Figure 5

Acetic acid stress leads to the activation of Snf1p kinase but does not appear to inhibit glucose uptake. Comparison of Snf1p activity (upper panel) and of glucose uptake rates (lower panel) in yeast cells of the parental strain BY4741 cultivated for 30 minutes in MM4 growth medium (at pH 4.0) (black squares) or cultivated in this same basal growth medium supplemented with 60 mM acetic (black triangles). The determination of Snf1p activity was performed by immunoblotting and was based on the relative quantification of Snf1p phosphorylation at Thr120 residue, as described in Materials and Methods. As a negative control, a similar immunoblot analysis was carried out using protein extracts of the Δsnf1 deletion mutant. To estimate the kinetic parameters K _M and V_max shown in the insert Table the experimental values of glucose uptake rates were fitted into an Eadie/Hofstee plots. The data presented are medium values from three independent experiments.* μmol per hour per 10⁸ cells; ** mmol per liter.