[The effect of guanosinetetraphosphate on rRNA synthesis in E. coli extracts]

The synthesis of rRNA in the ribosome-free extracts S100 of E. coli cells was about 30 and 60% of total transcript when E. coli DNA and DNA of lambda rifd 18 phage were used respectively. The synthesis of rRNA with both types of DNA was inhibited in 5--6 times by 0.8 mM ppGpp, while the synthesis of total RNA decreased only two-fold. Selective action of ppGpp on rRNA synthesis is due to the intensive inhibition of the initiation of transcription of the appropriate genes. The rRNA synthesis and the inhibitory capacity of ppGpp was shown to dependend on the KCl concentration in S 100 extracts. These results indicate that ppGpp is the main factor controlling rRNA synthesis both in isolated RNA polymerase system and in cell-free extracts.