Affinage · Toxoplasma gondii

GRA47

dense granule protein GRA47 · UniProt S8GIS3

Annotated
2026-09-08
5 papers in source corpus 3 papers cited in narrative 6 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GRA47 is a Toxoplasma gondii dense granule protein that localizes to the parasitophorous vacuole membrane (PVM), where it controls PVM permeability to small molecules and maintains normal PV morphology (PMID:38380952, PMID:38936501). Structural modelling predicts that GRA47 assembles into a heptameric pore lined by conserved histidine residues; mutation of these histidines abolishes function and loss of GRA47 alters membrane conductance, establishing a pore-forming role at the PVM (PMID:38380952). GRA47 physically interacts with GRA72 (PMID:38380952, PMID:38936501), and its deletion produces a 'bubble vacuole' morphology with reduced permeability, impaired in vitro proliferation, and attenuated virulence in mice, phenocopying Δgra17 and Δgra72 parasites (PMID:38380952, PMID:38936501). Complementation and epistasis experiments place GRA47/GRA72 in a shared functional pathway with GRA17 and GRA23 in nutrient acquisition and PVM permeability, though the GRA proteins are not fully functionally redundant (PMID:38936501).

Mechanistic history

Synthesis pass · year-by-year structured walk · 4 steps
  1. 2024 High

    Establishing that GRA47 is a PVM protein that physically partners with GRA72 and governs vacuole morphology and small-molecule permeability defined its cellular role in the host-parasite interface.

    Evidence Co-immunoprecipitation, Δgra47 knockout, permeability assays, and live imaging in T. gondii

    PMID:38380952 PMID:38936501

    Open questions at the time
    • Molecular basis of the GRA47-GRA72 interaction (interface, stoichiometry) not resolved
    • Which specific small-molecule metabolites traverse the pore not identified
  2. 2024 High

    Structural prediction combined with histidine mutagenesis and electrophysiology answered how GRA47 acts mechanistically, identifying it as a heptameric pore with conserved pore-lining histidines essential for conductance and permeability.

    Evidence Computational structural prediction, site-directed histidine mutagenesis with functional readout, and membrane conductance measurement in T. gondii

    PMID:38380952

    Open questions at the time
    • Experimental high-resolution structure of the pore not determined
    • Whether GRA47 homo-oligomerizes or forms hetero-oligomers with GRA72 in the pore not established
  3. 2024 High

    Deletion of GRA47 phenocopying Δgra17 and Δgra72 across proliferation and mouse virulence readouts connected pore function to parasite fitness and pathogenesis.

    Evidence Δgra47 knockout with plaque/proliferation assays and a mouse virulence model in T. gondii

    PMID:38380952 PMID:38936501

    Open questions at the time
    • Causal chain from permeability defect to virulence attenuation not dissected
    • Host cell type dependence of the phenotype not explored
  4. 2024 Medium

    Complementation with cognate GRAs and the Plasmodium ortholog PfExp2, plus Δgra23Δgra72 epistasis, positioned GRA47/GRA72 within a broader GRA17/GRA23 nutrient-acquisition pathway while showing the proteins are not fully redundant.

    Evidence Genetic complementation (GRA47/GRA72/GRA17/PfExp2 overexpression) and double-knockout epistasis with PV morphology quantification in T. gondii

    PMID:38936501

    Open questions at the time
    • Distinct mechanisms distinguishing the GRA pores not defined
    • GRA47 placement in the GRA23 pathway inferred indirectly through GRA72

Open questions

Synthesis pass · forward-looking unresolved questions
  • The identity of the substrates transported through the GRA47 pore and the precise architecture of the GRA47-GRA72 complex remain to be determined.
  • No experimental structure of the pore
  • Transported metabolites unidentified
  • Stoichiometry of GRA47-GRA72 assembly unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
GRA17GRA23GRA72
Complex memberships
GRA47-GRA72 complex

Evidence

Reading pass · 6 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2024 GRA47 physically interacts with GRA72, as demonstrated by immunoprecipitation experiments; GRA47 localizes to the parasitophorous vacuole membrane (PVM) and is required for normal PV morphology and PVM permeability to small molecules. Co-immunoprecipitation, genetic deletion (Δgra47), small molecule permeability assays, live imaging of vacuole morphology mBio High 38380952 38936501
2024 GRA47 is predicted by structural modelling to form a heptameric pore, with conserved histidine residues lining the pore channel; mutational analysis of these histidines abolished protein functionality (aberrant PV morphology, reduced permeability), and electrophysiology confirmed that loss of GRA47 alters membrane conductance, corroborating its pore-forming role. Computational structural prediction, site-directed mutagenesis of histidine residues, electrophysiology (membrane conductance assay), small molecule permeability assays mBio High 38380952
2024 Deletion of GRA47 causes 'bubble vacuole' morphology with reduced small molecule permeability across the PVM, reduced in vitro proliferation, and attenuated virulence in mice, phenocopying Δgra17 and Δgra72 parasites. Genetic knockout (Δgra47), in vitro plaque/proliferation assay, mouse virulence model, fluorescent small molecule permeability assay mBio High 38380952 38936501
2024 Overexpression of GRA47 (or GRA72 or GRA17) in Δgra47, Δgra72, or Δgra17 strains partially rescued aberrant PV morphology, while expression of the Plasmodium falciparum PVM protein PfExp2 (an ortholog of GRA17/GRA23) fully rescued PV morphological defects in all three knockout strains, indicating these GRA proteins are not fully functionally redundant but regulate nutrient acquisition through different mechanisms. Genetic complementation (overexpression of GRA47, GRA72, GRA17, and PfExp2), PV morphology quantification International journal for parasitology Medium 38936501
2024 Loss of GRA72 in a Δgra23 background (Δgra23Δgra72 double knockout) significantly increased the proportion of aberrant PVs compared with Δgra23 alone, placing GRA72 (and by association, GRA47 through its interaction with GRA72) in the same functional pathway as GRA23 in PV morphology maintenance. Double gene deletion (Δgra23Δgra72), PV morphology quantification International journal for parasitology Medium 38936501
2023 Preprint version of the mBio findings: GRA47 interacts with GRA72 (immunoprecipitation), forms a heptameric pore with pore-lining histidines critical for function (mutagenesis), and its deletion reduces PVM permeability and membrane conductance (electrophysiology), reducing parasite growth and virulence in mice. Immunoprecipitation, genetic deletion, structural prediction, histidine mutagenesis, electrophysiology, small molecule permeability assay, mouse virulence model bioRxivpreprint High 38014337

Source papers

Stage 0 corpus · 5 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2024 Two Toxoplasma gondii putative pore-forming proteins, GRA47 and GRA72, influence small molecule permeability of the parasitophorous vacuole. mBio 24 38380952
2024 GRA47 is important for the morphology and permeability of the parasitophorous vacuole in Toxoplasma gondii. International journal for parasitology 11 38936501
2023 GRA47 and GRA72 are Toxoplasma gondii pore-forming proteins that influence small molecule permeability of the parasitophorous vacuole. bioRxiv : the preprint server for biology 1 38014337
2026 Transcriptomic Profiling of GRA47 Deletion in Toxoplasma gondii Reveals Transcriptional Reprogramming of Stress Adaptation and Metabolic Compensation. Veterinary sciences 0 42357722
2026 Protective Immunity Induced by DNA Vaccines Encoding TgGRA47 and TgGRA72 Against Toxoplasma gondii Infection in BALB/c Mice. Transboundary and emerging diseases 0 42253329