Figure 4.

IPTG-dependent production and secretion of EspA and EspB by the RNase E-inducible strain TEA028-rne. TEA028-rne and its parental strain (TEA028) were grown statically overnight in DMEM supplemented with IPTG at the indicated concentrations. Cellular proteins from (A) bacterial pellets or (B) supernatants were subjected to SDS-PAGE and western blotting with antisera raised against EspA or EspB. Arrows indicate the EspA and EspB proteins, while asterisks indicate non-specific proteins that cross-reacted with the antisera. In panel C, secreted proteins in equivalent volumes of culture supernatants were precipitated and examined by SDS-PAGE and staining with lumitein. Asterisks indicate BSA, which was added to each supernatant as an internal control for the efficiency of protein precipitation.