Figure 7. Binding of the CPA at the C-terminal sugar binding motifs, C1 and C2, is critical to pyocin L1 cytotoxicity.

ITC binding isotherms of (A) wild-type (B) D180A (C) D150A and (D) D150A/D180A pyocin L1 all at (100 µM) titrated into isolated LPS-derived polysaccharide (1 mg ml⁻¹) from wild-type P. aeruginosa PAO1. Fit to a single binding site model is shown. (E) Spot tests to determine cytotoxic activity of wild-type and pyocin L1 variants against of P. aeruginosa PAO1. Purified protein (starting concentration 400 µg ml⁻¹ with 2-fold sequential dilutions) was spotted onto a growing lawn of P. aeruginosa PAO1. Clear zones indicate pyocin L1 cytotoxicity.