{"gene":"PF3D7_1360500","run_date":"2026-09-08T14:19:06","timeline":{"discoveries":[{"year":2000,"finding":"GCbeta (PfGCbeta) is a bifunctional integral membrane protein in P. falciparum whose carboxyl-terminal catalytic domains (C1 and C2) conform to the topology of G protein-dependent adenylyl cyclases but carry residues characteristic of guanylyl cyclases. Expression of the catalytic domains of GCbeta in E. coli produced guanylyl cyclase activity, directly demonstrating its enzymatic function. The amino-terminal region has strong similarity to P-type ATPases.","method":"Heterologous expression of catalytic domains in E. coli with guanylyl cyclase activity assay; sequence/structural analysis of domain architecture","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro enzyme activity assay in E. coli reconstitution, single lab but direct biochemical demonstration","pmids":["10747978"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2001,"finding":"Membrane-associated guanylyl cyclase activity in P. falciparum mature gametocyte preparations is stimulated by xanthurenic acid (the gametocyte-activating factor) in a Mg2+/Mn2+-dependent but Ca2+-inhibited manner, linking GCbeta-associated cGMP synthesis to the exflagellation signaling pathway.","method":"Guanylyl cyclase enzyme activity assay on gametocyte membrane preparations with pharmacological stimulation by xanthurenic acid","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct biochemical activity assay on native membranes, single lab, single method; GCbeta not individually purified but implicated as membrane GC","pmids":["11703675"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"Genetic disruption of PbGCbeta in P. berghei produced parasites that formed morphologically normal ookinetes but exhibited severe defects in gliding motility, causing failure to invade the midgut epithelium and produce oocysts in vivo. In vitro, disruptant ookinetes could still transform into oocysts and sporozoites, demonstrating that GCbeta is specifically required for ookinete motility during midgut traversal, not for subsequent parasite development.","method":"Gene disruption (knockout) in P. berghei; confocal microscopy; in vitro and in vivo phenotypic analysis of ookinete motility and invasion","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean genetic knockout with specific and well-defined cellular phenotype (motility defect), orthogonal in vivo and in vitro readouts","pmids":["17030505"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2008,"finding":"Disruption of PfGCbeta in P. falciparum decreased GC activity but had no significant effect on gametogenesis, indicating that GCbeta-derived cGMP is dispensable for male or female gamete formation from gametocytes. By contrast, disruption of PfPDEdelta (the cGMP phosphodiesterase) severely impaired gametogenesis, demonstrating that cGMP levels must be kept below a threshold during gametocyte development for normal differentiation.","method":"Gene disruption (knockout) of PfGCbeta and PfPDEdelta in P. falciparum; gametogenesis assays","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean genetic knockout with specific phenotypic readout (gametogenesis), single lab; negative result for GCbeta role in gametogenesis is the primary finding","pmids":["18452584"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"Genetic epistasis in P. berghei ookinetes showed that the rounding-up phenotype caused by deletion of PDEdelta (unregulated cGMP) was suppressed in a double mutant additionally lacking GCbeta, establishing that GCbeta is the primary source of cGMP in ookinetes and that PDEdelta is its relevant degrading enzyme. Additionally, cGMP-PKG signaling was shown to overlap partially with calcium-dependent pathways in regulating ookinete gliding speed.","method":"Genetic epistasis via double-mutant construction (PDEdelta/GCbeta double knockout) in P. berghei; live cell morphology and gliding motility assays; pharmacological inhibition of PKG","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — classical suppressor epistasis with double mutant rescue, replicated across multiple genetic backgrounds and pharmacological treatments, clearly positions GCbeta in pathway","pmids":["19779564"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2018,"finding":"In P. yoelii, GCbeta localizes to the cytoplasm and then translocates and polarizes to the parasite plasma membrane at the 'ookinete extrados site' (OES) during zygote-to-ookinete differentiation, as visualized by real-time imaging. This polarization of enzymatically active GCbeta at