Affinage · Toxoplasma gondii

AAP2

cyclic nucleotide-binding domain-containing protein · UniProt A0A125YQM1

Annotated
2026-09-10
1 papers in source corpus 1 papers cited in narrative 3 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

AAP2 is a component of the apical annuli of Toxoplasma gondii, ring-like structures embedded within the sutures of the inner membrane complex (IMC) (PMID:31470470). It was identified alongside AAP1, AAP3, AAP4, AAP5, Centrin2, and an apical annuli methyltransferase by reciprocal proximity biotinylation and super-resolution microscopy, which localized these proteins to a concentric, pore-like assembly of four rings measuring 200–400 nm in diameter at the junctions connecting alveolar vesicles (PMID:31470470). Beyond this localization within the apical annuli complex, no direct functional characterization of AAP2 has been established in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 3 steps
  1. 2019 Medium

    Establishing AAP2 as a bona fide constituent of the apical annuli answered where this protein resides and which molecular neighborhood it belongs to within the parasite cortex.

    Evidence Reciprocal BioID proximity biotinylation proteomics with super-resolution microscopy validation in Toxoplasma gondii

    PMID:31470470

    Open questions at the time
    • No functional assay (e.g. knockout/knockdown) defines what AAP2 contributes to the annuli
    • Direct binding partners of AAP2 versus mere proximity neighbors are not resolved
    • The molecular activity of AAP2 is undefined
  2. 2019 Medium

    Super-resolution imaging resolved the architecture of the annuli complex containing AAP2 as a concentric four-ring, pore-like structure within IMC sutures, giving a structural context for the assembly.

    Evidence Super-resolution microscopy of the apical annuli in Toxoplasma gondii

    PMID:31470470

    Open questions at the time
    • The specific radial position of AAP2 within the four rings is not resolved
    • Whether the ring forms a functional pore is not tested
    • The stoichiometry and assembly order of AAP2 relative to other components are unknown
  3. 2019 Low

    Domain and phylogenetic analysis linked AAP2-bearing annuli to centrosomal protein signatures and to coccidian parasites that replicate by internal budding, raising a candidate connection to the replication mechanism.

    Evidence Phylogenetic and domain-signature analysis (computational, no direct AAP2 functional experiment)

    PMID:31470470

    Open questions at the time
    • Computational inference only; no experimental test of an internal-budding role for AAP2
    • The functional significance of centrosomal domain signatures is not validated
    • No evidence connects AAP2 loss to a replication defect

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
AAP1AAP3AAP4AAP5APICAL ANNULI METHYLTRANSFERASECENTRIN2
Complex memberships
Apical annuli complex (AAP1, AAP2, AAP3, AAP4, AAP5, Centrin2, apical annuli methyltransferase)

Evidence

Reading pass · 3 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2019 AAP2 (along with AAP1, AAP3, AAP4, AAP5, Centrin2, and an apical annuli methyltransferase) was identified as a component of the apical annuli of Toxoplasma gondii, structures embedded within the inner membrane complex (IMC) sutures, validated by reciprocal proximity biotinylation (BioID). Reciprocal BioID proximity biotinylation proteomics; super-resolution microscopy Cellular microbiology Medium 31470470
2019 The apical annuli complex, which includes AAP2, is organized as a concentric structure comprising four rings with diameters ranging from 200 to 400 nm, located within IMC sutures connecting alveolar vesicles. Super-resolution microscopy Cellular microbiology Medium 31470470
2019 AAP2, as part of the apical annuli proteins, contains domain signatures shared with centrosomal proteins and is phylogenetically conserved narrowly in coccidian apicomplexan parasites that multiply by internal budding, suggesting a role tied to this replication mechanism. Phylogenetic analysis; domain signature analysis Cellular microbiology Low 31470470

Source papers

Stage 0 corpus · 1 paper · ranked by NIH iCite citations
Year Title Journal Citations PMID
2019 The apical annuli of Toxoplasma gondii are composed of coiled-coil and signalling proteins embedded in the inner membrane complex sutures. Cellular microbiology 38 31470470