This family consists of the SFI family of spider toxins. This family of toxins might share structural, evolutionary and functional relationships with other small, highly structurally constrained spider neurotoxins. These toxins are highly selective agonists/antagonists of different voltage-dependent calcium channels and are extremely valuable reagents in the analysis of neuromuscular function [1].

1: Novel insecticidal toxins from the venom of the spider Segestria florentina. Lipkin A, Kozlov S, Nosyreva E, Blake A, Windass JD, Grishin E; Toxicon. 2002;40:125-130. PMID:11689233