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.
Cholera toxin and native subunits all undergo treatment for the removal of contaminating endotoxin and are sterile as packaged.
Assay:Binding activity was assessed by hemagglutination using GM1 fixed sheep red blood cells. The hemagglutination for this lot was ~3ug/ml when examined by a modification of Sato, et. al. The binding affinity of Chloera Toxin to GM1 ganglioside was demonstrated using an ELISA plate coated with 1ug/ml GM1. The midpoint of the curve was ~45ng.ml Cholera Toxin.
Storage and Stability:Lyophilized and reconstituted products are stable for 6 months after receipt at 4°C. Do not freeze. Reconstitute with sterile ddH2O. Aliquot to avoid repeated freezing and thawing. Store at 4°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
仕様
Size：1mg
Purity：Migrates as a single major band in disc gel electrophoresis (nondenaturing conditions). The R280/260 of each preparation is reported. Endotoxin: ≤12EU/mg (LAL)
Form：Supplied as a lyophilized powder from 0.05M Tris, 0.2M sodium chloride, 0.001M EDTA Na2, pH 7.5. No preservative added. Reconstitute with 500ul sterile ddH2O. Do not vortex.