OES initiates gliding of mature ookinetes. Both the P4-ATPase-like domain and guanylate cyclase domain are required for GCbeta polarization and ookinete gliding. CDC50A binds to and stabilizes GCbeta during ookinete development. The inner membrane complex protein ISP1 anchors the GCbeta/CDC50A complex at the OES.","method":"Real-time live imaging; gene tagging; co-immunoprecipitation (GCbeta-CDC50A interaction); genetic disruption of ISP1; domain deletion analysis; screening of inner membrane complex proteins","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Strong — live-cell imaging of localization with functional consequence, reciprocal Co-IP for CDC50A interaction, domain mutagenesis, and ISP1 epistasis, multiple orthogonal methods in one study","pmids":["30146157"],"is_preprint":false,"attribution":[{"species":"Plasmodium yoelii","strain":""}]},{"year":2025,"finding":"In P. yoelii ookinetes, the NAD+-dependent sirtuin deacetylase Sir2A interacts with GCbeta throughout ookinete development (identified by protein proximity labeling as the top GCbeta-interacting protein). In mature ookinetes, Sir2A co-localizes with GCbeta at OES in a mutually dependent manner. Parasites lacking Sir2A lose GCbeta OES localization, ookinete gliding, and mosquito infection, phenocopying GCbeta deficiency. GCbeta is acetylated in gametocytes but is deacetylated by Sir2A for OES localization in mature ookinetes. Elevated NAD+ levels in mature ookinetes promote Sir2A-catalyzed GCbeta deacetylation, linking metabolic state to GCbeta localization and activation.","method":"Protein proximity labeling (BioID); co-immunoprecipitation; live imaging; genetic knockouts of Sir2A in P. yoelii; acetylation state analysis; NAD+ level measurements during ookinete development","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — proximity labeling plus Co-IP plus genetic phenocopy plus PTM (acetylation/deacetylation) analysis, multiple orthogonal methods establishing mechanism of GCbeta regulation","pmids":["40050296"],"is_preprint":false,"attribution":[{"species":"Plasmodium yoelii","strain":""}]}],"current_model":"GCbeta (PF3D7_1360500) is a bifunctional integral membrane protein with an N-terminal P4-ATPase-like domain and C-terminal guanylyl cyclase catalytic domains that synthesize cGMP; in ookinetes it is the primary source of cGMP, translocating from cytoplasm to the ookinete extrados site (OES) during zygote-to-ookinete differentiation via a mechanism involving acetylation/deacetylation by the NAD+-dependent sirtuin Sir2A, and anchored at OES by the ISP1-CDC50A complex, where its enzymatic activity drives cGMP-PKG signaling to initiate gliding motility required for mosquito midgut invasion; in gametocytes GCbeta-derived cGMP is dispensable for gamete formation, and in P. falciparum asexual blood stages the related paralog GCalpha (not GCbeta) is the dominant source of cGMP for egress."},"narrative":{"mechanistic_narrative":"GCbeta (PF3D7_1360500) is a bifunctional integral membrane protein that serves as the primary source of the second messenger cGMP driving ookinete gliding motility during malaria parasite transmission through the mosquito [PMID:10747978, PMID:19779564]. Its C-terminal C1/C2 catalytic domains carry residues characteristic of guanylyl cyclases and directly generate cGMP when expressed heterologously, while its N-terminal region resembles P-type ATPases, defining a two-part architecture [PMID:10747978]. In P. berghei ookinetes, GCbeta-derived cGMP acts through cGMP-PKG signaling — with PDEdelta as its relevant degrading phosphodiesterase — to power the gliding required for midgut epithelial traversal, and its genetic disruption abolishes motility and oocyst formation without blocking subsequent parasite development [PMID:17030505, PMID:19779564]. This role is spatially controlled: in P. yoelii, GCbeta translocates from the cytoplasm and polarizes to the ookinete extrados site (OES), a step requiring both its P4-ATPase-like and cyclase domains, where CDC50A binds and stabilizes it and the inner membrane complex protein ISP1 anchors the GCbeta/CDC50A complex [PMID:30146157]. The NAD+-dependent sirtuin Sir2A deacetylates GCbeta to license its OES localization and activation, coupling ookinete metabolic state to the initiation of gliding [PMID:40050296]. By contrast, GCbeta-derived cGMP is dispensable for gamete formation from gametocytes, where cGMP must instead be held below a threshold for normal differentiation [PMID:18452584].","teleology":[{"year":2000,"claim":"Establishing whether GCbeta actually possesses catalytic activity resolved that