Affinage · Plasmodium

PF3D7_1030800

calmodulin, putative

Annotated
2026-09-08
57 papers in source corpus 15 papers cited in narrative 15 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PF3D7_1030800 encodes the single-copy Plasmodium falciparum calmodulin, a Ca2+-sensing protein that couples intracellular calcium fluxes to blood-stage development and erythrocyte invasion (PMID:1852174, PMID:1915742, PMID:18165240). It is present as a single intron-containing gene on chromosome 14 with high homology to mammalian calmodulin, and its expression is developmentally regulated at both transcription and mRNA stability, rising from low levels in rings to a peak in late trophozoites/schizonts, with promoter activity directed by upstream poly(dA)poly(dT) tracts (PMID:1852174, PMID:1915742, PMID:8720124, PMID:15850701). The protein is diffusely cytoplasmic in mature parasites and concentrates at the apical end of merozoites within the rhoptry ductule, where calmodulin antagonists disrupt its localization and block erythrocyte invasion (PMID:3313391, PMID:3127214). Mechanistically, calmodulin acts downstream of phospholipase C–generated Ca2+ signals to activate the kinases PfPKB and PfPK2 in a calcium-dependent manner, with PfPKB in turn phosphorylating the glideosome component PfGAP45 to drive invasion (PMID:16809343, PMID:18165240, PMID:18762219). Beyond invasion, calmodulin participates in cytosolic calcium homeostasis and modulates calcium-dependent intracellular proteolysis, and interacts with the calcium-dependent phosphatase PP7 during early ring-stage development (PMID:26689736, PMID:29913151, PMID:39387582). Structurally, Ca2+-saturated PfCaM binds targets through non-classical recognition modes lacking canonical anchor interactions, and its greater conformational stability than human calmodulin—driven by a more stable C-terminal domain—is accompanied by biochemically similar function, making it unsuitable as a selective drug target (PMID:32821880, PMID:36906144).

Mechanistic history

Synthesis pass · year-by-year structured walk · 7 steps
  1. 1987 Medium

    Establishing whether calmodulin has a functional role in the parasite required localizing the protein and testing its requirement, which linked it to the invasion machinery.

    Evidence Radioimmunoassay and immunoelectron microscopy plus calmodulin-antagonist inhibition of invasion and maturation in P. falciparum cultures

    PMID:3127214 PMID:3313391

    Open questions at the time
    • Antagonists are not calmodulin-specific and could act on other targets
    • No genetic loss-of-function to confirm requirement
    • Molecular events downstream of apical calmodulin not defined
  2. 1991 High

    Defining the gene architecture answered whether P. falciparum encodes calmodulin as a distinct single-copy gene and excluded a role in chloroquine resistance.

    Evidence Gene cloning, Southern/Western blotting, primer extension, and comparison across resistant and sensitive isolates

    PMID:1852174 PMID:1915742

    Open questions at the time
    • Functional consequences of the sequence divergence from mammalian CaM not addressed
    • Regulatory basis of stage-specific expression not yet resolved
  3. 2005 Medium

    Characterizing developmental expression and its promoter answered how calmodulin abundance is timed to the blood-stage cycle rather than being constitutive.

    Evidence Northern blotting and pulse-chase mRNA stability assays across synchronized stages, plus CAT reporter deletions and EMSA of the pfcam promoter

    PMID:15850701 PMID:8720124

    Open questions at the time
    • Specific transcription factors binding the poly(dA)poly(dT) tracts not identified
    • Link between expression timing and functional demand not directly tested
  4. 2008 Medium

    Identifying calmodulin-activated kinases established the molecular effectors connecting Ca2+ signals to invasion.

    Evidence Reciprocal Co-IP and in vitro kinase assays for PfPKB, in vitro reconstitution with catalytic-lysine mutagenesis for PfPK2, plus invasion assays and PfGAP45 phosphorylation

    PMID:16809343 PMID:18165240 PMID:18762219

    Open questions at the time
    • Interactions shown largely in vitro/single lab without in-parasite genetic validation
    • Full effector network downstream of PfGAP45 phosphorylation not mapped
    • Contribution of each kinase to invasion not separately quantified genetically
  5. 2018 Medium

    Perturbing calmodulin levels tested its role in calcium handling itself, extending its function beyond kinase activation to Ca2+ homeostasis and proteolysis.

