Phosphorylation-independent interaction between 14-3-3 protein and the plant plasma membrane H⁺-ATPase

14-3-3 proteins interact with a novel phosphothreonine motif (Y⁹⁴⁶pTV) at the extreme C-terminal end of the plant plasma membrane H⁺-ATPase molecule. Phosphorylation-independent binding of 14-3-3 protein to the YTV motif can be induced by the fungal phytotoxin fusicoccin. The molecular basis for the phosphorylation-independent interaction between 14-3-3 and H⁺-ATPase in the presence of fusicoccin has been investigated in more detail. Fusicoccin binds to a heteromeric receptor that involves both 14-3-3 protein and H⁺-ATPase. Binding of fusicoccin is dependent upon the YTV motif in the H⁺-ATPase and, in addition, requires residues further upstream of this motif. Apparently, 14-3-3 proteins interact with the unusual epitope in H⁺-ATPase via its conserved amphipathic groove. This implies that very diverse epitopes bind to a common structure in the 14-3-3 protein.