title: ADP-ribosylation of membrane proteins catalyzed by cholera toxin: basis of the activation of adenylate cyclase.
abstract: In the presence of ATP and a cytosolic factor, cholera toxin fragment A1 catalyzes the transfer of ADP-ribose from NAD to a number of soluble and membrane-bound proteins of the pigeon erythrocyte. Evidence is presented that suggests that the most readily modified membrane protein (Mr 42,000) is the adenylate cyclase-associated GTP-binding protein. Its modification by toxin is stimulated by guanine nucleotides. Adenylate cyclase activity increases in parallel with the addition of ADP-ribose to this protein and decreases in parallel with the subsequent reversal of ADP-ribosylation by toxin and nicotinamide. The protein is only accessible to toxin A subunits if the erythrocytes are lysed. When adenylate cyclase activity reaches a maximum, the number of ADP-ribose residues bound to this protein (about 1500 per cell) is similar to the reported number of beta-adrenergic receptors.
mesh_terms: D000247:Adenosine Diphosphate Sugars / Q000378:metabolism*; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002772:Cholera Toxin / Q000378:metabolism*; D010856:Columbidae; D004789:Enzyme Activation; D004910:Erythrocyte Membrane / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism*; D008970:Molecular Weight; D009243:NAD / Q000378:metabolism; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D012266:Ribose
chemical_list: D000247:Adenosine Diphosphate Sugars; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009702:Nucleoside Diphosphate Sugars; D009243:NAD; D012266:Ribose; D006160:Guanosine Triphosphate; D002772:Cholera Toxin; D000262:Adenylyl Cyclases