Comparison of the acyl adducts of AmpC and imipenem (PDB entry 1LL5) (A), AmpC and moxalactam (PDB code 1FCO) (14) (B), and TEM-1 and imipenem (PDB code 1BT5) (10) (C), showing that AmpC binds imipenem differently than it does moxalactam but similarly to TEM-1. Atoms are colored as described for Fig. 2A, except the carbon atoms of imipenem in panel A are colored green, the carbon atoms of moxalactam in panel B are colored orange, and carbon atoms of imipenem in panel C are colored purple. Dashed yellow lines indicate hydrogen bonds of the oxyanion, or electrophilic, hole.