this large membrane protein is a genuine cGMP-synthesizing enzyme rather than an inactive scaffold, and revealed its unusual bipartite ATPase/cyclase architecture.","evidence":"Heterologous expression of the C-terminal catalytic domains in E. coli with guanylyl cyclase activity assay and domain sequence analysis in P. falciparum","pmids":["10747978"],"confidence":"High","gaps":["Function of the N-terminal P-type ATPase-like domain not tested","Activity of the full-length protein in situ not measured","Regulation of the enzyme not addressed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2001,"claim":"Linking membrane-associated GC activity to the gametocyte-activating factor xanthurenic acid connected cGMP synthesis to a defined physiological trigger of the sexual stage.","evidence":"Guanylyl cyclase activity assay on P. falciparum gametocyte membrane preparations with xanthurenic acid stimulation and divalent-cation dependence","pmids":["11703675"],"confidence":"Medium","gaps":["GCbeta not individually purified — activity attributed to membrane GC pool","Direct causal role of GCbeta in this response not genetically demonstrated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"Genetic disruption in P. berghei defined the specific cellular role of GCbeta, showing it is required for ookinete gliding motility and midgut invasion but not for ookinete morphogenesis or downstream development.","evidence":"Gene knockout in P. berghei with confocal microscopy and in vitro/in vivo motility and invasion phenotyping","pmids":["17030505"],"confidence":"High","gaps":["Downstream signaling mediating the motility defect not identified","Localization of GCbeta not resolved","Species specificity versus P. falciparum untested"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2008,"claim":"Comparing GCbeta and PDEdelta knockouts in gametocytes established that GCbeta-derived cGMP is dispensable for gamete formation and that cGMP must be kept low during gametocyte development, distinguishing the stage-specific requirements for GCbeta.","evidence":"Gene knockouts of GCbeta and PDEdelta in P. falciparum with gametogenesis assays","pmids":["18452584"],"confidence":"Medium","gaps":["Which cyclase supplies cGMP in gametocytes not defined here","Negative result for GCbeta does not exclude minor contributions"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"claim":"Suppressor epistasis positioned GCbeta as the primary cGMP source in ookinetes and PDEdelta as its counteracting phosphodiesterase, placing GCbeta upstream in a cGMP-PKG pathway that intersects calcium signaling to control gliding speed.","evidence":"PDEdelta/GCbeta double-mutant rescue in P. berghei with live morphology, gliding assays, and pharmacological PKG inhibition","pmids":["19779564"],"confidence":"High","gaps":["Molecular mechanism coupling cGMP-PKG to the motor not defined","Nature of the overlap with calcium pathways left mechanistically open"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2018,"claim":"Live imaging and interaction mapping revealed that GCbeta function is spatially gated — it polarizes to the ookinete extrados site, requires both its domains for this, and is stabilized by CDC50A and anchored by ISP1 — explaining how localized cGMP synthesis initiates directional gliding.","evidence":"Real-time imaging, gene tagging, GCbeta-CDC50A co-immunoprecipitation, ISP1 disruption, and domain-deletion analysis in P. yoelii","pmids":["30146157"],"confidence":"High","gaps":["Trigger initiating cytoplasm-to-OES translocation not identified in this study","Enzymatic regulation at OES not resolved"],"attribution":[{"species":"Plasmodium yoelii","strain":""}]},{"year":2025,"claim":"Identifying Sir2A as the top GCbeta-interacting protein and showing acetylation-dependent control established a metabolic switch: NAD+-driven Sir2A deacetylation of GCbeta licenses its OES localization and activation, coupling ookinete maturation state to gliding initiation.","evidence":"BioID proximity labeling, co-immunoprecipitation, live imaging, Sir2A knockouts, acetylation-state and NAD+ measurements in P. yoelii","pmids":["40050296"],"confidence":"High","gaps":["Specific acetylated residues on GCbeta not mapped","Direct effect of deacetylation on catalytic output not quantified","Whether the same regulation operates in P. falciparum untested"],"attribution":[{"species":"Plasmodium yoelii","strain":""}]},{"year":null,"claim":"How the P4-ATPase-like domain contributes biochemically, and what molecular event triggers GCbeta translocation and activation at the