Figure 5. CQ transport activity of the C101F and L272F variants of PfCRT in Xenopus oocytes.

(a,b) The uptake of [³H]CQ into oocytes expressing PfCRT was measured in the absence (closed bars) or presence of 250 μM VP (light grey bars; a), 100 μM BSD (dark grey bars; b), or 500 μM BSD (open bars; b). Within each experiment, measurements were made from 10 oocytes per treatment and uptake was expressed relative to that measured in the PfCRT^Dd2-expressing oocytes under control conditions. The normalized data obtained from 4–5 separate experiments (each using oocytes from different frogs) were then averaged and are shown + SEM. Both panels show PfCRT-mediated CQ uptake, calculated by subtracting CQ uptake measured in PfCRT^3D7-expressing oocytes (i.e. the component of CQ accumulation attributable to diffusion; see Supplementary Fig. S3) from that measured in oocytes expressing a variant of PfCRT. In the control treatments, the rates of CQ uptake (pmol/oocyte/h; n = 9 ± SEM) in oocytes expressing PfCRT^Dd2 and PfCRT^3D7 were 23.6 ± 2.3 and 1.3 ± 0.2, respectively. ‘ns’ denotes no significant difference (p > 0.05) in CQ accumulation between oocytes expressing a PfCRT variant (in the presence or absence of VP or BSD) and that measured in the PfCRT^3D7-expressing oocytes under control conditions.