An inhibitor of host sigma-stimulated core enzyme activity that purifies with DNA-dependent RNA polymerase of E. coli following T4 phage infection

The content of the sigma subunit (as detected by gel electrophoresis) and activity with T4 DNA were examined with RNA polymerase fractions from both normal and T4 phage-infected $\text{E. coli}$. Sigma-containing fractions and core enzymes were obtained by phosphocellulose column chromatography. The sigma-containing fraction of the enzyme from infected cells, although somewhat stimulatory to both core enzymes alone, inhibits the normal sigma-stimulated activity of the core enzyme from infected cells at both low and high KCl concentration. Normal core enzyme activity is inhibited only at high KCl concentration.