The addition of a peptide extension to the N terminus of KcsA does not affect its activity. I-V curves of WT (squares) and E71A (triangles) KcsA without (filled symbols) or with the G8N extension at the N terminus (open symbols). Each data point represents the mean ± SD from at least three separate bilayers. All the measurements were done in 200 mM KCl, buffered with 10 mM HEPES, pH 7.0, in the cis chamber and 200 mM KCl, buffered with 10 mM succinic acid, pH 4.0, in the trans chamber.