TIC20

PF3D7_1144700 (TIC20) is annotated as a putative pore-forming component of the Translocon of the Inner Chloroplast membrane (TIC) complex at the innermost membrane of the P. falciparum apicoplast, where it is proposed to mediate translocation of nuclear-encoded proteins into the apicoplast stroma (PMID:32388921). This assignment rests entirely on homology to characterized apicomplexan orthologs rather than on direct experiments with the P. falciparum protein: TIC20 is grouped with TIC22 and TOC75 as import components whose essentiality is inferred from T. gondii genetic data (PMID:22144892), and in T. gondii the ortholog's conditional ablation blocks apicoplast protein import and yields a non-viable phenotype resembling loss of the ERAD-derived component Der1Ap, placing it in the inner-membrane import pathway (PMID:23785288). A computational structural model of PF3D7_1144700 has been built and used for in silico docking of antimalarials, but no wet-lab characterization accompanied it (PMID:28595540). Beyond these homology-based and computational inferences, no direct in vitro or in vivo experiment on PF3D7_1144700 itself has been reported in the available corpus, and its pore-forming activity, interaction partners, and import function in P. falciparum remain uncharacterized.

1. 2011 Low

   To account for how nuclear-encoded proteins cross the innermost apicoplast membrane, TIC20 was placed among the candidate import components, establishing it as a member of the putative apicoplast TIC machinery.

   Evidence Review citing T. gondii mutant analysis and bioinformatic identification of the P. falciparum homolog; no direct experiment on PF3D7_1144700

   PMID:22144892

   Open questions at the time

   • No direct experiment on the P. falciparum protein; membership is inferred from T. gondii ortholog data
   • Import function of PF3D7_1144700 not tested
   • No evidence of physical association with TIC22 or TOC75 in P. falciparum
2. 2013 Low

   Whether TIC20 is functionally essential for apicoplast protein import was addressed in the T. gondii ortholog, showing that its ablation blocks import with a phenotype resembling loss of the ERAD component Der1Ap, positioning it in a defined inner-membrane import pathway.

   Evidence Conditional gene ablation in T. gondii with epistasis to the Der1Ap mutant phenotype

   PMID:23785288

   Open questions at the time

   • Not demonstrated for P. falciparum PF3D7_1144700, which is inferred by homology only
   • Mechanism of translocation (pore formation) not directly shown
   • Molecular connection between TIC20 and the ERAD-derived machinery not resolved at the protein level
3. 2017 Low

   To probe the druggability of PF3D7_1144700, a computational structural model and in silico docking of antimalarials were used, reinforcing its annotation as an apicoplast import protein but without wet-lab validation.

   Evidence In silico homology modeling (I-TASSER), docking, gene ontology and NLS motif analysis

   PMID:28595540

   Open questions at the time

   • Purely computational; no experimental structure or binding assay
   • Predicted active site and druggability not experimentally verified
   • No functional validation of the modeled protein
4. 2020 Low

   The prevailing model consolidates PF3D7_1144700 as a putative pore-forming TIC component mediating protein translocation across the innermost apicoplast membrane, framing the outstanding need for direct experimental testing.

   Evidence Bioinformatic identification and review of T. gondii ortholog genetic/functional data; no direct experiment on PF3D7_1144700

   PMID:32388921

   Open questions at the time

   • Pore-forming activity of PF3D7_1144700 never demonstrated
   • No P. falciparum genetic ablation or complementation reported
   • Interaction partners and complex composition in P. falciparum undefined

• No direct in vitro or in vivo experiment on P. falciparum PF3D7_1144700 has established its pore-forming activity, essentiality, or import function; all current claims are homology-based or computational.
• No experimental localization to the inner apicoplast membrane in P. falciparum
• No demonstration of protein translocation activity
• No mapped physical interactions with other TIC components in P. falciparum