sentences:  The ability of these other NPFs to bind the Arp2/3 complex while cortactin is also bound could come from new interactions with cortactin's SH3 domain, which is in a different conformation when phosphorylated by Ser/Thr kinases and thus may be more open to interactions with other NPFs.Having other NPFs bind to the Arp2/3 complex at the same time as cortactin may enhance nucleation site stability.Inactive cortactin diffuses throughout the cytoplasm, but upon phosphorylation, the protein begins to target certain areas in the cell.