Novel insights into K+ selectivity from high-resolution structures of an open K+ channel pore

Nat Struct Mol Biol. 2010 Aug;17(8):1019-23. doi: 10.1038/nsmb.1865. Epub 2010 Aug 1.


K+ channels are highly selective for K+ over Na+. Here we present several crystal structures of the MthK K+ channel pore at up to 1.45-A resolution. The MthK selectivity filter maintains a conductive conformation even in the absence of K+, allowing the channel to conduct Na+. The high-resolution structures, along with single-channel recordings, allow for an accurate analysis of how K+ competes with Na+ in a conductive selectivity filter. At high K+ concentrations, two K+ ions equivalently occupy the four sites in the selectivity filter, whereas at low K+/high Na+ concentrations, a single K+ ion remains bound in the selectivity filter, preferably at site 1 or site 3. This single K+ binding at low concentration effectively blocks the permeation of Na+, providing a structural basis for the anomalous mole-fraction effect, a key property of multi-ion pores.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism
  • Crystallography, X-Ray
  • Ion Channel Gating / drug effects
  • Ions
  • Methanobacterium / chemistry*
  • Potassium / metabolism*
  • Potassium / pharmacology
  • Potassium Channels / chemistry*
  • Potassium Channels / metabolism*
  • Protein Conformation
  • Static Electricity
  • Structure-Activity Relationship


  • Bacterial Proteins
  • Ions
  • Potassium Channels
  • Potassium

Associated data

  • PDB/3LDC
  • PDB/3LDD
  • PDB/3LDE