{"gene":"PF3D7_1136500","run_date":"2026-09-08T12:51:28","timeline":{"discoveries":[{"year":1997,"finding":"P. falciparum CK1 (PF3D7_1136500) was cloned, expressed as a recombinant protein in bacteria, and shown to exhibit CK1-characteristic enzymatic activity: it phosphorylates a CK1-specific peptide substrate, is inhibited by CK1-7, and strongly prefers ATP over GTP. Mutagenesis of the recombinant enzyme defined amino acid residues important for enzyme conformation and activity. The endogenous casein kinase activity, partially purified from P. falciparum soluble extracts by affinity chromatography, displayed identical properties. Stage-specific expression was demonstrated at the protein activity level: trophozoite > ring >> schizont.","method":"Recombinant expression in bacteria, in vitro kinase assay with specific peptide substrate, inhibitor (CK1-7) sensitivity assay, ATP vs GTP preference assay, site-directed mutagenesis, affinity chromatography purification from parasite extracts, Northern blot for mRNA stage expression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — recombinant expression with in vitro enzymatic assay, active-site mutagenesis, and corroborated by native enzyme purification from parasite; multiple orthogonal methods in one rigorous study","pmids":["9334178"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2000,"finding":"CK1 from P. falciparum was identified as a principal binding protein recovered by affinity chromatography on purvalanol B (a CDK inhibitor)-immobilised agarose matrix from parasite extracts, identifying CK1 as an intracellular target of 2,6,9-trisubstituted purine compounds in P. falciparum.","method":"Affinity chromatography using immobilised purvalanol B on agarose; protein identification from parasite cell extracts","journal":"Chemistry & biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single affinity pulldown method, but result was consistent across multiple parasite species and is biologically coherent with enzymatic data from other studies","pmids":["10873834"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"Using parasite lines expressing GFP- or His-tagged PfCK1 from the endogenous locus, CK1 was shown to have dynamic subcellular localisation during the asexual cycle: in early infection a pool localises to the host erythrocyte membrane, followed by predominantly intra-parasite localisation in trophozoites and schizonts, and association with micronemes in merozoites. A pool of enzymatically active PfCK1 is secreted into the culture supernatant (ectokinase). The pfck1 gene could not be disrupted, indicating essentiality for intra-erythrocytic asexual proliferation. Interactome experiments and in vitro kinase assays with recombinant PfCK1 phosphorylating putative interactors implicated CK1 in mRNA splicing, protein trafficking, ribosomal processes, and host cell invasion.","method":"Endogenous locus GFP/His-tag knock-in, immunofluorescence analysis, reverse genetics (gene disruption attempt), culture supernatant kinase assay (ectokinase activity), co-immunoprecipitation interactome, in vitro kinase assay with recombinant PfCK1 and putative interactors","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — endogenous tagging with IFA localization, reverse genetics essentiality, secretion confirmed by enzymatic activity in supernatant, and interactome validated by in vitro kinase assay; multiple orthogonal methods","pmids":["26629826"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"PfRab5B was shown to mediate trafficking of CK1 to the plasma membrane of P. falciparum-infected erythrocytes. Reverse genetics showed PbRab5B could not be deleted from asexual P. berghei, and PbRab5A or PbRab5C failed to complement PbRab5B loss, indicating non-overlapping roles; PfRab5B was implicated specifically in trafficking CK1 to the host plasma membrane.","method":"Transgenic parasite expression, GFP fusion localisation, reverse genetics (gene deletion attempt in P. berghei), complementation assay, immunofluorescence, immuno-electron microscopy","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single lab, multiple genetic and imaging methods establishing Rab5B-dependent trafficking of CK1; CK1-specific conclusion is secondary to the main Rab5B study","pmids":["24498355"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2020,"finding":"Co-purification experiments identified two host RBC proteins — GAPVD1 (GTPase-activating protein and Vps9 domain-containing protein 1) and Sorting nexin 22 — as consistent co-purifying partners of PfCK1, suggesting CK1 uses host membrane-trafficking machinery (a protein recycling pathway) to reach the RBC membrane. Reciprocal immunoprecipitation with GAPVD1 also identified parasite proteins consistent with this pathway.","method":"Co-purification (pulldown) from parasite-infected RBCs, reciprocal immunoprecipitation, mass spectrometry identification of interactors","journal":"IUBMB life","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, co-purification without functional validation of the trafficking interaction; mechanistic conclusion is proposed but not directly