K. Okihara et al., FUROSEMIDE - A SPECIFIC INHIBITOR OF P-I TRANSPORT ACROSS THE PLASMA-MEMBRANE OF PLANT-CELLS, Plant and Cell Physiology, 36(1), 1995, pp. 53-58
A search was made for inhibitors of P-i uptake that act directly on th
e P-i transporter in the plasma membranes of Catharanthus roseus cells
to inhibit P-i uptake without inhibition of proton pumping. Using sta
ndard electrodes, we monitored changes in pH and in the concentration
of K+ ions, as well as the rate of P-i uptake, when an inhibitor to be
tested was applied to the cells in unbuffered medium. A9C (28 mu M),
a blocker of anion channels, inhibited P-i uptake but it also inhibite
d the proton pump. However, a structurally similar inhibitor, furosemi
de, inhibited P-i uptake without inhibiting proton pumping. It is sugg
ested that the carboxylic group of these inhibitors interacts with the
P-i-binding site (probably an amino group) of the P-i transporter in
the plasma membrane and that the hydrophobic structure of these inhibi
tors facilitates their accumulation in the plasma membrane.