| Autor: |
Igor M. Andreev, Victor Koren'kov, Yu. G. Molotkovsky |
| Rok vydání: |
1990 |
| Předmět: |
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| Zdroj: |
Journal of Plant Physiology. 136:3-7 |
| ISSN: |
0176-1617 |
| DOI: |
10.1016/s0176-1617(11)81606-8 |
| Popis: |
Summary Using preparations of vacuoles and vacuolar membranes isolated from storage tissue of sugar beet ( Beta vulgaris L.), it was shown that Ca 2+ ions caused the dissipation of an ATP-generated or artificially formed transtonoplast pH gradient monitored by the absorption change of acridine orange. Ca 2+ -dependent Δ pH decreasing at the tonoplast is blocked by La 3+ and is due to the action of the Ca 2+ /nH + antiporter associated with this membrane and characterized by an apparent K m of 10 μM for Ca 2+ at pH 8.0. It was found that calmodulin greatly accelerated transtonoplast Δ pH dissipation in the presence of Ca 2+ . This effect is independent of ATP and blocked by La 3+ or removing Ca 2+ from the medium using EGTA. Calmodulin stimulation of Ca 2+ /H + exchange across the tonoplast was shown to be due to a dramatic drop (almost 1000-fold) in apparent K m of Ca 2+ /nH + antiporter for Ca 2+ . This result led us to suggest that calmodulin directly interacts with the carrier in question and such interaction takes place even at Ca 2+ concentrations lower than the K d of the Ca 2+ -calmodulin complex. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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