Fig. 2.

The 3-D structure of EnvSia156. a, b Van der Waals’ surface of a EnvSia156 homodimer with one unit colored in light blue and the other in light green. c “Top-down” view of the dimer with depth shading highlighting the continuous groove connecting the two binding sites. d, e Ribbon representation of the structure of EnvSia156 with rainbow coloring (N-terminus in blue, C-terminus in red) showing the (β/α)₈-barrel fold of the catalytic module and the eight stranded β-sandwich C-terminal module. A purple colored Neu5Ac molecule in stick representation can be seen bound in the active center of each unit present in panels b–e