An investigation into the feasibility of using yeast protoplasts to study the ion transport properties of the plasma membrane.

A method for studying ion uptake in enzymatically isolated protoplasts from the yeast, Saccharomyces cerevisiae, is described. The kinetics of K+ and Rb+ uptake, metabolic proton extrusion and cell electrophoretic mobility have been determined. Enzymic removal of the cell wall does not significantly alter the above-mentioned properties of the yeast cells. It is concluded that studies of these properties can be performed equally well with intact yeast cells or protoplasts. However, in studies aimed at determining effects of complex organic substances, e.g., antibiotics, on plasma membrane function the use of protoplasts is recommended. The effectiveness of the antibiotic, Dio-9, for example, in reversing the metabolic proton extrusion into a net proton influx is at least 50 times higher after enzymic removal of the yeast cell wall.