Localization of a σ70 binding site on the N terminus of the Escherichia coli RNA polymerase β' subunit

Abstract

The Escherichia coli genome encodes genes for seven different σ subunit species while only having single genes for the α,β, and β' subunits that make up the RNA polymerase core enzyme. The various σ factors compete for binding to the core enzyme, upon which they confer promoter DNA-specific transcription initiation to the polymerase. We have mapped a major interaction site between one of the σ species, σ70, and β'. Using far- Western blotting analysis of chemically cleaved and genetically engineered protein fragments, we have identified a N-terminal fragment of β' (residues 60-309) that could bind σ70. We were able to more precisely map the interaction domain to amino acid residues 260-309 of β' using nickel nitrilotriacetic acid co-immobilization assays.