Elongation factor 2 as the target of the reaction product between sodium selenite and glutathione (GSSeSG) in the inhibiting of amino acid incorporation in vitro.

The product of the reaction between sodium selenite and glutathione, designated as selenodiglutathione (GSSeSG), nearly completely inhibits amino acid incorporation from [14C]leucyl-tRNA by free polyribosomes isolated from rat liver. The mechanism of this inhibition was studied on the basis of the following three findings. Glutathione decomposes GSSeSG to harmless products; GSSeSG acts instantaneously on some component of the complete incubation system during preparation of the incubation vessels (at 0 degrees C); once GSSeSG has reacted its inhibitory effect cannot be reversed by glutathione. Accordingly, the effect of GSSeSG on the various steps of the amino acid incorporation process was studied by varying the sequence of additions of the reaction components, GSSeSG and GSH. The results of these and other experiments showed elongation factor 2 to be target of GSSeSG. The GSSeSG-B blocked factor could be regenerated by reduction with glutathione reductase and NADPH.