The Cysteine-Rich Interdomain Region from the Highly Variable Plasmodium falciparum Erythrocyte Membrane Protein-1 Exhibits a Conserved Structure
Figure 2
Refolded MC179 bound to CD36-transfected CHO cells as assayed by flow cytometry ([A,B]; blue hatched peaks). (A) Incubation of MC179 with CD36-Fc fusion protein (100 µg/ml) diminished MC179 binding to CD36 on cells (orange peak). MC179 binding was revealed with anti-MC179 Aotus immune serum. (B) MC179 binding to CD36 is inhibited by each of three anti-CD36 mAbs (peaks outlined in red, violet, and green). The violet peak is under the red peak and is only partially visible. Binding of MC179 was visualized with an anti-pentaHis mAb. In both panels, controls used untransfected cells (peaks outlined in black). In (A), Aotus preimmune serum yielded results (not shown) identical to the untransfected control. (C) Ribbon diagrams of MC179 in the same orientations as (D) and (E). Three-helix bundles are located towards the center of the figure and connecting helices are at the sides. (D) Two views of the hydrophobic surface 180° apart show a hydrophobic patch (green, at right) on the connecting helices of MC179. Labeled residues are those reported to affect CD36-binding (see text). (E) Surface views of MC179 showing the distribution of positive (blue) and negative (red) surface charge. The negatively charged region (red, at left) on the connecting helices is on the opposite face from the hydrophobic patch at the right in (D).