Figure 2.

A schematic illustration of the various ion channels identified in urethral smooth muscle. The architecture of the transmembrane α and β subunits is shown in the left panel. Dimeric and trimeric arrangements can be seen for K_2P and P2X channels, respectively. Most channels have tetrameric structures and several have β subunits associated. Abbreviations: N, amino-terminus; C, carboxyl-terminus; K_ir, inwardly-rectifying K⁺ channel; SUR, sulfonylurea; TMD, transmembrane domain; K_ATP, ATP-sensitive K⁺ channel; +, positively-charged residues; BK_Ca, large conductance, Ca²⁺-activated K⁺ channel; K_v, voltage-gated K⁺ channel; CaM, calmodulin; K2P, 2-pore domain K⁺ channel; IK_Ca, intermediate conductance K⁺ channel; SK_Ca, small conductance K⁺ channel; VGCC, voltage-gated Ca²⁺ channel; CaCC, Ca²⁺-activated Cl⁻ channel.