{"gene":"PF3D7_0714400","run_date":"2026-09-08T12:51:27","timeline":{"discoveries":[{"year":1991,"finding":"The P. falciparum calmodulin gene (PF3D7_0714400) exists as a single copy on chromosome 14, contains a single intron, and the predicted protein shares high sequence identity with calmodulins from other eukaryotes. Primer extension studies identified a major transcription start site 62 bases upstream of the initial ATG. The gene possesses consensus eukaryotic TATA, CAAT box, polyadenylation, and splice junction sequences.","method":"Southern blotting, DNA sequencing, primer extension","journal":"Molecular and biochemical parasitology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct molecular characterization of gene structure with multiple orthogonal methods (sequencing, Southern blot, primer extension), replicated by Cowman & Galatis 1991","pmids":["1852174","1915742"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1991,"finding":"The P. falciparum calmodulin gene is encoded as a single copy on chromosome 14 with a single intron of 506 bp with appropriate donor/acceptor splice sites. The calmodulin protein is expressed approximately equally in chloroquine-resistant and chloroquine-sensitive isolates, indicating that alterations in calmodulin play no role in chloroquine resistance in the isolates tested.","method":"Southern blotting, DNA sequencing, Western blot","journal":"Experimental parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Southern blot and protein expression comparison, single lab, two orthogonal methods","pmids":["1915742"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1987,"finding":"Calmodulin (PF3D7_0714400) was detected in free P. falciparum parasites by radioimmunoassay. Immunoelectron microscopy localized calmodulin diffusely within the cytoplasm of mature parasites and at the apical end of merozoites within the ductule of rhoptries, suggesting a calcium-dependent role in erythrocyte invasion.","method":"Radioimmunoassay, immunoelectron microscopy","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization by immunoelectron microscopy with functional correlation to invasion, corroborated by independent study (Matsumoto et al. 1987)","pmids":["3313391"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1987,"finding":"Calmodulin antagonists (W7, trifluoperazine, R24571) inhibited invasion of erythrocytes by merozoites and maturation of schizonts in P. falciparum culture; inhibition of invasion was more potent than inhibition of schizont maturation. Immunoelectron microscopy showed calmodulin concentrated at the apical end of both free and intraerythrocytic merozoites, implicating calmodulin in Ca2+-dependent attachment and/or invasion.","method":"In vitro culture inhibition assay, immunoelectron microscopy","journal":"European journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization linked to functional phenotype, two orthogonal methods, single lab","pmids":["3127214"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1995,"finding":"Calmodulin (PF3D7_0714400) mRNA and protein expression is low during early erythrocytic stages, increases steadily from 28 h, peaks around 40–44 h (late trophozoite/early schizont), then protein levels remain high. mRNA stability was lower in very mature trophozoites. This stage-specific regulation occurs at the level of transcription and RNA degradation, not as a constitutive housekeeping pattern.","method":"Northern blot, Western blot, pulse-chase mRNA stability assay, radioimmunoassay","journal":"Journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (Northern, Western, pulse-chase) in single lab establishing stage-specific expression pattern","pmids":["8720124"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"The P. falciparum calmodulin promoter (pfcam) drives transgene expression in P. falciparum blood stages. Transcription initiates from multiple start sites within 180 bp upstream of the ORF. Activity of the promoter diminished linearly upon step-wise removal of sequence between 625 and 230 bp upstream of the ATG. Nuclear factor binding to the upstream sequence correlated with the density of poly(dA)poly(dT) tracts, which lie just upstream of transcription-initiation sites. Splicing frequency was related to 5' UTR length.","method":"Oligo-capping/cDNA mapping, deletion analysis with reporter assay, electromobility-shift assay (EMSA)","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (transcription start mapping, deletion reporter assays, EMSA), single lab","pmids":["15850701"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"Calmodulin (PF3D7_0714400) was identified as the upstream activator of P. falciparum protein kinase B (PfPKB). A calmodulin-binding domain was mapped to the N-terminal region of PfPKB. CaM interacts with this domain in a calcium-dependent manner, activating PfPKB. CaM associates with PfPKB in parasite extracts. Phospholipase C acts upstream of this cascade by facilitating calcium release from intracellular stores.","method":"Co-immunoprecipitation, in vitro kinase assay, calmodulin-binding domain mapping, pharmacological inhibition of PLC","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus in vitro activity assay, domain mapping in single lab","pmids":["16809343"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"Blocking calmodulin function (upstream activator of PfPKB) impaired erythrocyte invasion by P. falciparum merozoites. PfPKB, activated by calmodulin/calcium, associates with the actin-myosin motor and phosphorylates PfGAP45, a glideosome component, providing a mechanistic link between the Ca2+/calmodulin-PfPKB pathway and erythrocyte invasion.","method":"Pharmacological inhibition, in vitro invasion assay, Co-immunoprecipitation, in vitro phosphorylation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (inhibitor assay, Co-IP, phosphorylation), single lab","pmids":["18165240"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"P. falciparum protein kinase 2 (PfPK2), expressed in merozoites, phosphorylates histone in a Ca2+- and calmodulin-dependent manner in vitro. Calmodulin antagonists blocked PfPK2 phosphorylation in vitro and markedly decreased parasitemia in a ring-form invasion assay, implicating calmodulin-dependent kinase activity in merozoite invasion.","method":"In vitro kinase assay, site-directed mutagenesis (catalytic lysine to alanine), pharmacological inhibition, invasion assay","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro reconstitution with mutagenesis and functional invasion assay, single lab","pmids":["18762219"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"Calmodulin (PF3D7_0714400) was localized to all erythrocytic stages of P. falciparum by knockin approach with live imaging. Treatment with the CaM inhibitor calmidazolium mobilized intracellular Ca2+ independently of the ER store, suggesting that a CaM-related protein serves as an intracellular Ca2+ reservoir. The mitochondrion participates in sequestration of the cytosolic Ca2+ rise elicited by calmidazolium.","method":"Knockin/live fluorescence imaging, calcium imaging with fluorescent indicators, pharmacological dissection","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization by knockin imaging linked to functional calcium signaling experiments, single lab","pmids":["26689736"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Overexpression of P. falciparum calmodulin (PfCaM, PF3D7_0714400) led to a higher [Ca2+]cyt rise upon challenge with the calmodulin inhibitor calmidazolium, and increased calcium-dependent proteolytic activity in the parasite, indicating that PfCaM participates in calcium homeostasis and modulation of intracellular proteolysis.","method":"Transgenic overexpression, calcium imaging, fluorogenic protease activity assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct overexpression with functional readouts (calcium imaging and protease activity), single lab","pmids":["29913151"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"Biophysical comparison of recombinant P. falciparum calmodulin (PfCaM) and human CaM showed that PfCaM has higher overall thermostability, particularly in the C-terminal domain, in both Ca2+-free and Ca2+-saturated states. In vitro binding assays showed PfCaM and human CaM exhibit similar affinities for small molecule inhibitors and target enzyme activation, differing at most by a factor of three. Some Malaria Box compounds showed inhibitory action on PfCaM comparable to known vertebrate CaM antagonists.","method":"Differential scanning fluorimetry/calorimetry, in vitro binding assay, enzyme activation assay","journal":"FASEB bioAdvances","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with multiple biophysical methods, single lab","pmids":["32821880"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"The crystal structure of P. falciparum calmodulin (PfCaM) in complex with melittin was determined, revealing three distinct binding modes of the peptide. Multiple conformers of the complex co-exist, with different sets of residues anchoring to PfCaM's hydrophobic pockets and with partial unfolding of the melittin C-terminal segment across modes. This indicates that nanomolar-affinity CaM-target binding can be achieved through an ensemble of sub-optimal interaction arrangements rather than one optimized mode.","method":"X-ray crystallography, molecular dynamics simulations","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of PfCaM determined at high resolution, complemented by molecular dynamics simulations, providing direct structural insight into target recognition","pmids":["36906144"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1999,"finding":"The P. falciparum PP2B-like (calcineurin) phosphatase is stimulated by calmodulin and Ca2+, and is strongly and specifically inhibited by cyclosporin A only in the presence of wild-type P. falciparum cyclophilin (not a mutant cyclophilin). This demonstrates that calmodulin functionally activates P. falciparum calcineurin.","method":"Enzyme purification, in vitro phosphatase activity assay, pharmacological inhibition","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstituted calcineurin activation by calmodulin, single lab","pmids":["10340482"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"P. falciparum calmodulin (PF3D7_0714400) physically interacts with PP7 phosphatase (and also with CDPK1) as determined by co-immunoprecipitation. PP7 is a calcium-dependent phosphatase, consistent with calmodulin's role in calcium-dependent signaling in blood stages.","method":"Co-immunoprecipitation, conditional knockdown (conditional disruption), phosphoproteomics","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP identifying calmodulin as PP7 binding partner, supported by phosphoproteomic analysis, single lab","pmids":["39387582"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"P. falciparum calmodulin homolog (PfCaM, encoded by PF3D7_0714400) was identified as capable of binding to the IQ2 motif of MyoB in vitro, along with four other putative regulatory light chains, establishing that PfCaM can act as a myosin light chain in vitro.","method":"In vitro binding/pulldown assay, biochemical characterization","journal":"The Journal of biological chemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single in vitro pulldown experiment, single lab; PfCaM identity as PF3D7_0714400 inferred from context","pmids":["36273584"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"finding":"PfMyoF (a class XXII myosin) was predicted and biochemically shown to bind up to six copies of the calmodulin homolog PfCaM (PF3D7_0714400) via its long neck region, as established by structural prediction and pulldown assays.","method":"Structural prediction (AlphaFold), pull-down assay, biochemical characterization","journal":"Communications biology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single pulldown experiment supported by structural prediction, single lab; specific identity of PfCaM as PF3D7_0714400 inferred from context","pmids":["42141018"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"P. falciparum calmodulin (PF3D7_0714400) is a single-copy, calcium-sensing protein encoded on chromosome 14 with a single intron, whose expression is developmentally regulated (peaking in late trophozoite/schizont stages at both mRNA and protein levels); it localizes to the cytoplasm and apical end of merozoites, where it activates downstream effectors including PfPKB (via a direct calcium-dependent interaction), calcineurin/PP2B (stimulating phosphatase activity), PP7 phosphatase, and myosins (MyoB, MyoF) as a light chain, collectively supporting erythrocyte invasion and calcium-dependent signaling during the intraerythrocytic cycle; its crystal structure in complex with melittin reveals multiple co-existing binding modes at its hydrophobic pockets, and while it is ~11% divergent from human calmodulin with slightly higher thermostability, its functional similarity to the host protein makes it a poor selective drug target."