Selective Inhibition of tRNATyr Transcription by Guanosine 3′‐Diphosphate 5′‐Diphosphate

Abstract

Guanosine 3''-diphosphate 5''-diphosphate (ppGpp) selectively reduces the synthesis of suIII+ tRNA from .vphi.80 psuIII+ [phage] DNA relative to the synthesis of .vphi.80 RNA in a system in vitro containing DNA and Escherichia coli RNA polymerase [EC 2.7.7.6] holoenzyme as the sole macromolecular components. The response of suIII+ tRNA synthesis to increasing salt and to temperature in the presence of ppGpp suggests that the nucleotide may reduce the affinity of the enzyme for suIII+ promoters. The Ki [inhibition constant] for the selective inhibition of tRNA synthesis by ppGpp is 4 .mu.M in contrast to the value of 150 .mu.M for the inhibition of rRNA synthesis.