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Publication Abstract from PubMed

BK channels are large-conductance calcium (Ca(2+))-activated potassium channels crucial for neuronal excitability, muscle contraction, and neurotransmitter release. The pore-forming (alpha) subunits co-assemble with auxiliary (beta and gamma) subunits that modulate their function. Previous studies demonstrated that the N-termini of beta2-subunits can inactivate BK channels, but with no structural correlate. Here, we investigate BK beta2-subunit inactivation using cryo-electron microscopy, electrophysiology and molecular dynamics simulations. We find that the beta2 N-terminus occludes the pore only in the Ca(2+)-bound open state, via a ball-and-chain mechanism. The first three hydrophobic residues of beta2 are crucial for occlusion, while the remainder of the N-terminus remains flexible. Neither the closed channel conformation obtained in the absence of Ca(2+) nor an intermediate conformation found in the presence of Ca(2+) show density for the N-terminus of the beta2 subunit in their pore, likely due to narrower side access portals preventing their entry into the channel pore.

Ball-and-chain inactivation of a human large conductance calcium-activated potassium channel.,Agarwal S, Kim ED, Lee S, Simon A, Accardi A, Nimigean CM Nat Commun. 2025 Feb 19;16(1):1769. doi: 10.1038/s41467-025-56844-4. PMID:39971906^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.