Distinct configurations of cations and water in the selectivity filter of the KcsA potassium channel probed by 3D-RISM theory

Saree Phongphanphanee, Norio Yoshida, Shigetoshi Oiki, Fumio Hirata

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The potassium channel is highly selective for K+ over other monovalent cations, and the narrow pore structure with 3 Å in diameter named the selectivity filter (SF) is responsible for the selective permeation. Here we applied the statistical mechanics of liquids called three-dimensional reference interaction site model (3D-RISM) theory, and the binding configurations of the monovalent cations, Li+, Na+ and K+, with special attention on the contribution of water in the KcsA potassium channel were examined. All the three types of cations are bound in the open SF with high affinity, but with different binding coordinations: the in-cage configuration by eight carbonyl oxygens for K+, and the in-plane configuration by four carbonyl oxygens for Li+, whereas both configurations are allowed for Na+. In each case, water contributes an integral part of the ion coordination. In the case of Li+, a linear water-Li+-water complex is settled into two adjacent cages with the Li+ centered at the in-plane site. Positions of water around Na+ are more flexible, which may allow a transition between in-plane and in-cage configurations. K+ stably occupied in-cage configuration, and water occupies adjacent cages. The results provide the distinct configuration of ion and water in the SF, and serves clues for elementary process of selectivity.

Original languageEnglish
Pages (from-to)52-58
Number of pages7
JournalJournal of Molecular Liquids
Volume200
Issue numberPA
DOIs
Publication statusPublished - Jan 1 2014

Fingerprint

Potassium Channels
Potassium
Cations
selectivity
Positive ions
filters
cations
Water
configurations
water
Monovalent Cations
Ions
Oxygen
Statistical mechanics
oxygen
Pore structure
statistical mechanics
Permeation
affinity
ions

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Spectroscopy
  • Physical and Theoretical Chemistry
  • Materials Chemistry

Cite this

Distinct configurations of cations and water in the selectivity filter of the KcsA potassium channel probed by 3D-RISM theory. / Phongphanphanee, Saree; Yoshida, Norio; Oiki, Shigetoshi; Hirata, Fumio.

In: Journal of Molecular Liquids, Vol. 200, No. PA, 01.01.2014, p. 52-58.

Research output: Contribution to journalArticle

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