Electrostatic interactions in the channel cavity as an important determinant of potassium channel selectivity

Biche et al. 10.1073/pnas.0606660103.

Supporting Figures

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Supporting Figure 6
Supporting Figure 7

Supporting Figure 6

Fig. 6. Acidic side chains at N184 (N184D/E) suppress the large Na⁺ current due to the S177W mutation. Different substitutions at the N184 position were introduced in the background of S177W and compared with the S177W and S177T mutant channels. Two-electrode voltage-clamp currents were recorded from Xenopus oocytes expressing Kir3.2 mutant channels, and the means ± SEM of measurements were plotted as I-V curves in 90 mM Na⁺ (filled circles) and in 90 mM K⁺ (open circles). S177T allows only K⁺ permeation, whereas K⁺ and Na⁺ can permeate the S177W channel. Substitution by an acidic residue at N184 (D or E) in S177W abolishes Na⁺ permeability, whereas other substitutions have no effect. For S177W-N184D and S177W-N184E, the current values in Na⁺ represent TPN_Q-corrected curves. For all curves, 6-10 oocytes were averaged from the same batch; similar results were obtained with different batches of oocytes.

Supporting Figure 7

Fig. 7. Profile of selectivity for Asp mutation at residues from the M2 helix of Kir3.2. Residues from two different faces of the M2 helix of Kir3.2 were mutated individually to D in the background of S177W, and their permeability was measured in Xenopus oocytes. Currents were recorded by using a two-electrode voltage clamp, and the means ± SEM of the measurements were plotted as I-V curves in 90 mM Na⁺ (filled circles) and in 90 mM K⁺ (open circles). Mutations to D at residues from one face of M2 (G180, N184, and V188) abolish Na⁺ permeability to the mutant channels, whereas mutations of residues from the adjacent face (S181, A185, and G189) have no effect. For S177W-G180D, S177W-N184D, and S177W-V188D, the current values in Na⁺ represent TPN_Q-corrected curves (n = 6-11 oocytes).