Neurotoxin certainly responsible of defensive persistent and painful stings of the giant stinging tree, since it provokes similar effects (PubMed:32938666). Acts by potently delaying voltage-gated sodium channel (Nav) inactivation in a concentration-dependent manner (EC(50)=58 nM) (PubMed:32938666). Mainly targets Nav1.7/SCN9A channels, since the two Nav1.7/SCN9A inhibitors tetrodotoxin and the spider toxin Pn3a potently reduce nocifensive behaviors it causes (PubMed:32938666). On the Nav1.7/SCN9A channel, this toxin causes a significant hyperpolarizing shift in the voltage dependence of activation, but has no significant effect on the voltage dependence of steady-state fast inactivation (PubMed:32938666). Its effects on Nav currents are irreversible, with no apparent reduction in activity even after repeated wash steps over 30 minutes (PubMed:32938666). In vivo, it causes nocifensive behavior in mice (licking or biting and shaking or lifting of the affected paw) lasting for approximately 1 hour (PubMed:32938666). Expressed in trichomes, that are stiff epidermal hairs located on the surface of petioles and leaves (PubMed:32938666). Not expressed in other aerial parts (PubMed:32938666). The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. The name 'gympietide' is derived from the name in the Gubbi-Gubbi language for the stinging trees (gympie-gympie). Belongs to the gympietide family.