title: Characterization of the interaction between the plasma membrane H-ATPase of Arabidopsis thaliana and a novel interactor (PPI1).
abstract: Proton pump interactor, isoform 1 (PPI1) is a novel interactor of the C-terminus of Arabidopsis thaliana plasma membrane H(+)-ATPase (EC 3.6.3.6). We produced two fusion proteins consisting of, respectively, the first 88 amino acids or the entire protein deleted of the last 24 hydrophobic amino acids, and we show that the latter protein has a threefold higher affinity for the H(+)-ATPase. PPI1-induced stimulation of H(+)-ATPase activity dramatically decreased with the increase of pH above pH 6.8, but became largely pH-independent when the enzyme C-terminus was displaced by fusicoccin-induced binding of 14-3-3 proteins. The latter treatment did not affect PPI1 affinity for the H(+)-ATPase. These results indicate that PPI1 can bind the H(+)-ATPase independently of the C-terminus conformation, but is not able to suppress the C-terminus auto-inhibitory action.
authors.affiliation: Dipartimento di Biologia 'L. Gorini', Università di Milano, CNR Istituto di Biofisica -- Sezione di Milano, Italy.
authors.forename: Corrado
authors.initials: C
authors.lastname: Viotti
authors.forename: Laura
authors.initials: L
authors.lastname: Luoni
authors.forename: Piero
authors.initials: P
authors.lastname: Morandini
authors.forename: Maria Ida
authors.initials: MI
authors.lastname: De Michelis
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005982:Glutathione Transferase / Q000378:metabolism; D006027:Glycosides / Q000494:pharmacology; D006639:Histidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D009183:Mycotoxins / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism
chemical_list: D048948:14-3-3 Proteins; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D006027:Glycosides; D009183:Mycotoxins; C469717:Ppi1 protein, Arabidopsis; D011993:Recombinant Fusion Proteins; C007808:fusicoccin; D006639:Histidine; D000255:Adenosine Triphosphate; D005982:Glutathione Transferase; D006180:Proton-Translocating ATPases