Organization of an activator

Initiation of transcription requires the conversion of complexes formed promoters consist of the RNA polymerase (RNAP) and double-stranded DNA to open promoter complex in which the enzyme is able to access to the DNA template in a single-stranded form. The complex between RNAP and sigma factor variant .sigma 54 in hydrolysis of ATP-dependent remodeling by activating proteins as a closure remains complex occurs. This conversion facilitates DNA background and made the transition to the open complex. We present cryo-electron microscopy bacterial RNAP reconstructions in complex with σ54alone and σ54 of RNAP with a AAA + activator. With photoréticulation data establishing the position of the promoter DNA in the complex, we explain why the σ54 RNAP gated complex is not able to provide the DNA template for access and how structural changes activator induced binding can initiate conformational changes that ultimately result in the formation of the open complex.