FIG 4.

degS_A323E partially activates basal levels of σ^E signaling. (A) DegS^A323 (red) is located at the PDZ/protease domain interface of DegS. These domains interact by a number of salt bridges (teal) that stabilize the inactive conformation of the protein. Dashed lines indicate polar contacts. The image was generated from the peptide-free structure of DegS (PDB code 1SOT) (48). (B and C) Measurement of the V_max of β-galactosidase activity driven from rpoHP3, a σ^E-dependent promoter, in the indicated strains (51). Graphs are plotted as means ± SEM (n = 3). Significance was calculated using a t test. Strains were grown at 37°C (B) and 30°C (C). n.s., not significant.