The barium site in a potassium channel by X-ray crystallography

Youxing Jiang, Roderick MacKinnon

Research output: Contribution to journalArticlepeer-review

172 Scopus citations


X-ray diffraction data were collected from frozen crystals (100°K) of the KcsA K+ channel equilibrated with solutions containing barium chloride. Difference electron density maps (F(barium) - F(native), 5.0 Å resolution) show that Ba2+ resides at a single location within the selectivity filter. The Ba2+ blocking site corresponds to the internal aspect (adjacent to the central cavity) of the 'inner ion' position where an alkali metal cation is found in the absence of the blocking Ba2+ ion. The location of Ba2+ with respect to Rb+ ions in the pore is in good agreement with the findings on the functional interaction of Ba2+ with K+ (and Rb+) in Ca2+-activated K+ channels (Neyton, J., and C. Miller. 1988. J. Gen. Physiol. 92:549-567). Taken together, these structural and functional data imply that at physiological ion concentrations a third ion may interact with two ions in the selectivity filter, perhaps by entering from one side and displacing an ion on the opposite side.

Original languageEnglish (US)
Pages (from-to)269-272
Number of pages4
JournalJournal of General Physiology
Issue number3
StatePublished - 2000


  • Barium
  • Ion channel
  • Ion conduction
  • Ion selectivity
  • Potassium channel

ASJC Scopus subject areas

  • Physiology


Dive into the research topics of 'The barium site in a potassium channel by X-ray crystallography'. Together they form a unique fingerprint.

Cite this