Localization of theEscherichia coliRNA Polymerase β′ Subunit Residue Phosphorylated by Bacteriophage T7 Kinase Gp0.7

During bacteriophage T7 infection, the Escherichia coli RNA polymerase beta' subunit is phosphorylated by the phage-encoded kinase Gp0.7. Here, we used proteolytic degradation and mutational analysis to localize the phosphorylation site to a single amino acid, Thr(1068), in the evolutionarily hypervariable segment of beta'. Using a phosphomimetic substitution of Thr(1068), we show that phosphorylation of beta' leads to increased rho-dependent transcription termination, which may help to switch from host to viral RNA polymerase transcription during phage development.