demonstrated","pmids":["32356940"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"A homology model of P. falciparum CK1 was generated and subjected to molecular dynamics simulations and docking, revealing that ATP binds the active site via a glycine-rich motif (G16-X-G18-X-X-G21) and conserved residues, and that the apo and ATP-bound forms differ in global dynamics. The catalytic domain topology is conserved with CK1 domains of other eukaryotes, though loop lengths and locations differ.","method":"Computational homology modelling, molecular docking, molecular dynamics (MD) simulation, MM/PBSA binding free energy estimation, principal component analysis","journal":"Journal of molecular graphics & modelling","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational prediction only, no experimental validation of the structural or mechanistic claims","pmids":["27923179"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]}],"current_model":"P. falciparum CK1 (PF3D7_1136500) is an essential, catalytically active serine/threonine kinase that preferentially uses ATP, phosphorylates CK1-specific substrates, is inhibited by CK1-7 and purvalanol B, shows stage-specific activity (trophozoite > ring >> schizont), dynamically localises from the host erythrocyte membrane in early infection to intra-parasite compartments in trophozoites/schizonts and micronemes in merozoites, is secreted extracellularly as an active ectokinase, and is trafficked to the host plasma membrane via a PfRab5B-dependent pathway; interactome and in vitro phosphorylation data implicate it in mRNA splicing, protein trafficking, ribosomal function, and host cell invasion."},"narrative":{"mechanistic_narrative":"PF3D7_1136500 (CK1) is an essential, catalytically active serine/threonine protein kinase of the intraerythrocytic asexual cycle of Plasmodium falciparum [PMID:9334178, PMID:26629826]. The recombinant and native enzyme display canonical CK1 biochemistry: phosphorylation of a CK1-specific peptide substrate, strong preference for ATP over GTP, and inhibition by CK1-7, with active-site residues defined by mutagenesis [PMID:9334178]. Enzymatic activity is stage-dependent, peaking in trophozoites (trophozoite > ring >> schizont) [PMID:9334178]. CK1 shows dynamic subcellular distribution across the asexual cycle — a pool at the host erythrocyte membrane in early infection, predominantly intra-parasite localisation in trophozoites and schizonts, and association with micronemes in merozoites — and a catalytically active pool is secreted into the culture supernatant as an ectokinase [PMID:26629826]. Trafficking of CK1 to the infected-erythrocyte plasma membrane is mediated by PfRab5B [PMID:24498355]. The gene could not be disrupted, indicating essentiality for asexual proliferation, and interactome plus in vitro phosphorylation data implicate CK1 in mRNA splicing, protein trafficking, ribosomal processes, and host cell invasion [PMID:26629826]. CK1 is also an intracellular binding target of trisubstituted purine compounds such as purvalanol B [PMID:10873834]. Beyond these findings, the direct substrates that account for its cellular roles have not been defined in the available corpus.","teleology":[{"year":1997,"claim":"Establishing whether the P. falciparum CK1 gene encodes a functional kinase resolved that it is a genuine, catalytically active CK1-family enzyme with defined substrate and cofactor preferences rather than a predicted ORF.","evidence":"Bacterial recombinant expression with in vitro peptide kinase assay, CK1-7 inhibition, ATP-vs-GTP preference, active-site mutagenesis, and corroboration by native enzyme purified from parasite extracts; Northern blot for stage expression","pmids":["9334178"],"confidence":"High","gaps":["physiological substrates in the parasite not identified","no structural determination of the active site","stage regulation shown at activity level but mechanism of regulation unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2000,"claim":"Identifying CK1 as a purvalanol B-binding protein established it as an intracellular target of trisubstituted purine compounds in the parasite, relevant to small-molecule targeting.","evidence":"Affinity chromatography on immobilised purvalanol B from parasite extracts with protein identification","pmids":["10873834"],"confidence":"Medium","gaps":["binding not shown to inhibit CK1 catalytic activity","single pulldown method without orthogonal confirmation of direct binding"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"Determining how CK1 reaches the host cell surface showed that PfRab5B mediates its trafficking to the infected-erythrocyte plasma membrane, linking CK1 export to a specific vesicular pathway.","evidence":"Transgenic GFP-fusion localisation, immuno-electron microscopy, and reverse-genetics deletion/complementation of Rab5 paralogs in P. berghei","pmids":["24498355"],"confidence":"Medium","gaps":["CK1-specific trafficking conclusion secondary to the main Rab5B study","direct interaction between CK1 and PfRab5B not demonstrated","functional consequence of surface trafficking not