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 heterotetramers.

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⁺ homeostasis.

K_ir3.1 is a member of the K_ir3.x subfamily that includes four members (K_ir3.1- K_ir3.4). The K_ir3 (GIRK) family is characterized by the fact that the channels can be activated by neurotransmitters and other factors acting via the activation of G-protein coupled receptors. Binding of the corresponding ligand to the G-protein receptor induces the dissociation of Gα-GTP from the Gβγ dimer. The latter directly binds to K_ir3 and activates the channel^1,2.