Three-dimensional reconstructions of actin filaments capped by Arp2/3 complex

Niels Volkmann, Christopher Page, Rong Li, Dorit Hanein

Research output: Contribution to journalArticlepeer-review


The primary function of Arp2/3 complex is the generation of free barbed ends by nucleating new filaments from the sides of pre-existing filaments. The pathway of branch formation is complex and involves nucleation promoting factors, actin monomers and nucleotides. A less prominent function of Arp2/3 complex is capping of actin filament pointed ends. Here we show, using electron microscopy, electron tomography, and image reconstruction of negatively-stained samples at ~2-3. nm resolution, that Arp2/3 complex bound to the pointed ends of actin filaments has a conformation similar to that in the branch junction with the Arps arranged in an actin-filament like configuration. This is direct evidence for the existence of two distinct activation pathways for Arp2/3 complex, one in the context of branch formation, one in the context of pointed-end capping, with essentially the same conformational end point.

Original languageEnglish (US)
Pages (from-to)179-183
Number of pages5
JournalEuropean journal of cell biology
Issue number5-6
StatePublished - May 2014
Externally publishedYes


  • Actin cytoskeleton
  • Cell motility
  • Electron microscopy
  • Fitting
  • Image analysis

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Histology
  • Cell Biology


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