title: Requirement for guanosine triphosphate for cholera-toxin-catalysed incorporation of adenosine diphosphate ribose into rat liver plasma membranes and for activation of adenylate cyclase.
abstract: 1. Cholera toxin was shown to require the presence of GTP to activate rat liver plasma-membrane adenylate cyclase. ATP did not affect the activation process. 2. Cholera toxin catalysed the incorporation of 32P from NAD labelled in the alpha-phosphate group of the ADP moiety into a rat liver plasma-membrane protein with a subunit mol.wt. of 42 500. This is taken to demonstrate ADP-ribosylation. The ADP-ribosylation of this protein also required GTP and was unaffected by ATP. 3. Nicotinamide inhibited both the activation of adenylate cyclase by cholera toxin and the ADP-ribosylation of the protein of 42 500 subunit mol wt. Neither the activation nor the ADP-ribosylation could be reversed by treatment with nicotinamide in the presence of cholera toxin.
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002772:Cholera Toxin / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006160:Guanosine Triphosphate / Q000378:metabolism*; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D009243:NAD / Q000494:pharmacology; D009536:Niacinamide / Q000494:pharmacology; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D051381:Rats
chemical_list: D009702:Nucleoside Diphosphate Sugars; D009243:NAD; D000246:Adenosine Diphosphate Ribose; D009536:Niacinamide; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D002772:Cholera Toxin; D000262:Adenylyl Cyclases