Fig. 6. Effect of α subunit linker length on open complex formation at the CC(–61.5) promoter. Complexes formed by RNAP reconstituted with the α subunits indicated in the presence or absence of wild-type CRP at the CC(–61.5) promoter were reacted with potassium permanganate. The location of the reactive thymidine residues was determined by PCR with a labelled primer followed by gel electrophoresis and autoradiography. Base co-ordinates are numbered relative to the transcription startpoint.