K(+)-dependent composite gating of the yeast K(+) channel, Tok1.
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.
Loukin
S H
SH
Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706 USA. shloukin@facstaff.wisc.edu
Saimi
Y
Y
D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D008954:Models, Biological; D009865:Oocytes / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature; D014981:Xenopus
D005656:Fungal Proteins; D015221:Potassium Channels; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C095220:TOK1 protein, S cerevisiae; D011188:Potassium