Arp2/3 complex

Arp2/3 complex (Actin Related Protein 2/3 complex) is a seven-subunit protein complex that plays a major role in the regulation of the actin cytoskeleton. It is a major component of the actin cytoskeleton and is found in most actin cytoskeleton-containing eukaryotic cells. Two of its subunits, the Actin-Related Proteins ARP2 and ARP3, closely resemble the structure of monomeric actin and serve as nucleation sites for new actin filaments. The complex binds to the sides of existing ("mother") filaments and initiates growth of a new ("daughter") filament at a distinctive 70 degree angle from the mother. Branched actin networks are created as a result of this nucleation of new filaments. The regulation of rearrangements of the actin cytoskeleton is important for processes like cell locomotion, phagocytosis, and intracellular motility of lipid vesicles.

The Arp2/3 complex was named after it was identified in 1994 by affinity chromatography from Acanthamoeba castellanii, though it had been previously isolated in 1989 in a search for proteins that bind to actin filaments in Drosophila melanogaster embryos. It is found in most eukaryotic organisms, but absent from a number of Chromalveolates and plants.