(A) Derepression of str transcription by ssap expression. Top, schematic representation of the blaZ transcriptional fusion generated in plasmid pJP1977. Bottom, strains containing pJP1977- and pCN51-derivative plasmids expressing the different SSAPs under study were assayed for β-lactamase activity in the absence of or 3 hr after induction with 5 μM CdCl2. Samples were normalized for total cell mass. Experiment data is in triplicate. Error bars represent SEM. A 2-way ANOVA with Sidak's multiple comparisons test was performed to compare mean differences within rows. Adjusted p values were as follows: Sak = 0.0001***, Sak4 = 0.0001***, Erf = 0.0001***, Redβ=0.0001***, chimera = 0.999ns. ns, not significant. (B) Affinity chromatography of 80α Sak (ORF16) using His6–StlSaPI2. E. coli strain expressing the pair was isopropyl-β-D-thiogalactoside (IPTG)-induced and, after disruption of the cells, the expressed proteins were applied to a Ni2+ agarose column and eluted. The presence of the different proteins was monitored in the elute fraction (E) by Coomassie staining. M: molecular weight marker. (C) Bacterial adenylate cyclase-based two-hybrid (BACTH) analysis. Spots in each row represent three independent colonies. Plasmid combinations are indicated in the right columns. Bottom, quantification of the BACTH analysis after 2 hr of IPTG (5 mM) induction. Experiment data is in triplicate. Error bars represent SEM. A 1-way ANOVA with Sidak's multiple comparisons test was performed to compare mean differences within rows. Adjusted p values were as follows; Sak = 0.0221*, Sak4 = 0.0030**, Erf = 0.0158*, Redβ=0.0014**, chimera (Chim) = 0.1980ns. ns, not significant.