Figure 9.

Working model for the role of VASP in actin-based motility. This scheme summarizes the conclusions from the present work concerning the role of VASP in Listeria movement. Step 0 represents nucleation of actin filaments on Arp2/3 complex in interaction with the NH₂-terminal domain of ActA. VASP (V) is bound to the central proline-rich repeats of ActA by its EVH1 domain and binds to the side of the growing filament by its EVH2 domain. Barbed end growth occurs from G-actin and from profilin (P)-actin complex. Capping of detached filaments by the capping protein (C) and cross-linking by α-actinin (x) is represented. Cycles of attachment–detachment of VASP to and from actin filaments allow insertional polymerization of actin or profilin-actin and movement as described in steps 1, 2, and 3. Insertion of subunits at the barbed end of cross-linked filaments generates compression forces used for propulsion.