{"gene":"PF3D7_0503600","run_date":"2026-09-07T10:55:52","timeline":{"discoveries":[{"year":2006,"finding":"In P. berghei ookinetes, MyoB (PbMyoB) displays a punctate pattern of expression around the entire cell periphery, distinct from MyoA and actin which co-localize at the apical tip; MyoB protein is expressed in gametocytes and zygotes as well as mature ookinetes, whereas MyoA is only present in fully mature ookinetes.","method":"Western immunoblot and immunofluorescence microscopy during ookinete development","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiment with subcellular resolution; single lab but two orthogonal methods (Western blot + immunofluorescence)","pmids":["17028009"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2005,"finding":"MyoB (Pfmyo-B) mRNA is transcribed throughout asexual blood-stage development in P. falciparum, but protein synthesis is temporally regulated to late schizogony, demonstrating post-transcriptional (translational) regulation.","method":"RT-PCR for transcript detection; Western blot / protein expression analysis across asexual stages","journal":"Cell motility and the cytoskeleton","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — two orthogonal methods (RT-PCR + protein detection) in a single lab establishing translational regulation","pmids":["15754360"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"MyoB is expressed in all invasive stages (merozoites, ookinetes, sporozoites) of P. falciparum, P. berghei, and P. knowlesi, localizes to a discrete apical location distinct from and anterior to rhoptries, rhoptry neck proteins, and micronemes. MyoB is not associated with glideosome complex proteins (including the MyoA light chain MTIP). A unique MyoB-specific light chain (MLC-B) was identified that contains a calmodulin-like domain at its C-terminus and an extended N-terminal region; MLC-B co-localizes with MyoB at the extreme apical pole and the two proteins form a complex.","method":"Immunofluorescence microscopy, co-immunoprecipitation, Western blot, use of multiple parasite species","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-localization, Co-IP establishing MyoB–MLC-B complex, negative result for glideosome association, replicated across three Plasmodium species with multiple orthogonal methods","pmids":["25802338"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium knowlesi","strain":""}]},{"year":2015,"finding":"MyoB is not associated with the glideosome complex proteins, including the MyoA light chain MTIP, distinguishing it mechanistically from MyoA.","method":"Co-immunoprecipitation and Western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — negative Co-IP result rigorously established, replicated across species, consistent with parallel localization data in same study","pmids":["25802338"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium knowlesi","strain":""}]},{"year":2018,"finding":"In vitro, MTIP (myosin A tail interacting protein) can interact with MyoB (PfMyoB) recombinant protein; competition and inhibition assays with specific peptides demonstrated this binding, suggesting MTIP can potentially act as a light chain of MyoB.","method":"Far Western blot and in vitro protein–protein interaction assays (competition and inhibition assays) using differentially tagged recombinant proteins","journal":"Parasitology research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single in vitro method; finding is in apparent tension with the Co-IP negative result from PMID:25802338 (no association in native parasite), reducing confidence","pmids":["30094538"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"Gene deletion of MyoB in P. berghei revealed it is not essential for parasite survival; however, MyoB and its essential light chain MLC-B are both localized at the apical end of ookinetes but are expressed at completely different time points during development.","method":"Gene deletion (knockout), immunofluorescence microscopy, Western blot across life cycle stages","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean gene knockout with defined phenotypic readout (non-essential), combined with direct localization experiments; multiple orthogonal methods, single lab","pmids":["31283102"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2020,"finding":"In P. falciparum, MyoB (PfMyoB) functions as an auxiliary motor during red blood cell invasion; conditional mutagenesis leading to complete motor absence (including MyoB) was used to define three distinct energetic barriers during invasion (RBC deformation, mid-invasion initiation, and completion of internalisation), each requiring an active parasite motor.","method":"Conditional mutagenesis combined with live video microscopy","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional mutagenesis with live imaging providing defined phenotypic stages; however MyoB's specific contribution is inferred from combined