A novel interaction partner for the C-terminus of Arabidopsis thaliana plasma membrane H+-ATPase (AHA1 isoform): site and mechanism of action on H+-ATPase activity differ from those of 14-3-3 proteins.

Using the two-hybrid technique we identified a novel protein whose N-terminal 88 amino acids (aa) interact with the C-terminal regulatory domain of the plasma membrane (PM) H+-ATPase from Arabidopsis thaliana (aa 847-949 of isoform AHA1). The corresponding gene has been named Ppi1 for Proton pump interactor 1. The encoded protein is 612 aa long and rich in charged and polar residues, except for the extreme C-terminus, where it presents a hydrophobic stretch of 24 aa.