Figure 2.

Structure of different cardiac potassium channel species: Schematic representation of selected potassium channel α-subunits. A, The 6-transmembrane 1-pore-region voltage-dependent K⁺ channel (K_v) α-subunits mediating I_Kur, I_to, I_Ks, I_Kr, and I_f. B, The 2-transmembrane 1-pore-region inward rectifying K⁺ channel (K_ir) α-subunits mediating I_K1, I_KATP, and I_KAch. C, The 4-transmembrane 2-pore-region K⁺ channel (K_2P) mediating “leak” K⁺ currents. The arrows indicate the location of the pore-forming region(s). HCN indicates hyperpolarization-activated cyclic nucleotide-gated channel; I_f, inward rectifier mixed Na⁺ and K⁺ “funny” current; I_K1, inward rectifier K⁺ current; I_KACH, acetylcholine-activated inward rectifier K⁺ current; I_KATP, ATP-sensitive K⁺ current; I_Kr, rapid component of the delayed rectifier K⁺ current; I_Ks, slow component of the delayed rectifier K⁺ current; I_Kur, ultrarapid component of the delayed rectifier K⁺ current; I_to, transient outward K⁺ current. Reprinted with permission from Giudicessi and Ackerman. Macmillan Publishers Ltd, copyright 2012.³