FIG. 8.

Effect of a dsbA mutation on secretion of SopB into the culture supernatant. Western blot analyses of whole-cell extracts (top panels) or culture supernatants (bottom panels) with anti-SopB antibody. (A) The strains were wild type (WT) or contained deletions of dsbA, invG, or dsbA invG as indicated above the lanes. The strains used were 14028 (wild type), JS326, JS740, and JS810. (B) The strains are pLacY(A177C) ΔaraBAD ΔaraE ΔaraFGH and contain the pHilA plasmid and mutations indicated above the lanes. The strains used were JS811 to JS813. Culture supernatants and whole-cell extracts were prepared as described in Materials and Methods. Equivalent amounts of culture supernatant or whole-cell extract from each strain were separated by 7.5% SDS-polyacrylamide gel electrophoresis. The resulting gels were blotted, and proteins were detected by using anti-SopB and horseradish peroxidase-labeled rabbit anti-mouse secondary antibody. The bar graph shows the β-galactosidase activity produced from a sopB-lacZ fusion in each of the strains assayed from an aliquot of each culture.