{"gene":"PF3D7_1315100","run_date":"2026-09-08T14:19:06","timeline":{"discoveries":[{"year":2007,"finding":"PK9 (PfPK9/PF13_0085) is catalytically active: recombinant PfPK9 autophosphorylated in vitro and phosphorylated the exogenous substrate histone H1. Autophosphorylation was mapped to three residues: T82, T265, and T269.","method":"In vitro kinase assay with recombinant protein; phosphopeptide mapping","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of kinase activity with phosphopeptide mapping, single lab but multiple orthogonal methods","pmids":["17452636"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"PK9 phosphorylates PfUBC13 (a P. falciparum E2 ubiquitin-conjugating enzyme homolog) at S106, a conserved regulatory residue among eukaryotic E2s, and this phosphorylation suppresses UBC13's ubiquitin-conjugating activity.","method":"In vitro kinase assay with recombinant proteins; phosphopeptide mapping; ubiquitin-conjugating activity assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with substrate identification, site-specific phosphorylation mapping, and functional consequence (suppression of UBC13 activity), single lab with multiple orthogonal methods","pmids":["17452636"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"PfPK9 protein expression is induced approximately 18 hours after red blood cell infection and localizes mainly to the parasitophorous vacuolar membrane and cytosol.","method":"Western blot (time-course); subcellular fractionation / immunolocalization","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiment with temporal expression data, single lab, localization not functionally linked","pmids":["17452636"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Pharmacological inhibition of PfPK9 with takinib or the Plasmodium-selective analog HS220 decreases K63-linked ubiquitination in P. falciparum cells, consistent with PfPK9 positively regulating PfUBC13-mediated K63-linkage-specific polyubiquitination in the parasite.","method":"Small-molecule inhibitor treatment (takinib, HS220) followed by K63-linked ubiquitination assay in P. falciparum culture","journal":"Cell chemical biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based inhibitor study with functional ubiquitination readout; single lab; indirect (pharmacological) inhibition rather than genetic KO","pmids":["30595530"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Inhibition of PK9 with takinib or HS220 induces a phenotype in which parasite size in hepatocytes increases, while high concentrations decrease parasite number, indicating PK9 has a role in regulating liver-stage parasite development.","method":"Pharmacological inhibition with takinib/HS220; fluorescence imaging of liver-stage parasites in hepatocytes","journal":"Cell chemical biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct imaging-based phenotypic readout after inhibitor treatment, single lab, indirect (pharmacological) approach","pmids":["30595530"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"Genetic depletion of PK9 in P. berghei does not alter UBC13 phosphorylation at S106 and does not affect parasite viability at any life cycle stage, demonstrating that PK9 is dispensable for completion of the P. berghei life cycle and that another kinase redundantly phosphorylates UBC13-S106 in this species.","method":"Genetic knockout of Pk9 in P. berghei; western blot for UBC13 S106 phosphorylation; life cycle phenotype assessment; co-localization of UBC13 and PK9 in cytosol","journal":"Microbiological research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic KO with defined molecular (phosphorylation) and life-cycle phenotype readout; single lab; directly contradicts essentiality inferred from P. falciparum pharmacological data","pmids":["35490588"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2022,"finding":"PK9 and UBC13 co-localize in the cytosol of erythrocytic and liver stages in P. berghei, confirmed by direct imaging.","method":"Co-localization imaging (fluorescence microscopy) in blood-stage and liver-stage P. berghei","journal":"Microbiological research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct co-localization imaging across two life cycle stages, single lab, no functional consequence tested beyond KO","pmids":["35490588"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]}],"current_model":"PK9 (PF3D7_1315100) is a catalytically active atypical serine/threonine kinase that autophosphorylates at T82, T265, and T269, localizes to the parasitophorous vacuolar membrane and cytosol during blood-stage infection in P. falciparum, phosphorylates the E2 ubiquitin-conjugating enzyme UBC13 at S106 to suppress its K63-linked ubiquitination activity in vitro and in P. falciparum cells, and regulates liver-stage parasite growth; however, genetic knockout in P. berghei shows PK9 is dispensable for all life cycle stages and that UBC13-S106 phosphorylation is maintained by a redundant kinase in that species."