OES, remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["Catalytic or lipid-transport function of the N-terminal ATPase-like domain not demonstrated","Signal initiating cytoplasm-to-OES translocation unknown","Structural basis of cGMP synthesis and its regulation uncharacterized"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["GCbeta/CDC50A complex anchored by ISP1 at the ookinete extrados site [#5]"],"partners":["CDC50A (BINDS AND STABILIZES GCBETA) [#5]","ISP1 (ANCHORS GCBETA/CDC50A AT OES) [#5]","SIR2A (NAD+-DEPENDENT DEACETYLASE; TOP GCBETA INTERACTOR) [#6]","PDEDELTA (CGMP PHOSPHODIESTERASE COUNTERACTING GCBETA) [#4]"],"other_free_text":["Bifunctional architecture: N-terminal P4-ATPase-like domain plus C-terminal C1/C2 guanylyl cyclase catalytic domains; both domains required for OES polarization and gliding [#0, #5]","Regulated by acetylation/deacetylation — acetylated in gametocytes, deacetylated by Sir2A in mature ookinetes; elevated NAD+ promotes deacetylation and OES localization [#6]","Guanylyl cyclase activity in gametocyte membranes stimulated by xanthurenic acid, Mg2+/Mn2+-dependent and Ca2+-inhibited [#1]","Required for ookinete gliding motility and mosquito midgut invasion but dispensable for gamete formation and for post-ookinete development [#2, #3]","Primary source of ookinete cGMP acting through cGMP-PKG signaling that overlaps with calcium-dependent pathways [#4]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"19779564","id":"PMC_19779564","title":"A cyclic GMP signalling module that regulates gliding motility in a malaria parasite.","date":"2009","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/19779564","citation_count":160,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["GCbeta","guanylyl cyclase","guanylyl cyclase beta"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"10428960","id":"PMC_10428960","title":"Guanylyl cyclases with the topology of mammalian adenylyl cyclases and an N-terminal P-type ATPase-like domain in Paramecium, Tetrahymena and Plasmodium.","date":"1999","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/10428960","citation_count":72,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"10747978","id":"PMC_10747978","title":"Guanylyl cyclase activity associated with putative bifunctional integral membrane proteins in Plasmodium falciparum.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10747978","citation_count":70,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"11703675","id":"PMC_11703675","title":"The gametocyte-activating factor xanthurenic acid stimulates an increase in membrane-associated guanylyl cyclase activity in the human malaria parasite Plasmodium falciparum.","date":"2001","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/11703675","citation_count":69,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"18452584","id":"PMC_18452584","title":"Disruption of a Plasmodium falciparum cyclic nucleotide phosphodiesterase gene causes aberrant gametogenesis.","date":"2008","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/18452584","citation_count":68,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30146157","id":"PMC_30146157","title":"ISP1-Anchored Polarization of GCβ/CDC50A Complex Initiates Malaria Ookinete Gliding Motility.","date":"2018","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/30146157","citation_count":57,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["GCbeta"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17030505","id":"PMC_17030505","title":"PbGCbeta is essential for Plasmodium ookinete motility to invade midgut cell and for successful completion of parasite life cycle in mosquitoes.","date":"2006","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17030505","citation_count":51,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PbGCbeta"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32669539","id":"PMC_32669539","title":"Co-option of Plasmodium falciparum PP1 for egress from host erythrocytes.","date":"2020","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/32669539","citation_count":40,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31701023","id":"PMC_31701023","title":"FRET-based cyclic GMP biosensors measure low cGMP concentrations in cardiomyocytes and neurons.","date":"2019","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/31701023","citation_count":37,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33500341","id":"PMC_33500341","title":"Plasmodium falciparum Guanylyl Cyclase-Alpha and the Activity of Its Appended P4-ATPase Domain Are Essential for cGMP Synthesis and Blood-Stage