Functional reconstitution of a prokaryotic K+ channel

SliK, a K+ channel encoded by the Streptomyces KcsA gene, was expressed, purified, and reconstituted in liposomes. A concentrative Rb-86(+) flux assay was used to assess the ion transport properties of SliK. SliK-mediated ionic flux shows strong selectivity for K+ over Na+ and is inhibited by micromolar concentrations of Ba2+, mirroring the basic permeation characteristic of eukaryotic K+ channels studied by electrophysiological methods. Rb-86(+) uptake kinetics and equilibrium measurements also demonstrate that the purified protein is fully active.