Cholera toxin is an oligomeric protein of MW 84kD. It consists of a single A subunit surrounded by five B subunits. The A subunit is a potent activator of adenylate cyclase. It is the pathogenic agent responsible for the symptoms of cholera. The B subunit (choleragenoid) is responsible for the binding of the holotoxin to GM1 ganglioside receptors on mammalian cell surfaces, facilitating entrance of the A subunit into the cell. The A subunit bears the ADP-ribosyl-transferase activity, which deregulates the G protein causing activation of adenylate cyclase. Due to the ubiquitous occurrence of the GM1 ganglioside receptor on eukaryotic cell membranes, cholera toxin activates adenylate cyclase in a wide variety of systems. Because of the effect on adenylate cyclase, cholera toxin and its purified A subunit are frequently used for the study of signal transduction mechanisms. Cholera toxin acts as an adjuvant through the stimulation of B-lymphocytes. The cholera toxin B subunit alone is used for track tracing in neurological research, taking advantage of GM1 ganglioside binding and retrograde transport. Cholera toxin is isolated from Vibrio cholerae type Inaba 569B by modification of the methods of Rappaport, et al. and Mekalanos, et al. When equal weights are compared, the A subunit exhibits 3-5 times the transferase activity of the holotoxin. The B subunit exhibits little to no transferase activity. Cholera toxin and native subunits all undergo treatment for the removal of contaminating endotoxin and are sterile as packaged.
Good laboratory technique should be employed in the safe handling of this product. This requires observing the following practices:
1. Wear appropriate laboratory attire including a lab coat, gloves and safety glasses.
2. Do not mouth pipette, inhale, ingest or allow to come into contact with open wounds. Wash thoroughly any area of the body which comes into contact with the product.
3. Avoid accidental autoinoculation by exercising extreme care when handling in conjunction with any injection device.
Storage and Stability:
Lyophilized powder stoppered under vacuum. It is recommended that this material be stored at 4 degrees C prior to and following reconstitution. DO NOT FREEZE.