TOM40

PF3D7_0617000 (TOM40) is a conserved core subunit of the translocase of the outer mitochondrial membrane (TOM complex) in Plasmodium falciparum, originally identified as a Tom40 ortholog by comparative sequence analysis (PMID:15155803). Cross-linking mass spectrometry in P. falciparum gametocytes detected residue-level cross-links between TOM40 (PF3D7_0617000) and TOM20 (PF3D7_0524700), providing the first direct experimental evidence that these proteins physically interact as part of a TOM complex mediating protein transport across the outer mitochondrial membrane in this parasite (PMID:41966402). Consistent with a mitochondrial localization, anti-TOM40 antibody staining serves as a validated mitochondrial marker in apicomplexan parasites, including P. falciparum (PMID:28810863). Beyond this complex membership and localization, no in vitro reconstitution, mutagenesis, channel activity assay, or structural study of PF3D7_0617000 has been characterized in the available corpus.

1. 2004 Low

   Whether P. falciparum encodes a recognizable channel subunit of the mitochondrial outer-membrane import machinery was addressed by identifying a Tom40 ortholog, establishing the candidate gene for TOM-complex-mediated import in the parasite.

   Evidence Comparative sequence analysis / bioinformatic ortholog identification

   PMID:15155803

   Open questions at the time

   • Computational assignment only; no functional experiment in Plasmodium
   • Does not demonstrate channel activity, complex membership, or import function
2. 2017 Low

   Whether TOM40 is a reliable readout of mitochondrial localization in P. falciparum was tested by using anti-TOM40 antibody as a marker, confirming its use as an experimental mitochondrial reference.

   Evidence Immunofluorescence with anti-TOM40 antibody in PfACT1 conditional knockout parasites

   PMID:28810863

   Open questions at the time

   • TOM40 used only as a marker; no mechanistic experiment on TOM40 itself
   • Does not establish import function or interaction partners
3. 2019 Low

   The utility of TOM40 as a mitochondrial marker was extended across apicomplexans by anti-TOM40 staining in Toxoplasma gondii, supporting conserved mitochondrial localization of the antigen.

   Evidence Immunofluorescence with anti-TOM40 antibody in T. gondii TgFRM2 conditional knockout

   PMID:31322501

   Open questions at the time

   • Attribution is to T. gondii, not P. falciparum
   • Marker-only use; no mechanistic characterization of the protein
4. 2021 Low

   Whether TOM40 abundance varies across the parasite life cycle was measured by complexome profiling, which found higher levels in asexual blood stages than gametocytes and used it as a mitochondrial content reference.

   Evidence Complexome profiling (blue-native PAGE-MS) and quantitative SDS-PAGE proteomics of mitochondria-enriched fractions

   PMID:34155201

   Open questions at the time

   • Abundance measurement only; no direct functional experiment on TOM40
   • Does not resolve complex composition or stoichiometry
5. 2026 Medium

   Whether the predicted TOM complex physically assembles in P. falciparum was addressed by detecting direct cross-links between TOM40 and TOM20, providing the first experimental evidence of TOM complex formation in the parasite.

   Evidence Cross-linking mass spectrometry with cofractionation mass spectrometry as orthogonal support, in P. falciparum gametocytes

   PMID:41966402

   Open questions at the time

   • No functional reconstitution or mutagenesis of the interaction
   • Interaction shown in gametocytes only; other stages not tested
   • Full complex composition and stoichiometry not defined

• The channel activity, substrate range, structure, and functional requirement of PF3D7_0617000 for mitochondrial protein import in P. falciparum remain uncharacterized.
• No demonstration of import channel activity
• No genetic knockdown/knockout phenotype for TOM40 itself
• No structure or defined substrate spectrum