Biophys J, February 2002, p. 781-792, Vol. 82, No. 2

Carboxyl Tail Prevents Yeast K⁺ Channel Closure: Proposal of an Integrated Model of TOK1 Gating

Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706 USA

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.

Biophys J, February 2002, p. 781-792, Vol. 82, No. 2
© 2002 by the Biophysical Society   0006-3495/02/02/781/12  $2.00

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