Alanine scanning of critically positioned residues in PqsE.

A–B) Sixteen residues were selected based on their potential role (s) in ligand stabilization, discrimination and/or catalytic function in the vicinity of the active site cavity. C–D) Six residues were targeted in the C-terminal α8/α9 motif unique to PqsE. E–F) Five residues were selected to verify the potential importance of the KH-like motif in substrate recognition and/or stabilization. Residue side chains are labeled, displayed in ball-and-stick representation, and colored according to their impact on pyocyanin production upon mutation (Figure 6). The two catalytic iron atoms are depicted as yellow spheres.