TAILIEUCHUNG - Báo cáo khoa học: Characterization of the interaction between the plasma membrane H+-ATPase of Arabidopsis thaliana and a novel interactor (PPI1)

Proton pump interactor, isoform 1 (PPI1) is a novel interactor of the C-ter-minus ofArabidopsis thalianaplasma membrane H + -ATPase (EC ) (Morandini P, Valera M, Albumi C, Bonza MC, Giacometti S, Ravera G, Murgia I, Soave C & De Michelis MI (2002)Plant J31,487–497). | iFEBS Journal Characterization of the interaction between the plasma membrane H -ATPase of Arabidopsis thaliana and a novel interactor PPI1 Corrado Viotti Laura Luoni Piero Morandini and Maria Ida De Michelis Dipartimento di Biologia L. Gorini Universita di Milano CNR Istituto di Biofisica - Sezione di Milano Italy Keywords Arabidopsis thaliana H -ATPase plasma membrane PPI1 14-3-3 proteins Correspondence M. I. De Michelis Dipartimento di Biologia L. Gorini Universita di Milano CNR Istituto di Biofisica - Sezione di Milano via G. Celoria 26 20133 Milano Italy Fax 39 02 50314815 Tel 39 02 50314822 E-mail Received 28 July 2005 revised 13 September 2005 accepted 20 September 2005 doi Proton pump interactor isoform 1 PPI1 is a novel interactor of the C-ter-minus of Arabidopsis thaliana plasma membrane H -ATPase EC Morandini P Valera M Albumi C Bonza MC Giacometti S Ravera G Murgia I Soave C De Michelis MI 2002 Plant J 31 487-497 . 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 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. The H -ATPase is the major electrogenic pump in the plasma membrane PM of plant cells. By pumping protons from the cytoplasm to the apoplast it generates an electrochemical proton gradient which drives the transport of mineral ions and organic solutes and plays a crucial role in

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