The requirement of the response regulator RisA for rgtA expression. (A) Schematic representation of RisA binding motifs in rgtA promoter region. (Left) Three plausible RisA binding sites (gray circles 1–3) are present in a 60-bp region (−277 to −217) upstream of the rgtA transcriptional start site. This 60-bp region has been deleted, resulting in the rgtAΔ277/217 mutant. (Right) Sequences of canonical RisA-binding motif as well of three RisA-binding motifs found upstream of the rgtA promoter are depicted; nucleotides different from consensus are in gray. (B) B. pertussis Tohama I strain (lane 1) and its isogenic ΔrisA (lane 2) and rgtAΔ277/217 (lane 3) mutants were grown in SS medium to exponential phase. RNA isolated from harvested cells was probed with biotinylated RgtA-specific probe and subjected to northern blot analysis (upper panel). Signals obtained upon rehybridization of the membrane with SsrA-specific probe (lower panel) served as loading control. Only relevant parts of the membranes are shown. The result is a representative of two experiments.
