Figure 4.

Binding of Nonamannoside to the 1GS-S Construct of GRFT

(A) Stereo view of the complex of nonamannoside and 1GS-S. One molecule of nonamannoside (yellow) bridges carbohydrate-binding pockets 1 and 3, whereas a symmetry-related molecule of nonamannoside (gray) binds into pocket 2. The β-mannose monomers bound in the binding pockets are numbered as in Figure 1.

(B) Computed surface electrostatic potential of 1GS-S monomer (space filling representation) colored by charge from negative (red) to positive (blue), with bound nonamannosides shown as sticks. One nonamannoside molecule (yellow) binds to two carbohydrate-binding pockets, with negative electrostatic potential due principally to Asp67 and Asp109. The second nonamannoside molecule (gray) binds to the third binding pocket formed in part by Ser26 instead of Asp in the equivalent position and carrying a more positive electrostatic potential.