Fig. 5.

Ceftolozane (pink) docked in the active site of the PDC-3 E219K variant. Hydrogen bonds between ceftolozane and residues are indicated with green dashed lines, the catalytic S64 is in cyan, and the Ω-loop in blue. Two conformations of Y221 showcase the increased flexibility of the variant: purple represents a conformation found in both PDC-3 and the PDC-3 E219K variant whereas green represents a conformation found only in the PDC-3 E219K variant, the E219K substitution enables the movement between these conformations, allowing ceftolozane to enter the active site and bind while maintaining residues in catalytically favorable conformations.