Genetic studies on the beta subunit of Escherichia coli RNA polymerase. IV. Structure-function correlates.

We have isolated a set of strains that synthesise 331 potential variants of E. coli DNA-dependent RNA polymerase making use of nonsense suppression of amber mutations in the beta structural gene; rpoB. Translational mapping, together with the effect of known amino acid substitutions, has allowed us to locate sites on the beta polypeptide involved in transcription termination, stringent response and resistance to the antibiotic rifampicin. In general, the C-terminal quarter appears to be less affected by such single amino acid exchanges than the rest of beta. These studies permit for the first time structure-function correlates for the beta subunit of RNA polymerase.