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Plant Physiology 77:69-73 (1985) © 1985 American Society of Plant Biologists Preparation of Membrane Vesicles Enriched in ATP-Dependent Proton Transport from Suspension Cultures of Tomato CellsARCO Plant Cell Research Institute, 6560 Trinity Court, Dublin, California 94568
Membranes enriched in ATP-dependent proton transport were prepared from suspension cultures of tomato cells (Lycopersicon esculentum Mill cv VF36). Suspension cultures were a source of large quantities of membranes from rapidly growing, undifferentiated cells. Proton transport activity was assayed as quench of acridine orange fluorescence. The activity of the proton translocating ATPase and of several other membrane enzymes was measured as a function of the cell culture cycle. The relative distribution of the enzymes between the 3,000, 10,000, and 100,000g pellets remained the same throughout the cell culture cycle, but yield of total activity and activity per gram fresh weight with time had a unique profile for each enzyme tested. Maximal yield of the proton translocating ATPase activity was obtained from cells in the middle logarithmic phase of growth, and from 50 to 90% of the activity was found in the 10,000g pellet. The proton translocating ATPase activity was separable from NADPH cytochrome c reductase and cytochrome c oxidase on a sucrose gradient. Proton transport activity had a broad pH optimum (7.0-8.0), was stimulated by KCl with a Km of 5 to 10 millimolar, stimulation being due to the anion, Cl, and not the cation, K+, and was not inhibited by vanadate, but was inhibited by NO3. The activity is tentatively identified as the tonoplast ATPase.
1 Present address: USDA Western Regional Laboratory, 800 Buchanan Street, Albany, CA 94710. 2 Present address: Department of Biological Sciences, Stanford University, Stanford, CA 94305.
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