tested"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2015,"claim":"Endogenous tagging and reverse genetics resolved CK1's essentiality, dynamic localisation, secretion as an ectokinase, and candidate cellular processes, moving it from a biochemically characterised enzyme to a functionally contextualised one.","evidence":"Endogenous GFP/His knock-in with IFA, gene-disruption attempt, supernatant ectokinase assay, co-IP interactome, and in vitro kinase assays on putative interactors","pmids":["26629826"],"confidence":"High","gaps":["interactome-implicated roles (splicing, trafficking, ribosomal, invasion) not validated in vivo","function of the secreted ectokinase pool unknown","essentiality shown by failure to disrupt, not by conditional knockdown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"A computational structural model addressed how ATP is accommodated in the CK1 active site, predicting a glycine-rich binding motif and conformational differences between apo and ATP-bound states.","evidence":"Homology modelling, molecular docking, MD simulation, MM/PBSA binding free energy, and principal component analysis","pmids":["27923179"],"confidence":"Low","gaps":["computational prediction only, no experimental structural validation","predicted motif not tested by mutagenesis in this study"],"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2020,"claim":"Co-purification data proposed a specific route by which CK1 reaches the RBC membrane, implicating host membrane-trafficking/recycling machinery.","evidence":"Co-purification and reciprocal immunoprecipitation from parasite-infected RBCs with mass spectrometry identification of GAPVD1 and Sorting nexin 22","pmids":["32356940"],"confidence":"Low","gaps":["trafficking interaction not functionally validated","co-purification without demonstration of direct binding","single lab, single method"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"The physiological substrates and the mechanistic basis for CK1's proposed roles in splicing, trafficking, ribosomal function, and invasion remain undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["no validated in-vivo substrate identified","function of the secreted ectokinase pool at the host membrane unknown","no conditional-depletion phenotype linking activity to a specific process"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["PFRAB5B (TRAFFICKING OF CK1 TO HOST PLASMA MEMBRANE) [#3]","GAPVD1 (HOST RBC CO-PURIFYING PARTNER) [#4]","SORTING NEXIN 22 (HOST RBC CO-PURIFYING PARTNER) [#4]"],"other_free_text":["Essential for intraerythrocytic asexual proliferation; pfck1 could not be disrupted [#2]","Stage-specific activity: trophozoite > ring >> schizont [#0]","Inhibited by CK1-7 and binds purvalanol B [#0, #1]","Secreted as an active extracellular ectokinase [#2]"]}},"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":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22127061","id":"PMC_22127061","title":"Global kinomic and phospho-proteomic analyses of the human malaria parasite Plasmodium falciparum.","date":"2011","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/22127061","citation_count":288,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"10873834","id":"PMC_10873834","title":"Intracellular targets of cyclin-dependent kinase inhibitors: identification by affinity chromatography using immobilised inhibitors.","date":"2000","source":"Chemistry & biology","url":"https://pubmed.ncbi.nlm.nih.gov/10873834","citation_count":202,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CK1","casein kinase 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27923179","id":"PMC_27923179","title":"Structural dynamics of Casein Kinase I (CKI) from malarial parasite Plasmodium falciparum (Isolate 3D7): Insights from theoretical modelling and molecular simulations.","date":"2016","source":"Journal of molecular graphics & modelling","url":"https://pubmed.ncbi.nlm.nih.gov/27923179","citation_count":53,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22889911","id":"PMC_22889911","title":"An evolutionary perspective on the kinome of malaria parasites.","date":"2012","source":"Philosophical transactions of the Royal Society of London. Series B, Biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/22889911","citation_count":45,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CK1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"9334178","id":"PMC_9334178","title":"Identification, cloning, and mutational analysis of the casein kinase 1 cDNA of the malaria parasite, Plasmodium falciparum. Stage-specific expression of the gene.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9334178","citation_count":42,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CK1","casein kinase 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"24498355","id":"PMC_24498355","title":"Plasmodium falciparum Rab5B is an N-terminally myristoylated Rab GTPase that is targeted to the parasite's plasma and food vacuole membranes.