Structural bases for blockade and activation of BK channels by Ba2+ ions

Ba2+ increases open probability and blocks the permeation pathway of BK channels. Here we discuss Cryo-EM structures of BK channels with Ba2+. They reveal that Ba2+ occupies site S3 in the selectivity filter, leading to blockade. Ba2+ are also detected at all high affinity Ca2+ binding sites of the gating ring. However, the architectures of this region in these structures represent intermediate transitions between the extreme close and open configurations. ### Competing Interest Statement The authors have declared no competing interest.