Binds to the sodium channels Nav1.1/SCN1A (EC(50)=453 nM), Nav1.5/SCN5A (EC(50)=440 nM) and Nav1.6/SCN8A (EC(50)=1740 nM), thereby delaying their inactivation (Ref.1, PubMed:21802465). Also inhibits Nav1.2/SCN2A, Nav1.3/SCN3A, and Nav1.4/SCN4A, but to a lesser extent (PubMed:21802465). Toxin effect on Nav1.1 and Nav1.6 (and on Nav1.5, but in a lesser extent) consists in an incomplete inactivation (PubMed:21802465). Does not show activity on Nav1.7/SCN9A. Belongs to the sea anemone sodium channel inhibitory toxin family. Type I subfamily. The sequence submitted as delta-AITX-Bcg1b (AC P86460) and renamed delta-AITX-Bcg1e is a deamidation product (at Asn-16 residue) of delta-AITX-Bcg1a (renamed delta-AITX-Bcg1d). This product does not show any activity on all Nav1 tested (Nav1.1 to Nav1.7).