Vacuolar ion channel of the yeast, Saccharomyces cerevisiae

Ionic flux is most likely to regulate the chemiosmotic potential differences across vacuolysosomal membranes in animal, plant, and fungal cells. We found a membrane potential-dependent cation channel in yeast vacuolar membrane and characterized its several features by an electrophysiological method using artificial planar bilayer membranes incorporated with isolated yeast vacuolar membrane vesicles. This ion channel conducts K+ (single channel conductance, 435 pS in 0.3 M KCl) and several other monovalent cations (Cs+, Na+, and Li+) with broad selectivity, but does not conduct Cl-. The opening of this channel is regulated by the membrane potential and the presence of calcium ion on the cytoplasmic face. These characteristics suggested that the vacuolar cation channel functions as one of essential components for formation and regulation of the chemical and electrical potential differences across the vacuolar membrane.