The protein cofactor necessary for ADP-ribosylation of G(s) by cholera toxin is itself a GTP binding protein

R. A. Kahn, A. G. Gilman

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Abstract

A membrane-bound protein cofactor (ARF) is required for the cholera toxin-dependent ADP-ribosylation of the stimulatory regulatory component (G(s)) of adenylate cyclase. Improved methods for the purification of ARF from bovine brain are described. ARF has a high-affinity binding site for guanine nucleotides. Binding of GTP or GTPγS to ARF is necessary for the activity of the cofactor; GDP·ARF does not support ADP-ribosylation of G(s). Although the protein as purified contains stoichiometric amounts of GDP, GTPase activity of isolated ARF was not detected. Cholera toxin-dependent activation of adenylate cyclase thus requires two guanine nucleotide binding proteins.

Original languageEnglish (US)
Pages (from-to)7906-7911
Number of pages6
JournalJournal of Biological Chemistry
Volume261
Issue number17
StatePublished - Dec 1 1986

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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