    Evidence Knockin localization and calmidazolium-triggered live Ca2+ imaging, plus overexpression with fluorogenic protease activity assays in P. falciparum

    PMID:26689736 PMID:29913151

    Open questions at the time
    • Identity of the calcium-dependent proteases modulated not defined
    • Mechanism linking calmodulin to a non-ER Ca2+ reservoir unresolved
    • Effects of overexpression may not reflect endogenous function
  6. 2023 High

    Biophysical and structural characterization answered whether PfCaM differs enough from human calmodulin to be a selective target and how it engages targets.

    Evidence Thermal/CD/fluorescence stability and comparative binding/activation assays on recombinant protein, and X-ray crystallography of Ca2+-saturated PfCaM with melittin plus MD simulations

    PMID:32821880 PMID:36906144

    Open questions at the time
    • Non-classical binding modes shown with melittin, not with a physiological parasite target
    • Functional significance of the more stable C-terminal domain in vivo unknown
  7. 2026 Low

    Continued interactome mapping expanded the calmodulin partner set to a phosphatase and a myosin, hinting at roles in ring-stage signaling and motor function.

    Evidence Co-immunoprecipitation of PP7, and pull-down plus structural prediction identifying PfCaM as a PfMyoF light chain

    PMID:39387582 PMID:42141018

    Open questions at the time
    • PfMyoF light-chain role rests on a single pull-down with structural prediction, not reconstituted motor assays
    • Functional consequences of the PP7 interaction not tested by loss-of-function
    • Stoichiometry of up to six CaM copies on the MyoF neck not experimentally verified

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved how essential calmodulin is in vivo and which of its many partners dominate specific stages, since most functional evidence relies on antagonists, overexpression, or in vitro interactions rather than conditional genetic depletion.
  • No genetic loss-of-function phenotype for the endogenous gene
  • Relative contribution of PfPKB, PfPK2, PP7, and PfMyoF interactions across stages unquantified
  • Physiological CaM-binding targets driving invasion not structurally captured

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
PFGAP45 (VIA PFPKB PHOSPHORYLATION)PFMYOFPFPK2PFPKBPP7 PHOSPHATASE
Complex memberships
PfMyoF motor complex (PfCaM as light chain)

