Furosemide: a Specific Inhibitor of Pi Transport across the Plasma Membrane of Plant Cells |
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Authors: | Okihara Kiyoshi; Mimura Tetsuro; Kiyota Seiichiro; Sakano Katsuhiro |
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Institution: | 1 Department of Applied Physiology, National Institute of Agrobiological Resources Tsukuba, 305 Japan
2 Department of Life Science, Himeji Institute of Technology Harima Science Park City, 678-22 Japan |
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Abstract: | A search was made for inhibitors of Pi uptake that act directlyon the Pi transporter in the plasma membranes of Catharanthusroseus cells to inhibit Pi uptake without inhibition of protonpumping. Using standard electrodes, we monitored changes inpH and in the concentration of K+ ions, as well as the rateof Pi uptake, when an inhibitor to be tested was applied tothe cells in unbuffered medium. A9C (28 µM), a blockerof anion channels, inhibited Pi uptake but it also inhibitedthe proton pump. However, a structurally similar inhibitor,furosemide, inhibited Pi uptake without inhibiting proton pumping. It is suggested that the carboxylic group of these inhibitorsinteracts with the Pi-binding site (probably an amino group)of the Pi transporter in the plasma membrane and that the hydrophobicstructure of these inhibitors facilitates their accumulationin the plasma membrane.
3Present address: Department of Biology, Hitotsubashi University,2-1 Naka, Kunitachi, Tokyo, 186 Japan |
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