Fast and slow activation of voltage-dependent ion channels in radish vacuoles.
The molecular processes associated with voltage-dependent opening and closing (gating) of ion channels were investigated using a new preparation from plant cells, i.e., voltage and calcium-activated ion channels in radish root vacuoles. These channels display a main single channel conductance of approximately 90 pS and are characterized by long activation times lasting several hundreds of milliseconds. Here, we demonstrate that these channels have a second kinetically distinct activation mode which is characterized by even longer activation times. Different membrane potential protocols allowed to switch between the fast and the slow mode in a controlled and reversible manner. At transmembrane potentials of -100 mV, the ratio between the fast and slow activation time constant was around 1:5. Correspondingly, activation times lasting several seconds were observed in the slow mode. The molecular process controlling fast and slow activation may represent an effective modulator of voltage-dependent gating of ion channels in other plant and animal systems.
Gambale
F
F
Istituto di Cibernetica e Biofisica, Genova, Italy.
Cantu
A M
AM
Carpaneto
A
A
Keller
B U
BU
D055592:Biophysical Phenomena; D001703:Biophysics; D002118:Calcium / Q000378:metabolism; D004594:Electrophysiology; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials; D008954:Models, Biological; D010944:Plants / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism; D014675:Vegetables / Q000378:metabolism
D007473:Ion Channels; D002118:Calcium