Members of this family assume a helical secondary structure, with two alpha helices forming a disulphide crosslinked alpha-helical hairpin. The disulphide bonds are crucial for the toxic activity of the protein, and are required for maintenance of the tertiary structure, and subsequent interaction with the particulate form of guanylate cyclase, increasing cyclic GMP levels within the host intestinal epithelial cells [1].

1: The structure of Escherichia coli heat-stable enterotoxin b by nuclear magnetic resonance and circular dichroism. Sukumar M, Rizo J, Wall M, Dreyfus LA, Kupersztoch YM, Gierasch LM; Protein Sci. 1995;4:1718-1729. PMID:8528070