Figure 1. . Molecular composition and membrane topology of K_ATP channels.

Four subunits of SUR and Kir6.x each co-assemble to form the functional hetero-octameric K_ATP channel complex. The Kir6.x comprises two membrane-spanning domains that flank a K⁺ selectivity P-loop, whereas SUR has total 17 transmembrane domains organized in three regions (TM0, TM1 and TM2). The two nucleotide binding domains NBD1 and NBD2 are shown in purple.