Cholera Toxin

IgG2a

Monoclonal Antibodies to Infectious Agents and Toxins

PBS pH 7. 4Applications Notes : Suitable for use in ELISA and Western blot. Each laboratory should determine an optimum working titer for use in its particular application. Other applications have not been tested but use in such assays should not necessarily be excluded

The A1 chain catalyzes the ADP-ribosylation of Gs alpha a GTP-binding regulatory protein to activate the adenylate cyclase. This leads to an overproduction of cAMP and eventually to a hypersecretion of chloride and bicarbonate followed by water resulting in the characteristic cholera stool. The A2 chain tethers A1 to the pentameric ring.

The holotoxin (choleragen) consists of a pentameric ring of B subunits whose central pore is occupied by the A subunit. The A subunit contains two chains A1 and A2 linked by a disulfide bridge.

After binding to gangliosides GM1 in lipid rafts through the subunit B pentamer the holotoxin and the gangliosides are internalized. The holotoxin remains bound to GM1 until arrival in the ER. The A subunit has previously been cleaved in the intestinal lumen but the A1 and A2 chains have remained associated. In the ER the A subunit disulfide bridge is reduced the A1 chain is unfolded by the PDI and disassembled from the rest of the toxin. Then the membrane-associated ER oxidase ERO1 oxidizes PDI which releases the unfolded A1 chain. The next step is the retrotranslocation of A1 into the cytosol. This might be mediated by the protein-conducting pore SEC61. Upon arrival in the cytosol A1 refolds and avoids proteasome degradation. In one way or another A1 finally reaches its target and induces toxicity.