Heat-Labile Enterotoxin, B subunit (LTB) from E. coli

Heat-Labile Enterotoxin, B subunit (LTB) from E. coli has been used in enzyme-linked immunosorbent assay (ELISA).

Enterotoxigenic Escherichia coli causes diarrhea through its heat-labile enterotoxin (LT). The LT is a periplasmic protein composed of one A subunit (LTA, 27 kDa) and five non-covalently associated B subunits (LTB, 11.6 kDa each) forming a ring-like pentamer. LTB has high affinity towards the toxin receptor ganglioside G_M1, a glycosphingolipid found ubiquitously on the surface of mammalian cells. Ganglioside G_M1 facilitates the delivery of the A subunit to the cytosol of the target cell resulting in persistent synthesis of cAMP and subsequently diarrhea. This characteristic makes LTB a good label for microglial cells (due to the enrichment of ganglioside GM₁ on their cell surface). In addition, studies made mostly with animal models demonstrated that recombinant LTB could stimulate strong serum and mucosal immune responses against LT. Other studies have indicated that LTB could be used as a potent mucosal adjuvant.

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Lyophilized from a solution containing Heat-Labile Enterotoxin, B subunit in 0.05 M Tris buffer, pH 7.5, 0.2 M NaCl, 3 mM NaN₃, and 1 mM sodium EDTA.

The activity is measured by ELISA using ganglioside G_M1-coated plates (Cat. No. G7641). LTB at various concentrations is incubated on the ganglioside G_M1 coated wells, followed by anti-cholera toxin antibody (Cat. No. C3062), and peroxidase-labeled goat anti-rabbit IgG (Cat.No. A0545) as the secondary antibody. Binding saturation of 50% may be achieved with = 0.12 μg/mL of LTB.