Binds to site 3 of voltage-gated sodium channels and inhibits the inactivation process (PubMed:18538344). Is highly active on DmNav1/TipE (drosophila) and is only extremely weakly active on rat Nav1.4-beta-1/SCN4A-SCN1B, and on human Nav1.5-beta-1/SCN5A-beta-1 (PubMed:18538344). This reveals high specificity for arthropod over mammalian channels (PubMed:18538344). In vivo, when released into the medium, this recombinant toxin induces impaired swimming, paralysis and death of the crustacean A.nauplii within several hours (PubMed:22048953). Also causes paralysis of cherry shrimps immediately after injection at very low doses (PubMed:29424690). Its effect on zebrafish (D.rerio) larvae is also rapid, since it induces tail twitching accompanied by impaired swimming after 20 minutes and complete paralysis within 45 minutes (PubMed:22048953). It has also been observed to cause death of zebrafish larvae within 1 hour (PubMed:31134275). Intron retention discovered for all transcripts, no experimental confirmation available for this specific sequence. Expressed in ectodermal glands and in clumps outside of the extodermal layer (PubMed:22048953). Is not expressed in nematocytes (PubMed:22048953). In adult female tissues, shows similar expression levels in mesenteries (gametes-producing tissue), tentacles, pharynx and physa (PubMed:29424690). Is detected in unfertilized eggs (at protein level) (PubMed:29424690, PubMed:31134275). Is also detected in late planulae, primary polyps and adults (both females and males) (at protein level) (PubMed:22048953, PubMed:29424690). Nv1 is transcribed throughout the complete life cycle and is found at multiple developmental stages including unfertilized eggs, blastulae, gastrulae, early planulae, planulae, metamorphosing planulae, primary polyps, juvenile polyps (2 and 4 months old), adult males, and adult females, with highest levels in juvenile polyps and adults (PubMed:18538344, PubMed:29424690). Importantly, Nv1 transcripts are not spliced in the embryo and planula due to intron retention and therefore Nv1 can be considered purely an adult toxin (PubMed:18538344). PD(50) is 76 nmol/kg into blowfly larvae. Nv1 toxin seems to be encoded by 8 different genes. 4 of them code for identical precursors, whereas 4 others code for very similar precursors. In the genome draft, 6 additional loci are also correlated to Nv1 toxin, but they are not predicted to be functional genes. This high similarity may be explained by concerted evolution. The primary structure of the mature peptide is identical in 9 entries (AC B1NWS4, AC B1NWS1, AC B1NWR6, AC P0CH90, AC P0CH46, AC B1NWS8, AC A7SCE5, AC B1NWR7 and AC P0CH45). Additional information can be found in entry AC B1NWS4. Due to an intron retention observed only in early life stages (embryo and planula). Has no activity on the rat brain channel Nav1.2a-beta-1/SCN2A-SCN1B. Belongs to the sea anemone sodium channel inhibitory toxin family. Type II subfamily.