Modulates channel gating kinetics. Causes negative shifts in the voltage dependence of activation of certain alpha sodium channels, but does not affect the voltage dependence of inactivation. Modulates the susceptibility of the sodium channel to inhibition by toxic peptides from spider, scorpion, wasp and sea anemone venom.
Subcellular locations: Cell membrane
Expressed at a high level in dorsal root ganglia, at a lower level in brain, spinal cord, skeletal muscle and heart. Expressed in the atrium.