Fig. 2.

rpoS::lacZ fusions activated by DsrA, RprA, and ArcZ. (A) A summary of in vitro results from (23) showing the importance of rpoS leader length and an (AAN)₄ element (red box) for the action of Hfq. The numbers indicate the nucleotide at the 5′ end of the rpoS leader RNA, relative to the natural start; the in vitro RNAs used both previously and in this work extended 12 nt into the ORF. The “double-mutant” construct had the properties of the (AAN)₄ mutant. Structure of the 5′ leader and sequence of the mutations in the A-rich elements are shown in Fig. S2. (B) The rpoS leader constructs carrying the truncations and mutations described in Fig. 2A were fused to lacZ to create translational fusions under the control of the arabinose-inducible P_BAD promoter; the (AAN)₄ and A₆ point mutations were introduced into the full-length fusion rather than the long fusion shown in Fig. 2A. The specific strains are described in Table S1. (C) sRNA activation of rpoS leader fusions. Strains containing the vector pBRplac (black bars) or plasmids overexpressing DsrA, RprA, or ArcZ, were grown in LB containing arabinose and IPTG at 37 °C to stationary phase before ß-galactosidase activity was measured. (D) sRNA activation of rpoS leader fusions in an hfq^- background. Same as in C, with hfq::cat derivatives; white bars contain vector plasmid. Note that y axis values are significantly less in D than in C.