Overview
- Chagot, B. et al. (2004) Protein Sci. 13, 1197.
Alomone Labs Phrixotoxin-1 inhibits KV4.2 channels expressed in Xenopus oocytes.A. Time course of Phrixotoxin-1 (#STP-700) action on KV4.2 current amplitude recorded at 10 mV. Current amplitudes were plotted as a function of time. Membrane potential was held at -100 mV and oocytes were stimulated by a 100 ms voltage ramp to +20 mV. 50 nM Phrixotoxin-1 was perfused as indicated by the bar (green) for 220 sec. B. Superimposed examples of KV4.2 channel current in the absence (control) and presence (green) of 50 nM Phrixotoxin-1 (taken from the experiment in A).
Phrixotoxin-1 (PaTx1) is a 29 amino acid peptidyl toxin isolated from the venom of the theraphosid Phrixotrichus auratus, which potently blocks A-type K+ currents.
PaTx1 specifically blocks KV4.3 and KV4.2 currents with a 5 nM < IC50 < 70 nM, by modifying the gating properties of these channels.1
As with other spider toxins, PaTx1 presents an active molecular surface, including a hydrophobic patch surrounded by charged residues, which are important for their binding on KV channels. Electrophysiological studies show that the PaTx1 blocks KV4 channels via a mechanism similar to that of hanatoxins on KV2 channels, as they bind and stabilize the preferentially closed state of the channel, in a voltage-dependent manner.2
PaTx1 is a crucial tool for understanding the contribution of KV4.3 and KV4.2 in cardiac electrogenesis. Treatment of mice with PaTx1 results in numerous transient cardiac adverse reactions including the occurrence of premature ventricular beats, ventricular tachycardia, different degrees of atrioventricular (AV) blockage and prolongation of the QT interval.1
Alomone Labs Phrixotoxin-1 blocks KV4 currents in mouse preoptic GABAergic neurons.K+ currents were elicited by a depolarizing step to 220 mV in control (left), during Phrixotoxin-1 (#STP-700), (600 nM) incubation (middle) and the Phrixotoxin-1-sensitive component obtained by subtraction (right). Phrixotoxin-1 blocked 76 ± 11% (n = 5, P,0.01 paired t-test relative to control amplitudes) of IA currents.Adapted from Sethi, J. et al. (2011) PLoS ONE 6, e29134. with permission of PLoS.
