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Updated: Jun 28, 2026

Aip1p Dynamics Are Altered by the R256H Mutation in Actin
Published on: July 30, 2014
Structure of Arp2/3 complex in its activated state and in actin filament branch junctions
N Volkmann1, K J Amann, S Stoilova-McPhie
1The Burnham Institute, La Jolla, CA 92037, USA.
Abstract:
The seven-subunit Arp2/3 complex choreographs the formation of branched actin networks at the leading edge of migrating cells. When activated by Wiskott-Aldrich Syndrome protein (WASp), the Arp2/3 complex initiates actin filament branches from the sides of existing filaments. Electron cryomicroscopy and three-dimensional reconstruction of Acanthamoeba castellanii and Saccharomyces cerevisiae Arp2/3 complexes bound to the WASp carboxy-terminal domain reveal asymmetric, oblate ellipsoids. Image analysis of actin branches indicates that the complex binds the side of the mother filament, and Arp2 and Arp3 (for actin-related protein) are the first two subunits of the daughter filament. Comparison to the actin-free, WASp-activated complexes suggests that branch initiation involves large-scale structural rearrangements within Arp2/3.
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