Illustration of K⁺ channel regions contributing to electrical resistance. (Far left) Vertical slice through the axis of symmetry of the Kv1.2 pore (Protein Data Bank accession no. 2R9R), with surface rendering of the inner cavity. Residues mutated to aspartate by Díaz-Franulic et al. (2015) are colored red; K⁺ is colored violet. The relative electrical resistance of permeation path segments in Shaker wild-type, Shaker P475D, and BK channels is schematized from left to right. Coloring crudely reflects the resistances reported by Díaz-Franulic et al.