A coiled-coil from the RNA polymerase beta ' subunit allosterically induces selective nontemplate strand binding by sigma(70)

For transcription to initiate, RNA polymerase must recognize and melt promo ters. Selective binding to the nontemplate strand of the -10 region of the promoter is central to this process. We show that a 48 amino acid (aa) coil ed-coil from the beta' subunit (aa 262-309) induces sigma (70) to perform t his function almost as efficiently as core RNA polymerase itself. We provid e evidence that interaction between the beta' coiled-coil and region 2.2 of sigma (70) promotes an allosteric transition that allows om to selectively recognize the nontemplate strand. As the beta' 262-309 peptide can functio n with the previously crystallized portion of sigma (70), nontemplate recog nition can be reconstituted with only 47 kDa, or 1/10 of holoenzyme.