Three-dimensional structure of Plasmodium vivax Duffy binding protein (DBP). A hypothetical molecule of DBPII depicted as a space-filling molecule (i) and respective helixes (ii) showing clusters of polymorphic residues. Structures are rotated in each representation by 90° along a horizontal axis to show all surfaces of the molecule (0° = front; 90° = top; 180° = back; 270° = bottom). Purple, blue, and light blue represent sub-domains 1, 2, and 3, respectively. A, Cluster of polymorphic residues from all eight isolates. Red, yellow (not exposed), orange, green, and gray represent polymorphic residues in at least 60%, 50%, 37%, 25%, and 12%, respectively, for all isolates. B, Cluster of polymorphic residues in the Palo Alto isolate alone. The area in white represents residues of the predicted binding pocket for receptor recognition. This figure appears in color at www.ajtmh.org.