The interaction of aminoacyl transferase II and ribosomes.

The kinetics of aminoacyl transfer from aminoacyl soluble ribonucleic acid to ribosomal protein has been examined with rat liver preparations. A lag in the initial rate of incorporation with resolved aminoacyl-transferring enzymes is observed with low (4 mu) concentrations of reduced glutathione; this lag is abolished when transferase II is incubated with a sulfhydryl compound, such as glutathione or Z-mercaptoethanol, prior to the addition of the other reaction components. The sulfhydryl activation is dependent on time and on glutathione concentration, and is inhibited by oxidized glutathione. The total extent of amino acid incorporation is also dependent on sulfhydryl concentration. A sulfhydryl requirement in aminoacyl transfer, other than for the activation of transferase II, was not detected. The initial rate of amino acid incorporation is markedly stimulated when transferase II, glutathione, ribosomes, guanosine triphosphate, and NH&l are incubated prior to the addition of aminoacyl soluble RNA and transferase I. This transferase II-ribosome interaction, which involves GTP and a monovalent cation, yields a product which is partially protected against inhibition by oxidized glutathione.