ATPk

ATPk (PF3D7_0107400) is a putative subunit of the mitochondrial ATP synthase in Plasmodium falciparum, established as a component of the complex rather than as an independently characterized enzyme (PMID:21984828). Epitope-tagging and immunofluorescence localize ATPk to the mitochondrion of blood-stage parasites, and blue native gel electrophoresis of mitochondrial membranes shows the ATP synthase it belongs to exceeds 1 MDa and assembles as a dimer, consistent with a divergent complex containing subunits beyond the canonical set (PMID:21984828). Failure to disrupt the genes encoding the catalytic β and γ subunits indicates the complex is essential in blood stages, though this evidence concerns those subunits rather than ATPk itself (PMID:21984828). Beyond membership in this complex and its mitochondrial localization (PMID:21984828), and an earlier bioinformatic placement of the locus in the Fo sector (PMID:19682605), no catalytic or structural role for ATPk has been experimentally defined in the available corpus.

1. 2009 Low

   Before any experimental work, it was unknown whether PF3D7_0107400 was part of the Plasmodium ATP synthase; bioinformatic and proteomic analysis first nominated it as a candidate Fo-sector subunit and flagged divergence from canonical architecture.

   Evidence Bioinformatic identification from structural fingerprints and proteomics data of related protists, noting loss of an essential Arg in a predicted transmembrane helix

   PMID:19682605

   Open questions at the time

   • Purely computational prediction with no direct experimental validation in Plasmodium
   • Assignment to the Fo sector and the subunit-a correspondence not confirmed biochemically
   • No evidence distinguishing ATPk's role from other predicted subunits
2. 2011 Medium

   It was unknown where ATPk resides and how the parasite ATP synthase is organized; tagging and native-gel analysis placed ATPk in the mitochondrion within a >1 MDa dimeric complex, establishing it as a bona fide component of an unusually large ATP synthase.

   Evidence Epitope-tagging and immunofluorescence localization plus blue native gel electrophoresis of mitochondrial membranes in transgenic P. falciparum; attempted disruption of β and γ subunit genes

   PMID:21984828

   Open questions at the time

   • ATPk's specific catalytic or structural function within the complex not defined
   • Essentiality demonstrated only for β and γ subunits, not directly for ATPk
   • Stoichiometry and position of ATPk in the dimer not resolved

• The precise role of ATPk within the ATP synthase — whether it contributes to catalysis, proton translocation, dimerization, or complex assembly — remains undefined.
• No direct genetic knockout/knockdown of ATPk to test essentiality
• No structural model placing ATPk within the complex
• No biochemical assignment of ATPk to a functional module (Fo vs F1)