},"narrative":{"mechanistic_narrative":"PK9 (PF3D7_1315100) is a catalytically active atypical serine/threonine protein kinase of Plasmodium that couples kinase signaling to the ubiquitin-conjugation machinery during parasite development [PMID:17452636]. Recombinant PK9 autophosphorylates at T82, T265, and T269 and phosphorylates an exogenous substrate in vitro, establishing intrinsic kinase activity [PMID:17452636]. Its identified physiological substrate is the E2 ubiquitin-conjugating enzyme UBC13, which PK9 phosphorylates at the conserved regulatory residue S106 to suppress UBC13's ubiquitin-conjugating activity [PMID:17452636]; in P. falciparum cells, pharmacological inhibition of PK9 lowers K63-linked polyubiquitination and enlarges liver-stage parasites, linking PK9 activity to regulation of K63-linkage ubiquitination and liver-stage development [PMID:30595530]. In P. falciparum, PK9 is expressed from roughly 18 hours post-infection and localizes to the parasitophorous vacuolar membrane and cytosol [PMID:17452636], while in P. berghei PK9 and UBC13 co-localize in the cytosol of erythrocytic and liver stages [PMID:35490588]. Species divergence is notable: genetic knockout of PK9 in P. berghei leaves UBC13-S106 phosphorylation intact and does not affect viability at any life cycle stage, indicating PK9 is dispensable there and that a redundant kinase maintains UBC13-S106 phosphorylation in that species [PMID:35490588].","teleology":[{"year":2007,"claim":"Whether PK9 is an active enzyme was unknown; demonstrating autophosphorylation and substrate phosphorylation established it as a bona fide catalytically active kinase and mapped its autoregulatory sites.","evidence":"In vitro kinase assay with recombinant PfPK9 and histone H1, with phosphopeptide mapping to T82/T265/T269","pmids":["17452636"],"confidence":"High","gaps":["Functional consequence of the three autophosphorylation sites for activity or regulation not defined","No structural model of the kinase domain","Endogenous activation trigger unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"claim":"The physiological target of PK9 was unknown; identifying UBC13 as a substrate phosphorylated at S106 and showing this suppresses its conjugating activity connected PK9 to control of the ubiquitin system.","evidence":"In vitro kinase assay with recombinant PfPK9 and PfUBC13, phosphosite mapping to S106, and ubiquitin-conjugating activity assay","pmids":["17452636"],"confidence":"High","gaps":["In vitro suppression not yet tied to a cellular phenotype at this stage","Whether UBC13 is the sole substrate not established","Stoichiometry and kinetics of the reaction not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"claim":"The timing and site of PK9 action were unknown; a temporal expression and localization profile placed PK9 at the parasitophorous vacuolar membrane and cytosol during blood-stage infection.","evidence":"Time-course western blot and subcellular fractionation/immunolocalization in P. falciparum","pmids":["17452636"],"confidence":"Medium","gaps":["Localization not functionally linked to UBC13 phosphorylation","Mechanism of PVM targeting unknown","Single-lab observation"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"Whether PK9's in vitro effect on UBC13 translates to cellular ubiquitination and parasite biology was unknown; selective inhibitors showed PK9 activity supports K63-linked ubiquitination and liver-stage development in P. falciparum.","evidence":"Takinib/HS220 inhibitor treatment with K63-linked ubiquitination assay and fluorescence imaging of liver-stage parasites in hepatocytes","pmids":["30595530"],"confidence":"Medium","gaps":["Pharmacological rather than genetic perturbation, leaving off-target effects possible","In vitro data showed PK9 suppresses UBC13 activity while cellular inhibition decreases K63 ubiquitination, so the directionality of regulation is unresolved","Molecular link between PK9 activity and the liver-stage size/number phenotype not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"claim":"Whether PK9 is essential and the exclusive kinase for UBC13-S106 was unknown; genetic knockout in P. berghei showed PK9 is dispensable across the life cycle and that UBC13-S106 phosphorylation persists via a redundant kinase.","evidence":"Genetic knockout of Pk9 in P. berghei with western blot for UBC13-S106 phosphorylation, life-cycle phenotyping, and cytosolic co-localization imaging of UBC13 and PK9","pmids":["35490588"],"confidence":"Medium","gaps":["Identity of the redundant UBC13-S106 kinase not determined","Species divergence from P. falciparum pharmacological data unexplained","Whether P. falciparum PK9 is genetically dispensable not directly tested"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":null,"claim":"The physiological role and essentiality of PK9 across Plasmodium species remain unresolved, particularly reconciling the P. falciparum inhibitor phenotypes with dispensability in P. berghei.