Control of actin assembly and disassembly at filament ends

The most important discovery in the field is that the Arp2/3 complex nuclea tes assembly of actin filaments with free barbed ends. Arp2/3 also binds th e sides of actin filaments to create a branched network. Arp2/3's nucleatio n activity is stimulated by WASP family proteins, some of which mediate sig naling from small G-proteins. Listeria movement caused by actin polymerizat ion can be reconstituted in vitro using purified proteins: Arp2/3 complex, capping protein, actin depolymerizing factor/cofilin, and actin. actin depo lymerizing factor/cofilin increases the rate at which actin subunits leave pointed ends, and capping protein caps barbed ends.