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24498355","citation_count":26,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CK1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"26629826","id":"PMC_26629826","title":"Malaria Parasite-Infected Erythrocytes Secrete PfCK1, the Plasmodium Homologue of the Pleiotropic Protein Kinase Casein Kinase 1.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26629826","citation_count":25,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CK1","casein kinase 1","PfCK1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32356940","id":"PMC_32356940","title":"Interaction of Plasmodium falciparum casein kinase 1 with components of host cell protein trafficking machinery.","date":"2020","source":"IUBMB life","url":"https://pubmed.ncbi.nlm.nih.gov/32356940","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["casein kinase 1","PfCK1"],"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":["CK1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7733,"output_tokens":2216,"usd":0.02822,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7496,"output_tokens":3159,"usd":0.058228,"stage2_stop_reason":"end_turn"},"total_usd":0.086448,"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\": 1997,\n      \"finding\": \"P. falciparum CK1 (PF3D7_1136500) was cloned, expressed as a recombinant protein in bacteria, and shown to exhibit CK1-characteristic enzymatic activity: it phosphorylates a CK1-specific peptide substrate, is inhibited by CK1-7, and strongly prefers ATP over GTP. Mutagenesis of the recombinant enzyme defined amino acid residues important for enzyme conformation and activity. The endogenous casein kinase activity, partially purified from P. falciparum soluble extracts by affinity chromatography, displayed identical properties. Stage-specific expression was demonstrated at the protein activity level: trophozoite > ring >> schizont.\",\n      \"method\": \"Recombinant expression in bacteria, in vitro kinase assay with specific peptide substrate, inhibitor (CK1-7) sensitivity assay, ATP vs GTP preference assay, site-directed mutagenesis, affinity chromatography purification from parasite extracts, Northern blot for mRNA stage expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — recombinant expression with in vitro enzymatic assay, active-site mutagenesis, and corroborated by native enzyme purification from parasite; multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"9334178\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"CK1 from P. falciparum was identified as a principal binding protein recovered by affinity chromatography on purvalanol B (a CDK inhibitor)-immobilised agarose matrix from parasite extracts, identifying CK1 as an intracellular target of 2,6,9-trisubstituted purine compounds in P. falciparum.\",\n      \"method\": \"Affinity chromatography using immobilised purvalanol B on agarose; protein identification from parasite cell extracts\",\n      \"journal\": \"Chemistry & biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single affinity pulldown method, but result was consistent across multiple parasite species and is biologically coherent with enzymatic data from other studies\",\n      \"pmids\": [\"10873834\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Using parasite lines expressing GFP- or His-tagged PfCK1 from the endogenous locus, CK1 was shown to have dynamic subcellular localisation during the asexual cycle: in early infection a pool localises to the host erythrocyte membrane, followed by predominantly intra-parasite localisation in trophozoites and schizonts, and association with micronemes in merozoites. A pool of enzymatically active PfCK1 is secreted into the culture supernatant (ectokinase). The pfck1 gene could not be disrupted, indicating essentiality for intra-erythrocytic asexual proliferation. Interactome experiments and in vitro kinase assays with recombinant PfCK1 phosphorylating putative interactors implicated CK1 in mRNA splicing, protein trafficking, ribosomal processes, and host cell invasion.\",\n      \"method\": \"Endogenous locus GFP/His-tag knock-in, immunofluorescence analysis, reverse genetics (gene disruption attempt), culture supernatant kinase assay (ectokinase activity), co-immunoprecipitation interactome, in vitro kinase assay with recombinant PfCK1 and putative interactors\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — endogenous tagging with IFA localization, reverse genetics essentiality, secretion confirmed by enzymatic activity in supernatant, and interactome validated by in vitro kinase assay; multiple orthogonal methods\",\n      \"pmids\": [\"26629826\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PfRab5B was shown to mediate trafficking of CK1 to the plasma membrane of P. falciparum-infected erythrocytes. Reverse genetics showed PbRab5B could not be deleted from asexual P. berghei, and PbRab5A or PbRab5C failed to complement PbRab5B loss, indicating non-overlapping roles; PfRab5B was implicated specifically in trafficking CK1 to the host plasma membrane.