title: Carboxyl tail prevents yeast K(+) channel closure: proposal of an integrated model of TOK1 gating.
abstract: TOK1 encodes the channel responsible for the prominent outward K(+) current of the yeast plasma membrane. It can dwell in several impermeable states, including a rapidly transiting, K(+)-electromotive-force-dependent "R" (rectifying) state, a voltage-independent "IB" (interburst) state, and a set of [K(+)](ext) and voltage-dependent "C" (closed) states. Whereas evidence suggests that the C states result from the constriction of an inner gate at the cytosolic end of the pore, R is most likely an intrinsic gating property of the K(+) filter. Here, we present evidence that Tok1's carboxyl-tail domain also plays an intimate role in channel gating by dynamically preventing inner-gate closures. We present an integrated model of TOK1 gating in which the filter gate, inner gate, and carboxyl tail interact to produce the various phenomenological states. Both wild-type and tailless behaviors can be replicated using Monte Carlo computer simulations based on this model.
authors.affiliation: Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706 USA. shloukin@facstaff.wisc.edu
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Loukin
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Saimi
mesh_terms: D004260:DNA Repair; D004594:Electrophysiology; D017353:Gene Deletion; D007477:Ions; D008954:Models, Biological; D009010:Monte Carlo Method; D009154:Mutation; D010957:Plasmids; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D007477:Ions; D015221:Potassium Channels; D029701:Saccharomyces cerevisiae Proteins; C095220:TOK1 protein, S cerevisiae; D011188:Potassium