},"narrative":{"mechanistic_narrative":"PF3D7_0714400 encodes the Plasmodium falciparum calmodulin, a single-copy, intron-containing gene on chromosome 14 whose product functions as a calcium-sensing signaling hub during the intraerythrocytic cycle [PMID:1852174, PMID:1915742, PMID:16809343]. Its mRNA and protein are developmentally regulated, peaking in the late trophozoite/early schizont stage through control at both transcription and RNA stability [PMID:8720124], and the protein localizes diffusely in the cytoplasm and concentrates at the apical end of merozoites, near the rhoptry ductule [PMID:3313391, PMID:26689736]. Calmodulin acts as a calcium-dependent activator of multiple downstream effectors: it binds and activates P. falciparum protein kinase B (PfPKB) through a mapped N-terminal calmodulin-binding domain [PMID:16809343], which in turn associates with the actin-myosin motor and phosphorylates the glideosome component PfGAP45, linking Ca2+/calmodulin signaling to erythrocyte invasion [PMID:18165240]; it stimulates the calcineurin/PP2B phosphatase [PMID:10340482] and physically interacts with PP7 phosphatase and CDPK1 [PMID:39387582]; and it supports Ca2+-dependent kinase activity attributed to PfPK2 [PMID:18762219]. Pharmacological antagonism of calmodulin blocks merozoite invasion and schizont maturation [PMID:3127214], and manipulation of calmodulin levels alters cytosolic Ca2+ dynamics and calcium-dependent proteolysis, implicating it in intracellular calcium homeostasis [PMID:26689736, PMID:29913151]. Structurally, the crystal structure of the protein in complex with melittin reveals an ensemble of co-existing binding modes anchored at its hydrophobic pockets [PMID:36906144], and biophysical comparison shows it is only modestly divergent from human calmodulin, with higher C-terminal thermostability but similar inhibitor affinities and target-activation behavior [PMID:32821880].","teleology":[{"year":1987,"claim":"Establishing where calmodulin resides in the parasite and whether it matters for invasion was the first mechanistic question, answered by localizing it to the merozoite apical end and showing antagonists block invasion.","evidence":"radioimmunoassay, immunoelectron microscopy, and in vitro culture inhibition with calmodulin antagonists in P. falciparum","pmids":["3313391","3127214"],"confidence":"Medium","gaps":["Antagonist effects are pharmacological and not gene-specific","Direct downstream effectors at the apical end not identified at this stage"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1991,"claim":"Defining the gene architecture established that calmodulin is a single-copy, intron-containing gene conserved with other eukaryotic calmodulins and unrelated to chloroquine resistance.","evidence":"Southern blotting, DNA sequencing, primer extension, and Western blot in P. falciparum","pmids":["1852174","1915742"],"confidence":"High","gaps":["Gene structure does not reveal protein function or partners"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1995,"claim":"Whether calmodulin is a constitutive housekeeping factor or a stage-regulated one was resolved by showing its expression peaks in late trophozoite/schizont stages via transcriptional and RNA-stability control.","evidence":"Northern blot, Western blot, and pulse-chase mRNA stability assays in P. falciparum","pmids":["8720124"],"confidence":"Medium","gaps":["Regulatory factors controlling stage-specific expression not identified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"claim":"Characterizing the calmodulin promoter clarified how its expression is driven, mapping multiple transcription start sites and nuclear-factor binding correlated with poly(dA)poly(dT) tracts.","evidence":"cDNA mapping, deletion reporter assays, and EMSA in P. falciparum","pmids":["15850701"],"confidence":"Medium","gaps":["Specific trans-acting factors not identified","Promoter behavior does not address protein-level mechanism"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"Identifying calmodulin as the calcium-dependent activator of PfPKB, with a mapped binding domain, provided the first direct effector linking calmodulin to a signaling kinase.","evidence":"Co-immunoprecipitation, in vitro kinase assay, and domain mapping in P. falciparum","pmids":["16809343"],"confidence":"Medium","gaps":["Interaction shown in extracts/in vitro, not by conditional genetics","Full effector network downstream of PfPKB incomplete at this stage"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"claim":"Connecting the calmodulin-PfPKB axis to the invasion motor answered how calcium signaling engages the glideosome, showing PfPKB phosphorylates PfGAP45 and its inhibition impairs invasion.","evidence":"pharmacological inhibition, invasion assay, Co-IP, and in vitro phosphorylation in P. falciparum","pmids":["18165240"],"confidence":"Medium","gaps":["Inhibitor-based, not calmodulin-specific genetic evidence","In vivo phosphorylation of PfGAP45 by this pathway not directly demonstrated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"claim":"Testing calmodulin dependence of another merozoite kinase showed PfPK2 phosphorylates substrate in a Ca2+/calmodulin-dependent manner, broadening the calmodulin-regulated kinase repertoire tied to invasion.","evidence":"in vitro kinase assay, catalytic-lysine mutagenesis, antagonist treatment, and invasion assay in P. falciparum","pmids":["18762219"],"confidence":"Medium","gaps":["Direct physical calmodulin-PfPK2 binding not defined","Physiological substrate of PfPK2 unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1999,"claim":"Establishing that calmodulin functionally activates the parasite PP2B/calcineurin phosphatase extended its role beyond kinases into calcium-dependent dephosphorylation signaling.","evidence":"enzyme purification, in vitro phosphatase assay, and cyclosporin A inhibition in P. falciparum","pmids":["10340482"],"confidence":"Medium","gaps":["In vitro reconstitution only","Cellular consequences of calcineurin activation not defined here"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"claim":"Live-imaging localization and calcium dissection addressed calmodulin's role in Ca2+ handling, implicating a calmodulin-related intracellular Ca2+ reservoir and mitochondrial sequestration.","evidence":"knockin live imaging, calcium imaging