Protein phosphatase 2A scaffolding subunit A interacts with plasma membrane H+‐ATPase C‐terminus in the same region as 14‐3‐3 protein

The activity of the plant plasma membrane H+‐ATPase is tightly regulated via phosphorylation and binding of 14‐3‐3 protein to the C‐terminus of the pump. Whereas the 14‐3‐3‐binding mechanism has been described in detail, the identity of specific protein kinases and phosphatases involved in the control of 14‐3‐3 binding has remained elusive. Using the yeast two‐hybrid system, GST pull‐down assays and overlay experiments, we report that scaffolding subunit A of protein phosphatase 2A (PP2A‐A) interacts with the C‐terminus of the Arabidopsis plasma membrane H+‐ATPase isoform 2. PP2A‐A binding is inhibited in the presence of 14‐3‐3 protein and fusicoccin, a fungal toxin which induces binding of 14‐3‐3 protein to the C‐terminal end of the plasma membrane H+‐ATPase. This indicates that PP2A‐A and 14‐3‐3 protein compete with each other for binding to the same region in the C‐terminus of the H+‐ATPase.