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Alomone Labs SsTx Toxin inhibits the current of KCNQ2 channels expressed in Xenopus oocytes.A. Representative time course of KCNQ2 channel current inhibition by SsTx Toxin (#STS-700). Membrane potential was held at -80 mV, current was elicited by a 1000 ms voltage step to 0 mV every 10 sec, and reversibly inhibited by application of 4 µM SsTx Toxin (green). B. Superimposed traces of KCNQ2 current following the application of control (black) and of 4 µM SsTx Toxin (green), taken from the recording in A.
SsTx Toxin is a peptide toxin originally isolated from the Chinese red-headed centipede venom. SsTx structure consists of amino acids in position 12 and 13 which form a positively charged surface and two disulphide bridges. It is the first peptide toxin found to potently and selectively block KCNQ (KV7) channels, members of voltage-gated potassium (KV) channel family1 with IC50 values of 2.5, 2.8, 2.7, and 2.7 μM for KCNQ4, KCNQ1, KCNQ2, and KCNQ5 respectively1. The the toxin also blocks KV1.3 channel with an IC50 value of ~5 μM3.
SsTx blocks progressively less when the membrane potential becomes more depolarized, and high K+ concentrations increase the IC50 values, suggesting that the toxin binds to the outer pore domain of KCNQ channels1.
KCNQ is a family of multifunctional K+ channels that are involved in a variety of physiological functions, including cardiac action potential repolarization, coronary circulation and reactive hyperemia, and cerebral neuron excitation. These channels are considered to be potential therapeutic targets for a variety of neuronal disorders1,2.