FIG. 3.

(A) Schematic diagrams of the ybcQ clone and its derivatives lacking one or two predicted stem-loops (SL) or almost the entire ybcQ gene (ipeX clone). Small leftward arrows indicate the location of IPTG-inducible pTrc99A promoter while small rightward arrows show the location of the predicted ybcQ transcription start site. (B) OmpC, OmpF, and OmpA were detected in whole cell envelopes by Western blot analyses with OmpC polyclonal antibodies that also recognize OmpF and OmpA. Shown are the names of the plasmids that were transformed into RAM415 (OmpC_2Cys). ipeX expression was not induced by IPTG; instead, it occurred from the leaky pTrc99A promoter. (C) OMPs were detected from whole cell envelopes. Shown are the names of plasmids transformed into RAM412 (OmpC_1Cys). pTrc-ipeX (SL-2*) refers to a mutant plasmid derived from pTrc-ipeX in which three residues of ipeX SL-2, which are complementary to the ompC and ompF SD sequences, have been altered by site-directed mutagenesis. ipeX expression was induced by IPTG.