Research Article

Crystal Structure of Arp2/3 Complex

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Science  23 Nov 2001:
Vol. 294, Issue 5547, pp. 1679-1684
DOI: 10.1126/science.1066333

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We determined a crystal structure of bovine Arp2/3 complex, an assembly of seven proteins that initiates actin polymerization in eukaryotic cells, at 2.0 angstrom resolution. Actin-related protein 2 (Arp2) and Arp3 are folded like actin, with distinctive surface features. Subunits ARPC2 p34 and ARPC4 p20 in the core of the complex associate through long carboxyl-terminal α helices and have similarly folded amino-terminal α/β domains. ARPC1 p40 is a seven-blade β propeller with an insertion that may associate with the side of an actin filament. ARPC3 p21 and ARPC5 p16 are globular α-helical subunits. We predict that WASp/Scar proteins activate Arp2/3 complex by bringing Arp2 into proximity with Arp3 for nucleation of a branch on the side of a preexisting actin filament.

  • * These authors contributed equally to this work.

  • Present address: Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.

  • Present address: Avidis, Biopole Clermont-Limagne, 63 360 Saint Beauzire, France.

  • § Present address: Department of Biochemistry, Dartmouth College, Hanover, NH 03755, USA.

  • || Present address: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA.

  • To whom correspondence should be addressed. E-mail: thomas.pollard{at}

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