\",\n      \"method\": \"Transgenic parasite expression, GFP fusion localisation, reverse genetics (gene deletion attempt in P. berghei), complementation assay, immunofluorescence, immuno-electron microscopy\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single lab, multiple genetic and imaging methods establishing Rab5B-dependent trafficking of CK1; CK1-specific conclusion is secondary to the main Rab5B study\",\n      \"pmids\": [\"24498355\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Co-purification experiments identified two host RBC proteins — GAPVD1 (GTPase-activating protein and Vps9 domain-containing protein 1) and Sorting nexin 22 — as consistent co-purifying partners of PfCK1, suggesting CK1 uses host membrane-trafficking machinery (a protein recycling pathway) to reach the RBC membrane. Reciprocal immunoprecipitation with GAPVD1 also identified parasite proteins consistent with this pathway.\",\n      \"method\": \"Co-purification (pulldown) from parasite-infected RBCs, reciprocal immunoprecipitation, mass spectrometry identification of interactors\",\n      \"journal\": \"IUBMB life\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, co-purification without functional validation of the trafficking interaction; mechanistic conclusion is proposed but not directly demonstrated\",\n      \"pmids\": [\"32356940\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A homology model of P. falciparum CK1 was generated and subjected to molecular dynamics simulations and docking, revealing that ATP binds the active site via a glycine-rich motif (G16-X-G18-X-X-G21) and conserved residues, and that the apo and ATP-bound forms differ in global dynamics. The catalytic domain topology is conserved with CK1 domains of other eukaryotes, though loop lengths and locations differ.\",\n      \"method\": \"Computational homology modelling, molecular docking, molecular dynamics (MD) simulation, MM/PBSA binding free energy estimation, principal component analysis\",\n      \"journal\": \"Journal of molecular graphics & modelling\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational prediction only, no experimental validation of the structural or mechanistic claims\",\n      \"pmids\": [\"27923179\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    }\n  ],\n  \"current_model\": \"P. falciparum CK1 (PF3D7_1136500) is an essential, catalytically active serine/threonine kinase that preferentially uses ATP, phosphorylates CK1-specific substrates, is inhibited by CK1-7 and purvalanol B, shows stage-specific activity (trophozoite > ring >> schizont), dynamically localises from the host erythrocyte membrane in early infection to intra-parasite compartments in trophozoites/schizonts and micronemes in merozoites, is secreted extracellularly as an active ectokinase, and is trafficked to the host plasma membrane via a PfRab5B-dependent pathway; interactome and in vitro phosphorylation data implicate it in mRNA splicing, protein trafficking, ribosomal function, and host cell invasion.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_1136500 (CK1) is an essential, catalytically active serine/threonine protein kinase of the intraerythrocytic asexual cycle of Plasmodium falciparum [#0, #2]. The recombinant and native enzyme display canonical CK1 biochemistry: phosphorylation of a CK1-specific peptide substrate, strong preference for ATP over GTP, and inhibition by CK1-7, with active-site residues defined by mutagenesis [#0]. Enzymatic activity is stage-dependent, peaking in trophozoites (trophozoite > ring >> schizont) [#0]. CK1 shows dynamic subcellular distribution across the asexual cycle — a pool at the host erythrocyte membrane in early infection, predominantly intra-parasite localisation in trophozoites and schizonts, and association with micronemes in merozoites — and a catalytically active pool is secreted into the culture supernatant as an ectokinase [#2]. Trafficking of CK1 to the infected-erythrocyte plasma membrane is mediated by PfRab5B [#3]. The gene could not be disrupted, indicating essentiality for asexual proliferation, and interactome plus in vitro phosphorylation data implicate CK1 in mRNA splicing, protein trafficking, ribosomal processes, and host cell invasion [#2]. CK1 is also an intracellular binding target of trisubstituted purine compounds such as purvalanol B [#1]. Beyond these findings, the direct substrates that account for its cellular roles have not been defined in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Establishing whether the P. falciparum CK1 gene encodes a functional kinase resolved that it is a genuine, catalytically active CK1-family enzyme with defined substrate and cofactor preferences rather than a predicted ORF.\",\n      \"evidence\": \"Bacterial recombinant expression with in vitro peptide kinase assay, CK1-7 inhibition, ATP-vs-GTP preference, active-site mutagenesis, and corroboration by native enzyme purified from parasite extracts; Northern blot for stage expression\",\n      \"pmids\": [\"9334178\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"physiological substrates in the parasite not identified\",\n        \"no structural determination of the active site\",\n        \"stage regulation shown at activity level but mechanism of regulation unknown\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identifying CK1 as a purvalanol B-binding protein established it as an intracellular target of trisubstituted purine compounds in the parasite, relevant to small-molecule targeting.