AAP5

AAP5 is a component of the apical annuli of Toxoplasma gondii, a set of structures embedded within the inner membrane complex (IMC) sutures, where it was identified and validated by reciprocal proximity biotinylation (BioID) proteomics and super-resolution microscopy as one of five apical annuli proteins (AAP1–5) (PMID:31470470). Within this structure, AAP5 forms part of a concentric, pore-like ring assembly of 200–400 nm diameter built from coiled-coil and signalling domain-containing proteins together with Centrin2 (PMID:31470470). No direct functional mechanism for AAP5 itself has been experimentally defined in the available corpus; its narrow conservation among internally budding coccidians is the only basis for an inferred role.

1. 2019 Medium

   Establishing what proteins constitute the apical annuli answered where AAP5 resides in the parasite, placing it as a bona fide structural component of the IMC sutures rather than a diffuse cytoplasmic factor.

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

   PMID:31470470

   Open questions at the time

   • No functional rescue or mutagenesis of AAP5 specifically
   • Molecular activity of AAP5 within the complex not defined
2. 2019 Medium

   Resolving the architecture of the apical annuli showed AAP5 sits within a concentric pore-like ring, defining the structural context in which it operates alongside Centrin2 and coiled-coil/signalling proteins.

   Evidence Super-resolution microscopy, BioID, and domain analysis in Toxoplasma gondii

   PMID:31470470

   Open questions at the time

   • AAP5's specific contribution to ring assembly or integrity untested
   • Function of the pore-like structure unknown
3. 2019 Low

   Phylogenetic restriction of AAP5 to internally budding coccidians offered a first hypothesis linking the protein to replication by internal budding, though without direct functional testing.

   Evidence Phylogenetic analysis

   PMID:31470470

   Open questions at the time

   • Computational inference only, no functional experiment
   • Connection to internal budding untested experimentally