This toxin potently and selectively inhibits ASIC1a (IC(50)=0.4 nM on rASIC1a and IC(50)=0.52 nM on hASIC1a), an isoform of the gene ASIC1 (PubMed:28320941). It incompletely inhibits ASIC1a activation in a pH-independent and slowly reversible manner (Tau(off)=14.2 min for rASIC1a and 31.8 min for hASIC1a) (PubMed:28320941). This toxin acts by binding to and stabilizing the closed state of the channel, thereby impeding the transition into a conducting state (PubMed:28320941). 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 (PubMed:28320941). In addition, it shows antiparasitic activities, since it moderately inhibits the larval development of the major pathogenic nematode of ruminants (H.contortus, IC(50)=22.9 uM) (PubMed:31213240). In vivo, this toxin protects the brain from neuronal injury when administered up to 8 hours after stroke onset (PubMed:28320941). 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. This toxin is a promising lead for the development of therapeutics to protect the brain from ischemic injury. Belongs to the psalmotoxin-1 family. Double-knot toxin subfamily.