title: Endogenous ADP-ribosylation for eukaryotic elongation factor 2: evidence of two different sites and reactions.
abstract: Eukaryotic elongation factor 2 can undergo ADP-ribosylation in the absence of diphtheria toxin under the action of an endogenous transferase. The investigation which aimed to gain insight into the nature of endogenous ADP-ribosylation revealed that this reaction may be, in some cases, due to covalent binding of free ADP-ribose to elongation factor 2. Binding of free ADP-ribose, and NAD- and endogenous transferase-dependent ADP-ribosylation were suggested to be distinct reactions by different findings. Free ADP-ribose could bind to elongation factor 2 previously subjected to ADP-ribosylation by diphtheria toxin or endogenous transferase. The binding of free ADP-ribose was inhibited by neutral NH2OH, L-lysine and picrylsulfonate, whereas endogenous ADP-ribosyltransferase was inhibited by NAD glycohydrolase inhibitors and L-arginine. The ADP-ribosyl-elongation factor 2 adduct which formed upon binding of free ADP-ribose was resistant to neutral NH2OH, but decomposed almost completely upon treatment with NaOH. The product of endogenous transferase-dependent ADP- ribosylation was partially resistant to NH2OH and NaOH treatment. Moreover, this reaction was reversed in the presence of diphtheria toxin and nicotinamide. Both types of endogenous ADP-ribosylation gave rise to inhibition of polyphenylalanine synthesis. This study thus provides evidence for the presence of two different types of endogenous ADP-ribosylation of eukaryotic elongation factor 2. The respective sites involved in these reactions are distinct from one another as well as from diphthamide, the site of attack by diphtheria toxin.
authors.affiliation: Istanbul University, Istanbul Faculty of Medicine, Department of Biophysics, 34390 Capa, Istanbul, Turkey. muhbektas@hotmail.com
authors.forename: Muhammet
authors.initials: M
authors.lastname: Bektaş
authors.forename: Rüstem
authors.initials: R
authors.lastname: Nurten
authors.forename: Kivanç
authors.initials: K
authors.lastname: Ergen
authors.forename: Engin
authors.initials: E
authors.lastname: Bermek
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism*; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D002250:Carbon Radioisotopes / Q000378:metabolism / Q000494:pharmacology; D002855:Chromatography, Thin Layer; D004167:Diphtheria Toxin / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D020652:Peptide Elongation Factor 2 / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051381:Rats
chemical_list: D002250:Carbon Radioisotopes; D004167:Diphtheria Toxin; D020652:Peptide Elongation Factor 2; D000246:Adenosine Diphosphate Ribose; D036002:ADP Ribose Transferases