K_ir1.1 (ROMK1) was the first member of the family of inward rectifying K⁺ channels to be cloned¹. The family includes 15 members that are structurally and functionally different from the voltage-dependent K⁺ channels.

The family’s topology consists of two transmembrane domains that flank a single and highly conserved pore region with intracellular N- and C-termini. As is the case for the voltage-dependent K⁺ channels the functional unit for the K_ir channels is composed of four subunits that can assemble as either homo- or hetero-tetramers.

K_ir channels are characterized by a K⁺ efflux that is limited by depolarizing membrane potentials thus making them essential for controlling resting membrane potential and K⁺ homeostasis².