Figure 6.

Effects of substitutions at positions 192 and 197 on interaction of λcI CTDs. Strain KS1 was cotransformed with a derivative of plasmid pACλcI encoding λcI with the wild-type or a mutant amino acid at position 192 and a derivative of plasmid pBRα–cI encoding the α–cI chimera with the wild-type or a mutant amino acid at position 197. For the experiment in C, the α–cI chimeras tested bore a mutant residue at position 197 and either the wild-type or a mutant residue at position 196. Graph labels list the λcI first and the α–cI allele second. β-Galactosidase activities were measured in cultures grown in the presence of 0, 1, 5, 10, and 20 μm IPTG. Each panel presents results of an individual representative experiment. Similar experiments performed on separate days yielded the same relative patterns of activation.