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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 of the United States of America
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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