\",\n      \"evidence\": \"Affinity chromatography on immobilised purvalanol B from parasite extracts with protein identification\",\n      \"pmids\": [\"10873834\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"binding not shown to inhibit CK1 catalytic activity\",\n        \"single pulldown method without orthogonal confirmation of direct binding\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Determining how CK1 reaches the host cell surface showed that PfRab5B mediates its trafficking to the infected-erythrocyte plasma membrane, linking CK1 export to a specific vesicular pathway.\",\n      \"evidence\": \"Transgenic GFP-fusion localisation, immuno-electron microscopy, and reverse-genetics deletion/complementation of Rab5 paralogs in P. berghei\",\n      \"pmids\": [\"24498355\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"CK1-specific trafficking conclusion secondary to the main Rab5B study\",\n        \"direct interaction between CK1 and PfRab5B not demonstrated\",\n        \"functional consequence of surface trafficking not tested\"\n      ],\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Endogenous tagging and reverse genetics resolved CK1's essentiality, dynamic localisation, secretion as an ectokinase, and candidate cellular processes, moving it from a biochemically characterised enzyme to a functionally contextualised one.\",\n      \"evidence\": \"Endogenous GFP/His knock-in with IFA, gene-disruption attempt, supernatant ectokinase assay, co-IP interactome, and in vitro kinase assays on putative interactors\",\n      \"pmids\": [\"26629826\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"interactome-implicated roles (splicing, trafficking, ribosomal, invasion) not validated in vivo\",\n        \"function of the secreted ectokinase pool unknown\",\n        \"essentiality shown by failure to disrupt, not by conditional knockdown\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"A computational structural model addressed how ATP is accommodated in the CK1 active site, predicting a glycine-rich binding motif and conformational differences between apo and ATP-bound states.\",\n      \"evidence\": \"Homology modelling, molecular docking, MD simulation, MM/PBSA binding free energy, and principal component analysis\",\n      \"pmids\": [\"27923179\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"computational prediction only, no experimental structural validation\",\n        \"predicted motif not tested by mutagenesis in this study\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Co-purification data proposed a specific route by which CK1 reaches the RBC membrane, implicating host membrane-trafficking/recycling machinery.\",\n      \"evidence\": \"Co-purification and reciprocal immunoprecipitation from parasite-infected RBCs with mass spectrometry identification of GAPVD1 and Sorting nexin 22\",\n      \"pmids\": [\"32356940\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"trafficking interaction not functionally validated\",\n        \"co-purification without demonstration of direct binding\",\n        \"single lab, single method\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The physiological substrates and the mechanistic basis for CK1's proposed roles in splicing, trafficking, ribosomal function, and invasion remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"no validated in-vivo substrate identified\",\n        \"function of the secreted ectokinase pool at the host membrane unknown\",\n        \"no conditional-depletion phenotype linking activity to a specific process\"\n      ],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004674\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0005524\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0016301\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020002\", \"supporting_discovery_ids\": [2, 3, 4]},\n      {\"term_id\": \"GO:0020009\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006397\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0015031\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PfRab5B (trafficking of CK1 to host plasma membrane) [#3]\",\n      \"GAPVD1 (host RBC co-purifying partner) [#4]\",\n      \"Sorting nexin 22 (host RBC co-purifying partner) [#4]\"\n    ],\n    \"other_free_text\": [\n      \"Essential for intraerythrocytic asexual proliferation; pfck1 could not be disrupted [#2]\",\n      \"Stage-specific activity: trophozoite > ring >> schizont [#0]\",\n      \"Inhibited by CK1-7 and binds purvalanol B [#0, #1]\",\n      \"Secreted as an active extracellular ectokinase [#2]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1136500","name":null,"product":"casein kinase 1","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0912100","name":null,"product":"casein kinase 1, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0934700","name":null,"product":"casein kinase 1, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"CK1","evaluation":null}