The identification of PC mutations of Rob that reduce transcription activation of class II promoters. Derivatives of strainRA4468 lysogenic for a single-copy λ prophage carrying a transcriptional fusion of lac to the fumC promoter (a) or to the micF promoter (b) were transformed with plasmid pBAD33-Rob or single alanine substitutions of it. The β-galactosidase activity produced by eachmutant strain is given as the percentage of the activity produced by the strain expressing wild-type Rob. (c) EMSAs showing the effect on binding fumC DNA of increasing concentrations (0, 8, 80, and 800 nM) of wild-type Rob and PCmutants K30A, L74A, D75A, and L78A were carried out as described in Materials and Methods.