Abstract
The effect of fusicoccin on Mg:ATP-dependent H+-pumping in microsomal vesicles from 24-hour-old radish (Raphanus sativus L.) seedlings was investigated by measuring the initial rate of decrease in the absorbance of the ΔpH probe acridine orange. Fusicoccin stimulated Mg:ATP-dependent H+-pumping when the pH of the assay medium was in the range 7.0 to 7.6 while no effect of fusicoccin was detected between pH 6.6 and pH 6.0. Both basal and fusicoccin-stimulated H+-pumping were completely inhibited by vanadate and almost unaffected by nitrate. Fusicoccin did not change membrane permeability to protons and fusicoccin-induced stimulation of Mg:ATP-dependent H+-pumping was not affected by changes in the buffer capacity of the incubation medium. Deacetylfusicoccin stimulated H+-pumping as much as fusicoccin, while the physiologically inactive derivative 8-oxo-9-epideacetylfusicoccin did not. Stimulation of H+-pumping was saturated by 100 nanomolar fusicoccin. These data indicate that fusicoccin activates the plasma membrane H+-ATPase by acting at the membrane level independently of the involvement of other cell components. The percent stimulation by fusicoccin was the same at all ATP concentrations tested (0.5-5.0 millimolar), thus suggesting that with fusicoccin there is an increase in Vmax of the plasma membrane H+-ATPase rather than a decrease in its apparent Km for Mg:ATP.
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Selected References
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- Lew R. R., Spanswick R. M. Characterization of Anion Effects on the Nitrate-Sensitive ATP-Dependent Proton Pumping Activity of Soybean (Glycine max L.) Seedling Root Microsomes. Plant Physiol. 1985 Feb;77(2):352–357. doi: 10.1104/pp.77.2.352. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rasi-Caldogno F., Pugliarello M. C., De Michelis M. I. Electrogenic transport of protons driven by the plasma membrane ATPase in membrane vesicles from radish : biochemical characterization. Plant Physiol. 1985 Jan;77(1):200–205. doi: 10.1104/pp.77.1.200. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rasi-Caldogno F., Pugliarello M. C. Fusicoccin stimulates the H+-ATPase of plasmalemma in isolated membrane vesicles from radish. Biochem Biophys Res Commun. 1985 Nov 27;133(1):280–285. doi: 10.1016/0006-291x(85)91872-8. [DOI] [PubMed] [Google Scholar]
- Romani G., Marrè M. T., Bellando M., Alloatti G., Marrè E. H extrusion and potassium uptake associated with potential hyperpolarization in maize and wheat root segments treated with permeant weak acids. Plant Physiol. 1985 Nov;79(3):734–739. doi: 10.1104/pp.79.3.734. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tognoli L. Partial purification and characterization of an anion-activated ATPase from radish microsomes. Eur J Biochem. 1985 Feb 1;146(3):581–588. doi: 10.1111/j.1432-1033.1985.tb08691.x. [DOI] [PubMed] [Google Scholar]