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No genetic loss-of-function study of PK9 in P. falciparum","Identity of the redundant UBC13-S106 kinase unknown","Upstream signals activating PK9 and the biological output of UBC13 regulation undefined"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["UBC13 (E2 UBIQUITIN-CONJUGATING ENZYME; SUBSTRATE PHOSPHORYLATED AT S106) [#1, #5, #6]"],"other_free_text":["Autophosphorylation sites mapped to T82, T265, and T269 [#0]","In P. falciparum, PK9 inhibition (takinib/HS220) reduces K63-linked ubiquitination and enlarges liver-stage parasites [#3, #4]","In P. berghei, PK9 is dispensable at all life-cycle stages and a redundant kinase maintains UBC13-S106 phosphorylation [#5]"]}},"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":"17452636","id":"PMC_17452636","title":"Characterization of a UBC13 kinase in Plasmodium falciparum.","date":"2007","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/17452636","citation_count":25,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfPK9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30595530","id":"PMC_30595530","title":"Plasmodium PK9 Inhibitors Promote Growth of Liver-Stage Parasites.","date":"2018","source":"Cell chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/30595530","citation_count":14,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PK9","PfPK9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35490588","id":"PMC_35490588","title":"Protein kinase 9 is not required for completion of the Plasmodium berghei life cycle.","date":"2022","source":"Microbiological research","url":"https://pubmed.ncbi.nlm.nih.gov/35490588","citation_count":13,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PK9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"38116430","id":"PMC_38116430","title":"Characterization of 2,4-Dianilinopyrimidines Against Five P. falciparum Kinases PfARK1, PfARK3, PfNEK3, PfPK9, and PfPKB.","date":"2023","source":"ACS medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/38116430","citation_count":5,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfPK9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":5127,"output_tokens":1905,"usd":0.021978,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7047,"output_tokens":2809,"usd":0.05273,"stage2_stop_reason":"end_turn"},"total_usd":0.074708,"stage1_batch_id":"msgbatch_011BPjN2BL33F8cJXD1r7V7T","stage2_batch_id":"msgbatch_01Qwg6vP7qxkpL6Gsc7tajsb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"PK9 (PfPK9/PF13_0085) is catalytically active: recombinant PfPK9 autophosphorylated in vitro and phosphorylated the exogenous substrate histone H1. Autophosphorylation was mapped to three residues: T82, T265, and T269.\",\n      \"method\": \"In vitro kinase assay with recombinant protein; phosphopeptide mapping\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of kinase activity with phosphopeptide mapping, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"17452636\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PK9 phosphorylates PfUBC13 (a P. falciparum E2 ubiquitin-conjugating enzyme homolog) at S106, a conserved regulatory residue among eukaryotic E2s, and this phosphorylation suppresses UBC13's ubiquitin-conjugating activity.\",\n      \"method\": \"In vitro kinase assay with recombinant proteins; phosphopeptide mapping; ubiquitin-conjugating activity assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with substrate identification, site-specific phosphorylation mapping, and functional consequence (suppression of UBC13 activity), single lab with multiple orthogonal methods\",\n      \"pmids\": [\"17452636\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PfPK9 protein expression is induced approximately 18 hours after red blood cell infection and localizes mainly to the parasitophorous vacuolar membrane and cytosol.\",\n      \"method\": \"Western blot (time-course); subcellular fractionation / immunolocalization\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiment with temporal expression data, single lab, localization not functionally linked\",\n      \"pmids\": [\"17452636\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Pharmacological inhibition of PfPK9 with takinib or the Plasmodium-selective analog HS220 decreases K63-linked ubiquitination in P. falciparum cells, consistent with PfPK9 positively regulating PfUBC13-mediated K63-linkage-specific polyubiquitination in the parasite.