The open gate of the BK-type K+ channel is stabilized when the voltage-sensor domains (VSDs) are activated by depolarization and the intracellular Mg2+ sensors are occupied. A systematic investigation reveals that each Mg2+ is bound by the transmembrane VSD and cytoplasmic ligand-sensing domain from two adjacent subunits, suggesting that relative positions of sensor and gate domains of BK channels may differ substantially from those suggested by homology models.
- Frank T Horrigan
- Toshinori Hoshi