FIG. 8.

An open complex at P_R is required for the inhibition of repressor-mediated activation of P_RM. A DNA fragment containing wild-type P_R and the P_RM promoter was transcribed in vitro in the presence of the repressor. Transcription conditions are given in Materials and Methods. Repressor concentrations were increased in 2.5-fold steps starting at 250 nM protein. Positions of transcripts resulting from initiation of transcription from P_RM and P_R are indicated. RNAP, RNA polymerase.