motor-absence experiments alongside MyoA mutants, single lab","pmids":["33104759"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"Recombinant P. falciparum MyoB, produced with parasite-specific chaperones Hsp90 and Unc45, exhibits actin-activated ATPase activity and moves actin filaments in vitro. MyoB binds actin with high affinity. The ADP release rate is faster than the ATP turnover number, indicating ADP release is not rate-limiting. The calmodulin-like domain of light chain MLC-B binds to MyoB, and four additional putative regulatory light chains bind to the MyoB IQ2 motif in vitro. Low-resolution solution structure was determined by small-angle X-ray scattering (SAXS), confirming MyoB adopts the overall shape of a myosin.","method":"Recombinant protein expression with chaperones Hsp90/Unc45, in vitro ATPase activity assay, actin-gliding assay, biochemical binding assays (actin binding, light chain binding), SAXS structural analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with functional ATPase and motility assays, kinetic characterization, structural analysis, and multiple binding assays in a single rigorous study","pmids":["36273584"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"Knockout of MyoB in P. falciparum causes a delay in the initial stages of red blood cell invasion, resulting in a growth defect correlated with reduced invasion success, but the parasite is not lethally dependent on MyoB. MyoB remains at the apical tip of the merozoite during invasion but is no longer detectable once invasion is completed.","method":"Gene knockout (loss-of-function), growth/invasion assays, immunofluorescence microscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout with defined phenotypic readout (invasion delay, growth defect) and direct localization during invasion; multiple methods, single rigorous study","pmids":["36273584"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"MyoB (PF3D7_0503600) is a class XIV myosin expressed in all invasive stages of Plasmodium that localizes to the extreme apical tip of merozoites, ookinetes, and sporozoites independently of the glideosome complex; it forms a specific complex with its unique light chain MLC-B, exhibits actin-activated ATPase activity and actin filament motility in vitro (aided by chaperones Hsp90/Unc45), and while non-essential for parasite survival, its absence delays the initial stages of red blood cell invasion in P. falciparum and causes a growth defect, suggesting a role in force sensing or tethering during early invasion."},"narrative":{"mechanistic_narrative":"MyoB (PF3D7_0503600) is a class XIV myosin motor of Plasmodium expressed in all invasive stages—merozoites, ookinetes, and sporozoites—that occupies a discrete position at the extreme apical tip, anterior to and distinct from rhoptries, rhoptry-neck proteins, and micronemes [PMID:25802338]. Unlike the glideosome motor MyoA, MyoB is not associated with glideosome components including the MyoA light chain MTIP, marking it as a mechanistically separate apical motor [PMID:25802338]. MyoB partners with a dedicated, essential light chain, MLC-B, which carries a C-terminal calmodulin-like domain and co-localizes with MyoB at the apical pole to form a specific complex [PMID:25802338, PMID:31283102]. Reconstitution of recombinant MyoB with the parasite chaperones Hsp90 and Unc45 demonstrated that it is a bona fide motor: it binds actin with high affinity, has actin-activated ATPase activity, and drives actin-filament motility in vitro, with ADP release faster than the overall ATP turnover; SAXS confirmed an overall myosin shape [PMID:36273584]. Functionally, MyoB is non-essential for survival, but its loss delays the initial stages of red blood cell invasion and produces a growth defect correlated with reduced invasion success, consistent with a role as an auxiliary invasion motor at the apical tip [PMID:33104759, PMID:36273584]. Expression of MyoB is post-transcriptionally controlled, with transcript present through asexual development but protein restricted to late schizogony [PMID:15754360].","teleology":[{"year":2005,"claim":"Establishing when MyoB protein is made addressed whether its abundant transcript reflects constitutive activity or staged deployment, revealing translational control that times the motor to the invasive phase.","evidence":"RT-PCR for transcript plus protein detection across asexual blood stages in P. falciparum","pmids":["15754360"],"confidence":"Medium","gaps":["Mechanism of translational repression/derepression not identified","Does not address MyoB localization or partners"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"Comparing MyoB and MyoA distribution in ookinetes tested whether MyoB simply mirrors the known apical motor, and instead showed a distinct peripheral, earlier-expressed pattern, hinting at a separate role.","evidence":"Western blot and immunofluorescence across ookinete development