Fig. 1: Screening of a solute library for cis-inhibitory activity identified potential substrates of PfCRT.

a Schematic showing the cis-inhibition of [³H]CQ uptake via PfCRT^Dd2 or PfCRT^Ecu1110 by an unlabelled solute in the Xenopus oocyte system. The library included solutes known to exist in the parasitised erythrocyte, such as vitamins, carbohydrates, metal ions, lipids, amino acids, peptides and other organic and inorganic molecules. b, c The effect on [³H]CQ transport via PfCRT by a subset of solutes (2 mM) (b) or host-derived peptides (2 mM) (c). Non-expressing oocytes and those expressing PfCRT^3D7 were included as negative controls; these oocytes accumulate a low level of [³H]CQ via simple diffusion of the neutral species^15,16, reflecting the background level of [³H]CQ transport. Note that aspartate and vitamins E and B6 caused modest reductions in PfCRT^Dd2-mediated transport, but only aspartate was found to inhibit PfCRT^Ecu1110. A diverse range of peptides cause potent inhibition of both PfCRT^Dd2 or PfCRT^Ecu1110. d Heatmap of the cis-inhibition of [³H]CQ transport via PfCRT^Dd2 and PfCRT^Ecu1110 by 173 different solutes. e VF-6 (top) and HM-5 (bottom) inhibit [³H]CQ transport via PfCRT^Dd2 in a concentration-dependent manner. The half-maximum inhibitory concentrations (IC₅₀) for VF-6 and HM-5 are 207 ± 12 and 167 ± 14 µM, respectively. The data are the mean of n = 4 independent experiments (each yielding similar results and overlaid as individual data points in b and c), and the error is the SEM. Where not visible, the error bars fall within the symbols. The asterisks denote a significant difference from the relevant PfCRT^Dd2 (red asterisks) or PfCRT^Ecu1110 (orange asterisks) control; *P < 0.05, **P < 0.01, ***P < 0.001 (one-way ANOVA). The source datasets are provided as a Source Data file.