ProTx-II

ProTx-II (ProTx-2, Protoxin II) is a toxin that was originally isolated from Thrixopelma pruriens (Peruvian green velvet tarantula) . ProTx-II inhibits both tetrodotoxin-sensitive and tetrodotoxin-resistant voltage-gated sodium channels. ProTx-II inhibits activation by shifting the voltage-dependence of channel activation to more positive potentials. ProTx-II blocks Nav1.7 with an IC50 value of around 300 pM, Nav1.2, Nav1.5 and Nav1.6 with IC50 values of 41 nM, 79 nM and 26 nM respectively. It also acts on Cav3.1/CACNA1G and interacts more weakly with the related T-Type channel Cav3.2/CACNA1H but potently inhibits the L-type calcium channel Cav1.2/CACNA1C. ProTx-II blocks action potential propagation in nociceptors.