\",\n      \"method\": \"Small-molecule inhibitor treatment (takinib, HS220) followed by K63-linked ubiquitination assay in P. falciparum culture\",\n      \"journal\": \"Cell chemical biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based inhibitor study with functional ubiquitination readout; single lab; indirect (pharmacological) inhibition rather than genetic KO\",\n      \"pmids\": [\"30595530\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Inhibition of PK9 with takinib or HS220 induces a phenotype in which parasite size in hepatocytes increases, while high concentrations decrease parasite number, indicating PK9 has a role in regulating liver-stage parasite development.\",\n      \"method\": \"Pharmacological inhibition with takinib/HS220; fluorescence imaging of liver-stage parasites in hepatocytes\",\n      \"journal\": \"Cell chemical biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct imaging-based phenotypic readout after inhibitor treatment, single lab, indirect (pharmacological) approach\",\n      \"pmids\": [\"30595530\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Genetic depletion of PK9 in P. berghei does not alter UBC13 phosphorylation at S106 and does not affect parasite viability at any life cycle stage, demonstrating that PK9 is dispensable for completion of the P. berghei life cycle and that another kinase redundantly phosphorylates UBC13-S106 in this species.\",\n      \"method\": \"Genetic knockout of Pk9 in P. berghei; western blot for UBC13 S106 phosphorylation; life cycle phenotype assessment; co-localization of UBC13 and PK9 in cytosol\",\n      \"journal\": \"Microbiological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic KO with defined molecular (phosphorylation) and life-cycle phenotype readout; single lab; directly contradicts essentiality inferred from P. falciparum pharmacological data\",\n      \"pmids\": [\"35490588\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PK9 and UBC13 co-localize in the cytosol of erythrocytic and liver stages in P. berghei, confirmed by direct imaging.\",\n      \"method\": \"Co-localization imaging (fluorescence microscopy) in blood-stage and liver-stage P. berghei\",\n      \"journal\": \"Microbiological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct co-localization imaging across two life cycle stages, single lab, no functional consequence tested beyond KO\",\n      \"pmids\": [\"35490588\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"PK9 (PF3D7_1315100) is a catalytically active atypical serine/threonine kinase that autophosphorylates at T82, T265, and T269, localizes to the parasitophorous vacuolar membrane and cytosol during blood-stage infection in P. falciparum, phosphorylates the E2 ubiquitin-conjugating enzyme UBC13 at S106 to suppress its K63-linked ubiquitination activity in vitro and in P. falciparum cells, and regulates liver-stage parasite growth; however, genetic knockout in P. berghei shows PK9 is dispensable for all life cycle stages and that UBC13-S106 phosphorylation is maintained by a redundant kinase in that species.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PK9 (PF3D7_1315100) is a catalytically active atypical serine/threonine protein kinase of Plasmodium that couples kinase signaling to the ubiquitin-conjugation machinery during parasite development [#0, #1]. Recombinant PK9 autophosphorylates at T82, T265, and T269 and phosphorylates an exogenous substrate in vitro, establishing intrinsic kinase activity [#0]. Its identified physiological substrate is the E2 ubiquitin-conjugating enzyme UBC13, which PK9 phosphorylates at the conserved regulatory residue S106 to suppress UBC13's ubiquitin-conjugating activity [#1]; in P. falciparum cells, pharmacological inhibition of PK9 lowers K63-linked polyubiquitination and enlarges liver-stage parasites, linking PK9 activity to regulation of K63-linkage ubiquitination and liver-stage development [#3, #4]. In P. falciparum, PK9 is expressed from roughly 18 hours post-infection and localizes to the parasitophorous vacuolar membrane and cytosol [#2], while in P. berghei PK9 and UBC13 co-localize in the cytosol of erythrocytic and liver stages [#6]. Species divergence is notable: genetic knockout of PK9 in P. berghei leaves UBC13-S106 phosphorylation intact and does not affect viability at any life cycle stage, indicating PK9 is dispensable there and that a redundant kinase maintains UBC13-S106 phosphorylation in that species [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Whether PK9 is an active enzyme was unknown; demonstrating autophosphorylation and substrate phosphorylation established it as a bona fide catalytically active kinase and mapped its autoregulatory sites.