FIG. 2.

Effect of the sen1-1 mutation on the yeast Pma1 proton pump. Cells of strains SKY697 (wt) and AG151 (sen1 mutant) were grown in YPD, and the in vivo activity (A) and amount (B) of the Pma1 proton-pumping ATPase were determined as described in the text. (A) pH changes of yeast suspensions induced by glucose. Cells (50 mg) were suspended in 10 ml of assay buffer, and pH changes were recorded after addition of 200 μmol of glucose. Calibration with 400 nmol of HCl was made as indicated. (B) Immunological quantification of Pma1 in yeast. Total membrane protein (25 μg) from strains SKY697 (wild type [wt] for PTK2, lanes 1 and 2) and AG151 (sen1-1, lanes 3 and 4) was immunodetected with anti-Pma1 antibody after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electroblotting. Lane 5 contains molecular size standards as indicated.