with fluorescent indicators, and pharmacological dissection in P. falciparum","pmids":["26689736"],"confidence":"Medium","gaps":["Calmidazolium effects are pharmacological and not calmodulin-specific","Molecular identity of the proposed Ca2+ reservoir not resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"Overexpression established a direct causal link between calmodulin abundance and cytosolic Ca2+ dynamics and calcium-dependent proteolysis.","evidence":"transgenic overexpression, calcium imaging, and fluorogenic protease assay in P. falciparum","pmids":["29913151"],"confidence":"Medium","gaps":["Protease targets of the calcium-dependent activity not identified","Loss-of-function counterpart not tested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"Biophysical comparison to human calmodulin evaluated drug-target selectivity, showing higher parasite C-terminal thermostability but similar inhibitor affinities and target activation.","evidence":"differential scanning fluorimetry/calorimetry, in vitro binding, and enzyme activation assays with recombinant PfCaM and human CaM","pmids":["32821880"],"confidence":"Medium","gaps":["Functional similarity to host limits selective targeting","Cellular validation of Malaria Box compound effects not shown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"claim":"In vitro binding to the MyoB IQ2 motif raised the possibility that calmodulin serves as a myosin light chain, expanding its potential structural role in the motor complex.","evidence":"in vitro binding/pulldown assay in P. falciparum","pmids":["36273584"],"confidence":"Low","gaps":["Single in vitro pulldown; PfCaM identity as PF3D7_0714400 inferred from context","In vivo myosin light-chain role not demonstrated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"claim":"The crystal structure with melittin defined how calmodulin achieves high-affinity target binding, revealing an ensemble of co-existing sub-optimal binding modes at its hydrophobic pockets.","evidence":"X-ray crystallography and molecular dynamics simulations of PfCaM","pmids":["36906144"],"confidence":"High","gaps":["Melittin is a model peptide, not a physiological parasite target","Structures with native effectors (PfPKB, calcineurin) not determined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"claim":"Interaction proteomics identified PP7 phosphatase and CDPK1 as calmodulin partners, adding a further calcium-dependent phosphatase to its effector network.","evidence":"co-immunoprecipitation, conditional knockdown, and phosphoproteomics in P. falciparum","pmids":["39387582"],"confidence":"Medium","gaps":["Functional consequence of the calmodulin-PP7 interaction not isolated to calmodulin","Direct calmodulin-CDPK1 dependence not mechanistically dissected"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"claim":"Structural prediction and pulldown indicated calmodulin binds up to six copies along the neck of the class XXII myosin PfMyoF, reinforcing a possible light-chain role for a second myosin.","evidence":"AlphaFold structural prediction and pull-down assay in P. falciparum","pmids":["42141018"],"confidence":"Low","gaps":["Single pulldown supported by prediction; PfCaM identity inferred from context","In vivo stoichiometry and functional role not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"It remains unresolved whether calmodulin is genetically essential for invasion and which of its many effector interactions are the physiologically dominant ones in vivo, as most links rest on pharmacology, overexpression, or in vitro binding.","evidence":"no conditional loss-of-function dissection of calmodulin's individual effector arms in the corpus","pmids":[],"confidence":"Low","gaps":["No calmodulin-specific conditional knockout phenotype reported","Relative in vivo contribution of PfPKB, calcineurin, PP7, and myosin binding not ranked","Native effector-bound structures absent"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["calcineurin/PP2B phosphatase complex (calmodulin-activated) [#13]","actin-myosin glideosome motor (via PfPKB association) [#7]"],"partners":["PFPKB (PROTEIN KINASE B) [#6, #7]","PFPK2 (CA2+/CALMODULIN-DEPENDENT KINASE ACTIVITY) [#8]","CALCINEURIN/PP2B PHOSPHATASE [#13]","PP7 PHOSPHATASE [#14]","CDPK1 [#14]","MYOB (IQ2 MOTIF) [#15]","PFMYOF (CLASS XXII MYOSIN NECK) [#16]"],"other_free_text":["Single-copy gene on chromosome 14 with a single intron and conserved eukaryotic regulatory elements [#0, #1].","Stage-regulated expression peaking in late trophozoite/schizont stages via transcription and RNA stability [#4].","Crystal structure with melittin reveals an ensemble of co-existing binding modes at hydrophobic pockets [#12].","Only modestly divergent from human calmodulin with higher C-terminal thermostability and similar inhibitor affinities, limiting selective drug targeting [#11]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"16072038","id":"PMC_16072038","title":"Plants, symbiosis and parasites: a calcium signalling connection.","date":"2005","source":"Nature reviews. Molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/16072038","citation_count":281,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["calmodulin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"8692985","id":"PMC_8692985","title":"Characterization of promoters and stable transfection by homologous and nonhomologous recombination in Plasmodium falciparum.","date":"1996","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/8692985","citation_count":234,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["calmodulin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"9497038","id":"PMC_9497038","title":"Stable transgene expression in Plasmodium falciparum.","date":"1997","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/9497038","citation_count":119,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["calmodulin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"3313391","id":"PMC_3313391","title":"Calcium and calmodulin antagonists inhibit human malaria parasites (Plasmodium falciparum): implications for drug design.","date":"1987","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/3313391","citation_count":115,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["calmodulin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"2172816","id":"PMC_2172816","title":"Possible roles of Ca2+ and cGMP as mediators of the exflagellation of Plasmodium berghei and Plasmodium falciparum.","date":"1990","source":"Molecular and 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calmodulins from other eukaryotes. Primer extension studies identified a major transcription start site 62 bases upstream of the initial ATG. The gene possesses consensus eukaryotic TATA, CAAT box, polyadenylation, and splice junction sequences.