Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Potassium channels selectively conduct K(+), primarily to the exclusion of Na(+), despite the fact that both ions can bind within the selectivity filter. Here we perform crystallographic titration and single-channel electrophysiology to examine the competition of Na(+) and K(+) binding within the filter of two NaK channel mutants; one is the potassium-selective NaK2K mutant and the other is the non-selective NaK2CNG, a CNG channel pore mimic. With high-resolution structures of these engineered NaK channel constructs, we explicitly describe the changes in K(+) occupancy within the filter upon Na(+) competition by anomalous diffraction. Our results demonstrate that the non-selective NaK2CNG still retains a K(+)-selective site at equilibrium, whereas the NaK2K channel filter maintains two high-affinity K(+) sites. A double-barrier mechanism is proposed to explain K(+) channel selectivity at low K(+) concentrations.

Original publication

DOI

10.1038/ncomms3721

Type

Journal article

Journal

Nature communications

Publication Date

01/2013

Volume

4

Addresses

1] Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9040, USA [2].

Keywords

Bacillus cereus, Bacillus subtilis, Escherichia coli, Potassium, Sodium, Bacterial Proteins, Potassium Channels, Liposomes, Crystallography, X-Ray, Electrophysiology, Ion Channel Gating, Binding Sites, Binding, Competitive, Protein Conformation, Mutation