The structural basis of actin filament branching by the Arp2/3 complex

Isabelle Rouiller, Xiao Ping Xu, Kurt J. Amann, Coumaran Egile, Stephan Nickell, Daniela Nicastro, Rong Li, Thomas D. Pollard, Niels Volkmann, Dorit Hanein

Research output: Contribution to journalArticlepeer-review

213 Scopus citations


The actin-related protein 2/3 (Arp2/3) complex mediates the formation of branched actin filaments at the leading edge of motile cells and in the comet tails moving certain intracellular pathogens. Crystal structures of the Arp2/3 complex are available, but the architecture of the junction formed by the Arp2/3 complex at the base of the branch was not known. In this study, we use electron tomography to reconstruct the branch junction with sufficient resolution to show how the Arp2/3 complex interacts with the mother filament. Our analysis reveals conformational changes in both the mother filament and Arp2/3 complex upon branch formation. The Arp2 and Arp3 subunits reorganize into a dimer, providing a short-pitch template for elongation of the daughter filament. Two subunits of the mother filament undergo conformational changes that increase stability of the branch. These data provide a rationale for why branch formation requires cooperative interactions among the Arp2/3 complex, nucleation-promoting factors, an actin monomer, and the mother filament.

Original languageEnglish (US)
Pages (from-to)887-895
Number of pages9
JournalJournal of Cell Biology
Issue number5
StatePublished - Mar 10 2008

ASJC Scopus subject areas

  • Cell Biology


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