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. 2005 Jan;12(1):26-31.
doi: 10.1038/nsmb870. Epub 2004 Dec 12.

Conformational Changes in the Arp2/3 Complex Leading to Actin Nucleation

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Conformational Changes in the Arp2/3 Complex Leading to Actin Nucleation

Avital A Rodal et al. Nat Struct Mol Biol. .

Abstract

The two actin-related subunits of the Arp2/3 complex, Arp2 and Arp3, are proposed to form a pseudo actin dimer that nucleates actin polymerization. However, in the crystal structure of the inactive complex, they are too far apart to form such a nucleus. Here, we show using EM that yeast and bovine Arp2/3 complexes exist in a distribution among open, intermediate and closed conformations. The crystal structure docks well into the open conformation. The activator WASp binds at the cleft between Arp2 and Arp3, and all WASp-bound complexes are closed. The inhibitor coronin binds near the p35 subunit, and all coronin-bound complexes are open. Activating and loss-of-function mutations in the p35 subunit skew conformational distribution in opposite directions, closed and open, respectively. We conclude that WASp stabilizes p35-dependent closure of the complex, holding Arp2 and Arp3 closer together to nucleate an actin filament.

Comment in

  • Lessons from Listeria.
    Nat Struct Mol Biol. 2005 Jan;12(1):1. doi: 10.1038/nsmb0105-1. Nat Struct Mol Biol. 2005. PMID: 15689965 No abstract available.

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