Involvement of the RNA polymerase α subunit C‐terminal region in co‐operative interaction and transcriptional activation with OxyR protein

Summary The role of the α subunit of Escherichia coli RNA polymerase in transcription activation by the OxyR protein was investigated using in‐vitro ‐reconstituted RNA polymerase containing α subunits carrying C ‐terminal truncations or an amino acid substitution. Mutant RNA polymerases failed to respond to transcription activation of the E. coli OxyR‐dependent promoters. DNase I footprinting analysis indicates that the OxyR protein exerts a co‐operative effect on the binding of wild‐type RNA polymerase, but not the mutant RNA polymerases, to the katG promoter. Together, these results suggest that direct protein‐protein contact between the OxyR protein and the C ‐terminal contact site I region of the RNA polymerase α subunit plays an essential role in transcription activation at the OxyR‐dependent promoters.