Abstract

ICln is an ion channel cloned from renal epithelial cells. The reconstitution of the protein in 1,2-diphytanoyl-sn-glycero-3-phosphocholine (Diph-PC) bilayer membranes reveals potassium-selective channels, which become more chloride selective in the presence of calcium. Here we show that the ion selectivity of lCln also depends on the lipid environment in which the channels are reconstituted. Diph-PC is a synthetic lipid commonly used for reconstituting ion channels. However, since this lipid is not found in native membranes, we reconstituted the lCln ion channels in a polar heart-lipid extract. Using this lipid mixture the reconstituted lCln ion channels are chloride selective in the presence of calcium and an acidic pH. The relative ion selectivity of lCln under these conditions is similar to the cation versus anion selectivity of native ion channels activated by cell swelling.