Overview
- Xiao, Y. et al. (2004) J. Biol. Chem. 279, 26220.
Alomone Labs Jingzhaotoxin-III inhibits KV2.1 channels heterologously expressed in Xenopus oocytes.A. Time course of Jingzhaotoxin-III (#STJ-200) action on KV2.1 currents. Current amplitude at +40 mV was plotted as a function of time. Membrane potential was held at -80 mV and oocyte were stimulated by a 100 ms voltage ramp to +40 mV. 200 nM Jingzhaotoxin-III (applied for 160 sec, green) was perfused during the period marked by the bar, as indicated and showed 80% inhibition of control current. B. Superimposed traces of channel current in the absence (black) and presence (green) of 200 nM Jingzhaotoxin-III (taken from experiment in A).
Jingzhaotoxin-III (JZTX–III), a peptide toxin isolated from the venom of the Chinese tarantula Chilobrachys Jingzhao, is composed of 36 amino acid residues including 6 cysteines cross-linked in a pattern of I-IV, II-V, and III-VI1.
Electrophysiological recordings carried out in Xenopus laevis oocytes show that this toxin acts as a gating modifier of voltage-dependent K+ channels. It slows the rate of KV2.1 channel activation and increases the tail current deactivation, suggesting that toxin-bound channels can still open but are modified. JZTX- III selectively inhibits KV2.1 channels2. JZTX- III blocks KV2.1 currents with an IC50 value of 430 nM in Xenopus oocytes3. It has also been shown to block NaV1.5 with an IC50 value of 0.38 μM in rat cardiac myocytes1.
