Fig. 1: Ι pH dependence of PfCRT^Dd2.

a CQ transport activity of PfCRT^Dd2 (blue symbols) and E207A (red symbols) as a function of the pH. Specific CQ transport was determined from an extracellular medium containing 50 µM of CQ. Each data point represents the mean ± SEM of n biologically independent samples, with n being from left to right for PfCRT^Dd2: 12, 11, 13, 26, 12, and 15; and E207A: 9, 3, 3, 9, 3, and 3. b PfCRT^Dd2-mediated CQ transport activity at a pH of 6.0 and 4.5. The number of biologically independent samples (n) are indicated. c R-value of PfCRT^Dd2, as defined by the ratio of the CQ transport activity at pH 4.5 over that at pH 6.0. d Left, Identification of E207 as a critical pH sensor in PfCRT. Shown is a plot of R-values against PfCRT-mediated CQ uptake at pH 6.0 of 53 PfCRT^Dd2-derived mutants, in which titratable and aromatic, π-interacting residues were replaced by alanine or asparagine in the case of aspartic acid. Relevant mutants are highlighted. For further information on the mutants see Supplementary Table 1. Right, Shown is a plot of R-values against transport activity at pH 6.0 for PfCRT^Dd2 (circle) and E207A (triangle) with the substrates, CQ (black), quinine (QN, light blue), quinidine (QD, purple), and piperaquine (PPQ, orange). Each data point represents the mean ± SEM of 3 to 9 biologically independent samples, with the number of biologically independent sample varying from mutant to mutant. e Substrate selectivity of PfCRT^Dd2 and E207A. The transport activities were normalized to that of CQ at pH 6.0. Verapamil (VP), vincristine (VNC), vinblastine (VNB), amantadine (AMA). Data were analyzed using bar charts, with the mean ± SEM of n biologically independent samples being shown, with n being from top to bottom for E207A: 9, 5, 5, 7, 3, 3, 3, and 4; and for PfCRT^Dd2: 26, 4, 5, 6, 3, 3, 3, and 4. The bar charts were overlaid with the individual data points. Source data for all subfigures are provided as a Source Data file⁸⁶.