Cholera toxin is an oligomeric protein of MW 84kD and consists of a single A subunit surrounded by five B subunits. It is a potent activator of adenylate cyclase and is the pathogenic agent responsible for the symptoms of cholera. The B subunit (choleragenoid) is responsible for the binding of the holotoxin to G M1 ganglioside receptors on mammalian cell surfaces and facilitates entrance of the A subunit into the cell. The A subunit bears the ADP-ribosyl-transferase activity, which deregulates the G sprotein 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.
Cholera toxin has become a powerful research tool not only in microbiology, but in the fields of physiology, cell biology and biochemistry, as well. Because of the effect on adenylate cyclase, cholera toxin and its purified A subunit are frequently used for the study of signal transduction mechanisms. In addition, 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 to 5 times the transferase activity of the holotoxin. The B subunit exhibits little to no transferase activity.
Purity: Migrates as a single major band in slab gel electrophoresis under non-denaturing conditions.
Contaminants: Transferase activity is nearly zero when compared to an equivalent amount of holotoxin in an ADP-ribosyltransferase assay.
Activity: Exhibits comparable ganglioside binding activity in a hemagglutination assay, when compared to a standard solution of B subunit at the same protein concentration.
Concentration: ~5mg/ml
Form: Supplied as a lyophilized powder in 0.05M Tris, 0.2M sodium chloride, 0.001M EDTA•Na2, pH 7.5, 0.003M sodium azide. Cholera toxin and native subunits all undergo treatment for the removal of contaminating endotoxin and are sterile as packaged.
Reconstitution: Reconstitute with 100ul sterile dH2O
Note: Cholera toxin and native subunits all undergo treatment for the removal of contaminating endotoxin and are sterile as packaged.
Storage:Lyophilized powder stoppered under vacuum. It is recommended that this material be stored at 4°C prior to and following reconstitution. DO NOT FREEZE.
