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Calcium- and voltage-dependent ion channels in Saccharomyces cerevisiae.

Bertl, A. and Gradmann, D. and Slayman, C. L. (1992):
Calcium- and voltage-dependent ion channels in Saccharomyces cerevisiae.
In: Philosophical transactions of the Royal Society of London. Series B, Biological sciences, pp. 63-72, 338, (1283), ISSN 0962-8436,
[Online-Edition: http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=199...],
[Article]

Abstract

Ion channels in both the tonoplast and the plasma membrane of Saccharomyces cerevisiae have been characterized at the single channel level by patch-clamp techniques. The predominant tonoplast channel is cation selective, has an open-channel conductance of 120 pS in 100 mM KCl, and conducts Na+ or K+ equally well, and Ca2+ to a lesser extent. Its open probability (Po) is voltage-dependent, peaking at about -80 mV (cytoplasm negative), and falling to near zero at +80 mV. Elevated cytoplasmic Ca2+, alkaline cytoplasmic pH, and reducing agents activate the channel. The predominant plasma membrane channel is highly selective for K+ over anions and other cations, and shows strong outward rectification of the time-averaged current-voltage curves in cell-attached experiments. In isolated inside-out patches with micromolar cytoplasmic Ca2+, this channel is activated by positive going membrane voltages: mean Po is zero at negative membrane voltages and near unity at 100 mV. At moderate positive membrane voltages (20-40 mV), elevating cytoplasmic Ca2+ activates the channel to open in bursts of several hundred milliseconds duration. At higher positive membrane voltages, however, elevating cytoplasmic Ca2+ blocks the channel in a voltage-dependent fashion for periods of 2-3 ms. The frequency of these blocking events depends on cytoplasmic Ca2+ and membrane voltage according to second-order kinetics. Alternative cations, such as Mg2+ or Na+, block the yeast plasma-membrane K+ channel in a similar but less pronounced manner.

Item Type: Article
Erschienen: 1992
Creators: Bertl, A. and Gradmann, D. and Slayman, C. L.
Title: Calcium- and voltage-dependent ion channels in Saccharomyces cerevisiae.
Language: English
Abstract:

Ion channels in both the tonoplast and the plasma membrane of Saccharomyces cerevisiae have been characterized at the single channel level by patch-clamp techniques. The predominant tonoplast channel is cation selective, has an open-channel conductance of 120 pS in 100 mM KCl, and conducts Na+ or K+ equally well, and Ca2+ to a lesser extent. Its open probability (Po) is voltage-dependent, peaking at about -80 mV (cytoplasm negative), and falling to near zero at +80 mV. Elevated cytoplasmic Ca2+, alkaline cytoplasmic pH, and reducing agents activate the channel. The predominant plasma membrane channel is highly selective for K+ over anions and other cations, and shows strong outward rectification of the time-averaged current-voltage curves in cell-attached experiments. In isolated inside-out patches with micromolar cytoplasmic Ca2+, this channel is activated by positive going membrane voltages: mean Po is zero at negative membrane voltages and near unity at 100 mV. At moderate positive membrane voltages (20-40 mV), elevating cytoplasmic Ca2+ activates the channel to open in bursts of several hundred milliseconds duration. At higher positive membrane voltages, however, elevating cytoplasmic Ca2+ blocks the channel in a voltage-dependent fashion for periods of 2-3 ms. The frequency of these blocking events depends on cytoplasmic Ca2+ and membrane voltage according to second-order kinetics. Alternative cations, such as Mg2+ or Na+, block the yeast plasma-membrane K+ channel in a similar but less pronounced manner.

Journal or Publication Title: Philosophical transactions of the Royal Society of London. Series B, Biological sciences
Volume: 338
Number: 1283
Divisions: 10 Department of Biology
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10 Department of Biology > Yeast Membrane Biology
Date Deposited: 25 Nov 2010 15:26
Official URL: http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=199...
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