Figure 3.

Potassium release assay for pore formation in liposomes by F427A-containing prepores. Pore formation was assayed by potassium release from DOPC LUVs containing 100 mM KCl into medium containing 100 mM NaCl. [WT]₇, [F427A]₇, or [WT]₆[F427A]₁ prepores were preincubated with the PA-binding domain of anthrax receptor 2 and then added to liposomes in buffer at pH 5.0. K⁺ release was measured with a K⁺-selective probe. Representative traces are shown. Rates were biphasic, with similar rate constants for one phase (k₂ = 0.006 s⁻¹ for all three heptamers), representing nonspecific release, and different for the other phase (k₁ = 0.33 s⁻¹ for [WT]₇, 0.19 s⁻¹ for [WT]₆[F427A]₁ and 0.078 s⁻¹ for [F427A]₇), representing the pore-mediated release. Representative data are shown from n ≥ 3 trials.