The mechanisms which enable cholera toxin ct and the escherichia coli heatstable enterotoxins sta and stb to stimulate intestinal secretion of water and electrolytes are only partially understood. Cholera toxin, the enterotoxin of cholera vibrio, is an 87 kda protein composed of six subunits ab 5 in which the five identical b subunits form a pentagonal ring surrounding the a subunit. Comparison of the mechanisms of action of cholera toxin. Introduction molecular aspects of cholera toxin action practical aspects of cholera toxin use summary. Ct evokes the synthesis of 3,5cyclic amp camp, and sta is known to elevate intestinal levels of 3,5cyclic gmp cgmp. Comparison of the mechanisms of action of cholera toxin and the heatstable enterotoxins of escherichia coli. Symptoms are caused by the action of cholera toxin, secreted by the bacterium vibrio cholerae, or by a closely related heatlabile enterotoxin, produced by escherichia coli, that causes a milder. The relevance of these findings to the mechanism of action of cholera toxin is considered. Here we show that endocytosis and the ability of ct to increase the level of camp were unaltered in. Mechanism of action of vibrio cholerae enterotoxin. Neither of these recognized second messengers appears to mediate e. Vibrio cholerae produce a variety of extracellular products that have deleterious effects on eukaryotic cells. The b subunits harbor the binding sites for the cell surface receptor.
Biologists uncover mechanisms for cholera toxins deadly. Adpribosylation factors as stimulators of cholera toxincatalyzed adpribosylation and effectors in. Pdf mechanism of action of cholera toxin and the mobile. Cholera toxin thus induces profound and nearly permanent changes in adenylate cyclase by a unique process which mimics the stimulation by hormones in important ways, and which also accentuates the normal hormonal response. The mechanism of cholera toxin ct internalization has been investigated using caco2 cells transfected with caveolin to induce formation of caveolae, hela cells with inducible synthesis of mutant dynamin k44a and bhk cells in which antisense mrna to clathrin heavy chain can be induced. Mechanism of action of cholera toxin and the mobile receptor therory of hormone receptoradenylate cyclase activity proc february 1975 proceedings of the national academy of sciences 721. Internalization of cholera toxin by different endocytic. Mechanisms of action of the cholera toxin ct, heatlabile lt and heatstable enterotoxin sta from escherichia coli, and endogenous peptide ligands of guan. J w peterson and s c whipp department of microbiology and immunology, university of texas medical branch, galveston 775551019. Using solid supported membranes, binding of cholera toxin to g ml containing popcmembranes was quantified 47. Vibrio cholerae enterotoxin and its mode of action. Inhibition of cholera toxin action in the rabbit by cycloheximide. Pmc free article serebro ha, iber fl, yardley jh, hendrix tr. Biologists uncover mechanisms for cholera toxins deadly effects 11 september 20 biologists at the university of california, san diego have identified an underlying biochemical.