Protoxin-II is a neurotoxin that is derived from the venom of the Peruvian green velvet tarantula (Thrixopelma pruriens).
The toxin inhibits the activation of Nav channels by binding to the linker in the L3-4 loop (between the S3 and S4 segments) above the central cavity of VSD-II, which is known as site 4.
[6] ProTx-II inhibits sodium currents by shifting the voltage-dependence of the channel activation to more positive potentials.
The toxin acts on free nerve endings and primary sensory neurons after burn injury.
ProTx-II produces an inhibitory effect on spinal nociceptive processing by inhibiting the Nav1.7 sodium channel.