To determine the mechanism by which N-WASp mediates activation by Cdc42, actin polymerization was measured in the presence of purified components. In the presence of the Arp2/3 complex (ARP), N-WASp stimulates actin polymerization substantially over ARP or N- WASp alone, but not nearly so dramatically as the C-terminal segment of N-WASp that contains just the verprolin (V), cofilin (C), and acidic (A) domains (VCA) (Panel A Below). To account for the difference between N-WASp and its C-terminal VCA segment, N-WASp and ARP were mixed with combinations of Cdc42-GTPS and vesicles containing PIP2 [PI(4,5)P2] (Panel B Below). What is required for full-length N-WASp to stimulate actin polymerization as efficiently as its C- terminal VCA segment? Explain your reasoning..