes [PMID:42525717]. FIKK1 directly phosphorylates the PfEMP1 variant adhesin VAR2CSA in vitro, targeting several residues in the DBL1-3 domains including S429 and T934, and this phosphorylation increases binding of recombinant VAR2CSA to the placental receptor chondroitin sulphate A (CSA) [PMID:42525717]. Within infected erythrocytes FIKK1 localizes to punctate foci in Maurer's clefts where it co-localizes with VAR2CSA, placing the kinase and its substrate in the same trafficking compartment [PMID:42525717]. Conditional knockout of FIKK1 reduces infected-erythrocyte cytoadhesion to CSA without changing VAR2CSA surface abundance, establishing that FIKK1 activity — rather than adhesin display — is required for full placental cytoadhesion [PMID:42525717]. Beyond this phosphorylation-dependent regulation of VAR2CSA-mediated CSA adhesion, no further mechanistic detail for PF3D7_0102600 has been characterized in the available corpus.","teleology":[{"year":2026,"claim":"It was unknown whether a specific FIKK-family kinase directly modifies VAR2CSA; the in vitro kinase assay showed FIKK1 phosphorylates VAR2CSA DBL1-3 at defined residues and that this modification enhances CSA binding, establishing FIKK1 as a direct regulator of adhesin receptor engagement.","evidence":"In vitro phosphorylation assay with recombinant FIKK1 and VAR2CSA plus site-specific phosphosite mapping and CSA-binding readout","pmids":["42525717"],"confidence":"High","gaps":["Whether S429/T934 phosphorylation is sufficient versus one of several required modifications is not resolved","The structural basis for how phosphorylation increases CSA affinity is not defined","In vitro phosphorylation may not fully reflect stoichiometry or kinetics in the parasite"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"claim":"The subcellular site of FIKK1 action was undefined; tagged-protein imaging placed FIKK1 in punctate Maurer's cleft foci co-localizing with VAR2CSA, providing the spatial context in which the kinase and substrate meet.","evidence":"Immunofluorescence of HA-tagged FIKK1 in an inducible transgenic P. falciparum line","pmids":["42525717"],"confidence":"Medium","gaps":["Single-method localization without orthogonal fractionation or reciprocal co-IP","Whether co-localization reflects direct physical interaction at Maurer's clefts is not shown","The trafficking route bringing FIKK1 to the clefts is uncharacterized"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"claim":"Whether FIKK1 activity is functionally required for cytoadhesion, rather than merely biochemically capable of phosphorylating VAR2CSA, was untested; conditional knockout reduced CSA cytoadhesion while leaving VAR2CSA surface levels intact, establishing a phosphorylation-dependent (not display-dependent) role in placental adhesion.","evidence":"Rapamycin-inducible conditional knockout of FIKK1 followed by CSA cytoadhesion assay","pmids":["42525717"],"confidence":"High","gaps":["Residual cytoadhesion in the knockout implies additional contributing factors not identified","Direct demonstration that the adhesion defect is caused by loss of VAR2CSA phosphorylation in vivo is not shown","In vivo relevance to placental sequestration and pathology not tested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"It remains unknown whether FIKK1 has substrates beyond VAR2CSA, how its kinase activity is regulated, and whether its adhesion role generalizes beyond CSA-mediated placental cytoadhesion.","evidence":"","pmids":[],"confidence":"Low","gaps":["No substrate repertoire beyond VAR2CSA established","No regulatory or activation mechanism for the kinase characterized","No structural model of FIKK1 or its substrate complex"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["VAR2CSA (PFEMP1 ADHESIN; SUBSTRATE AND MAURER'S CLEFT CO-LOCALIZATION PARTNER)"],"other_free_text":["FIKK1 phosphorylates VAR2CSA DBL1-3 domains at multiple sites including S429 and T934 [#0]","Phosphorylation increases recombinant VAR2CSA binding to chondroitin sulphate A [#0]","Conditional knockout reduces CSA cytoadhesion without altering VAR2CSA surface levels [#2]","Exported kinase of the FIKK family (as given in the gene definition); no substrates beyond VAR2CSA characterized in the corpus"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"15479470","id":"PMC_15479470","title":"Protein kinases of the human malaria parasite Plasmodium falciparum: the kinome of a divergent eukaryote.","date":"2004","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/15479470","citation_count":421,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17181785","id":"PMC_17181785","title":"A novel protein kinase family in Plasmodium falciparum is differentially transcribed and secreted to various cellular compartments of the host cell.","date":"2007","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/17181785","citation_count":102,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"15752424","id":"PMC_15752424","title":"A new Apicomplexa-specific protein kinase family: multiple members in Plasmodium falciparum, all with an export signature.","date":"2005","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/15752424","citation_count":91,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"20668526","id":"PMC_20668526","title":"Plasmodium falciparum FIKK kinase members target distinct components of the erythrocyte membrane.