Characterization of Vacuolar Malate and K Channels under Physiological Conditions.
Patch-clamp techniques were employed to study the electrical properties of vacuoles from sugar beet (Beta vulgaris) cell suspensions at physiological concentrations of cytoplasmic Ca(2+). Vacuoles exposed to K(+) malate revealed the activation of instantaneous and time-dependent outward currents by positive membrane potentials. Negative potentials induced only instantaneous inward currents. The time-dependent outward currents were 10 times more selective for malate than for K(+) and were completely blocked by zinc. Vacuoles exposed to KCl developed instantaneous currents when polarized to positive or negative membrane potentials. The time-dependent outward channels could serve as the route for the movement of malate into the vacuole, whereas K(+) could move through the time-independent inward and outward channels.
Pantoja
O
O
Centre for Plant Biotechnology, Toronto, Ontario M5S 3B2, Canada.
Gelli
A
A
Blumwald
E
E