Effect of polynucleotides on aminoacyl transfer ribonucleic acid synthetases. III. Inhibition of glutamyl transfer ribonucleic acid synthetase by natural polynucleotides

The inhibitory effects of several natural polynucleotides on the formation of glutamyl-tRNA by purified rat liver glutamyl-tRNA synthetase were investigated. Yeast and Escherichia coli tRNA's, which were inactive as acceptors with the liver enzyme, inhibited to a small extent. Low levels of inhibition were also observed with intact or degraded ribosomal RNA. Deoxyribonucleic acid from several species was a potent inhibitor of glutamyl-tRNA formation, although it exhibited a mixed type of inhibition with respect to tRNA. An unknown RNA component was isolated from pH 5 fractions of beef liver and was found to be a potent, competitive inhibitor of glutamyl-tRNA formation. This RNA had a low molecular weight, but no amino acid acceptor activity. It was a much more effective inhibitor than either degraded ribosomal RNA or tRNA whose terminal adenosine moiety had been removed, suggesting that this RNA is distinct from either of these two species. Studies with periodate-oxidized tRNA and tRNA whose terminal adenosine had been removed indicated the involvement of this terminal nucleoside moiety in the interaction of glutamate-specific tRNA and its synthetase. The observation that several naturally occurring nucleic acids can inhibit aminoacyl-tRNA formation warns against the use of impure tRNA preparations in the study of aminoacyl-tRNA synthetases. The possible regulatory significance of the inhibition of aminoacyl-tRNA formation is discussed.