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

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183 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
Publication statusPublished - Mar 10 2008


ASJC Scopus subject areas

  • Cell Biology

Cite this

Rouiller, I., Xu, X. P., Amann, K. J., Egile, C., Nickell, S., Nicastro, D., ... Hanein, D. (2008). The structural basis of actin filament branching by the Arp2/3 complex. Journal of Cell Biology, 180(5), 887-895.