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

Youxing Jiang, Roderick MacKinnon

Research output: Contribution to journalArticle

158 Citations (Scopus)

Abstract

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
Volume115
Issue number3
DOIs
StatePublished - 2000

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Potassium Channels
X Ray Crystallography
Barium
Ions
Alkali Metals
Calcium-Activated Potassium Channels
X-Ray Diffraction
Cations
Electrons

Keywords

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

ASJC Scopus subject areas

  • Physiology

Cite this

The barium site in a potassium channel by X-ray crystallography. / Jiang, Youxing; MacKinnon, Roderick.

In: Journal of General Physiology, Vol. 115, No. 3, 2000, p. 269-272.

Research output: Contribution to journalArticle

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abstract = "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 {\AA} 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.",
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AB - 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.

KW - Barium

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