ARFGAP1

PF3D7_1244600 (ARFGAP1) encodes a zinc-finger-containing ADP-ribosylation factor GTPase-activating protein of Plasmodium falciparum whose catalytic domain adopts a fold similar to mammalian ARFGAPs but carries residues unique to P. falciparum at both the ARF1-interaction surface and the crystal dimer interface (PMID:22102228). Its recombinant GAP domain stimulates GTP hydrolysis on truncated PfArf1 in vitro to a level equivalent to human ArfGAP1, establishing it as a catalytically active ARF GTPase-activating protein (PMID:32144363). Unlike human ArfGAP1, the P. falciparum GAP domain is insensitive to the inhibitor QS11, and a distinct compound selectively inhibiting a P. falciparum GAP domain was identified (PMID:32144363). Beyond this structural and in vitro enzymatic characterization, the cellular localization, in vivo function, and physiological role of PF3D7_1244600 have not been characterized in the available corpus.

1. 2011 High

   Whether P. falciparum ARFGAP1 shares the architecture of mammalian ARFGAPs and whether it presents parasite-specific features was unknown; solving its catalytic domain structure defined both its conserved fold and the residues distinguishing it from the host enzyme.

   Evidence X-ray crystallography of the catalytic domain by MAD phasing at 2.4 Å resolution using the zinc-finger Zn2+ ion

   PMID:22102228

   Open questions at the time

   • Structure captures only the isolated catalytic domain, not the full-length protein or an ARF1-bound complex
   • Functional consequence of the parasite-unique ARF1-interaction surface residues was not tested in this study
   • No cellular localization or in vivo role established
2. 2020 Medium

   Whether the ARFGAP1 catalytic domain is enzymatically functional and pharmacologically distinct from the human enzyme was untested; an in vitro GTPase assay demonstrated GAP activity on PfArf1 and revealed insensitivity to the human inhibitor QS11 plus a selective inhibitor of a parasite GAP domain.

   Evidence In vitro colorimetric microtiter plate GTPase assay with recombinant GAP domain proteins and inhibitor testing

   PMID:32144363

   Open questions at the time

   • The two P. falciparum ArfGAPs were not individually distinguished, so activity cannot be attributed solely to PF3D7_1244600 from the abstract
   • Assay used truncated PfArf1 rather than the full-length substrate in a membrane context
   • The selective inhibitor's target GAP domain identity and cellular efficacy remain undefined

• The in vivo function, subcellular localization, vesicular-trafficking role, and essentiality of PF3D7_1244600 in the parasite remain unestablished.
• No cellular or genetic characterization (knockout, knockdown, localization) in the corpus
• No demonstration of a trafficking phenotype linked to ARFGAP1 activity
• No confirmation that observed GAP activity operates on native membrane-bound PfArf1 in vivo