Effect of ATPase Inhibitors on the Proton Pump of Respiratory‐Deficient Yeast

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Abstract
Diethylstilbestrol and dicyclohexylcarbodiimide inhibit the ATPase of the plasma membranes and the proton-pumping activity of the cells in a respiratory-deficient mutant of Saccharomyces cerevisiae. The effects of the inhibitors in vivo seem to be specific because neither the proton permeability nor the ATP levels of the cells are affected. These results indicate that the yeast plasma-membrane ATPase corresponds to the proton pump of the cells. The fact that both inhibitors of the ATPase delay the fall of ATP levels which follows a block of fermentation indicates that ATPase function is one of the major ATP-consuming pathways in yeast. In addition, diethylstilbestrol prevents the fall of ATP levels produced by dinitrophenol, suggesting that this fall was caused by partial dissipation of the proton gradient and consequent stimulation of the proton-pumping ATPase.