The selectivity filter may act as the agonist-activated gate in the G protein-activated Kir3.1/Kir3.4 K+ channel.

The Kir3.1/Kir3.4 channel is activated by Gbetagamma subunits released on binding of acetylcholine to the M2 muscarinic receptor.

Molecular basis of ion selectivity, block, and rectification of the inward rectifier Kir3.1/Kir3.4 K(+) channel.

The glycine-tyrosine-glycine (GYG) sequence in the p-loop of K+ channel subunits lines a narrow pore through which K+ ions pass in single file intercalated by water molecules. Mutation of the motif can give rise to non-selective channels, but it is clear that other structural features are also required for selectivity because, for instance, a recently identified class of cyclic nucleotide-gated pacemaker channels has the GYG motif but are poorly K+ selective. We show that mutation of charged glutamate and arginine residues behind the selectivity filter in the Kir3.