in P. berghei","pmids":["17028009"],"confidence":"Medium","gaps":["Single species and single lab","Peripheral pattern in ookinetes not reconciled with later apical-tip localization in merozoites","No functional readout"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2015,"claim":"Determining MyoB's precise location and binding partners answered whether it belongs to the glideosome, establishing it as a glideosome-independent apical-tip motor with its own dedicated light chain MLC-B.","evidence":"Immunofluorescence, reciprocal co-immunoprecipitation, and Western blot across P. falciparum, P. berghei, and P. knowlesi","pmids":["25802338"],"confidence":"High","gaps":["Functional consequence of apical localization not tested","Whether MLC-B is the only physiological light chain unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium knowlesi","strain":""}]},{"year":2018,"claim":"An in vitro binding test asked whether the MyoA light chain MTIP could also serve MyoB, reporting a recombinant interaction that stands in tension with the native co-IP showing no glideosome association.","evidence":"Far Western and in vitro competition/inhibition assays with recombinant proteins in P. falciparum","pmids":["30094538"],"confidence":"Low","gaps":["In vitro only, not confirmed in native parasite","Directly conflicts with the negative co-IP result for MTIP association [#3]","Physiological relevance unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"Gene deletion asked whether MyoB is required for the parasite, showing it is dispensable for survival while confirming MLC-B is essential and temporally offset from MyoB in ookinetes.","evidence":"Gene knockout with life-cycle immunofluorescence and Western blot in P. berghei","pmids":["31283102"],"confidence":"High","gaps":["Why MLC-B is essential while MyoB is not is unexplained","Temporal mismatch between MyoB and MLC-B expression not mechanistically resolved"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2020,"claim":"Conditional removal of parasite motors during invasion tested where motor force is needed, defining three energetic barriers and placing MyoB as an auxiliary motor in RBC invasion.","evidence":"Conditional mutagenesis with live video microscopy of invasion in P. falciparum","pmids":["33104759"],"confidence":"Medium","gaps":["MyoB's specific contribution inferred from combined motor-absence experiments rather than isolated","Which barrier MyoB acts on not separately resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"claim":"In vitro reconstitution and a targeted knockout together answered whether MyoB is a genuine functional motor and what its loss costs, showing actin-activated motor activity and an invasion-stage delay/growth defect upon deletion.","evidence":"Recombinant MyoB with Hsp90/Unc45 chaperones, ATPase and actin-gliding assays, kinetics, light-chain and actin binding, SAXS; plus knockout with growth/invasion assays and immunofluorescence in P. falciparum","pmids":["36273584"],"confidence":"High","gaps":["High-resolution structure not determined (only low-resolution SAXS)","The in vivo cargo or tethering substrate at the apical tip not identified","Roles of the four additional IQ2-binding candidate light chains untested in vivo"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"The precise mechanical role of MyoB at the apical tip during invasion—whether it senses force, tethers, or generates directional force, and against which substrate—remains undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No identified in vivo binding partner beyond MLC-B and actin","Molecular basis of the invasion delay phenotype unresolved","Physiological light-chain composition of the native complex unconfirmed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["MyoB-MLC-B complex"],"partners":["MLC-B (MYOB-SPECIFIC LIGHT CHAIN, CALMODULIN-LIKE DOMAIN)","ACTIN (FILAMENTS)","HSP90 (CHAPERONE FOR FOLDING/ACTIVITY IN VITRO)","UNC45 (CHAPERONE FOR FOLDING/ACTIVITY IN VITRO)","MTIP (IN VITRO INTERACTION ONLY, IN TENSION WITH NATIVE CO-IP)"],"other_free_text":["Class XIV myosin expressed in all invasive stages (merozoites, ookinetes, sporozoites) across P. falciparum, P. berghei, P. knowlesi [#2].","Localizes to the extreme apical tip anterior to rhoptries, rhoptry-neck proteins, and micronemes, and is glideosome-independent (not associated with MTIP/glideosome in native parasite) [#2, #3].","Non-essential in P. berghei and P. falciparum; knockout delays early RBC invasion and causes a growth defect [#5, #8].","Protein expression translationally regulated to late schizogony despite transcript present throughout asexual development [#1].","Four additional putative regulatory light chains bind the MyoB IQ2 motif in vitro; ADP release is faster than ATP turnover [#7]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"17028009","id":"PMC_17028009","title":"Involvement of actin and myosins in Plasmodium berghei ookinete motility.","date":"2006","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/17028009","citation_count":38,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["MyoB","PbMyoB"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31283102","id":"PMC_31283102","title":"Systematic analysis of Plasmodium myosins reveals differential expression, localisation, and function in invasive and proliferative parasite stages.","date":"2019","source":"Cellular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/31283102","citation_count":29,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["MyoB"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25802338","id":"PMC_25802338","title":"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.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25802338","citation_count":28,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["MyoB","myosin B"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33104759","id":"PMC_33104759","title":"Actomyosin forces and the energetics of red blood cell invasion by the malaria parasite Plasmodium falciparum.","date":"2020","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/33104759","citation_count":24,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfMyoB"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"15754360","id":"PMC_15754360","title":"Plasmodium falciparum myosins: transcription and translation during asexual parasite development.","date":"2005","source":"Cell motility and the cytoskeleton","url":"https://pubmed.ncbi.nlm.nih.gov/15754360","citation_count":17,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfMyoB"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30259259","id":"PMC_30259259","title":"Systematic Comparison of Strategies to Achieve Soluble Expression of Plasmodium falciparum Recombinant Proteins in E. coli.","date":"2018","source":"Molecular biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/30259259","citation_count":5,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["myosin B"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"28265752","id":"PMC_28265752","title":"Myosin B of Plasmodium falciparum (PfMyoB): in silico prediction of its three-dimensional structure and its possible interaction with MTIP.","date":"2017","source":"Parasitology research","url":"https://pubmed.ncbi.nlm.nih.gov/28265752","citation_count":4,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["myosin B","PfMyoB"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30094538","id":"PMC_30094538","title":"In vitro interaction between Plasmodium falciparum myosin B (PfMyoB) and myosin A tail interacting protein (MTIP).","date":"2018","source":"Parasitology research","url":"https://pubmed.ncbi.nlm.nih.gov/30094538","citation_count":2,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["myosin B","PfMyoB"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"36273584","id":"PMC_36273584","title":"Analysis of Plasmodium falciparum myosin B ATPase activity and structure in complex with the calmodulin-like domain of its light chain MLC-B.","date":"2022","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/36273584","citation_count":1,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["MyoB","myosin B"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7180,"output_tokens":2626,"usd":0.030465,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8117,"output_tokens":3418,"usd":0.063018,"stage2_stop_reason":"end_turn"},"total_usd":0.093483,"stage1_batch_id":"msgbatch_01DbiymDmubkPpYvdbAu5a7V","stage2_batch_id":"msgbatch_012TbrWvMRH129T7PQ4SmvrJ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"In P. berghei ookinetes, MyoB (PbMyoB) displays a punctate pattern of expression around the entire cell periphery, distinct from MyoA and actin which co-localize at the apical tip; MyoB protein is expressed in gametocytes and zygotes as well as mature ookinetes, whereas MyoA is only present in fully mature ookinetes.\",\n      \"method\": \"Western immunoblot and immunofluorescence microscopy during ookinete development\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiment with subcellular resolution; single lab but two orthogonal methods (Western blot + immunofluorescence)\",\n      \"pmids\": [\"17028009\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MyoB (Pfmyo-B) mRNA is transcribed throughout asexual blood-stage development in P. falciparum, but protein synthesis is temporally regulated to late schizogony, demonstrating post-transcriptional (translational) regulation.