Interactions of tyrosyl transfer ribonucleic acid synthetase from Escherichia coli with its substrates. Inhibition by transfer ribonucleic acid.

Transfer RNA inhibited the tyrosine-dependent ATPpyrophosphate exchange catalyzed by tyrosyl-tRNA synthetase from IIscherichia coli. The inhibition was specific for tRNATY’; it was competitive with tyrosine and noncompetitive with ATP. tRNA modified by periodate oxidation or by limited digestion with phosphodiesterase proved to be a stronger inhibitor of the enzyme than native tRNA; the inhibition by these tRNA’s, however, was no longer purely competitive with tyrosine. Measurements of the binding of tRNATV to the enzyme by means of nitrocellulose filters revealed 1 mole of tRNATY’ bound per mole of enzyme.