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Potassium channels selectively conduct K(+) ions across cell membranes and have key roles in cell excitability. Their opening and closing can be spontaneous or controlled by membrane voltage or ligand binding. We used Ba(2+) as a probe to determine the location of the ligand-sensitive gate in an inwardly rectifying K(+) channel (Kir6.2). To a K(+) channel, Ba(2+) and K(+) are of similar sizes, but Ba(2+) blocks the pore by binding within the selectivity filter. We found that internal Ba(2+) could still access its binding site when the channel was shut, which indicates that the ligand-sensitive gate lies above the Ba(2+)-block site, and thus within or above the selectivity filter. This is in marked contrast to the voltage-dependent gate of K(V) channels, which is located at the intracellular mouth of the pore.

Original publication




Journal article



Publication Date





70 - 75


Adenosine Triphosphate, Amino Acid Substitution, Animals, Barium, Binding Sites, Cadmium, Cations, Divalent, Female, Ion Channel Gating, Ion Transport, Ligands, Mice, Models, Biological, Molecular Weight, Mutation, Missense, Oocytes, Point Mutation, Potassium, Potassium Channels, Inwardly Rectifying, Protein Conformation, Protein Structure, Tertiary, Recombinant Proteins, Silver, Xenopus laevis