Na+ block and permeation in a K+ channel of known structure

J Gen Physiol. 2002 Sep;120(3):323-35. doi: 10.1085/jgp.20028614.


The effects of intracellular Na(+) were studied on K(+) and Rb(+) currents through single KcsA channels. At low voltage, Na(+) produces voltage-dependent block, which becomes relieved at high voltage by a "punchthrough" mechanism representing Na(+) escaping from its blocking site through the selectivity filter. The Na(+) blocking site is located in the wide, hydrated vestibule, and it displays unexpected selectivity for K(+) and Rb(+) against Na(+). The voltage dependence of Na(+) block reflects coordinated movements of the blocker with permeant ions in the selectivity filter.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism*
  • Cell Membrane Permeability / drug effects
  • Cell Membrane Permeability / physiology*
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / physiology
  • Lipid Bilayers / metabolism
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Membranes, Artificial*
  • Potassium Channels / chemistry
  • Potassium Channels / metabolism*
  • Sodium / metabolism*
  • Sodium / pharmacology


  • Bacterial Proteins
  • Lipid Bilayers
  • Membranes, Artificial
  • Potassium Channels
  • prokaryotic potassium channel
  • Sodium