Transfer of the voltage sensor paddle motifs from hNav1.9 to Kv2.1. (A) Cartoon representing a top view of Nav1.9 (left) and Kv2.1 (right). The central Na⁺- or K⁺-selective pore is surrounded by the four voltage sensors of the four domains (DI–DIV, delineated by the dotted line). In Nav1.9, the paddle motifs are not identical and are therefore colored differently: purple, domain I paddle (DI); red, domain II paddle (DII); blue, domain III paddle (DIII); green, domain IV paddle (DIV). This color code is used in the other figures. In Kv2.1, the paddle motifs are identical and therefore have the same color (gray). (B and C) Transfer of the hNav1.9 paddle motifs into Kv2.1. Families of potassium currents (B) and tail current voltage–activation relationships (C) for each chimeric construct (n = 16; error bars represent SEM). Holding voltage was −90 mV, and the tail voltage was −50 mV (−80 mV for DII). Bars in B are 1 µA and 100 ms.