An inhibitory protein of Escherichia coli RNA polymerase in bacteriophage T3-infected cells (core polymerase-sigma factor-host polymerase-phage polymerase-initiation).

A partially purified protein isolated from bacteriophage T3-infected cells of Escherichia coli B markedly inhibits the activity of E. coli RNA polymerase, slightly inhibits the activity of purified T3 polymerase, and does not inhibit the activity of either core polymerase or the ribosome-bound T3 polymerase. The properties of this protein and its mechanism of action have been studied. It appears to antagonize the action of the sigma factor component of RNA polymerase.