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20668526","citation_count":68,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32284562","id":"PMC_32284562","title":"An exported kinase family mediates species-specific erythrocyte remodelling and virulence in human malaria.","date":"2020","source":"Nature microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/32284562","citation_count":52,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"24530877","id":"PMC_24530877","title":"An exported kinase (FIKK4.2) that mediates virulence-associated changes in Plasmodium falciparum-infected red blood cells.","date":"2014","source":"International journal for parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/24530877","citation_count":47,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31650539","id":"PMC_31650539","title":"Identification of essential exported Plasmodium falciparum protein kinases in malaria-infected red blood cells.","date":"2019","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/31650539","citation_count":22,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"23973789","id":"PMC_23973789","title":"Dematin, a human erythrocyte cytoskeletal protein, is a substrate for a recombinant FIKK kinase from Plasmodium falciparum.","date":"2013","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/23973789","citation_count":21,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30023525","id":"PMC_30023525","title":"FIKK Kinase, a Ser/Thr Kinase Important to Malaria Parasites, Is Inhibited by Tyrosine Kinase Inhibitors.","date":"2017","source":"ACS omega","url":"https://pubmed.ncbi.nlm.nih.gov/30023525","citation_count":17,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"21112415","id":"PMC_21112415","title":"Computational identification of signalling pathways in Plasmodium falciparum.","date":"2010","source":"Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases","url":"https://pubmed.ncbi.nlm.nih.gov/21112415","citation_count":13,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"26112892","id":"PMC_26112892","title":"Biochemical characterization of FIKK8--A unique protein kinase from the malaria parasite Plasmodium falciparum and other apicomplexans.","date":"2015","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/26112892","citation_count":13,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27995998","id":"PMC_27995998","title":"A novel FIKK kinase regulates the development of mosquito and liver stages of the malaria.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27995998","citation_count":12,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"28987877","id":"PMC_28987877","title":"The anthraquinone emodin inhibits the non-exported FIKK kinase from Plasmodium falciparum.","date":"2017","source":"Bioorganic chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/28987877","citation_count":11,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33486853","id":"PMC_33486853","title":"Plasmodium falciparum FIKK9.1 is a monomeric serine-threonine protein kinase with features to exploit as a drug target.","date":"2021","source":"Chemical biology & drug design","url":"https://pubmed.ncbi.nlm.nih.gov/33486853","citation_count":9,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37655748","id":"PMC_37655748","title":"Hybrid molecules based on an emodin scaffold. Synthesis and activity against SARS-CoV-2 and Plasmodium.","date":"2023","source":"Organic & biomolecular chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/37655748","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37737226","id":"PMC_37737226","title":"PerTurboID, a targeted in situ method reveals the impact of kinase deletion on its local protein environment in the cytoadhesion complex of malaria-causing parasites.","date":"2023","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/37737226","citation_count":6,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35891792","id":"PMC_35891792","title":"Update and elucidation of Plasmodium kinomes: Prioritization of kinases as potential drug targets for malaria.","date":"2022","source":"Computational and structural biotechnology journal","url":"https://pubmed.ncbi.nlm.nih.gov/35891792","citation_count":5,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"40389650","id":"PMC_40389650","title":"The fast-evolving FIKK kinase family of Plasmodium falciparum can be inhibited by a single compound.","date":"2025","source":"Nature microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/40389650","citation_count":3,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31566726","id":"PMC_31566726","title":"Plasmodium kinase disruption: new hopes for anti-malarial drug discovery.","date":"2019","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/31566726","citation_count":2,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"39621256","id":"PMC_39621256","title":"Molecular Investigation of FIKK Kinase Family to Develop