ATG7

PF3D7_1126100 (ATG7) encodes an E1-like activating enzyme that operates at the apex of the ATG8 conjugation pathway in Plasmodium, driving ATG8 lipidation and membrane association during parasite development (PMID:39714137). In P. berghei, conditional depletion of ATG7 abolishes ATG8 lipidation and eliminates ATG8 localization to the apicoplast membrane, which in turn disrupts organelle biogenesis, impairs microneme exocytosis, and prevents merozoite formation during liver-stage metamorphosis; ATG7 itself resides in the parasite cytosol across blood, sporozoite, and liver stages (PMID:39714137, PMID:40395990). In P. falciparum, endogenously tagged PfATG7 is expressed as distinct protein species during erythrocytic stages, and conditional attenuation of its protein level produces a slow-growth phenotype, establishing that PfATG7 is required for normal blood-stage growth (PMID:23825614). Beyond its role as the E1-like activator upstream of ATG8 lipidation, no further catalytic mechanism or direct enzymatic characterization of PF3D7_1126100 has been established in the available corpus.

1. 2013 Low

   Before functional data existed, it was unknown whether the parasite ATG7 ortholog was engaged in the ATG8 conjugation system at all; co-expression analysis placed it within that pathway.

   Evidence Transcriptional analysis of ATG gene expression across P. berghei life-cycle stages, showing co-transcription with ATG3 and ATG8

   PMID:24342964

   Open questions at the time

   • Co-transcription only; no direct enzymatic or functional validation of ATG7 activity
   • Does not demonstrate physical or biochemical interaction with ATG8/ATG3
   • No P. falciparum-specific data in this study
2. 2013 Medium

   It was unknown whether PfATG7 is required for parasite viability; conditional protein depletion established that it is essential for normal erythrocytic-stage growth.

   Evidence C-terminal HA tagging of the endogenous PfATG7 locus with western blot detection and an inducible degradation-domain knock-in for conditional depletion, coupled to growth assays in P. falciparum

   PMID:23825614

   Open questions at the time

   • Growth phenotype does not identify the molecular defect underlying slow growth
   • No demonstration of ATG8 lipidation or enzymatic activity in P. falciparum
   • Identity of the two protein species and their processing is unresolved
3. 2024 High

   The catalytic role of ATG7 was undefined; conditional depletion showed it is the E1-like activator required for ATG8 lipidation and membrane conjugation, linking it to apicoplast biology and organelle biogenesis.

   Evidence Conditional mutagenesis (ATG7 depletion) in P. berghei with western blot for ATG8 lipidation, fluorescence microscopy for ATG8 and organelle markers, and functional assays for microneme exocytosis and merozoite formation

   PMID:39714137

   Open questions at the time

   • Direct in vitro reconstitution of ATG7 E1 activity not shown
   • Mechanism connecting loss of ATG8 lipidation to microneme exocytosis defect not resolved
   • Cytosolic localization does not explain how ATG7 output reaches the apicoplast membrane
4. 2025 Medium

   It was unclear whether ATG7 function extends to liver-stage metamorphosis; depletion during liver-stage development confirmed it is required for ATG8 lipidation, microneme exocytosis, and maturation into hepatic merozoites.

   Evidence Conditional mutagenesis system (ATG7 depletion) in P. berghei liver-stage parasites with functional assays for ATG8 lipidation, microneme exocytosis, and merozoite maturation

   PMID:40395990

   Open questions at the time

   • Overlaps with and only partially replicates the same lab's prior work rather than independent confirmation
   • Does not resolve the downstream homeostatic target of ATG8 lipidation in liver stage

• Whether PF3D7_1126100 possesses direct, biochemically reconstituted E1 activity and how its cytosolic activity is spatially coupled to ATG8 membrane conjugation in P. falciparum remain unresolved.
• No in vitro demonstration of ATG7 adenylation/thioester chemistry
• No structural model of PF3D7_1126100
• P. falciparum functional data limited to a growth phenotype without lipidation readout