Referenced in: none

Automatically associated channels: Kir7.1

Title: Stable cation coordination at a single outer pore residue defines permeation properties in Kir channels.

Authors: E Wischmeyer, F Döring, A Karschin

Journal, date & volume: FEBS Lett., 2000 Jan 21 , 466, 115-20

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/10648824

Abstract
In epithelial Kir7.1 channels a non-conserved methionine in the outer pore region adjacent to the G-Y-G selectivity filter (position +2) was found to determine unique properties for permeant and blocking ions characteristic of a K(+) channel in a single-occupancy state. The monovalent cation permeability sequence of Kir7.1 channels expressed in Xenopus oocytes was Tl(+)>K(+)>Rb(+)NH(4)(+)>Cs(+)>Na(+)>Li(+), but the macroscopic conductance for Rb(+) was approximately 8-fold larger than for the smaller K(+) ions, and decreased approximately 40-fold with the conserved arginine at the +2 position (Kir7.1M125R). Moreover, in Kir7.1 Rb(+) restored the typical permeation properties of other multi-ion channels indicating that a stable coordination of permeant ions at the +2 position defines the initial step in the conduction pathway of Kir channels.