Gating behaviors of a voltage-dependent and Ca2+-activated cation channel of yeast vacuolar membrane incorporated into planar lipid bilayer |
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Authors: | Manabu Tanifuji Masayuki Sato Yoh Wada Yasuhiro Anraku Michiki Kasai |
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Institution: | (1) Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560, Japan;(2) Department of Biology, Faculty of Science, University of Tokyo, Hongo, Tokyo 113, Japan;(3) Present address: National Institute for Physiological Sciences, Myodaiji, Okazaki 444, Japan |
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Abstract: | Summary 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 thecis 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 1mm, were required on thecis side for opening the slow gate in a voltage-dependent manner. DIDS increased the open-channel probability of the fast gate when added to thecis side, but was ineffective on the slow gate. |
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Keywords: | vacuole lipid bilayer K-channel single channel DIDS yeast Saccharomyces cerevisiae Ca2+ activation |
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