\",\n      \"method\": \"RT-PCR for transcript detection; Western blot / protein expression analysis across asexual stages\",\n      \"journal\": \"Cell motility and the cytoskeleton\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — two orthogonal methods (RT-PCR + protein detection) in a single lab establishing translational regulation\",\n      \"pmids\": [\"15754360\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"MyoB is expressed in all invasive stages (merozoites, ookinetes, sporozoites) of P. falciparum, P. berghei, and P. knowlesi, localizes to a discrete apical location distinct from and anterior to rhoptries, rhoptry neck proteins, and micronemes. MyoB is not associated with glideosome complex proteins (including the MyoA light chain MTIP). A unique MyoB-specific light chain (MLC-B) was identified that contains a calmodulin-like domain at its C-terminus and an extended N-terminal region; MLC-B co-localizes with MyoB at the extreme apical pole and the two proteins form a complex.\",\n      \"method\": \"Immunofluorescence microscopy, co-immunoprecipitation, Western blot, use of multiple parasite species\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-localization, Co-IP establishing MyoB–MLC-B complex, negative result for glideosome association, replicated across three Plasmodium species with multiple orthogonal methods\",\n      \"pmids\": [\"25802338\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium knowlesi\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"MyoB is not associated with the glideosome complex proteins, including the MyoA light chain MTIP, distinguishing it mechanistically from MyoA.\",\n      \"method\": \"Co-immunoprecipitation and Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — negative Co-IP result rigorously established, replicated across species, consistent with parallel localization data in same study\",\n      \"pmids\": [\"25802338\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium knowlesi\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In vitro, MTIP (myosin A tail interacting protein) can interact with MyoB (PfMyoB) recombinant protein; competition and inhibition assays with specific peptides demonstrated this binding, suggesting MTIP can potentially act as a light chain of MyoB.\",\n      \"method\": \"Far Western blot and in vitro protein–protein interaction assays (competition and inhibition assays) using differentially tagged recombinant proteins\",\n      \"journal\": \"Parasitology research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single in vitro method; finding is in apparent tension with the Co-IP negative result from PMID:25802338 (no association in native parasite), reducing confidence\",\n      \"pmids\": [\"30094538\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Gene deletion of MyoB in P. berghei revealed it is not essential for parasite survival; however, MyoB and its essential light chain MLC-B are both localized at the apical end of ookinetes but are expressed at completely different time points during development.\",\n      \"method\": \"Gene deletion (knockout), immunofluorescence microscopy, Western blot across life cycle stages\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean gene knockout with defined phenotypic readout (non-essential), combined with direct localization experiments; multiple orthogonal methods, single lab\",\n      \"pmids\": [\"31283102\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In P. falciparum, MyoB (PfMyoB) functions as an auxiliary motor during red blood cell invasion; conditional mutagenesis leading to complete motor absence (including MyoB) was used to define three distinct energetic barriers during invasion (RBC deformation, mid-invasion initiation, and completion of internalisation), each requiring an active parasite motor.\",\n      \"method\": \"Conditional mutagenesis combined with live video microscopy\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional mutagenesis with live imaging providing defined phenotypic stages; however MyoB's specific contribution is inferred from combined motor-absence experiments alongside MyoA mutants, single lab\",\n      \"pmids\": [\"33104759\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Recombinant P. falciparum MyoB, produced with parasite-specific chaperones Hsp90 and Unc45, exhibits actin-activated ATPase activity and moves actin filaments in vitro. MyoB binds actin with high affinity. The ADP release rate is faster than the ATP turnover number, indicating ADP release is not rate-limiting. The calmodulin-like domain of light chain MLC-B binds to MyoB, and four additional putative regulatory light chains bind to the MyoB IQ2 motif in vitro. Low-resolution solution structure was determined by small-angle X-ray scattering (SAXS), confirming MyoB adopts the overall shape of a myosin.\",\n      \"method\": \"Recombinant protein expression with chaperones Hsp90/Unc45, in vitro ATPase activity assay, actin-gliding assay, biochemical binding assays (actin binding, light chain binding), SAXS structural analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with functional ATPase and motility assays, kinetic characterization, structural analysis, and multiple binding assays in a single rigorous study\",\n      \"pmids\": [\"36273584\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Knockout of MyoB in P. falciparum causes a delay in the initial stages of red blood cell invasion, resulting in a growth defect correlated with reduced invasion success, but the parasite is not lethally dependent on MyoB. MyoB remains at the apical tip of the merozoite during invasion but is no longer detectable once invasion is completed.