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1991 The P. falciparum calmodulin gene (PF3D7_1030800) exists as a single copy on chromosome 14, contains a single intron of ~506 bp with appropriate splice sites, and encodes a protein with high sequence homology (89%) to mammalian calmodulin. Primer extension studies mapped the major transcription start site 62 bases upstream of the initial ATG. Gene cloning, Southern blotting, primer extension, sequence analysis Molecular and biochemical parasitology High 1852174 1915742
1987 Calmodulin (PF3D7_1030800) was detected by radioimmunoassay in free P. falciparum parasites, with levels proportional to parasite maturity. Immunoelectron microscopy localized CaM diffusely in the cytoplasm of mature parasites and concentrated at the apical end of merozoites within the ductule of rhoptries. Radioimmunoassay, immunoelectron microscopy Proceedings of the National Academy of Sciences of the United States of America Medium 3313391
1987 Calmodulin antagonists (W7, trifluoperazine, R24571) inhibited erythrocyte invasion by merozoites and schizont maturation in P. falciparum, with invasion being more sensitive than maturation; calmodulin accumulated at the apical end of merozoites was shown by immunoelectron microscopy to be disrupted by TFP treatment, suggesting CaM at the merozoite apex plays a role in erythrocyte invasion. Calmodulin antagonist treatment of P. falciparum cultures, immunoelectron microscopy European journal of cell biology Medium 3127214
1991 The calmodulin gene of P. falciparum is expressed approximately equally in chloroquine-resistant and chloroquine-sensitive isolates; it is not amplified or overexpressed in resistant strains, indicating that calmodulin is not involved in the mechanism of chloroquine resistance. Southern blotting, Western blotting, quantitative comparison across resistant and sensitive isolates Experimental parasitology Medium 1915742
1995 Calmodulin mRNA and protein levels in P. falciparum are low in early ring stages, rise to a peak around 40 h (late trophozoite/early schizont), and the protein continues to accumulate through schizogony; mRNA stability differs across stages with rapid degradation in mature trophozoites. This demonstrates that calmodulin expression is regulated at the level of transcription and mRNA degradation rather than following a constitutive housekeeping pattern. Northern blotting, pulse-chase mRNA stability assays, quantitative protein measurement across synchronized stages Journal of biochemistry Medium 8720124
2005 The P. falciparum calmodulin gene promoter (pfcam) contains multiple transcription-initiation sites within 180 bp upstream of the ORF, clustered in four ~30 bp regions; activity diminishes upon stepwise removal of sequence between -625 and -230 bp upstream. Nuclear factor binding to pfcam upstream sequences correlates with density of poly(dA)poly(dT) tracts, and transcription-initiation sites lie just downstream of 25 bp poly(dA)poly(dT) tracts, indicating these tracts direct promoter activity. Oligo-capping/transcript mapping, CAT reporter assays with serial deletions, electromobility-shift assays (EMSA) with poly(dA)poly(dT) competition Molecular and biochemical parasitology Medium 15850701
2006 P. falciparum calmodulin (PF3D7_1030800) interacts in a calcium-dependent manner with a mapped CaM-binding domain in the N-terminal region of PfPKB, and co-associates with PfPKB in parasite lysates; this interaction activates PfPKB kinase activity, constituting part of a phospholipase C → calcium → calmodulin → PfPKB signaling cascade. Co-immunoprecipitation, in vitro binding assays, calmodulin-domain mapping, kinase activity assays with/without calmodulin and calcium The Journal of biological chemistry Medium 16809343
2007 Blocking calmodulin function (along with phospholipase C) impaired erythrocyte invasion by P. falciparum merozoites, demonstrating that the Ca2+/calmodulin pathway is required for invasion; downstream, calmodulin-activated PfPKB phosphorylates PfGAP45, a glideosome component. Pharmacological inhibition of calmodulin and PLC in invasion assays, in vitro phosphorylation of PfGAP45 The Journal of biological chemistry Medium 18165240
2008 P. falciparum calmodulin activates PfPK2 (a CaMK homolog) in a calcium-dependent manner in vitro; calmodulin antagonists inhibited PfPK2 phosphorylation of histone II(AS) in vitro and reduced ring-stage parasitemia in invasion assays. PfPK2 localizes to merozoites. In vitro kinase assay with purified PfPK2, calmodulin, and Ca2+; site-directed mutagenesis of catalytic lysine; invasion assays with calmodulin antagonists; immunoelectron microscopy Molecular and biochemical parasitology Medium 18762219
2015 Calmodulin (PF3D7_1030800) is expressed in all erythrocytic stages of P. falciparum as shown by a knockin approach. In trophozoites, the calmodulin inhibitor calmidazolium (CZ) mobilizes intracellular calcium (not from the ER) under Ca2+-free extracellular conditions, indicating that calmodulin-related proteins act as intracellular Ca2+ reservoirs; the mitochondrion participates in sequestering the CZ-induced cytosolic Ca2+ rise. Knockin tagging for localization, live fluorescence Ca2+ imaging with/without CZ, ER depletion (thapsigargin), ionophore controls, mitochondrial Ca2+ buffering assay Cellular signalling Medium 26689736
2018 Overexpression of P. falciparum calmodulin (PfCaM) in parasites resulted in a higher cytosolic Ca2+ rise after calmidazolium challenge compared to wild-type, and increased calcium-dependent proteolytic activity, indicating that PfCaM participates in calcium homeostasis and modulates intracellular proteolysis during the erythrocytic cycle. Stable transfection/overexpression, live Ca2+ imaging with calmidazolium challenge, fluorogenic protease activity assay Biochemical and biophysical research communications Medium 29913151
2020 Recombinant P. falciparum calmodulin (PfCaM) shows higher overall conformational stability than human CaM, attributed to a more stable C-terminal domain in both Ca2+-free and Ca2+-saturated states, but exhibits similar biochemical function: comparable affinities (within ~3-fold) for small-molecule inhibitors and comparable activation of a target enzyme. These minor differences make PfCaM an unsuitable selective drug target. Biophysical characterization (thermal stability, CD, fluorescence), in vitro binding assays, enzyme activation assays comparing Pf and human CaM FASEB bioAdvances Medium 32821880
2023 Crystal structures of Ca2+-saturated P. falciparum calmodulin (PfCaM) in complex with melittin were determined, revealing multiple binding modes lacking classical anchor interactions; different sets of residues anchor at the hydrophobic pockets compared to the canonical CaM-target recognition, and molecular dynamics simulations showed co-existing conformers of similar stability. X-ray crystallography, molecular dynamics simulations The Journal of biological chemistry High 36906144
2024 P. falciparum calmodulin (PF3D7_1030800) physically interacts with the calcium-dependent phosphatase PP7 (as shown by co-immunoprecipitation), consistent with a role for calmodulin in regulating PP7-dependent calcium signaling during early ring-stage development. Co-immunoprecipitation of PP7 with calmodulin mBio Medium 39387582
2026 P. falciparum calmodulin (PfCaM / PF3D7_1030800) was identified as the light chain for PfMyoF, with the MyoF neck predicted to bind up to six copies of PfCaM; pull-down experiments confirmed PfCaM as part of the PfMyoF motor complex. Pull-down assays, structural prediction Communications biology Low 42141018