Egress.","date":"2021","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/33500341","citation_count":25,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35862778","id":"PMC_35862778","title":"CDC50 Orthologues in Plasmodium falciparum Have Distinct Roles in Merozoite Egress and Trophozoite Maturation.","date":"2022","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/35862778","citation_count":16,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"39808636","id":"PMC_39808636","title":"The malaria parasite PP1 phosphatase controls the initiation of the egress pathway of asexual blood-stages by regulating the rounding-up of the vacuole.","date":"2025","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/39808636","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"40050296","id":"PMC_40050296","title":"Elevated NAD+ drives Sir2A-mediated GCβ deacetylation and OES localization for Plasmodium ookinete gliding and mosquito infection.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/40050296","citation_count":1,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["GCbeta"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"41270172","id":"PMC_41270172","title":"An acyclic nucleoside phosphonate effectively blocks the egress of the malaria parasite by inhibiting the synthesis of cyclic GMP.","date":"2025","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/41270172","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"40623036","id":"PMC_40623036","title":"Loss of serine/threonine protein phosphatase 6 severely impairs sexual stage development in malaria parasite Plasmodium berghei.","date":"2025","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/40623036","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["guanylyl cyclase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10339,"output_tokens":2508,"usd":0.034319,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7955,"output_tokens":3573,"usd":0.06455,"stage2_stop_reason":"end_turn"},"total_usd":0.098869,"stage1_batch_id":"msgbatch_011BPjN2BL33F8cJXD1r7V7T","stage2_batch_id":"msgbatch_01Qwg6vP7qxkpL6Gsc7tajsb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"GCbeta (PfGCbeta) is a bifunctional integral membrane protein in P. falciparum whose carboxyl-terminal catalytic domains (C1 and C2) conform to the topology of G protein-dependent adenylyl cyclases but carry residues characteristic of guanylyl cyclases. Expression of the catalytic domains of GCbeta in E. coli produced guanylyl cyclase activity, directly demonstrating its enzymatic function. The amino-terminal region has strong similarity to P-type ATPases.\",\n      \"method\": \"Heterologous expression of catalytic domains in E. coli with guanylyl cyclase activity assay; sequence/structural analysis of domain architecture\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro enzyme activity assay in E. coli reconstitution, single lab but direct biochemical demonstration\",\n      \"pmids\": [\"10747978\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Membrane-associated guanylyl cyclase activity in P. falciparum mature gametocyte preparations is stimulated by xanthurenic acid (the gametocyte-activating factor) in a Mg2+/Mn2+-dependent but Ca2+-inhibited manner, linking GCbeta-associated cGMP synthesis to the exflagellation signaling pathway.\",\n      \"method\": \"Guanylyl cyclase enzyme activity assay on gametocyte membrane preparations with pharmacological stimulation by xanthurenic acid\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct biochemical activity assay on native membranes, single lab, single method; GCbeta not individually purified but implicated as membrane GC\",\n      \"pmids\": [\"11703675\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Genetic disruption of PbGCbeta in P. berghei produced parasites that formed morphologically normal ookinetes but exhibited severe defects in gliding motility, causing failure to invade the midgut epithelium and produce oocysts in vivo. In vitro, disruptant ookinetes could still transform into oocysts and sporozoites, demonstrating that GCbeta is specifically required for ookinete motility during midgut traversal, not for subsequent parasite development.