Fusicoccin Activates the Plasma Membrane H+-ATPase by a Mechanism Involving the C-Terminal Inhibitory Domain.
AUTOR(ES)
Johansson, F
RESUMO
Plasma membrane vesicles isolated from spinach leaves incubated with the fungal toxin fusicoccin showed a twofold increase in ATP hydrolytic activity and a threefold increase in H+ pumping compared to controls. This increase in H+-ATPase activity was largely completed within 4 min of incubation and was not due to de novo synthesis of H+-ATPase as demonstrated by immunoblotting. Incubation with fusicoccin also resulted in a decrease in the apparent Km for ATP of the H+-ATPase from 0.22 to 0.10 mM. The fusicoccin-mediated activation of H+-ATPase activity and the accompanying decrease in the Km for ATP are changes very similar to those observed upon trypsin activation of the H+-ATPase, where an autoinhibitory domain in the C-terminal region of the H+-ATPase is removed. Thus, trypsin treatment of plasma membrane vesicles from control leaves gave a twofold increase in ATP hydrolytic activity and a threefold increase in H+ pumping, as well as a decrease in the apparent Km for ATP of the H+-ATPase from 0.22 to 0.10 mM. Trypsin treatment of plasma membranes from fusicoccin-incubated leaves did not further enhance the H+-ATPase activity, however, and neither was the Km for ATP further decreased. That trypsin really removed a small segment from the fusicoccin-activated H+-ATPase was confirmed by immunoblotting, which showed the appearance of a 90-kD band in addition to the native 100-kD H+-ATPase band upon trypsin treatment. Taken together, our data suggest that in vivo activation of the H+-ATPase by fusicoccin proceeds by a mechanism involving a displacement of the C-terminal inhibitory domain.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=160273Documentos Relacionados
- A Phosphothreonine Residue at the C-Terminal End of the Plasma Membrane H+-ATPase Is Protected by Fusicoccin-Induced 14–3–3 Binding1
- Fusicoccin Binding to Its Plasma Membrane Receptor and the Activation of the Plasma Membrane H+-ATPase1 : IV. Fusicoccin Induces the Association between the Plasma Membrane H+-ATPase and the Fusicoccin Receptor
- Fusicoccin Binding to Its Plasma Membrane Receptor and the Activation of the Plasma Membrane H+-ATPase (III. Is There a Direct Interaction between the Fusicoccin Receptor and the Plasma Membrane H+-ATPase?).
- The 14-3-3 protein interacts directly with the C-terminal region of the plant plasma membrane H(+)-ATPase.
- C-terminal deletion analysis of plant plasma membrane H(+)-ATPase: yeast as a model system for solute transport across the plant plasma membrane.