Specific phosphoantibodies reveal two phosphorylation sites in yeast Pma1 in response to glucose

Glucose triggers post-translational modifications of the Saccharomyces cerevisiae plasma membrane H+-ATPase (Pma1) that lead to an increase in enzyme activity. The activation results from changes in two kinetic parameters: an increase in the affinity of the enzyme for ATP, depending on Ser899, and an increase in the Vmax involving Ser911/Thr912. Using phosphospecific antibodies, we show that Ser899 and Ser911/Thr912 are phosphorylated in vivo during glucose activation and that protein phosphatase Glc7 is involved in the dephosphorylation of Ser899 upon glucose starvation. The authors have developed two antiphosphopeptide antibodies that specifically recognize Pma1 protein phosphorylated on Ser899 or Ser911/Thr912.