FIG 9.

(A) Overlay of the PenI (purple) and C69F (orange) apo-enzyme models showing that the oxyanion hole water position was ∼1 Å deeper in the electrophilic center in the C69F variant than with PenI. (B) Molecular modeling of the C69F variant acyl-enzyme with ceftazidime showing the possibility of up to 13 hydrogen-bonding partners, including residue D240. (C) Molecular modeling of the PenI acyl-enzyme with ceftazidime in the active site revealed a limited number of hydrogen-bonding interactions.