Control of actin assembly at filament ends

Actin filament polymerization involves exchange of subunits of filament ends, which can be controlled in vitro and in vivo by other proteins that bind actin filaments and inhibit subunit addition or loss at the ends. Proteins that bind to the barbed end, including capping protein, the gelsolin super-family, tensin, and profilin are discussed, as are proteins that bind to the pointed end, including tropomodulin and spectrin/band 4.1. Some proteins that bind along the sides of filaments and influence assembly at ends are also discussed. Functional roles in vivo are emphasized.