K(+)-dependent composite gating of the yeast K(+) channel, Tok1 |
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| Authors: | Loukin S H Saimi Y |
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| Affiliation: | Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706 USA. shloukin@facstaff.wisc.edu |
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| Abstract: | ![]()
TOK1 encodes an outwardly rectifying K(+) channel in the plasma membrane of the budding yeast Saccharomyces cerevisiae. It is capable of dwelling in two kinetically distinct impermeable states, a near-instantaneously activating R state and a set of related delayed activating C states (formerly called C(2) and C(1), respectively). Dwell in the R state is dependent on membrane potential and both internal and external K(+) in a manner consistent with the K(+) electrochemical potential being its determinant, where dwell in the C states is dependent on voltage and only external K(+). Whereas activation from the C states showed high temperature dependencies, typical of gating transitions in other Shaker-like channels, activation from the R state had a temperature dependence nearly as low as that of simple ionic diffusion. These findings lead us to conclude that although the C states reflect the activity of an internally oriented channel gate, the R state results from an intrinsic gating property of the channel filter region. |
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