A 22 kDa ras‐related G‐protein is the substrate for an ADP‐ribosyltransferase from Clostridium botulinum

Abstract

A ribosyltransferase from C. botulinurn type D ADP-ribosylated a protein of 22 kDa (~22) in human astrocytoma (1321Nl) cells. ADP-ribosylation of membrane-bound p22 was potentiated by 2 mM MgCI, or guanine nucleotides but was much reduced in the presence of 10 mM MgZ+ plus GTPyS. p22 was immunoprecipitated by a monoclonal antibody (142-24E05) raised against a peptide sequence common to the ras gene family but not by other ras or G-protein antibodies. p22 was also ADP-ribosylated in Drosophila but was not detected in Dicfyosfelium. These data suggest that the 22 kDa botulinurn toxin substrate is a GTP-binding protein and a member of the ras protein family.