Genetic studies on the β subunit of Escherichia coli RNA polymerase

Abstract
We have previously isolated an E. coli derivative carrying a small internal deletion (Δ(rpoB) 1570-1) of the β structural gene. This RNA polymerase deletion mutant has no noticeable phenotype other than a slightly increased generation time in minimal medium. The deletion, which removes about 165 bp, has been localised to between codons 965 and 1,083, indicating it excises part of a tandem repeat structure present in the C-terminal region of β. Analysis in vitro of purified RNA polymerase from the deletion mutant indicates that this enzyme has an altered promoter selectivity. These observations allow locatisation of a site on the β polypeptide of E. coli RNA polymerase involved in transcriptional initiation.