Affinage · Toxoplasma gondii

FNT3

formate/nitrite transporter protein · UniProt S8GBB9

Annotated
2026-09-10
1 papers in source corpus 1 papers cited in narrative 2 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

FNT3 is a plasma membrane-localized formate/nitrite transporter (FNT)-family monocarboxylate/proton symporter of the Toxoplasma gondii tachyzoite that mediates pH-dependent transport of both l-lactate and formate (PMID:30237165). Substrate selectivity and inhibitor sensitivity are governed by specific residues in its substrate-selectivity region, and FNT3 is blocked by 2-hydroxy-chromanone compounds (PMID:30237165). Beyond these transport and inhibition properties, no further mechanistic detail has been characterized in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 2 steps
  1. 2018 Medium

    Establishing whether FNT3 is a functional transporter and where it acts defined its role as a plasma membrane symporter handling l-lactate and formate under pH control.

    Evidence Heterologous expression/transport assays with pH-dependence testing plus subcellular localization in T. gondii tachyzoites

    PMID:30237165

    Open questions at the time
    • Directionality (efflux vs influx) and physiological substrate load in vivo not resolved
    • Contribution of FNT3 relative to the other two FNTs to parasite metabolism not dissected
  2. 2018 Medium

    Mapping which residues set substrate and inhibitor preference identified the substrate-selectivity region as the determinant of FNT3 specificity and revealed 2-hydroxy-chromanones as inhibitors.

    Evidence Chemical biology with mutagenesis of substrate-selectivity residues and inhibitor sensitivity assays

    PMID:30237165

    Open questions at the time
    • No structural model of the substrate-selectivity region
    • Whether inhibition translates to selective anti-parasite efficacy in vivo not established

Mechanism profile

Synthesis pass · controlled-vocabulary classification
No controlled-vocabulary terms were assigned to this entry.

Evidence

Reading pass · 2 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2018 FNT3 (TG_229170) is one of three FNT-type monocarboxylate/proton symporters localized to the plasma membrane of the T. gondii tachyzoite stage; it transports both l-lactate and formate in a pH-dependent manner. Heterologous expression/transport assay and subcellular localization (plasma membrane fractionation/imaging) The Journal of biological chemistry Medium 30237165
2018 FNT3, along with the other two T. gondii FNTs, is inhibited by 2-hydroxy-chromanones; critical residues in the substrate-selectivity region of FNT3 determine differential specificity and sensitivity toward both substrates (l-lactate, formate) and these inhibitors, as identified by chemical biology and mutagenesis. Chemical biology approach with mutagenesis of substrate-selectivity residues; inhibitor sensitivity assays The Journal of biological chemistry Medium 30237165

Source papers

Stage 0 corpus · 1 paper · ranked by NIH iCite citations
Year Title Journal Citations PMID
2018 The intracellular parasite Toxoplasma gondii harbors three druggable FNT-type formate and l-lactate transporters in the plasma membrane. The Journal of biological chemistry 29 30237165