Abstract
A voltage-dependent and Ca2+-activated cation channel recent-ly found in the vacuolar membrane of the yeast Saccharomyces cerevisiae was incorporated into planar lipid bilayers and further characterized in macroscopic and single channel levels. Single channel conductances for various cations were in the order: NH4+ > K+ > Rb+ > Cs+ > Na+ > Li+, and were nearly consistent with the order of permeability ratio estimated from reversal potentials determin-ed by macroscopic measurement. Up to 6 mM of Ca2+ added to the cis (cytoplasmic) side opened the channel, but higher concentrations closed the channel without affecting the single channel conductance. Ba2+ closed the chan-nel without opening. Further, large anions such as gluconate closed thechannel from the cis side. In addition to the above channel, a small cation-selective chan-nel of about 40 pS was found.
