FIGURE 2.

Effect of polymorphism at position 394 on PfENT1 function. A, amino acid sequences of the region in and flanking PfENT1 TM11 from eight distinct P. falciparum strains. The specific strain is indicated to the left, the solid bar above indicates the predicted extent of TM11. The glycines in the absolutely conserved GXXXG motif are highlighted by the vertical stripes, and the 394 position of the polymorphism is indicated by the vertical arrow below the sequences. Note that 7G8 and W2 have a leucine at position 394, whereas all of the other strains have a phenylalanine. B, effect of 10 μm dipyridamole on 1 μm [³H]adenosine uptake by oocytes expressing either Phe-394 or Leu-394 PfENT1 expressed as a percent of the untreated. The differences in the presence and absence of 10 μm dipyridamole are not significant by paired two-tailed Student's t test. Of note, the dipyridamole K_i for the sensitive human ENT1 transporter is 48 nm (25). C, concentration dependence of [³H]hypoxanthine uptake by oocytes expressing either Phe-394 (open triangles) or Leu-394 (solid triangles). Lines represent Michaelis-Menten fits to the data. D, concentration dependence of [³H]adenosine uptake by oocytes expressing either Phe-394 (open squares) or L394 (solid squares). Lines represent Michaelis-Menten fits to the data.