\",\n      \"evidence\": \"In vitro kinase assay with recombinant PfPK9 and histone H1, with phosphopeptide mapping to T82/T265/T269\",\n      \"pmids\": [\"17452636\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of the three autophosphorylation sites for activity or regulation not defined\", \"No structural model of the kinase domain\", \"Endogenous activation trigger unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"The physiological target of PK9 was unknown; identifying UBC13 as a substrate phosphorylated at S106 and showing this suppresses its conjugating activity connected PK9 to control of the ubiquitin system.\",\n      \"evidence\": \"In vitro kinase assay with recombinant PfPK9 and PfUBC13, phosphosite mapping to S106, and ubiquitin-conjugating activity assay\",\n      \"pmids\": [\"17452636\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro suppression not yet tied to a cellular phenotype at this stage\", \"Whether UBC13 is the sole substrate not established\", \"Stoichiometry and kinetics of the reaction not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"The timing and site of PK9 action were unknown; a temporal expression and localization profile placed PK9 at the parasitophorous vacuolar membrane and cytosol during blood-stage infection.\",\n      \"evidence\": \"Time-course western blot and subcellular fractionation/immunolocalization in P. falciparum\",\n      \"pmids\": [\"17452636\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Localization not functionally linked to UBC13 phosphorylation\", \"Mechanism of PVM targeting unknown\", \"Single-lab observation\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Whether PK9's in vitro effect on UBC13 translates to cellular ubiquitination and parasite biology was unknown; selective inhibitors showed PK9 activity supports K63-linked ubiquitination and liver-stage development in P. falciparum.\",\n      \"evidence\": \"Takinib/HS220 inhibitor treatment with K63-linked ubiquitination assay and fluorescence imaging of liver-stage parasites in hepatocytes\",\n      \"pmids\": [\"30595530\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Pharmacological rather than genetic perturbation, leaving off-target effects possible\", \"In vitro data showed PK9 suppresses UBC13 activity while cellular inhibition decreases K63 ubiquitination, so the directionality of regulation is unresolved\", \"Molecular link between PK9 activity and the liver-stage size/number phenotype not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Whether PK9 is essential and the exclusive kinase for UBC13-S106 was unknown; genetic knockout in P. berghei showed PK9 is dispensable across the life cycle and that UBC13-S106 phosphorylation persists via a redundant kinase.\",\n      \"evidence\": \"Genetic knockout of Pk9 in P. berghei with western blot for UBC13-S106 phosphorylation, life-cycle phenotyping, and cytosolic co-localization imaging of UBC13 and PK9\",\n      \"pmids\": [\"35490588\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the redundant UBC13-S106 kinase not determined\", \"Species divergence from P. falciparum pharmacological data unexplained\", \"Whether P. falciparum PK9 is genetically dispensable not directly tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The physiological role and essentiality of PK9 across Plasmodium species remain unresolved, particularly reconciling the P. falciparum inhibitor phenotypes with dispensability in P. berghei.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No genetic loss-of-function study of PK9 in P. falciparum\", \"Identity of the redundant UBC13-S106 kinase unknown\", \"Upstream signals activating PK9 and the biological output of UBC13 regulation undefined\"],\n      \"attribution\": []\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004674\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0046777\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0018105\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 6]},\n      {\"term_id\": \"GO:0020005\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0070534\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"GO:0043687\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"UBC13 (E2 ubiquitin-conjugating enzyme; substrate phosphorylated at S106) [#1, #5, #6]\"\n    ],\n    \"other_free_text\": [\n      \"Autophosphorylation sites mapped to T82, T265, and T269 [#0]\",\n      \"In P. falciparum, PK9 inhibition (takinib/HS220) reduces K63-linked ubiquitination and enlarges liver-stage parasites [#3, #4]\",\n      \"In P. berghei, PK9 is dispensable at all life-cycle stages and a redundant kinase maintains UBC13-S106 phosphorylation [#5]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1315100","name":null,"product":"serine/threonine protein kinase PK9","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1413600","name":null,"product":"serine/threonine protein kinase PK9, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1415800","name":null,"product":"serine/threonine protein kinase PK9, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"PK9","evaluation":null}