Fig. 1.

KSI⋅intermediate and ${\mathrm{K}\mathrm{S}\mathrm{I}}^{D40N}\cdot$inhibitor complex. Schematic depiction of (A) the KSI⋅intermediate complex during the catalytic cycle (Fig. S1) and (B) a complex between ${\mathrm{K}\mathrm{S}\mathrm{I}}^{D40N}$ and phenol, an inhibitor that acts as an intermediate analog. Both the intermediate and the inhibitor are stabilized by a hydrogen-bond network in the active site of KSI. (C) Image of ${\mathrm{K}\mathrm{S}\mathrm{I}}^{D40N}$ with the tyrosine triad enlarged and the atoms O16, H16, O32, H32, and O57 labeled (shown with Tyr57 deprotonated) (16).