title: Stimulation of adenylate cyclase by Vibrio cholerae toxin and its active subunit.
abstract: The mechanism by which Vibrio cholerae toxin and its active subunit A stimulate adenylate cyclase of rat liver plasma membrane after in vivo or in vitro exposure was investigated. Stimulation of adenylate cyclase was more efficient with cholera toxin than with subunit A in whole animals and in "soluble" preparations of adenylate cyclase. Toxin-stimulated plasma membrane adenylate cyclase activity persisted after solubilization from the membrane by detergent, while subunit A stimulation was destroyed by detergent treatment. Detergent-free "soluble" enzyme could be stimulated in vitro by cholera toxin, but such stimulation by subunit A was very weak. Binding studies with iodotoxin or iodosubunit A confirmed that the interaction of toxin with adenylate cyclase in "soluble" preparations could be the result of specific binding to the enzyme. The uncertainty as to whether G M1 ganglioside (galactosyl-N-acetylgalactosaminyl [sialosyl] lactosyl ceramide; GGnSLC) is present in these fractions limited the interpretation of the data on binding. A biological modification of subunit A prior to the activation of adenylate cyclase is inferred from these data.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D005459:Fluorides / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology; D008099:Liver / Q000201:enzymology; D051379:Mice; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D014734:Vibrio cholerae
chemical_list: D005934:Glucagon; D012964:Sodium; D000262:Adenylyl Cyclases; D005459:Fluorides; D004837:Epinephrine