\",\n      \"method\": \"Southern blotting, DNA sequencing, primer extension\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct molecular characterization of gene structure with multiple orthogonal methods (sequencing, Southern blot, primer extension), replicated by Cowman & Galatis 1991\",\n      \"pmids\": [\"1852174\", \"1915742\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"The P. falciparum calmodulin gene is encoded as a single copy on chromosome 14 with a single intron of 506 bp with appropriate donor/acceptor splice sites. The calmodulin protein is expressed approximately equally in chloroquine-resistant and chloroquine-sensitive isolates, indicating that alterations in calmodulin play no role in chloroquine resistance in the isolates tested.\",\n      \"method\": \"Southern blotting, DNA sequencing, Western blot\",\n      \"journal\": \"Experimental parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Southern blot and protein expression comparison, single lab, two orthogonal methods\",\n      \"pmids\": [\"1915742\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"Calmodulin (PF3D7_0714400) was detected in free P. falciparum parasites by radioimmunoassay. Immunoelectron microscopy localized calmodulin diffusely within the cytoplasm of mature parasites and at the apical end of merozoites within the ductule of rhoptries, suggesting a calcium-dependent role in erythrocyte invasion.\",\n      \"method\": \"Radioimmunoassay, immunoelectron microscopy\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization by immunoelectron microscopy with functional correlation to invasion, corroborated by independent study (Matsumoto et al. 1987)\",\n      \"pmids\": [\"3313391\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"Calmodulin antagonists (W7, trifluoperazine, R24571) inhibited invasion of erythrocytes by merozoites and maturation of schizonts in P. falciparum culture; inhibition of invasion was more potent than inhibition of schizont maturation. Immunoelectron microscopy showed calmodulin concentrated at the apical end of both free and intraerythrocytic merozoites, implicating calmodulin in Ca2+-dependent attachment and/or invasion.\",\n      \"method\": \"In vitro culture inhibition assay, immunoelectron microscopy\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization linked to functional phenotype, two orthogonal methods, single lab\",\n      \"pmids\": [\"3127214\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Calmodulin (PF3D7_0714400) mRNA and protein expression is low during early erythrocytic stages, increases steadily from 28 h, peaks around 40–44 h (late trophozoite/early schizont), then protein levels remain high. mRNA stability was lower in very mature trophozoites. This stage-specific regulation occurs at the level of transcription and RNA degradation, not as a constitutive housekeeping pattern.\",\n      \"method\": \"Northern blot, Western blot, pulse-chase mRNA stability assay, radioimmunoassay\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (Northern, Western, pulse-chase) in single lab establishing stage-specific expression pattern\",\n      \"pmids\": [\"8720124\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The P. falciparum calmodulin promoter (pfcam) drives transgene expression in P. falciparum blood stages. Transcription initiates from multiple start sites within 180 bp upstream of the ORF. Activity of the promoter diminished linearly upon step-wise removal of sequence between 625 and 230 bp upstream of the ATG. Nuclear factor binding to the upstream sequence correlated with the density of poly(dA)poly(dT) tracts, which lie just upstream of transcription-initiation sites. Splicing frequency was related to 5' UTR length.\",\n      \"method\": \"Oligo-capping/cDNA mapping, deletion analysis with reporter assay, electromobility-shift assay (EMSA)\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (transcription start mapping, deletion reporter assays, EMSA), single lab\",\n      \"pmids\": [\"15850701\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Calmodulin (PF3D7_0714400) was identified as the upstream activator of P. falciparum protein kinase B (PfPKB). A calmodulin-binding domain was mapped to the N-terminal region of PfPKB. CaM interacts with this domain in a calcium-dependent manner, activating PfPKB. CaM associates with PfPKB in parasite extracts. Phospholipase C acts upstream of this cascade by facilitating calcium release from intracellular stores.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, calmodulin-binding domain mapping, pharmacological inhibition of PLC\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus in vitro activity assay, domain mapping in single lab\",\n      \"pmids\": [\"16809343\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Blocking calmodulin function (upstream activator of PfPKB) impaired erythrocyte invasion by P. falciparum merozoites. PfPKB, activated by calmodulin/calcium, associates with the actin-myosin motor and phosphorylates PfGAP45, a glideosome component, providing a mechanistic link between the Ca2+/calmodulin-PfPKB pathway and erythrocyte invasion.\",\n      \"method\": \"Pharmacological inhibition, in vitro invasion assay, Co-immunoprecipitation, in vitro phosphorylation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (inhibitor assay, Co-IP, phosphorylation), single lab\",\n      \"pmids\": [\"18165240\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"P. falciparum protein kinase 2 (PfPK2), expressed in merozoites, phosphorylates histone in a Ca2+- and calmodulin-dependent manner in vitro. Calmodulin antagonists blocked PfPK2 phosphorylation in vitro and markedly decreased parasitemia in a ring-form invasion assay, implicating calmodulin-dependent kinase activity in merozoite invasion.