\",\n      \"method\": \"Gene knockout (loss-of-function), growth/invasion assays, immunofluorescence microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout with defined phenotypic readout (invasion delay, growth defect) and direct localization during invasion; multiple methods, single rigorous study\",\n      \"pmids\": [\"36273584\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"MyoB (PF3D7_0503600) is a class XIV myosin expressed in all invasive stages of Plasmodium that localizes to the extreme apical tip of merozoites, ookinetes, and sporozoites independently of the glideosome complex; it forms a specific complex with its unique light chain MLC-B, exhibits actin-activated ATPase activity and actin filament motility in vitro (aided by chaperones Hsp90/Unc45), and while non-essential for parasite survival, its absence delays the initial stages of red blood cell invasion in P. falciparum and causes a growth defect, suggesting a role in force sensing or tethering during early invasion.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MyoB (PF3D7_0503600) is a class XIV myosin motor of Plasmodium expressed in all invasive stages—merozoites, ookinetes, and sporozoites—that occupies a discrete position at the extreme apical tip, anterior to and distinct from rhoptries, rhoptry-neck proteins, and micronemes [#2]. Unlike the glideosome motor MyoA, MyoB is not associated with glideosome components including the MyoA light chain MTIP, marking it as a mechanistically separate apical motor [#2, #3]. MyoB partners with a dedicated, essential light chain, MLC-B, which carries a C-terminal calmodulin-like domain and co-localizes with MyoB at the apical pole to form a specific complex [#2, #5]. Reconstitution of recombinant MyoB with the parasite chaperones Hsp90 and Unc45 demonstrated that it is a bona fide motor: it binds actin with high affinity, has actin-activated ATPase activity, and drives actin-filament motility in vitro, with ADP release faster than the overall ATP turnover; SAXS confirmed an overall myosin shape [#7]. Functionally, MyoB is non-essential for survival, but its loss delays the initial stages of red blood cell invasion and produces a growth defect correlated with reduced invasion success, consistent with a role as an auxiliary invasion motor at the apical tip [#6, #8]. Expression of MyoB is post-transcriptionally controlled, with transcript present through asexual development but protein restricted to late schizogony [#1].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Establishing when MyoB protein is made addressed whether its abundant transcript reflects constitutive activity or staged deployment, revealing translational control that times the motor to the invasive phase.\",\n      \"evidence\": \"RT-PCR for transcript plus protein detection across asexual blood stages in P. falciparum\",\n      \"pmids\": [\"15754360\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of translational repression/derepression not identified\", \"Does not address MyoB localization or partners\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Comparing MyoB and MyoA distribution in ookinetes tested whether MyoB simply mirrors the known apical motor, and instead showed a distinct peripheral, earlier-expressed pattern, hinting at a separate role.\",\n      \"evidence\": \"Western blot and immunofluorescence across ookinete development in P. berghei\",\n      \"pmids\": [\"17028009\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single species and single lab\", \"Peripheral pattern in ookinetes not reconciled with later apical-tip localization in merozoites\", \"No functional readout\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Determining MyoB's precise location and binding partners answered whether it belongs to the glideosome, establishing it as a glideosome-independent apical-tip motor with its own dedicated light chain MLC-B.\",\n      \"evidence\": \"Immunofluorescence, reciprocal co-immunoprecipitation, and Western blot across P. falciparum, P. berghei, and P. knowlesi\",\n      \"pmids\": [\"25802338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of apical localization not tested\", \"Whether MLC-B is the only physiological light chain unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}, {\"species\": \"Plasmodium knowlesi\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"An in vitro binding test asked whether the MyoA light chain MTIP could also serve MyoB, reporting a recombinant interaction that stands in tension with the native co-IP showing no glideosome association.