TOC75

TOC75 (PF3D7_1234600) is an Omp85-family protein encoded in the Plasmodium falciparum genome that has been assigned, on evolutionary grounds, as the candidate pore-forming component of the Translocon of the Outer Chloroplast membrane (TOC) at an inner membrane of the apicoplast, a role inferred from electrophysiological characterization of the related diatom Omp85 homolog rather than from direct study of the Plasmodium protein (PMID:20042599). It has additionally been listed among the small set of putative TOC/TIC translocon components involved in apicoplast protein import (PMID:22144892). Beyond this evolutionary assignment and its citation as a mutant-validated import factor, no direct in vitro, biochemical, or structural characterization of TOC75 itself has been reported in the available corpus.

1. 2009 Low

   To identify the machinery importing nuclear-encoded proteins across apicoplast membranes, TOC75 was recognized as an apicomplexan Omp85-family protein and assigned a pore-forming TOC role, establishing the first mechanistic hypothesis for the protein.

   Evidence Bioinformatic identification and evolutionary comparison in P. falciparum, with function inferred from electrophysiology of the diatom Omp85 ortholog

   PMID:20042599

   Open questions at the time

   • Function inferred computationally and by analogy to the diatom ortholog; no direct experiment performed on the Plasmodium TOC75 protein
   • No demonstration that PF3D7_1234600 forms a channel or resides in the proposed membrane
   • No structural model of the Plasmodium protein
2. 2011 Low

   To place TOC75 within the apicoplast import apparatus, it was cataloged among the putative TOC/TIC translocon components and cited as having a mutant-validated import role, reinforcing its assignment to the import machinery.

   Evidence Systematic bioinformatic screen with epitope-tagging and conditional mutant analysis of apicoplast proteins in P. falciparum; TOC75 role cited as prior work

   PMID:22144892

   Open questions at the time

   • Mutant validation of TOC75 is cited as prior work rather than directly demonstrated, with no full experimental detail for TOC75 itself
   • Membership in the translocon is asserted without direct interaction data for PF3D7_1234600
   • No biochemical evidence linking TOC75 loss to failed protein import

• Whether PF3D7_1234600 itself forms a translocation pore, its precise membrane localization, its interaction partners within a TOC/TIC complex, and its substrate spectrum remain unestablished by direct experiment.
• No channel/reconstitution assay on the Plasmodium protein
• No structural data
• No direct demonstration of complex membership or import substrates for PF3D7_1234600