Source papers

Stage 0 corpus · 57 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 Plants, symbiosis and parasites: a calcium signalling connection. Nature reviews. Molecular cell biology 281 16072038
1996 Characterization of promoters and stable transfection by homologous and nonhomologous recombination in Plasmodium falciparum. Proceedings of the National Academy of Sciences of the United States of America 234 8692985
1997 Stable transgene expression in Plasmodium falciparum. Molecular and biochemical parasitology 119 9497038
1987 Calcium and calmodulin antagonists inhibit human malaria parasites (Plasmodium falciparum): implications for drug design. Proceedings of the National Academy of Sciences of the United States of America 115 3313391
1990 Possible roles of Ca2+ and cGMP as mediators of the exflagellation of Plasmodium berghei and Plasmodium falciparum. Molecular and biochemical parasitology 92 2172816
2002 Thioredoxin reductase is essential for the survival of Plasmodium falciparum erythrocytic stages. The Journal of biological chemistry 91 12004069
2005 Tetracycline analogue-regulated transgene expression in Plasmodium falciparum blood stages using Toxoplasma gondii transactivators. Proceedings of the National Academy of Sciences of the United States of America 89 15710888
2007 Role of Ca2+/calmodulin-PfPKB signaling pathway in erythrocyte invasion by Plasmodium falciparum. The Journal of biological chemistry 85 18165240
2008 Ortholog-based protein-protein interaction prediction and its application to inter-species interactions. BMC bioinformatics 76 19091010
1991 The structure of the calmodulin gene of Plasmodium falciparum. Molecular and biochemical parasitology 75 1852174
1987 Role of calmodulin in Plasmodium falciparum: implications for erythrocyte invasion by the merozoite. European journal of cell biology 68 3127214
2004 Evidence for a substrate specific and inhibitable drug efflux system in chloroquine resistant Plasmodium falciparum strains. Biochemistry 59 15610031
2006 PfPKB, a protein kinase B-like enzyme from Plasmodium falciparum: II. Identification of calcium/calmodulin as its upstream activator and dissection of a novel signaling pathway. The Journal of biological chemistry 58 16809343
2004 Evidence for differing roles for each lobe of the calmodulin-like domain in a calcium-dependent protein kinase. The Journal of biological chemistry 53 15126505
1999 Characterization of protein Ser/Thr phosphatases of the malaria parasite, Plasmodium falciparum: inhibition of the parasitic calcineurin by cyclophilin-cyclosporin complex. Molecular and biochemical parasitology 53 10340482
1993 The roles of Ca2+/calmodulin- and cGMP-dependent pathways in gametogenesis of a rodent malaria parasite, Plasmodium berghei. European journal of cell biology 49 8385016
2010 Investigations into the role of the Plasmodium falciparum SERCA (PfATP6) L263E mutation in artemisinin action and resistance. Antimicrobial agents and chemotherapy 48 20566762
2005 Structure of the regulatory apparatus of a calcium-dependent protein kinase (CDPK): a novel mode of calmodulin-target recognition. Journal of molecular biology 48 16430916
1989 Stage-dependent inhibition of Plasmodium falciparum by potent Ca2+ and calmodulin modulators. The Journal of protozoology 48 2657032
2009 Dissection of mechanisms involved in the regulation of Plasmodium falciparum calcium-dependent protein kinase 4. The Journal of biological chemistry 45 19307175
2000 Sexual stage-specific expression of a third calcium-dependent protein kinase from Plasmodium falciparum. Biochimica et biophysica acta 43 10760601
2006 Chloroquine resistance reversal agents as promising antimalarial drugs. Current drug targets 42 16918322
1994 Plasmodium falciparum calcium-dependent protein kinase phosphorylates proteins of the host erythrocytic membrane. Molecular and biochemical parasitology 42 7808482
2016 Rapid Generation of Marker-Free P. falciparum Fluorescent Reporter Lines Using Modified CRISPR/Cas9 Constructs and Selection Protocol. PloS one 40 27997583
1990 Cyclic AMP- and Ca2(+)-dependent protein kinases in Plasmodium falciparum. Experimental parasitology 39 2191871
1986 Effect of calmodulin inhibitors on viability and mitochondrial potential of Plasmodium falciparum in culture. Antimicrobial agents and chemotherapy 32 3541784
2002 Inhibition of Ca2+/calmodulin-dependent protein kinase blocks morphological differentiation of plasmodium gallinaceum zygotes to ookinetes. The Journal of biological chemistry 30 11827960
