This toxin potently and selectively inhibits ASIC1a, an isoform of the gene ASIC1. It incompletely inhibits ASIC1a activation in a pH-independent and slowly reversible manner. This toxin acts by binding to and stabilizing the closed state of the channel, thereby impeding the transition into a conducting state. This toxin may bind to the acidic pocket of ASIC1a, since mutation of a key residue of this pocket (Arg-350) abolishes the ability of the toxin to inhibit ASIC1a. In vivo, this toxin protects the brain from neuronal injury when administered up to 8 hours after stroke onset. Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. This toxin contains 2 'disulfide through disulfide knots' that are separated by a short linker. Belongs to the psalmotoxin-1 family. Double-knot toxin subfamily.