The Response Regulator BvgA and RNA Polymerase α Subunit C-Terminal Domain Bind Simultaneously to Different Faces of the Same Segment of Promoter DNA

Abstract

Examination of the binding of FeBABE-conjugated BvgA to the fha promoter of Bordetella pertussis has revealed that three dimers, formed by head-to-head association of monomers, bind one face of the DNA helix from the inverted-heptad primary binding site to the −35 region. The orientation of BvgA monomers within the dimers is the same as that recently demonstrated by X-ray crystallographic methods for a dimer of the C-terminal domain of NarL bound to DNA. Use of FeBABE conjugates of RNAP α subunit C-terminal domain showed that binding of this domain is linearly coincident with binding of the BvgA dimers, but to a different helical face. These results reveal a previously undescribed mode of interaction between RNAP α-CTD and a transcriptional activator.