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis (catalytic lysine to alanine), pharmacological inhibition, invasion assay\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro reconstitution with mutagenesis and functional invasion assay, single lab\",\n      \"pmids\": [\"18762219\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Calmodulin (PF3D7_0714400) was localized to all erythrocytic stages of P. falciparum by knockin approach with live imaging. Treatment with the CaM inhibitor calmidazolium mobilized intracellular Ca2+ independently of the ER store, suggesting that a CaM-related protein serves as an intracellular Ca2+ reservoir. The mitochondrion participates in sequestration of the cytosolic Ca2+ rise elicited by calmidazolium.\",\n      \"method\": \"Knockin/live fluorescence imaging, calcium imaging with fluorescent indicators, pharmacological dissection\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization by knockin imaging linked to functional calcium signaling experiments, single lab\",\n      \"pmids\": [\"26689736\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Overexpression of P. falciparum calmodulin (PfCaM, PF3D7_0714400) led to a higher [Ca2+]cyt rise upon challenge with the calmodulin inhibitor calmidazolium, and increased calcium-dependent proteolytic activity in the parasite, indicating that PfCaM participates in calcium homeostasis and modulation of intracellular proteolysis.\",\n      \"method\": \"Transgenic overexpression, calcium imaging, fluorogenic protease activity assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct overexpression with functional readouts (calcium imaging and protease activity), single lab\",\n      \"pmids\": [\"29913151\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Biophysical comparison of recombinant P. falciparum calmodulin (PfCaM) and human CaM showed that PfCaM has higher overall thermostability, particularly in the C-terminal domain, in both Ca2+-free and Ca2+-saturated states. In vitro binding assays showed PfCaM and human CaM exhibit similar affinities for small molecule inhibitors and target enzyme activation, differing at most by a factor of three. Some Malaria Box compounds showed inhibitory action on PfCaM comparable to known vertebrate CaM antagonists.\",\n      \"method\": \"Differential scanning fluorimetry/calorimetry, in vitro binding assay, enzyme activation assay\",\n      \"journal\": \"FASEB bioAdvances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with multiple biophysical methods, single lab\",\n      \"pmids\": [\"32821880\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The crystal structure of P. falciparum calmodulin (PfCaM) in complex with melittin was determined, revealing three distinct binding modes of the peptide. Multiple conformers of the complex co-exist, with different sets of residues anchoring to PfCaM's hydrophobic pockets and with partial unfolding of the melittin C-terminal segment across modes. This indicates that nanomolar-affinity CaM-target binding can be achieved through an ensemble of sub-optimal interaction arrangements rather than one optimized mode.\",\n      \"method\": \"X-ray crystallography, molecular dynamics simulations\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of PfCaM determined at high resolution, complemented by molecular dynamics simulations, providing direct structural insight into target recognition\",\n      \"pmids\": [\"36906144\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The P. falciparum PP2B-like (calcineurin) phosphatase is stimulated by calmodulin and Ca2+, and is strongly and specifically inhibited by cyclosporin A only in the presence of wild-type P. falciparum cyclophilin (not a mutant cyclophilin). This demonstrates that calmodulin functionally activates P. falciparum calcineurin.\",\n      \"method\": \"Enzyme purification, in vitro phosphatase activity assay, pharmacological inhibition\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstituted calcineurin activation by calmodulin, single lab\",\n      \"pmids\": [\"10340482\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"P. falciparum calmodulin (PF3D7_0714400) physically interacts with PP7 phosphatase (and also with CDPK1) as determined by co-immunoprecipitation. PP7 is a calcium-dependent phosphatase, consistent with calmodulin's role in calcium-dependent signaling in blood stages.\",\n      \"method\": \"Co-immunoprecipitation, conditional knockdown (conditional disruption), phosphoproteomics\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP identifying calmodulin as PP7 binding partner, supported by phosphoproteomic analysis, single lab\",\n      \"pmids\": [\"39387582\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"P. falciparum calmodulin homolog (PfCaM, encoded by PF3D7_0714400) was identified as capable of binding to the IQ2 motif of MyoB in vitro, along with four other putative regulatory light chains, establishing that PfCaM can act as a myosin light chain in vitro.\",\n      \"method\": \"In vitro binding/pulldown assay, biochemical characterization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single in vitro pulldown experiment, single lab; PfCaM identity as PF3D7_0714400 inferred from context\",\n      \"pmids\": [\"36273584\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"PfMyoF (a class XXII myosin) was predicted and biochemically shown to bind up to six copies of the calmodulin homolog PfCaM (PF3D7_0714400) via its long neck region, as established by structural prediction and pulldown assays.\",\n      \"method\": \"Structural prediction (AlphaFold), pull-down assay, biochemical characterization\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single pulldown experiment supported by structural prediction, single lab; specific identity of PfCaM as PF3D7_0714400 inferred from context\",\n      \"pmids\": [\"42141018\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"P. falciparum calmodulin (PF3D7_0714400) is a single-copy, calcium-sensing protein encoded on chromosome 14 with a single intron, whose expression is developmentally regulated (peaking in late trophozoite/schizont stages at both mRNA and protein levels); it localizes to the cytoplasm and apical end of merozoites, where it activates downstream effectors including PfPKB (via a direct calcium-dependent interaction), calcineurin/PP2B (stimulating phosphatase activity), PP7 phosphatase, and myosins (MyoB, MyoF) as a light chain, collectively supporting erythrocyte invasion and calcium-dependent signaling during the intraerythrocytic cycle; its crystal structure in complex with melittin reveals multiple co-existing binding modes at its hydrophobic pockets, and while it is ~11% divergent from human calmodulin with slightly higher thermostability, its functional similarity to the host protein makes it a poor selective drug target.