Requirement of Thiols in the Adenosine-Diphosphate Ribosylaton of Elongaton Factor-2 by Pseudomonas Aeruginosa Exotoxin A

Abstract

The extent of the transfer of the adenosine 5'-diphosphate ribose (ADPR) moiety of nicotinamide adenine dinucleotide onto elongation factor 2 (EF-2) catalyzed by Pseudomonas aeruginosa exotoxin A (PA-toxin) was dependent upon the presence of a reducing agent, dithiotheritol (DTT). The reaction requires DTT in low concentration (1 to 10 mM) and in the absence of DTT less product, ADPR-EF 2, was formed. PA-toxin was fully activated by treatment with a denaturing agent, sodium dodecyl sulphate (SDS), in conjunction with DTT. In the presence of activated toxin, the maximum transfer of ADPR onto EF-2 was observed when EF-2 had been previously reduced with DTT. Denaturation of EF-2 prior to reduction did not produce a further increase in its ability to act as a substrate for PA-toxin.