\",\n      \"evidence\": \"Far Western and in vitro competition/inhibition assays with recombinant proteins in P. falciparum\",\n      \"pmids\": [\"30094538\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"In vitro only, not confirmed in native parasite\", \"Directly conflicts with the negative co-IP result for MTIP association [#3]\", \"Physiological relevance unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Gene deletion asked whether MyoB is required for the parasite, showing it is dispensable for survival while confirming MLC-B is essential and temporally offset from MyoB in ookinetes.\",\n      \"evidence\": \"Gene knockout with life-cycle immunofluorescence and Western blot in P. berghei\",\n      \"pmids\": [\"31283102\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why MLC-B is essential while MyoB is not is unexplained\", \"Temporal mismatch between MyoB and MLC-B expression not mechanistically resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Conditional removal of parasite motors during invasion tested where motor force is needed, defining three energetic barriers and placing MyoB as an auxiliary motor in RBC invasion.\",\n      \"evidence\": \"Conditional mutagenesis with live video microscopy of invasion in P. falciparum\",\n      \"pmids\": [\"33104759\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MyoB's specific contribution inferred from combined motor-absence experiments rather than isolated\", \"Which barrier MyoB acts on not separately resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"In vitro reconstitution and a targeted knockout together answered whether MyoB is a genuine functional motor and what its loss costs, showing actin-activated motor activity and an invasion-stage delay/growth defect upon deletion.\",\n      \"evidence\": \"Recombinant MyoB with Hsp90/Unc45 chaperones, ATPase and actin-gliding assays, kinetics, light-chain and actin binding, SAXS; plus knockout with growth/invasion assays and immunofluorescence in P. falciparum\",\n      \"pmids\": [\"36273584\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution structure not determined (only low-resolution SAXS)\", \"The in vivo cargo or tethering substrate at the apical tip not identified\", \"Roles of the four additional IQ2-binding candidate light chains untested in vivo\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The precise mechanical role of MyoB at the apical tip during invasion—whether it senses force, tethers, or generates directional force, and against which substrate—remains undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No identified in vivo binding partner beyond MLC-B and actin\", \"Molecular basis of the invasion delay phenotype unresolved\", \"Physiological light-chain composition of the native complex unconfirmed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0000146\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0016887\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0051015\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0005516\", \"supporting_discovery_ids\": [2, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020007\", \"supporting_discovery_ids\": [2, 5, 8]},\n      {\"term_id\": \"GO:0016459\", \"supporting_discovery_ids\": [2, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"GO:0030048\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [\n      \"MyoB-MLC-B complex\"\n    ],\n    \"partners\": [\n      \"MLC-B (MyoB-specific light chain, calmodulin-like domain)\",\n      \"actin (filaments)\",\n      \"Hsp90 (chaperone for folding/activity in vitro)\",\n      \"Unc45 (chaperone for folding/activity in vitro)\",\n      \"MTIP (in vitro interaction only, in tension with native co-IP)\"\n    ],\n    \"other_free_text\": [\n      \"Class XIV myosin expressed in all invasive stages (merozoites, ookinetes, sporozoites) across P. falciparum, P. berghei, P. knowlesi [#2].\",\n      \"Localizes to the extreme apical tip anterior to rhoptries, rhoptry-neck proteins, and micronemes, and is glideosome-independent (not associated with MTIP/glideosome in native parasite) [#2, #3].\",\n      \"Non-essential in P. berghei and P. falciparum; knockout delays early RBC invasion and causes a growth defect [#5, #8].\",\n      \"Protein expression translationally regulated to late schizogony despite transcript present throughout asexual development [#1].\",\n      \"Four additional putative regulatory light chains bind the MyoB IQ2 motif in vitro; ADP release is faster than ATP turnover [#7].\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0503600","name":null,"product":"myosin B","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1103300","name":null,"product":"myosin B","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1029900","name":null,"product":"myosin B, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"MyoB","evaluation":null}