The stringent response alarmone guanosine tetraphosphate (ppGpp) affects transcription from many promoters. ppGpp binds directly to the transcription enzyme of Escherichia coli, RNA polymerase. Analysis of the crystal structure of RNA polymerase with ppGpp suggested that binding of this nucleotide may result in some conformational or post-translational alterations to the enzyme. These changes might affect in vitroperformance of the enzyme. Here, a comparison of the in vitroproperties of RNA polymerases isolated from wild type and ppGpp-deficient bacteria shows that both enzymes do not differ in i) transcription activity of various promoters (e.g. σ70rrnBP1, λpL, T7A1), ii) response to ppGpp, iii) promoter-RNA polymerase open complex stability. Thus, it may be concluded that ppGpp present in the bacterial cell prior to purification of the RNA polymerase does not result in the alterations to the enzyme that could be permanent and affect its in vitrotranscription capacity.
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