BK channel opening involves side-chain reorientation of multiple deep-pore residues

Three deep-pore locations, L312, A313, and A316, were identified in a scanning mutagenesis study of the BK (Ca ²⁺-activated, large-conductance K ⁺) channel S6 pore, where single aspartate substitutions led to constitutively open mutant channels (L312D, A313D, and A316D). To understand the mechanisms...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2014-01, Vol.111 (1), p.E79-E88
Main Authors: Chen, Xixi, Yan, Jiusheng, Aldrich, Richard W
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Amino acids
Biological Sciences
Calcium - chemistry
Electrophysiological Phenomena
HEK293 Cells
Humans
Ion Channel Gating
Large-Conductance Calcium-Activated Potassium Channels - chemistry
Large-Conductance Calcium-Activated Potassium Channels - metabolism
Molecular Sequence Data
Mutagenesis
Mutagenesis, Site-Directed
Mutation
Phenotype
PNAS Plus
Potassium
Probability
Protein Binding
Protein Conformation
Sequence Homology, Amino Acid
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Summary:Three deep-pore locations, L312, A313, and A316, were identified in a scanning mutagenesis study of the BK (Ca ²⁺-activated, large-conductance K ⁺) channel S6 pore, where single aspartate substitutions led to constitutively open mutant channels (L312D, A313D, and A316D). To understand the mechanisms of the constitutive openness of these mutant channels, we individually mutated these three sites into the other 18 amino acids. We found that charged or polar side-chain substitutions at each of the sites resulted in constitutively open mutant BK channels, with high open probability at negative voltages, as well as a loss of voltage and Ca ²⁺ dependence. Given the fact that multiple pore residues in BK displayed side-chain hydrophilicity-dependent constitutive openness, we propose that BK channel opening involves structural rearrangement of the deep-pore region, where multiple residues undergo conformational changes that may increase the exposure of their side chains to the polar environment of the pore.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1321697111