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_0714400 encodes the Plasmodium falciparum calmodulin, a single-copy, intron-containing gene on chromosome 14 whose product functions as a calcium-sensing signaling hub during the intraerythrocytic cycle [#0, #6]. Its mRNA and protein are developmentally regulated, peaking in the late trophozoite/early schizont stage through control at both transcription and RNA stability [#4], and the protein localizes diffusely in the cytoplasm and concentrates at the apical end of merozoites, near the rhoptry ductule [#2, #9]. Calmodulin acts as a calcium-dependent activator of multiple downstream effectors: it binds and activates P. falciparum protein kinase B (PfPKB) through a mapped N-terminal calmodulin-binding domain [#6], which in turn associates with the actin-myosin motor and phosphorylates the glideosome component PfGAP45, linking Ca2+/calmodulin signaling to erythrocyte invasion [#7]; it stimulates the calcineurin/PP2B phosphatase [#13] and physically interacts with PP7 phosphatase and CDPK1 [#14]; and it supports Ca2+-dependent kinase activity attributed to PfPK2 [#8]. Pharmacological antagonism of calmodulin blocks merozoite invasion and schizont maturation [#3], and manipulation of calmodulin levels alters cytosolic Ca2+ dynamics and calcium-dependent proteolysis, implicating it in intracellular calcium homeostasis [#9, #10]. Structurally, the crystal structure of the protein in complex with melittin reveals an ensemble of co-existing binding modes anchored at its hydrophobic pockets [#12], and biophysical comparison shows it is only modestly divergent from human calmodulin, with higher C-terminal thermostability but similar inhibitor affinities and target-activation behavior [#11].\",\n  \"teleology\": [\n    {\n      \"year\": 1987,\n      \"claim\": \"Establishing where calmodulin resides in the parasite and whether it matters for invasion was the first mechanistic question, answered by localizing it to the merozoite apical end and showing antagonists block invasion.\",\n      \"evidence\": \"radioimmunoassay, immunoelectron microscopy, and in vitro culture inhibition with calmodulin antagonists in P. falciparum\",\n      \"pmids\": [\"3313391\", \"3127214\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Antagonist effects are pharmacological and not gene-specific\", \"Direct downstream effectors at the apical end not identified at this stage\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Defining the gene architecture established that calmodulin is a single-copy, intron-containing gene conserved with other eukaryotic calmodulins and unrelated to chloroquine resistance.\",\n      \"evidence\": \"Southern blotting, DNA sequencing, primer extension, and Western blot in P. falciparum\",\n      \"pmids\": [\"1852174\", \"1915742\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Gene structure does not reveal protein function or partners\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Whether calmodulin is a constitutive housekeeping factor or a stage-regulated one was resolved by showing its expression peaks in late trophozoite/schizont stages via transcriptional and RNA-stability control.\",\n      \"evidence\": \"Northern blot, Western blot, and pulse-chase mRNA stability assays in P. falciparum\",\n      \"pmids\": [\"8720124\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Regulatory factors controlling stage-specific expression not identified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Characterizing the calmodulin promoter clarified how its expression is driven, mapping multiple transcription start sites and nuclear-factor binding correlated with poly(dA)poly(dT) tracts.\",\n      \"evidence\": \"cDNA mapping, deletion reporter assays, and EMSA in P. falciparum\",\n      \"pmids\": [\"15850701\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific trans-acting factors not identified\", \"Promoter behavior does not address protein-level mechanism\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identifying calmodulin as the calcium-dependent activator of PfPKB, with a mapped binding domain, provided the first direct effector linking calmodulin to a signaling kinase.\",\n      \"evidence\": \"Co-immunoprecipitation, in vitro kinase assay, and domain mapping in P. falciparum\",\n      \"pmids\": [\"16809343\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interaction shown in extracts/in vitro, not by conditional genetics\", \"Full effector network downstream of PfPKB incomplete at this stage\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connecting the calmodulin-PfPKB axis to the invasion motor answered how calcium signaling engages the glideosome, showing PfPKB phosphorylates PfGAP45 and its inhibition impairs invasion.\",\n      \"evidence\": \"pharmacological inhibition, invasion assay, Co-IP, and in vitro phosphorylation in P. falciparum\",\n      \"pmids\": [\"18165240\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Inhibitor-based, not calmodulin-specific genetic evidence\", \"In vivo phosphorylation of PfGAP45 by this pathway not directly demonstrated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Testing calmodulin dependence of another merozoite kinase showed PfPK2 phosphorylates substrate in a Ca2+/calmodulin-dependent manner, broadening the calmodulin-regulated kinase repertoire tied to invasion.\",\n      \"evidence\": \"in vitro kinase assay, catalytic-lysine mutagenesis, antagonist treatment, and invasion assay in P. falciparum\",\n      \"pmids\": [\"18762219\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical calmodulin-PfPK2 binding not defined\", \"Physiological substrate of PfPK2 unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing that calmodulin functionally activates the parasite PP2B/calcineurin phosphatase extended its role beyond kinases into calcium-dependent dephosphorylation signaling.\",\n      \"evidence\": \"enzyme purification, in vitro phosphatase assay, and cyclosporin A inhibition in P. falciparum\",\n      \"pmids\": [\"10340482\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vitro reconstitution only\", \"Cellular consequences of calcineurin activation not defined here\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Live-imaging localization and calcium dissection addressed calmodulin's role in Ca2+ handling, implicating a calmodulin-related intracellular Ca2+ reservoir and mitochondrial sequestration.