Proton-symport of L-valine in plasma membrane vesicles isolated from leaves of the wild-type and the Val(r)-2 mutant of Nicotiana tabacum L
| Autor: | Adrianus C. Borstlap, Jolanda A. M. J. Schuurmans |
|---|---|
| Rok vydání: | 2000 |
| Předmět: |
Chlorophyll
Time Factors Physiology Nicotiana tabacum Plant Science Membrane Potentials Electron Transport Complex IV Valine Microsomes Tobacco Plant Proteins chemistry.chemical_classification Adenosine Triphosphatases biology Dose-Response Relationship Drug Vesicle Cell Membrane Wild type Biological Transport NADH Dehydrogenase Cell Biology General Medicine Membrane transport Hydrogen-Ion Concentration biology.organism_classification Amino acid Plant Leaves Plants Toxic Membrane Biochemistry chemistry Symporter Mutation |
| Zdroj: | Plantcell physiology. 41(11) |
| ISSN: | 0032-0781 |
| Popis: | Transport of amino acids across the plasma membranes of various cell types is a key process in controlling the nitrogen balance of leaves. We studied the transport of the neutral amino acid L-valine into plasma membrane vesicles obtained by aqueous polymer two-phase partitioning of a microsomal fraction isolated from leaves of the wild-type and the Val(r)-2 mutant of tobacco (Nicotiana tabacum L.). Initial influxes were determined after the imposition of a pH-gradient (DeltapH, inside alkaline) and/or an electrical gradient (Deltapsi, inside negative) across the vesicle membrane. The initial magnitudes of the imposed gradients were DeltapH=2 and Deltapsi=-68 mV. In vesicles from the wild-type, the DeltapH-dependent valine influx could be analysed into a high-affinity (Km approximately 20 microM) and a low-affinity (Km approximately 3 mM) component. The influx of valine by the low-affinity system was stimulated about twofold, and that by the high-affinity system more than sixfold by the imposition of Deltapsi. This strong stimulation of the high-affinity system may indicate that it transports 2H+/amino acid. In the Val(r)-2 mutant the high-affinity component appeared to be completely absent. |
| Databáze: | OpenAIRE |
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