\",\n      \"method\": \"Gene disruption (knockout) in P. berghei; confocal microscopy; in vitro and in vivo phenotypic analysis of ookinete motility and invasion\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic knockout with specific and well-defined cellular phenotype (motility defect), orthogonal in vivo and in vitro readouts\",\n      \"pmids\": [\"17030505\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Disruption of PfGCbeta in P. falciparum decreased GC activity but had no significant effect on gametogenesis, indicating that GCbeta-derived cGMP is dispensable for male or female gamete formation from gametocytes. By contrast, disruption of PfPDEdelta (the cGMP phosphodiesterase) severely impaired gametogenesis, demonstrating that cGMP levels must be kept below a threshold during gametocyte development for normal differentiation.\",\n      \"method\": \"Gene disruption (knockout) of PfGCbeta and PfPDEdelta in P. falciparum; gametogenesis assays\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean genetic knockout with specific phenotypic readout (gametogenesis), single lab; negative result for GCbeta role in gametogenesis is the primary finding\",\n      \"pmids\": [\"18452584\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Genetic epistasis in P. berghei ookinetes showed that the rounding-up phenotype caused by deletion of PDEdelta (unregulated cGMP) was suppressed in a double mutant additionally lacking GCbeta, establishing that GCbeta is the primary source of cGMP in ookinetes and that PDEdelta is its relevant degrading enzyme. Additionally, cGMP-PKG signaling was shown to overlap partially with calcium-dependent pathways in regulating ookinete gliding speed.\",\n      \"method\": \"Genetic epistasis via double-mutant construction (PDEdelta/GCbeta double knockout) in P. berghei; live cell morphology and gliding motility assays; pharmacological inhibition of PKG\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — classical suppressor epistasis with double mutant rescue, replicated across multiple genetic backgrounds and pharmacological treatments, clearly positions GCbeta in pathway\",\n      \"pmids\": [\"19779564\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In P. yoelii, GCbeta localizes to the cytoplasm and then translocates and polarizes to the parasite plasma membrane at the 'ookinete extrados site' (OES) during zygote-to-ookinete differentiation, as visualized by real-time imaging. This polarization of enzymatically active GCbeta at OES initiates gliding of mature ookinetes. Both the P4-ATPase-like domain and guanylate cyclase domain are required for GCbeta polarization and ookinete gliding. CDC50A binds to and stabilizes GCbeta during ookinete development. The inner membrane complex protein ISP1 anchors the GCbeta/CDC50A complex at the OES.\",\n      \"method\": \"Real-time live imaging; gene tagging; co-immunoprecipitation (GCbeta-CDC50A interaction); genetic disruption of ISP1; domain deletion analysis; screening of inner membrane complex proteins\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live-cell imaging of localization with functional consequence, reciprocal Co-IP for CDC50A interaction, domain mutagenesis, and ISP1 epistasis, multiple orthogonal methods in one study\",\n      \"pmids\": [\"30146157\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium yoelii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In P. yoelii ookinetes, the NAD+-dependent sirtuin deacetylase Sir2A interacts with GCbeta throughout ookinete development (identified by protein proximity labeling as the top GCbeta-interacting protein). In mature ookinetes, Sir2A co-localizes with GCbeta at OES in a mutually dependent manner. Parasites lacking Sir2A lose GCbeta OES localization, ookinete gliding, and mosquito infection, phenocopying GCbeta deficiency. GCbeta is acetylated in gametocytes but is deacetylated by Sir2A for OES localization in mature ookinetes. Elevated NAD+ levels in mature ookinetes promote Sir2A-catalyzed GCbeta deacetylation, linking metabolic state to GCbeta localization and activation.\",\n      \"method\": \"Protein proximity labeling (BioID); co-immunoprecipitation; live imaging; genetic knockouts of Sir2A in P. yoelii; acetylation state analysis; NAD+ level measurements during ookinete development\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proximity labeling plus Co-IP plus genetic phenocopy plus PTM (acetylation/deacetylation) analysis, multiple orthogonal methods establishing mechanism of GCbeta regulation\",\n      \"pmids\": [\"40050296\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium yoelii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"GCbeta (PF3D7_1360500) is a bifunctional integral membrane protein with an N-terminal P4-ATPase-like domain and C-terminal guanylyl cyclase catalytic domains that synthesize cGMP; in ookinetes it is the primary source of cGMP, translocating from cytoplasm to the ookinete extrados site (OES) during zygote-to-ookinete differentiation via a mechanism involving acetylation/deacetylation by the NAD+-dependent sirtuin Sir2A, and anchored at OES by the ISP1-CDC50A complex, where its enzymatic activity drives cGMP-PKG signaling to initiate gliding motility required for mosquito midgut invasion; in gametocytes GCbeta-derived cGMP is dispensable for gamete formation, and in P. falciparum asexual blood stages the related paralog GCalpha (not GCbeta) is the dominant source of cGMP for egress.