Stimulation of lac Transcription by Guanosine 5′-Diphosphate 2′(or 3′)-Diphosphate and Transfer Ribonucleic Acid

In the presence of cyclic adenosine 3':5'-monophosphate, guanosine 5'-diphosphate 2'(or 3')-diphosphate (ppGpp) stimulates lac transcription by cell-free extracts of Escherichia coli. This effect of ppGpp is observed with an impure prepparation of RNA polymerase obtained by washing ribosomes with 0.5 m KCl but not with highly purified RNA polymerase. One of the factors required for ppGpp action has several of the properties of tRNA and can be replaced by E. coli tRNA.