Potassium Uptake Through the TOK1 K+ Channel in the Budding Yeast

Potassium Uptake Through the TOK1 K+ Channel in the Budding Yeast The current through TOK1 (YKC1), the outward-rectifying K+ channel in Saccharomyces cerevisiae, was amplified by expressing TOK1 from a plasmid driven by a strong constitutive promoter. TOK1 so hyper-expressed could overcome the K+ auxotrophy of a mutant missing the two K+ transporters, TRK1 and TRK2. This trk1Δtrk2Δ double mutant hyperexpressing the TOK1 transgene had a higher internal K+ content than one expressing the empty plasmid. We examined protoplasts of these TOK1-hyperexpressing cells under a patch clamp. Besides the expected K+ outward current activating at membrane potential (V m ) above the K+ equilibrium potential (E K+ ), a small inward current was consistently observed when the V m was slightly below E K+ . The inward and the outward currents are similar in their activation rates, deactivation rates, ion specificities and Ba2+ inhibition, indicating that they flow through the same channel. Thus, the yeast outwardly rectifying K+ channel can take up K+ into yeast cells, at least under certain conditions. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Potassium Uptake Through the TOK1 K+ Channel in the Budding Yeast

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Publisher
Springer Journals
Copyright
Copyright © Inc. by 1999 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900505
Publisher site
See Article on Publisher Site

Abstract

The current through TOK1 (YKC1), the outward-rectifying K+ channel in Saccharomyces cerevisiae, was amplified by expressing TOK1 from a plasmid driven by a strong constitutive promoter. TOK1 so hyper-expressed could overcome the K+ auxotrophy of a mutant missing the two K+ transporters, TRK1 and TRK2. This trk1Δtrk2Δ double mutant hyperexpressing the TOK1 transgene had a higher internal K+ content than one expressing the empty plasmid. We examined protoplasts of these TOK1-hyperexpressing cells under a patch clamp. Besides the expected K+ outward current activating at membrane potential (V m ) above the K+ equilibrium potential (E K+ ), a small inward current was consistently observed when the V m was slightly below E K+ . The inward and the outward currents are similar in their activation rates, deactivation rates, ion specificities and Ba2+ inhibition, indicating that they flow through the same channel. Thus, the yeast outwardly rectifying K+ channel can take up K+ into yeast cells, at least under certain conditions.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Mar 15, 1999

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