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A ring of eight conserved negatively charged amino acids doubles the conductance of BK channels and prevents inward rectification.

Authors
  • Brelidze, Tinatin I
  • Niu, Xiaowei
  • Magleby, Karl L
Type
Published Article
Journal
Proceedings of the National Academy of Sciences
Publisher
Proceedings of the National Academy of Sciences
Publication Date
Jul 22, 2003
Volume
100
Issue
15
Pages
9017–9022
Identifiers
PMID: 12843404
Source
Medline
License
Unknown

Abstract

Large-conductance Ca2+-voltage-activated K+ channels (BK channels) control many key physiological processes, such as neurotransmitter release and muscle contraction. A signature feature of BK channels is that they have the largest single channel conductance of all K+ channels. Here we examine the mechanism of this large conductance. Comparison of the sequence of BK channels to lower-conductance K+ channels and to a crystallized bacterial K+ channel (MthK) revealed that BK channels have a ring of eight negatively charged glutamate residues at the entrance to the intracellular vestibule. This ring of charge, which is absent in lower-conductance K+ channels, is shown to double the conductance of BK channels for outward currents by increasing the concentration of K+ in the vestibule through an electrostatic mechanism. Removing the ring of charge converts BK channels to inwardly rectifying channels. Thus, a simple electrostatic mechanism contributes to the large conductance of BK channels.

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