A cold-sensitive beta subunit mutant RNA polymerase from Escherichia coli with defects in promoter opening in vitro.

A cold-sensitive mutation in the rpoB gene for the RNA polymerase beta subunit increasing the temperature of promoter opening on T2 phage DNA was obtained in Escherichia coli. The mutation also affects the stages preceding promoter opening by increasing the dissociation rate of RNA polymerase--DNA closed complexes. The affinity of RNA polymerase to T2 and lambda DNA is differentially changed by the mutation. The relative efficiency of transcription of these two templates is also changed. These results suggest a participation of the RNA polymerase beta subunit in the interaction with promoters.