Fig. 3. Suramin binds in the cavity between the VSGsur monomers.

(a) On the left is the overall structure of the VSGsur-suramin co-crystal structure in ribbon diagram form similar to that depicted in Fig. 1. Suramin is shown in purple as a space-filling representation. The red box around the drug is expanded in the boxed image on the right (rotated 90 degrees counterclockwise about a vertical axis), showing a ball-and-stick rendering of the compound with a blue wire-cage of the 1σ contour of the 1.9Å 2Fo-Fc electron density map of the refined molecule drawn around it. Suramin is shown as a ball-and-stick chemical representation with oxygen atoms are shown in red, nitrogen in blue, and carbon gray. (b) VSGsur is depicted as in Fig. 1 and suramin as in panel (a). Side-chains from VSGsur are shown in ball-and-stick representation and colored according to the chain to which they belong (blue and gold). Hydrogen bonds are shown as red-dashed lines. (c) Contacts between the N-linked glycan (with carbon atoms colored green, oxygen red, and nitrogen blue) and VSGsur, shown and colored as in (b). GlcNAc indicates N-Acetylglucosamine, MAN indicates mannose, and βMAN indicates β-mannose. (d) Schematic illustrating the contacts of VSGsur to suramin, focused on the ligand (generated by PDBsum⁵⁵ using LigPlot⁵⁶). Structures were illustrated with CCP4mg⁴⁸.