K channel gating by an affinity-switching selectivity filter.

Published

Journal Article

A universal property of ion channels is their ability to alternate stochastically between two permeation states, open and closed. This behavior is thought to be controlled by a steric "gate", a structure that physically impedes ion flow in the closed state and moves out of the way during channel opening. Experiments employing macroscopic currents in the Shaker K channel have suggested a cytoplasmic localization for the gate. Crystallographic structures of the KcsA K channel indeed reveal a cytoplasmic constriction, implying that the gate and selectivity filter are localized to opposite ends of the permeation pathway. However, analysis of K channel subconductance behavior has suggested a strict coupling between channel opening (gating) and permeation. The idea that the selectivity filter is the gate was therefore investigated by using Monte Carlo simulations. Gating is accomplished by allowing the filter to alternate stochastically between two conformations: a high-affinity state, which selectively binds K ions (but not Na ions) and traps them, and a completely nonselective, low-affinity state, which allows both Na and K ions to permeate. The results of these simulations indicate that affinity switching not only endows the selectivity filter with gating abilities, it also allows efficient permeation without jeopardizing ion selectivity. In this model, permeation and gating result from the same process.

Full Text

Duke Authors

Cited Authors

  • VanDongen, AMJ

Published Date

  • March 2, 2004

Published In

Volume / Issue

  • 101 / 9

Start / End Page

  • 3248 - 3252

PubMed ID

  • 14976245

Pubmed Central ID

  • 14976245

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.0308743101

Language

  • eng

Conference Location

  • United States