2011 Unusual anchor of a motor complex (MyoD-MLC2) to the plasma membrane of Toxoplasma gondii. Traffic (Copenhagen, Denmark) 28 21143563
2015 The Plasmodium Class XIV Myosin, MyoB, Has a Distinct Subcellular Location in Invasive and Motile Stages of the Malaria Parasite and an Unusual Light Chain. The Journal of biological chemistry 27 25802338
2019 Plasmodium centrin PbCEN-4 localizes to the putative MTOC and is dispensable for malaria parasite proliferation. Biology open 24 30541825
2004 Post-translational generation of constitutively active cores from larger phosphatases in the malaria parasite, Plasmodium falciparum: implications for proteomics. BMC molecular biology 24 15230980
2008 Characterization of Plasmodium falciparum protein kinase 2. Molecular and biochemical parasitology 20 18762219
1991 Plasmodium falciparum: the calmodulin gene is not amplified or overexpressed in chloroquine resistant or sensitive isolates. Experimental parasitology 19 1915742
1983 Transport of ions in erythrocytes infected by plasmodia. Ciba Foundation symposium 19 6132784
2005 A role for poly(dA)poly(dT) tracts in directing activity of the Plasmodium falciparum calmodulin gene promoter. Molecular and biochemical parasitology 15 15850701
2005 Chemosensitizers in drug transport mechanisms involved in protozoan resistance. Current drug targets. Infectious disorders 15 16535862
2009 Phenotypic and transcriptomic analyses of Plasmodium falciparum protein kinase A catalytic subunit inhibition. Parasitology research 14 19779742
1993 Sequence diversity in the intron of the calmodulin gene from Plasmodium falciparum. Molecular and biochemical parasitology 13 8366883
1989 Gametocytogenesis induction in cultured Plasmodium falciparum and further development of the gametocytes to ookinetes in prolonged culture. Parasitology research 13 2657715
2023 Structures of calmodulin-melittin complexes show multiple binding modes lacking classical anchoring interactions. The Journal of biological chemistry 11 36906144
1995 Stage-specific expression of the calmodulin gene in Plasmodium falciparum. Journal of biochemistry 11 8720124
1994 Signal transduction pathways involved in tumour necrosis factor secretion by Plasmodium falciparum-stimulated human monocytes. Immunology 9 7821969
2002 Expression of housekeeping genes during the asexual cell cycle of Plasmodium falciparum. Parasitology research 8 11954914
1993 Molecular modelling of malaria calmodulin suggests that it is not a suitable target for novel antimalarials. Philosophical transactions of the Royal Society of London. Series B, Biological sciences 8 8099744
1989 Calcium/calmodulin functions in P. falciparum in vitro--implications for antiprotozoal drug design. Progress in clinical parasitology 8 2491694
2015 Calmidazolium evokes high calcium fluctuations in Plasmodium falciparum. Cellular signalling 7 26689736
2013 Crystal structure of Plasmodium vivax FK506-binding protein 25 reveals conformational changes responsible for its noncanonical activity. Proteins 6 24302348
2020 Comparison of ligand binding and conformational stability of human calmodulin with its homolog from the malaria parasite Plasmodium falciparum. FASEB bioAdvances 5 32821880
2023 Microwaves can kill malaria parasites non-thermally. Frontiers in cellular and infection microbiology 4 36816585
2018 Plasmodium falciparum histidine triad protein and calmodulin modulates calcium homeostasis and intracellular proteolysis. Biochemical and biophysical research communications 3 29913151
2024 Plasmodium falciparum protein phosphatase PP7 is required for early ring-stage development. mBio 2 39387582
2021 Overexpression of Plasmodium falciparum M1 Aminopeptidase Promotes an Increase in Intracellular Proteolysis and Modifies the Asexual Erythrocytic Cycle Development. Pathogens (Basel, Switzerland) 2 34832608
2022 Analysis of Plasmodium falciparum myosin B ATPase activity and structure in complex with the calmodulin-like domain of its light chain MLC-B. The Journal of biological chemistry 1 36273584
2017 Biophysical characterization of the calmodulin-like domain of Plasmodium falciparum calcium dependent protein kinase 3. PloS one 1 28746405
1993 Approaches to studying genetic diversity of Plasmodium falciparum using a DNA sequence variation. Parassitologia 1 7901832
2026 Plasmodium falciparum PfMyoF contains a Rab-like tail domain and associates with perinuclear membrane trafficking proteins. Communications biology 0 42141018
2002 [Preparation of DNA libraries of Plasmodium falciparum for searching calmodulin binding protein genes, GOGAT and Pfmyo A]. Biomedica : revista del Instituto Nacional de Salud 0 12404924