Detection of E. coli and M. tuberculosis SmpB proteins in E. coli IW764 cells used in the in vivo tagging assay illustrated in Figure2. Lanes 1-6 are as in Figure 2. Both SmpB proteins had C-terminal epitope Tag-100. Lysates of IPTG-induced E. coli IW764 cells harboring plasmid pWOW derivatives were fractionated on a 12.5% SDS-polyacrylamide gel. SmpB proteins were visualized by Western blotting with anti-Tag-100 antibodies. Positions of 6, 16 and 36 kDa molecular markers are shown on the left side of the gel image.