PCR-Based Diagnosis of Plasmodium falciparum.","date":"2024","source":"Molecular biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/39621256","citation_count":2,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"41238081","id":"PMC_41238081","title":"Plasmodium falciparum gene expression signatures and antibody profiling implicate the fikk, phist, and surf multigene families in severe malaria syndromes.","date":"2025","source":"The Journal of infection","url":"https://pubmed.ncbi.nlm.nih.gov/41238081","citation_count":1,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37476548","id":"PMC_37476548","title":"Plasmodium falciparum FIKK 9.1 kinase modeling to screen and identify potent antimalarial agents from chemical library.","date":"2023","source":"3 Biotech","url":"https://pubmed.ncbi.nlm.nih.gov/37476548","citation_count":1,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"34569223","id":"PMC_34569223","title":"Chemogenomic Fingerprints Associated with Stage-Specific Gametocytocidal Compound Action against Human Malaria Parasites.","date":"2021","source":"ACS infectious diseases","url":"https://pubmed.ncbi.nlm.nih.gov/34569223","citation_count":1,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"41045976","id":"PMC_41045976","title":"Antigenic determinant analysis of FIKK Kinase family to identify novel candidates for diagnosis of Plasmodium falciparum.","date":"2025","source":"Microbial pathogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/41045976","citation_count":1,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"42525717","id":"PMC_42525717","title":"FIKK1, a member of the FIKK kinase family, phosphorylates VAR2CSA and regulates adhesion of Plasmodium falciparum-infected erythrocytes to the placental receptor CSA.","date":"2026","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/42525717","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK1","FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"39727019","id":"PMC_39727019","title":"An in-silico study of FIKK9.5 protein of Plasmodium falciparum for identification of therapeutics.","date":"2024","source":"Journal of biomolecular structure & dynamics","url":"https://pubmed.ncbi.nlm.nih.gov/39727019","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["FIKK"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15319,"output_tokens":1008,"usd":0.030538,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5723,"output_tokens":2194,"usd":0.041732,"stage2_stop_reason":"end_turn"},"total_usd":0.07227,"stage1_batch_id":"msgbatch_01DbiymDmubkPpYvdbAu5a7V","stage2_batch_id":"msgbatch_012TbrWvMRH129T7PQ4SmvrJ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2026,\n      \"finding\": \"FIKK1 (PF3D7_0102600) phosphorylates VAR2CSA in vitro, and this phosphorylation increases binding of recombinant VAR2CSA to the placental receptor chondroitin sulphate A (CSA). In vitro phosphorylation assays show FIKK1 phosphorylates recombinant DBL1-3 domains of VAR2CSA on several residues including S429 and T934, previously implicated in in vitro binding and infected erythrocyte cytoadhesion to CSA.\",\n      \"method\": \"In vitro phosphorylation assay with recombinant kinase and substrate; site-specific phosphorylation mapping\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro kinase assay with recombinant FIKK1 and VAR2CSA, site-specific phosphorylation identified, functional consequence (increased CSA binding) demonstrated, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"42525717\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"FIKK1 (PF3D7_0102600) localizes to punctuated foci within Maurer's clefts, co-localizing with VAR2CSA, as determined by immunofluorescence assay in an inducible transgenic parasite line expressing HA-tagged FIKK1.\",\n      \"method\": \"Immunofluorescence assay (IFA) with HA-tagged FIKK1 in transgenic P. falciparum\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct localization experiment with tagged protein in transgenic parasites, single lab, single method\",\n      \"pmids\": [\"42525717\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Rapamycin-induced knockout of FIKK1 (PF3D7_0102600) reduces infected erythrocyte cytoadhesion to CSA without affecting VAR2CSA surface levels, establishing that FIKK1 kinase activity (via VAR2CSA phosphorylation) is required for full cytoadhesion to the placental receptor.\",\n      \"method\": \"Inducible (rapamycin-mediated) conditional knockout of FIKK1 followed by cytoadhesion assay to CSA\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean conditional KO with defined cellular phenotype (reduced CSA cytoadhesion), combined with in vitro phosphorylation and localization data in same study, single lab\",\n      \"pmids\": [\"42525717\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"FIKK1 (PF3D7_0102600) is an exported serine/threonine kinase that localizes to Maurer's clefts in infected erythrocytes, where it phosphorylates the PfEMP1 adhesin VAR2CSA at specific residues (including S429 and T934 of the DBL1-3 domains), thereby enhancing VAR2CSA binding to the placental receptor chondroitin sulphate A and promoting infected erythrocyte