Novel insights into K[superscript +] selectivity from high-resolution structures of an open K[superscript +] channel pore
- Chinese Aca. Sci.
K{sup +} channels are highly selective for K{sup +} over Na{sup +}. Here we present several crystal structures of the MthK K{sup +} channel pore at up to 1.45-{angstrom} resolution. The MthK selectivity filter maintains a conductive conformation even in the absence of K{sup +}, allowing the channel to conduct Na{sup +}. The high-resolution structures, along with single-channel recordings, allow for an accurate analysis of how K{sup +} competes with Na{sup +} in a conductive selectivity filter. At high K{sup +} concentrations, two K{sup +} ions equivalently occupy the four sites in the selectivity filter, whereas at low K{sup +}/high Na{sup +} concentrations, a single K{sup +} ion remains bound in the selectivity filter, preferably at site 1 or site 3. This single K{sup +} binding at low concentration effectively blocks the permeation of Na{sup +}, providing a structural basis for the anomalous mole-fraction effect, a key property of multi-ion pores.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1002556
- Journal Information:
- Nat. Struct. Mol. Biol., Vol. 17, Issue (8) ; 08, 2010
- Country of Publication:
- United States
- Language:
- ENGLISH
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