Mechanism of cholera toxin activation by a guanine nucleotide-dependent 19 kDa protein

• Published in: Biochimica et biophysica acta Vol. 1034; no. 2; pp. 195 - 199
• Main Authors: Noda, Masatoshi, Tsai, Su-Chen, Adamik, Ronald, Moss, Joel, Vaughan, Martha
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 16.05.1990; Elsevier; North-Holland
• Subjects: Adenosine Diphosphate Ribose - metabolism; Adenylyl cyclase; Adenylyl Cyclases - metabolism; ADP Ribose Transferases - metabolism; ADP-ribosylation; AdP-ribosylation factor; ADP-Ribosylation Factors; Animals; Bacteriology; Biological and medical sciences; Brain Chemistry; Cattle; Cholera toxin; Cholera Toxin - metabolism; Enzyme Activation - drug effects; Fundamental and applied biological sciences. Psychology; GTP-Binding Proteins - metabolism; Guanine nucleotide-binding protein; Guanosine Triphosphate - pharmacology; Kinetics; Membrane Proteins - pharmacology; Microbiology; Molecular Weight; Octoxynol; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Polyethylene Glycols - pharmacology; Sodium Dodecyl Sulfate - pharmacology; SDS; Adenylyl cyclase; ARF; sARF II; DTT; G sα; AdP-ribosylation factor; PAGE; Cholera toxin; Guanine nucleotide-binding protein; CHAPS; ADP-ribosylation; Adenylate cyclase; Binding protein; Toxin; ADP ribosylation; Vibrio cholerae; Bacteria; Vibrionaceae; Molecular interaction; Activation; Mechanism of action; G protein
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/0304-4165(90)90076-9

Cholera toxin causes the devastating diarrheal syndrome characteristic of cholera by catalyzing the ADP-ribosylation of G sα, a GTP-binding regulatory protein, resulting in activation of adenylyl cyclase. ADP-ribosylation of G sα is enhanced by 19 kDa guanine nucleotide-binding proteins known as ADP-ribosylation factors or ARFs. We investigated the effects of agents known to alter toxin-catalyzed activation of adenylyl cyclase on the stimulation of toxin- and toxin subunit-catalyzed ADP-ribosylation of G sα and other substrates by an ADP-ribosylation factor purified from a soluble fraction of bovine brain (sARF II). In the presence of GTP, sARF II enhanced activity of both the toxin catalytic unit and a reduced and alkylated fragment (‘A 1’), as a result of an increase in substrate affinity with no significant effects on V max. Activation of toxin was independent of G sα and was stimulated 4-fold sodiuim dodecyl sulfate, but abolished by Triton X-100. sARF II therefore serves as a direct allosteric activator of the A 1 protein and may thus amplify the pathological effects of cholera toxin.