Figure 2. ERG24 deletion impairs the function of V-ATPase but not Pma1p.

(A) Vacuolar pH of WT, erg24Δ and vma2Δ strains measured with pH sensitive fluorophore BCECF-AM, which accumulates in the yeast vacuole. (B) Initial H⁺ pumping rate was calculated from ΔA_490–540 during the first 60 s after initiating the reaction. ATPase activity was calculated from drop of A₃₄₀ between 3 and 6 minutes after initiating the reaction. Means and standard deviations are plotted from data for at least three independent vacuolar vesicle preparations. p values of two-tailed t-test are shown. (C) Medium acidification by Pma1 upon glucose activation was measured as described in Methods. Extracellular pH (pH_out) was recorded after glucose was added to 2% at time 0.