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(a) 2F o − F c electron-density map contoured at the 1.5σ level above the mean (0.4 e Å−3) showing the MES molecule, water 147 and the catalytic Tyr-L36. Heavy and light chains are shown in magenta and cyan, respectively. (b) An extended hydrogen-bonding pattern involving the MES molecule and five intact water molecules located close to the A17λ active centre (red dashed lines).
