Gating behaviors of a voltage-dependent and Ca2+-activated cation channel of yeast vacuolar membrane incorporated into planar lipid bilayer.
A voltage-dependent and Ca2+-activated cation channel found in the vacuolar membrane of the yeast, Saccharomyces cerevisiae, was incorporated into planar lipid bilayer and its gating characteristics were studied at the macroscopic and single-channel levels. The open-channel probability at steady state, which was estimated by the macroscopic current measurement, gave a maximum value at -10 mV and decreased in a graded fashion as the voltage became more positive or more negative. The steady-state voltage dependence was explained by assuming two independent gates, which had different rate constants and opposite voltage dependence. The fast-responding gate opened when the voltage of the cis side (the side to which the vesicles were added) was made more negative and the slow-responding gate behaved in the opposite direction. Relatively high concentrations of Ca2+, about 1 mM, were required on the cis side for opening the slow gate in a voltage-dependent manner. DIDS increased the open-channel probability of the fast gate when added to the cis side, but was ineffective on the slow gate.
Tanifuji
M
M
Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University, Japan.
Sato
M
M
Wada
Y
Y
Anraku
Y
Y
Kasai
M
M
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D004553:Electric Conductivity; D007425:Intracellular Membranes / Q000378:metabolism*; D007473:Ion Channels / Q000502:physiology*; D008051:Lipid Bilayers / Q000378:metabolism*; D008564:Membrane Potentials; D008954:Models, Biological; D015221:Potassium Channels / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*
D007473:Ion Channels; D008051:Lipid Bilayers; D015221:Potassium Channels; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium