Fig. 2. InlB-induced actin-based processes. (A) InlB-mediated internalization by the `zipper-like' mechanism. On the left is a transmission electron microscopy section of an InlB-coated bead being internalized into an epithelial cell [reproduced from (Braun et al., 1998)]. The particle is engulfed within tightly adherent membranous structures before lying in a phagocytic vacuole. Note the presence of small membrane projections at the entry site of the particle. On the right, the F-actin phagocytic cup is stained with FITC-phalloidin (in green) at the entry site of two InlB-coated beads (in blue). (B) InlB-induced membrane ruffling in Vero cells. A cell untreated (left) or incubated with 4.5 nM purified InlB for 5 minutes (right) and stained with FITC-phalloidin to detect F-actin.