title: ADP-ribosyltransferase from beef liver which ADP-ribosylates elongation factor-2.
abstract: Fragment A of diphtheria toxin and Pseudomonas toxin A intoxicate cells by ADP-ribosylating the diphthamide residue of elongation factor-2 (EF-2) resulting in an inhibition of protein synthesis [1-3]. A cellular enzyme from polyoma virus transformed baby hamster kidney (pyBHK) cells ADP-ribosylates EF-2 in an identical manner [4]. Here we describe a similar cellular enzyme from beef liver which transfers [adenosine-14C]ADP-ribose from NAD to EF-2. The 14C-label can be removed from the EF-2 by snake venom phosphodiesterase as a soluble product which comigrates with AMP on TLC plates, indicating the 14C-label is present on EF-2 as monomeric units of ADP-ribose. Furthermore, the forward transferase reaction catalyzed by the beef liver ADP-ribosyltransferase is reversible by excess diphtheria toxin fragment A, with the formation of 14C-labeled NAD, indicating that both transferases ADP-ribosylate the same site on the diphthamide residue of EF-2. Thus, beef liver and pyBHK mono(ADP-ribosyl)transferases both modify the diphthamide residue of EF-2, in a manner identical to diphtheria toxin fragment A and Pseudomonas toxin A. These results suggest the cellular enzyme is probably ubiquitous among eukaryotic cells.
mesh_terms: D036002:ADP Ribose Transferases; D000818:Animals; D002417:Cattle; D008099:Liver / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000378:metabolism*; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases; D013379:Substrate Specificity
chemical_list: D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors; D009243:NAD; D036002:ADP Ribose Transferases; D011065:Poly(ADP-ribose) Polymerases; D009713:Nucleotidyltransferases