cytoadhesion relevant to placental malaria pathogenesis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FIKK1 (PF3D7_0102600) is an exported serine/threonine kinase of the FIKK family that modifies the placental cytoadhesion machinery of P. falciparum-infected erythrocytes [#0, #2]. FIKK1 directly phosphorylates the PfEMP1 variant adhesin VAR2CSA in vitro, targeting several residues in the DBL1-3 domains including S429 and T934, and this phosphorylation increases binding of recombinant VAR2CSA to the placental receptor chondroitin sulphate A (CSA) [#0]. Within infected erythrocytes FIKK1 localizes to punctate foci in Maurer's clefts where it co-localizes with VAR2CSA, placing the kinase and its substrate in the same trafficking compartment [#1]. Conditional knockout of FIKK1 reduces infected-erythrocyte cytoadhesion to CSA without changing VAR2CSA surface abundance, establishing that FIKK1 activity — rather than adhesin display — is required for full placental cytoadhesion [#2]. Beyond this phosphorylation-dependent regulation of VAR2CSA-mediated CSA adhesion, no further mechanistic detail for PF3D7_0102600 has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2026,\n      \"claim\": \"It was unknown whether a specific FIKK-family kinase directly modifies VAR2CSA; the in vitro kinase assay showed FIKK1 phosphorylates VAR2CSA DBL1-3 at defined residues and that this modification enhances CSA binding, establishing FIKK1 as a direct regulator of adhesin receptor engagement.\",\n      \"evidence\": \"In vitro phosphorylation assay with recombinant FIKK1 and VAR2CSA plus site-specific phosphosite mapping and CSA-binding readout\",\n      \"pmids\": [\"42525717\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether S429/T934 phosphorylation is sufficient versus one of several required modifications is not resolved\",\n        \"The structural basis for how phosphorylation increases CSA affinity is not defined\",\n        \"In vitro phosphorylation may not fully reflect stoichiometry or kinetics in the parasite\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"The subcellular site of FIKK1 action was undefined; tagged-protein imaging placed FIKK1 in punctate Maurer's cleft foci co-localizing with VAR2CSA, providing the spatial context in which the kinase and substrate meet.\",\n      \"evidence\": \"Immunofluorescence of HA-tagged FIKK1 in an inducible transgenic P. falciparum line\",\n      \"pmids\": [\"42525717\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-method localization without orthogonal fractionation or reciprocal co-IP\",\n        \"Whether co-localization reflects direct physical interaction at Maurer's clefts is not shown\",\n        \"The trafficking route bringing FIKK1 to the clefts is uncharacterized\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Whether FIKK1 activity is functionally required for cytoadhesion, rather than merely biochemically capable of phosphorylating VAR2CSA, was untested; conditional knockout reduced CSA cytoadhesion while leaving VAR2CSA surface levels intact, establishing a phosphorylation-dependent (not display-dependent) role in placental adhesion.\",\n      \"evidence\": \"Rapamycin-inducible conditional knockout of FIKK1 followed by CSA cytoadhesion assay\",\n      \"pmids\": [\"42525717\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Residual cytoadhesion in the knockout implies additional contributing factors not identified\",\n        \"Direct demonstration that the adhesion defect is caused by loss of VAR2CSA phosphorylation in vivo is not shown\",\n        \"In vivo relevance to placental sequestration and pathology not tested\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown whether FIKK1 has substrates beyond VAR2CSA, how its kinase activity is regulated, and whether its adhesion role generalizes beyond CSA-mediated placental cytoadhesion.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No substrate repertoire beyond VAR2CSA established\",\n        \"No regulatory or activation mechanism for the kinase characterized\",\n        \"No structural model of FIKK1 or its substrate complex\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004674\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0006468\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020030\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0007155\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"VAR2CSA (PfEMP1 adhesin; substrate and Maurer's cleft co-localization partner)\"],\n    \"other_free_text\": [\n      \"FIKK1 phosphorylates VAR2CSA DBL1-3 domains at multiple sites including S429 and T934 [#0]\",\n      \"Phosphorylation increases recombinant VAR2CSA binding to chondroitin sulphate A [#0]\",\n      \"Conditional knockout reduces CSA cytoadhesion without altering VAR2CSA surface levels [#2]\",\n      \"Exported kinase of the FIKK family (as given in the gene definition); no substrates beyond VAR2CSA characterized in the corpus\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0102600","name":null,"product":"serine/threonine protein kinase, FIKK family","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"FIKK1","evaluation":null}