Genetic studies on the beta subunit of Escherichia coli RNA polymerase. VII. RNA polymerase is a target for ppGpp.

RNA polymerase was isolated from two suppressed rpoB amber strains exhibiting relaxed control over RNA synthesis in vivo. In vitro transcription analysis of these mutant holoenzymes carrying defined substitutions at known sites in the beta subunit clearly shows that single amino acid changes in beta render RNA polymerase resistant to ppGpp. This unambiguously demonstrates that RNA polymerase is indeed the target for ppGpp.