FIG 4.

DNA binding site for transcriptional regulation by StpA and H-NS. Previous work has shown that H-NS and StpA can bind to P_cas, and the DNA binding site (DBS) for H-NS was predicted. (A) The putative DBS of H-NS/StpA was mutated by replacing the conserved sequence ATAAA to CGCAC. P_cas with a disrupted DBS was named P_cas*. Refer to Fig. S5 in the supplemental material for details about plasmid construction. (B) With the reporter GFP as an indicator, activities of P_cas and P_cas* were compared in the hns null mutant that expressed StpA or H-NS from the multicopy-number plasmid pSU19 in LB broth. Activities of P_cas-gfp and P_cas*-gfp were compared in hns and hns stpA null mutants that were grown in M9 minimal medium supplemented with 0.32% (wt/vol) fructose (C) or 1% (wt/vol) glucose (D) as the carbon source. TSS, transcriptional start site. Data are shown as means ± standard deviations (n = 4). Statistical significance was determined using a two-tailed Student's t test (*, P ≤ 0.05; **, P ≤ 0.01; ****, P ≤ 0.001).