Heat labile enterotoxin AB, EltAB, ItpAB, ToxAB, LT-AB, cholera toxin (258 aas and 124 aas, respectively). The biological activity of the toxin is produced by the A chain, which activates intracellular adenyl cyclase. The A2 domain of LTA has cell penitration function (Liu et al. 2016). LT holotoxin can enter intestinal epithelial cells and cause diarrhea. The A2 domain might be useful as a transport vehicle for other proteins (Liu et al. 2016). A biotinylated cholera toxin becomes a fusogenic lectin upon cross-linking with streptavidin. This reengineered protein brings about hemifusion and fusion of vesicles as demonstrated by mixing of fluorescently labeled lipids between vesicles as well as content mixing of liposomes filled with fluorescently labeled dextran (Wehrum et al. 2022).