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GCbeta (PF3D7_1360500) is a bifunctional integral membrane protein that serves as the primary source of the second messenger cGMP driving ookinete gliding motility during malaria parasite transmission through the mosquito [#0, #4]. Its C-terminal C1/C2 catalytic domains carry residues characteristic of guanylyl cyclases and directly generate cGMP when expressed heterologously, while its N-terminal region resembles P-type ATPases, defining a two-part architecture [#0]. In P. berghei ookinetes, GCbeta-derived cGMP acts through cGMP-PKG signaling — with PDEdelta as its relevant degrading phosphodiesterase — to power the gliding required for midgut epithelial traversal, and its genetic disruption abolishes motility and oocyst formation without blocking subsequent parasite development [#2, #4]. This role is spatially controlled: in P. yoelii, GCbeta translocates from the cytoplasm and polarizes to the ookinete extrados site (OES), a step requiring both its P4-ATPase-like and cyclase domains, where CDC50A binds and stabilizes it and the inner membrane complex protein ISP1 anchors the GCbeta/CDC50A complex [#5]. The NAD+-dependent sirtuin Sir2A deacetylates GCbeta to license its OES localization and activation, coupling ookinete metabolic state to the initiation of gliding [#6]. By contrast, GCbeta-derived cGMP is dispensable for gamete formation from gametocytes, where cGMP must instead be held below a threshold for normal differentiation [#3].\"\n  ,\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing whether GCbeta actually possesses catalytic activity resolved that this large membrane protein is a genuine cGMP-synthesizing enzyme rather than an inactive scaffold, and revealed its unusual bipartite ATPase/cyclase architecture.\",\n      \"evidence\": \"Heterologous expression of the C-terminal catalytic domains in E. coli with guanylyl cyclase activity assay and domain sequence analysis in P. falciparum\",\n      \"pmids\": [\"10747978\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Function of the N-terminal P-type ATPase-like domain not tested\", \"Activity of the full-length protein in situ not measured\", \"Regulation of the enzyme not addressed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Linking membrane-associated GC activity to the gametocyte-activating factor xanthurenic acid connected cGMP synthesis to a defined physiological trigger of the sexual stage.\",\n      \"evidence\": \"Guanylyl cyclase activity assay on P. falciparum gametocyte membrane preparations with xanthurenic acid stimulation and divalent-cation dependence\",\n      \"pmids\": [\"11703675\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"GCbeta not individually purified — activity attributed to membrane GC pool\", \"Direct causal role of GCbeta in this response not genetically demonstrated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Genetic disruption in P. berghei defined the specific cellular role of GCbeta, showing it is required for ookinete gliding motility and midgut invasion but not for ookinete morphogenesis or downstream development.\",\n      \"evidence\": \"Gene knockout in P. berghei with confocal microscopy and in vitro/in vivo motility and invasion phenotyping\",\n      \"pmids\": [\"17030505\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream signaling mediating the motility defect not identified\", \"Localization of GCbeta not resolved\", \"Species specificity versus P. falciparum untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Comparing GCbeta and PDEdelta knockouts in gametocytes established that GCbeta-derived cGMP is dispensable for gamete formation and that cGMP must be kept low during gametocyte development, distinguishing the stage-specific requirements for GCbeta.\",\n      \"evidence\": \"Gene knockouts of GCbeta and PDEdelta in P. falciparum with gametogenesis assays\",\n      \"pmids\": [\"18452584\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which cyclase supplies cGMP in gametocytes not defined here\", \"Negative result for GCbeta does not exclude minor contributions\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Suppressor epistasis positioned GCbeta as the primary cGMP source in ookinetes and PDEdelta as its counteracting phosphodiesterase, placing GCbeta upstream in a cGMP-PKG pathway that intersects calcium signaling to control gliding speed.