Cholera Toxin, A Subunit

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 GM1 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 Gs 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 model systems.\n\nCholera 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 GM 1 ganglioside binding and retrograde transport.\n\nEndotoxin: As Reported\n\nActivity:\nADP-ribosylation assay: In a direct comparison with the enzymatic activity of a cholera toxin standard assayed in parallel, the specific enzymatic activity of A subunit is at least 1.2 times the specific activity of the reference cholera toxin on a molar basis or 3.5 times that of cholera toxin on a weight basis.\n\nStorage and Stability:\nLyophilized powder may be stored at 4 degrees C. Stable for 12 months at 4 degrees C. Reconstitute with ddH2O. Store at 4 degrees 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.

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SPECIFICATIONS

Catalog Number

C4275-36B

Size

250ug

Form

Supplied as a lyophilized powder from 0.05M Tris, 0.2M sodium chloride, 0.001M Na2EDTA, pH 7.5, 0.003M sodium azide. Reconstitute with 500ul sterile ddH2O. Do not vortex

Purity

~95% (Densitometric analysis)

References

Spangler, Brenda, D. (1992) Microbiological Reviews 56(4), 622-647