8FZ7 image
Entry Detail
PDB ID:
8FZ7
EMDB ID:
Title:
TpeA bound closed MthK-A88F mutant in nanodisc
Biological Source:
PDB Version:
Deposition Date:
2023-01-27
Release Date:
2023-10-11
Method Details:
Experimental Method:
Resolution:
2.88 Å
Aggregation State:
PARTICLE
Reconstruction Method:
SINGLE PARTICLE
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Calcium-gated potassium channel MthK
Chain IDs:A, B (auth: C), C (auth: E), D (auth: G), E (auth: B), F (auth: D), G (auth: F), H
Chain Length:336
Number of Molecules:8
Biological Source:Methanothermobacter thermautotrophicus
Primary Citation
Calcium-gated potassium channel blockade via membrane-facing fenestrations.
Nat.Chem.Biol. 20 52 61 (2024)
PMID: 37653172 DOI: 10.1038/s41589-023-01406-2

Abstact

Quaternary ammonium blockers were previously shown to bind in the pore to block both open and closed conformations of large-conductance calcium-activated potassium (BK and MthK) channels. Because blocker entry was assumed through the intracellular entryway (bundle crossing), closed-pore access suggested that the gate was not at the bundle crossing. Structures of closed MthK, a Methanobacterium thermoautotrophicum homolog of BK channels, revealed a tightly constricted intracellular gate, leading us to investigate the membrane-facing fenestrations as alternative pathways for blocker access directly from the membrane. Atomistic free energy simulations showed that intracellular blockers indeed access the pore through the fenestrations, and a mutant channel with narrower fenestrations displayed no closed-state TPeA block at concentrations that blocked the wild-type channel. Apo BK channels display similar fenestrations, suggesting that blockers may use them as access paths into closed channels. Thus, membrane fenestrations represent a non-canonical pathway for selective targeting of specific channel conformations, opening novel ways to selectively drug BK channels.

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