\",\n      \"evidence\": \"knockin live imaging, calcium imaging with fluorescent indicators, and pharmacological dissection in P. falciparum\",\n      \"pmids\": [\"26689736\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Calmidazolium effects are pharmacological and not calmodulin-specific\", \"Molecular identity of the proposed Ca2+ reservoir not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Overexpression established a direct causal link between calmodulin abundance and cytosolic Ca2+ dynamics and calcium-dependent proteolysis.\",\n      \"evidence\": \"transgenic overexpression, calcium imaging, and fluorogenic protease assay in P. falciparum\",\n      \"pmids\": [\"29913151\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Protease targets of the calcium-dependent activity not identified\", \"Loss-of-function counterpart not tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Biophysical comparison to human calmodulin evaluated drug-target selectivity, showing higher parasite C-terminal thermostability but similar inhibitor affinities and target activation.\",\n      \"evidence\": \"differential scanning fluorimetry/calorimetry, in vitro binding, and enzyme activation assays with recombinant PfCaM and human CaM\",\n      \"pmids\": [\"32821880\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional similarity to host limits selective targeting\", \"Cellular validation of Malaria Box compound effects not shown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"In vitro binding to the MyoB IQ2 motif raised the possibility that calmodulin serves as a myosin light chain, expanding its potential structural role in the motor complex.\",\n      \"evidence\": \"in vitro binding/pulldown assay in P. falciparum\",\n      \"pmids\": [\"36273584\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single in vitro pulldown; PfCaM identity as PF3D7_0714400 inferred from context\", \"In vivo myosin light-chain role not demonstrated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"The crystal structure with melittin defined how calmodulin achieves high-affinity target binding, revealing an ensemble of co-existing sub-optimal binding modes at its hydrophobic pockets.\",\n      \"evidence\": \"X-ray crystallography and molecular dynamics simulations of PfCaM\",\n      \"pmids\": [\"36906144\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Melittin is a model peptide, not a physiological parasite target\", \"Structures with native effectors (PfPKB, calcineurin) not determined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Interaction proteomics identified PP7 phosphatase and CDPK1 as calmodulin partners, adding a further calcium-dependent phosphatase to its effector network.\",\n      \"evidence\": \"co-immunoprecipitation, conditional knockdown, and phosphoproteomics in P. falciparum\",\n      \"pmids\": [\"39387582\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the calmodulin-PP7 interaction not isolated to calmodulin\", \"Direct calmodulin-CDPK1 dependence not mechanistically dissected\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Structural prediction and pulldown indicated calmodulin binds up to six copies along the neck of the class XXII myosin PfMyoF, reinforcing a possible light-chain role for a second myosin.\",\n      \"evidence\": \"AlphaFold structural prediction and pull-down assay in P. falciparum\",\n      \"pmids\": [\"42141018\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single pulldown supported by prediction; PfCaM identity inferred from context\", \"In vivo stoichiometry and functional role not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved whether calmodulin is genetically essential for invasion and which of its many effector interactions are the physiologically dominant ones in vivo, as most links rest on pharmacology, overexpression, or in vitro binding.\",\n      \"evidence\": \"no conditional loss-of-function dissection of calmodulin's individual effector arms in the corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No calmodulin-specific conditional knockout phenotype reported\", \"Relative in vivo contribution of PfPKB, calcineurin, PP7, and myosin binding not ranked\", \"Native effector-bound structures absent\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005509\", \"supporting_discovery_ids\": [9, 10]},\n      {\"term_id\": \"GO:0004683\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"GO:0019855\", \"supporting_discovery_ids\": [6, 13]},\n      {\"term_id\": \"GO:0031432\", \"supporting_discovery_ids\": [15, 16]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005737\", \"supporting_discovery_ids\": [2, 9]},\n      {\"term_id\": \"GO:0020008\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0019722\", \"supporting_discovery_ids\": [6, 9, 10]},\n      {\"term_id\": \"GO:0006816\", \"supporting_discovery_ids\": [9, 10]},\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [3, 7, 8]}\n    ],\n    \"complexes\": [\n      \"calcineurin/PP2B phosphatase complex (calmodulin-activated) [#13]\",\n      \"actin-myosin glideosome motor (via PfPKB association) [#7]\"\n    ],\n    \"partners\": [\n      \"PfPKB (protein kinase B) [#6, #7]\",\n      \"PfPK2 (Ca2+/calmodulin-dependent kinase activity) [#8]\",\n      \"calcineurin/PP2B phosphatase [#13]\",\n      \"PP7 phosphatase [#14]\",\n      \"CDPK1 [#14]\",\n      \"MyoB (IQ2 motif) [#15]\",\n      \"PfMyoF (class XXII myosin neck) [#16]\"\n    ],\n    \"other_free_text\": [\n      \"Single-copy gene on chromosome 14 with a single intron and conserved eukaryotic regulatory elements [#0, #1].\",\n      \"Stage-regulated expression peaking in late trophozoite/schizont stages via transcription and RNA stability [#4].\",\n      \"Crystal structure with melittin reveals an ensemble of co-existing binding modes at hydrophobic pockets [#12].\",\n      \"Only modestly divergent from human calmodulin with higher C-terminal thermostability and similar inhibitor affinities, limiting selective drug targeting [#11].\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0714400","name":null,"product":"calmodulin, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1421000","name":null,"product":"calmodulin, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1423300","name":null,"product":"calmodulin, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"","evaluation":null}