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

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Abstract
During bacteriophage T7 infection, the Escherichia coli RNA polymerase β′ 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, Thr1068, in the evolutionarily hypervariable segment of β′. Using a phosphomimetic substitution of Thr1068, we show that phosphorylation of β′ leads to increased ρ-dependent transcription termination, which may help to switch from host to viral RNA polymerase transcription during phage development.