Actin-related protein 3 (IPR015623)

Short name: Arp3

Overlapping homologous superfamilies


Family relationships

  • Actin family (IPR004000)
    • Actin-related protein 3 (IPR015623)


This family consists of Arp3 proteins.

Actin-related proteins are defined broadly as proteins that have significant (30-60%) amino acid identity to conventional actin. Ten members, named Arp1-Arp10, have been identified in budding yeast [PMID: 9290209] and play diverse roles in the cell, ranging from the regulation of actin to chromatin remodeling. Actin and Arps are part of a large, ancient family of ATPases that include heat shock proteins and sugar kinases.

Actin-related protein 3 (Arp3) shares about 35-40% amino acid identity with conventional actin [PMID: 7593166]. Arp3 is only found in the cell as a member of a 7-subunit complex, known as the Arp2/3 complex. The Arp2/3 complex is composed of Arp3, Arp2 and five novel proteins: p40 (ARPC1), p35 (ARPC2), p19 (ARPC3), p18 (ARPC4), and p14 (ARPC5). The Arp2/3 complex has been found in all eukaryotes and is highly conserved across species. The crystal structures of the Arp2/3 complex have been solved [PMID: 15505213].

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 [PMID: 9600938]. In order to nucleate filaments, Arp2/3 must bind to a member of the N-WASp/SCAR family protein [PMID: 9889097]. 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.

GO terms

Biological Process

GO:0034314 Arp2/3 complex-mediated actin nucleation
GO:0007015 actin filament organization

Molecular Function

GO:0005524 ATP binding

Cellular Component

GO:0005885 Arp2/3 protein complex

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.