\",\n      \"evidence\": \"PDEdelta/GCbeta double-mutant rescue in P. berghei with live morphology, gliding assays, and pharmacological PKG inhibition\",\n      \"pmids\": [\"19779564\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism coupling cGMP-PKG to the motor not defined\", \"Nature of the overlap with calcium pathways left mechanistically open\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Live imaging and interaction mapping revealed that GCbeta function is spatially gated — it polarizes to the ookinete extrados site, requires both its domains for this, and is stabilized by CDC50A and anchored by ISP1 — explaining how localized cGMP synthesis initiates directional gliding.\",\n      \"evidence\": \"Real-time imaging, gene tagging, GCbeta-CDC50A co-immunoprecipitation, ISP1 disruption, and domain-deletion analysis in P. yoelii\",\n      \"pmids\": [\"30146157\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger initiating cytoplasm-to-OES translocation not identified in this study\", \"Enzymatic regulation at OES not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium yoelii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identifying Sir2A as the top GCbeta-interacting protein and showing acetylation-dependent control established a metabolic switch: NAD+-driven Sir2A deacetylation of GCbeta licenses its OES localization and activation, coupling ookinete maturation state to gliding initiation.\",\n      \"evidence\": \"BioID proximity labeling, co-immunoprecipitation, live imaging, Sir2A knockouts, acetylation-state and NAD+ measurements in P. yoelii\",\n      \"pmids\": [\"40050296\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific acetylated residues on GCbeta not mapped\", \"Direct effect of deacetylation on catalytic output not quantified\", \"Whether the same regulation operates in P. falciparum untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium yoelii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the P4-ATPase-like domain contributes biochemically, and what molecular event triggers GCbeta translocation and activation at the OES, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Catalytic or lipid-transport function of the N-terminal ATPase-like domain not demonstrated\", \"Signal initiating cytoplasm-to-OES translocation unknown\", \"Structural basis of cGMP synthesis and its regulation uncharacterized\"],\n      \"attribution\": []\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004383\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005737\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006182\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0071902\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [\n      \"GCbeta/CDC50A complex anchored by ISP1 at the ookinete extrados site [#5]\"\n    ],\n    \"partners\": [\n      \"CDC50A (binds and stabilizes GCbeta) [#5]\",\n      \"ISP1 (anchors GCbeta/CDC50A at OES) [#5]\",\n      \"Sir2A (NAD+-dependent deacetylase; top GCbeta interactor) [#6]\",\n      \"PDEdelta (cGMP phosphodiesterase counteracting GCbeta) [#4]\"\n    ],\n    \"other_free_text\": [\n      \"Bifunctional architecture: N-terminal P4-ATPase-like domain plus C-terminal C1/C2 guanylyl cyclase catalytic domains; both domains required for OES polarization and gliding [#0, #5]\",\n      \"Regulated by acetylation/deacetylation — acetylated in gametocytes, deacetylated by Sir2A in mature ookinetes; elevated NAD+ promotes deacetylation and OES localization [#6]\",\n      \"Guanylyl cyclase activity in gametocyte membranes stimulated by xanthurenic acid, Mg2+/Mn2+-dependent and Ca2+-inhibited [#1]\",\n      \"Required for ookinete gliding motility and mosquito midgut invasion but dispensable for gamete formation and for post-ookinete development [#2, #3]\",\n      \"Primary source of ookinete cGMP acting through cGMP-PKG signaling that overlaps with calcium-dependent pathways [#4]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1360500","name":null,"product":"guanylyl cyclase beta","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1136700","name":null,"product":"guanylyl cyclase beta","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1110800","name":null,"product":"guanylyl cyclase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"GCbeta","evaluation":null}