Fig. 4.

Effects of substitutions in Region 2.4 of σ³² in suppressing promoter mutations at positions −14 and −13. A. Effect of W108A σ³² and W108R σ³² on the groE promoter with single-base changes at the −14 or −13 positions.

B. Effect of E112A σ³² on groE and grpE promoters with single-base changes at the −13 position.

C. Effect of E112A σ³² on groE promoter with a single-base changes at positions −14, −15 and −16. β-galactosidase activity driven by each σ³² variant from mutant groE or grpE promoters is shown as a percentage of β-galactosidase activity driven by each σ³² variant from the wt promoter. Assay strains are as described in Fig. 1A. Below the x-axis, mutation and position indicate the base change at the different promoter positions; promoter indicates the groE or grpE promoter; σ³² indicates the σ³² wt or mutant derivative. All values are averages of at least three independent experiments; error bars indicate one standard deviation.