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. 1993 Oct;65(4):1613-9.
doi: 10.1016/S0006-3495(93)81200-1.

Mechanism of charybdotoxin block of a voltage-gated K+ channel

S A Goldstein  1 , C Miller
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Mechanism of charybdotoxin block of a voltage-gated K+ channel

S A Goldstein et al. Biophys J. 1993 Oct.

Abstract

Charybdotoxin block of a Shaker K+ channel was studied in Xenopus oocyte macropatches. Toxin on rate increases linearly with toxin concentration in an ionic strength-dependent fashion and is competitively diminished by tetraethylammonium. On rate is insensitive to transmembrane voltage and to K+ on the opposite side of the membrane. Conversely, toxin off rate is insensitive to toxin concentration, ionic strength, and added tetraethylammonium but is enhanced by membrane depolarization or K+ (or Na+) in the trans solution. Charge neutralization of charybdotoxin Lys27, however, renders off rate voltage insensitive. Our results argue that block of voltage-gated K+ channels results from the binding of one toxin molecule, so that Lys27 enters the pore and interacts with K+ (or Na+) in the ion conduction pathway.

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