title: Botulinum ADP-ribosyltransferase C3 but not botulinum neurotoxins C1 and D ADP-ribosylates low molecular mass GTP-binding proteins.
abstract: Botulinum ADP-ribosyltransferase C3 modified 21-24 kDa proteins in a guanine nucleotide-dependent manner similar to that described for botulinum neurotoxin C1 and D. Whereas GTP and GTP gamma S stimulated C3-catalyzed ADP-ribosylation in the absence of Mg2+, in the presence of added Mg2+ ADP-ribosylation was impaired by GTP gamma S. C3 was about 1000-fold more potent than botulinum C1 neurotoxin in ADP-ribosylation of the 21-24 kDa protein(s) in human platelet membranes. Antibodies raised against C3 blocked ADP-ribosylation of the 21-24 kDa protein by C3 and neurotoxin C1 but neither cross reacted with neurotoxin C1 immunoblots nor neutralized the toxicity of neurotoxin C1 in mice. The data indicate that the ADP-ribosylation of low molecular mass GTP-binding proteins in various eukaryotic cells is not caused by botulinum neurotoxins but is due to the action of botulinum ADP-ribosyltransferase C3. The weak enzymatic activities described for botulinum neurotoxins appear to be due to the contamination of C1 and D preparations with ADP-ribosyltransferase C3.
mesh_terms: D036002:ADP Ribose Transferases; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D001905:Botulinum Toxins / Q000276:immunology / Q000378:metabolism*; D003014:Clostridium botulinum / Q000201:enzymology* / Q000276:immunology; D003429:Cross Reactions; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D010430:Pentosyltransferases / Q000276:immunology / Q000378:metabolism*; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D008565:Membrane Proteins; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D036002:ADP Ribose Transferases; D010430:Pentosyltransferases; D001905:Botulinum Toxins; D019204:GTP-Binding Proteins; D008274:Magnesium