Hcp release assay. FLAG-tagged Hcp (HcpFL) release was assessed by separating cells (C) and cell-free culture supernatant (S) fractions from 109 cells of the indicated strains. Proteins were separated by 12.5%-acrylamide SDS-PAGE and TolB and HcpFL were immunodetected using anti-TolB (upper panel) and anti-FLAG (lower panel) antibodies. Molecular weight markers (in kDa) are indicated on the left. The experiment was performed in triplicate and a representative result is shown. 