ProTx-II (ProTx-2, Protoxin II) is a gating-modifier toxin that targets voltage-gated sodium channels with a preferential activity on Nav1.7/SCN9A. It inhibits both activation and inactivation.
For inhibition of activation, it is 100-fold more selective for Nav1.7/SCN9A (IC50=0.3-3) than for other sodium channels (Nav1.2/SCN2A IC50=40-540 nM, Nav1.3/SCN3A IC50=102 nM, Nav1.4/SCN4A IC50=30-39 nM, Nav1.5/SCN5A IC50=19-90 nM, Nav1.6/SCN8A IC50=26 nM, and Nav1.8/SCN10A IC50=146 nM).
For inhibition of inactivation, it is 20-fold more potent in inhibiting inactivation on Nav1.7/SCN9A (IC50=250 nM) than other channels (about 4.6 µM for all channels).
It also inhibits Cav1.2/CACNA1C, Cav3.2/CACNA1H (29% block at 1 µM). It inhibits Nav1.7/SCN9A activation by interacting with DII and impairs Nav1.7/SCN9A inactivation by interacting with DIV. This toxin binds to lipid membrane. This ability correlates with hNav1.7/SCN9A inhibition, showing that membrane binding is the first step in the inhibitory mechanism of this toxin.

Stable at room temperature, store preferably at 4°C