InterPro domain: IPR034666

Arp2/3 binds to pre-existing actin filaments and nucleates new daughter filaments, and thus becomes incorporated into the dynamic actin network at the leading edge of motile cells and other actin-based protrusive structures [ 1 ]. In order to nucleate filaments, Arp2/3 must bind to a member of the N-WASp/SCAR family protein [ 2 ]. Arp2 and Arp3 are thought to be brought together after activation, forming an actin-like nucleus for actin monomers to bind and create a new actin filament. In the absence of an activating protein, Arp2/3 shows very little nucleation activity. Recent research has focused on the binding and hydrolysis of ATP by Arp2 and Arp3 [ 3 ], and crystal structures of the Arp2/3 complex have been solved [ 4 ].

The human complex consists of Arp2/3 complex composed of ARP2, ARP3, ARPC1B/p41-ARC, ARPC2/p34-ARC, ARPC3/p21-ARC, ARPC4/p20-ARC and ARPC5/p16-ARC. This superfamily represents the ARPC2/4 subunits.

1. The interaction of Arp2/3 complex with actin: nucleation, high affinity pointed end capping, and formation of branching networks of filaments. Proc. Natl. Acad. Sci. U.S.A. 95, 6181-6
2. Scar1 and the related Wiskott-Aldrich syndrome protein, WASP, regulate the actin cytoskeleton through the Arp2/3 complex. Curr. Biol. 8, 1347-56
3. Arp2/3 complex requires hydrolyzable ATP for nucleation of new actin filaments. Proc. Natl. Acad. Sci. U.S.A. 98, 14871-6
4. Crystal structures of actin-related protein 2/3 complex with bound ATP or ADP. Proc. Natl. Acad. Sci. U.S.A. 101, 15627-32