FIGURE 6.

ES* deacylation structure shows “revert-back” conformation of His-166 to serve as exclusive general base for deacylation. The active site of the ES* deacylation structure with “revert-back” conformation for His-166 at the start of the deacylation reaction (a) and tracked by time-dependent X-ray crystallography over a period of 6 min focusing on the disappearance of the acyl adduct (b). F_o − F_c omit map (purple) is drawn in mesh format and contoured at 2.0 σ. The dashed lines indicate hydrogen bonds.