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.