cholera toxin is secreted
by the gram-negative bacterium Vibrio cholerae. It is a gastrointestinal
toxin that increases adenylate cyclase activity of mucosa
of the small intestine, thereby increasing cyclic AMP within
these cells. Cyclic AMP stimulates active transport of ions by
these epithelial cells, resulting in a large efflux of Na+ and water
into the gut. The toxin enters cells by interacting with a GM1
ganglioside on the cell surface. After entry, the A1 subunit catalyzes
the transfer of an ADP-ribose unit from NAD+ to an arginine
side chain of the adenylate cyclase regulatory G protein,
blocking its GTPase activity. Thus the adenylate cyclase deactivation
mechanism is destroyed, and cyclic AMP is continually
produced. The major sign of cholera poisoning is severe diarrhea;
several liters of body water may be lost within a few hours,
leading to shock and death if fluid is not replaced. Treatment
involves physiological support (including i.v. fluids) and antibiotics.
Bildanzeige (GHS)
Alarmwort
Achtung
Gefahrenhinweise
Code
Gefahrenhinweise
Gefahrenklasse
Abteilung
Alarmwort
Symbol
P-Code
H332
Gesundheitssch?dlich bei Einatmen.
Akute Toxizit?t inhalativ
Kategorie 4
Warnung
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P261, P271, P304+P340, P312
H412
Sch?dlich für Wasserorganismen, mit langfristiger Wirkung.
Langfristig (chronisch) gew?ssergef?hrdend
Kategorie 3
P273, P501
Sicherheit
P262
Nicht in die Augen, auf die Haut oder auf die Kleidung gelangen lassen.
BEI VERSCHLUCKEN: Sofort GIFTINFORMATIONSZENTRUM/Arzt/... (geeignete Stelle für medizinische Notfallversorgung vom Hersteller/Lieferanten anzugeben) anrufen.
Cholera Toxin from Vibrio cholerae has been used as a positive control in cAMP (cyclic AMP) assay for enterotoxins. It has been added as a supplement in cell culture media of primary tumors and epithelial cells.
Biochem/physiol Actions
Toxin consisting of an A subunit (27 kDa) surrounded by five B subunits (approximately 12 kDa each), which attach the toxin to ganglioside GM1 on the cell surface. The A subunit catalyzes ADP-ribosylation of the α-subunit of the stimulatory G protein (Gαs), reducing GTPase activity and activating the α-subunit. This activation of Gαs leads to an increase in the activity of adenylyl cyclase, resulting in increased levels of cAMP. Also ADP-ribosylates transducin in the eye rod outer segments, inactivating its GTPase activity. Cholera toxin has also been reported to ADP-ribosylate tubulin. Shown to be a potent mucosal vaccine adjuvant, inducing T helper cell type 2 responses by inhibiting the production of interleukin-12.
CHOLERA TOXIN Upstream-Materialien And Downstream Produkte