The sites on the regulatory component of adenylate cyclase which are ADP-ribosylated by cholera toxin |
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Authors: | W H Ward S van Heyningen |
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Institution: | Department of Biochemistry, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, U.K. |
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Abstract: | In rat liver membranes cholera toxin ADP-ribosylated two polypeptides (Mr 42000 and 47000) in the regulatory component of adenylate cyclase. L-arginine methyl ester specifically inhibited both the activation of adenylate cyclase and ADP-ribosylation by cholera toxin, suggesting that cholera toxin modified arginine, or arginine-like, residues. A hydrolysis-resistant analogue of GTP (β, γ-imidoguanosine 5′-triphosphate, p(NH)ppG) bound to the regulatory protein in an essentially irreversible manner. Pretreatment with the analogue failed to inhibit the labelling of polypeptides by cholera toxin showing that the sites for ADP-ribosylation were different from those at which guanyl nucleotides were bound. |
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Keywords: | p(NH)ppG β γ-imidoguanosine 5′-triphosphate SDS sodium dodecyl sulphate PAGE polyacrylamide-gel electrophoresis |
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