Mechanism of filament nucleation and branch stability revealed by the structure of the Arp2/3 complex at actin branch junctions

Coumaran Egile, Isabelle Rouiller, Xiao Ping Xu, Niels Volkmann, Rong Li, Dorit Hanein

Research output: Contribution to journalArticlepeer-review

Abstract

Actin branch junctions are conserved cytoskeletal elements critical for the generation of protrusive force during actin polymerization-driven cellular motility. Assembly of actin branch junctions requires the Arp2/3 complex, upon activation, to initiate a new actin (daughter) filament branch from the side of an existing (mother) filament, leading to the formation of a dendritic actin network with the fast growing (barbed) ends facing the direction of movement. Using genetic labeling and electron microscopy, we have determined the structural organization of actin branch junctions assembled in vitro with 1-nm precision. We show here that the activators of the Arp2/3 complex, except cortactin, dissociate after branch formation. The Arp2/3 complex associates with the mother filament through a comprehensive network of interactions, with the long axis of the complex aligned nearly perpendicular to the mother filament. The actin-related proteins, Arp2 and Arp3, are positioned with their barbed ends facing the direction of daughter filament growth. This subunit map brings direct structural insights into the mechanism of assembly and mechanical stability of actin branch junctions.

Original languageEnglish (US)
Article numbere383
Pages (from-to)1902-1909
Number of pages8
JournalPLoS biology
Volume3
Issue number11
DOIs
StatePublished - Nov 2005
Externally publishedYes

ASJC Scopus subject areas

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Agricultural and Biological Sciences(all)

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