5BKI

Blocker-free closed MthK channel in nanodisc

Summary for 5BKI

• Entry DOI: 10.2210/pdb5bki/pdb
• EMDB information: 9405 9406 9407
• Descriptor: Calcium-gated potassium channel MthK, CADMIUM ION, (1R)-2-{[(S)-{[(2S)-2,3-dihydroxypropyl]oxy}(hydroxy)phosphoryl]oxy}-1-[(hexadecanoyloxy)methyl]ethyl (9Z)-octadec-9-enoate, ... (5 entities in total)
• Functional Keywords: ion channel, transport protein
• Biological source: Methanothermobacter thermautotrophicus
• Total number of polymer chains: 8
• Total formula weight: 303389.73

Authors

Fan, C.,Nimigean, C.M. (deposition date: 2021-03-19, release date: 2022-09-21, Last modification date: 2023-10-04)

Primary citation

Fan, C.,Flood, E.,Sukomon, N.,Agarwal, S.,Allen, T.W.,Nimigean, C.M.
Calcium-gated potassium channel blockade via membrane-facing fenestrations.
Nat.Chem.Biol., 2023

PubMed Abstract: 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.

PubMed: 37653172
DOI: 10.1038/s41589-023-01406-2

Experimental method

ELECTRON MICROSCOPY (3.1 Å)