Observations on Mechanism of Action of the Antifungal Peptide, Ro2-7758.

Abstract

Summary Inhibitory action of the antifungal sulfur-containing peptide, Ro2-7758 (formerly X-5079C), against the growth of Mucor corymbifera was annulled by sulfite and cysteine, but not by sulfate or 96 other substances tested. Experiments with S³⁵O₄ showed that the drug had no effect on permeability of yeast cells to sulfate. However, production of S³⁵O₃ from S³⁵O₄ by a cell-free sulfate reductase system from yeast was first stimulated at low drug concentrations and then inhibited at higher concentrations. It was concluded that this action of the drug on sulfate reductase may be involved in its antibiotic activity.