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

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Abstract
The role of the alpha subunit of Escherichia coli RNA polymerase in transcription activation by the OxyR protein was investigated using in-vitro-reconstituted RNA polymerase containing alpha 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 alpha subunit plays an essential role in transcription activation at the OxyR-dependent promoters.