Fig. 3.

Effects of single amino acid substitutions in Regions 2.4 and 3.0 of σ³² on activity of the groE and grpE promoters.

A. Amino acid sequence of Regions 2.3, 2.4 and 3.0 of σ³². Numbers at each end of the sequence indicate amino acid positions. Single-amino acid substitutions of σ³² used in this study are shown in light grey below the main sequence. The location of the RpoH box is denoted as a grey box (Nakahigashi et al., 1995); positions of the αhelices in each region are shown above the sequence. These data are derived both from structural data indicating that these s subregions are virtually identical in σ⁷⁰, a Group 1 σ, and σ²⁸, a Group 3 σ (Campbell et al., 2002; Sorenson et al., 2004), and secondary structure predictions for σ³² that are completely consistent with these assignments (E. Campbell, data not shown).

B. Activity of the σ³² Regions 2.4 and 3.0 mutants at the wt groE and grpE promoters. β-galactosidase activity driven by each mutant σ³² from the wt groE or grpE promoters is shown as a percentage of that driven by wt σ³². Assay strains are as described in Fig. 1A. The different σ³² amino-acid substitutions and their locations are shown on the x-axis. Note the effects of several σ³² substitutions (W108R, A111G, A111E, W121A and from L135 to K141) were not measured at the grpE promoter. All values are averages of at least three independent experiments; error bars indicate one standard deviation; black bars, groE promoter activities; grey bars, grpE promoter activities.