Structure of Arp2/3 complex in its activated state and in actin filament branch junctions.
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.
Volkmann
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N
The Burnham Institute, La Jolla, CA 92037, USA.
Amann
K J
KJ
Stoilova-McPhie
S
S
Egile
C
C
Winter
D C
DC
Hazelwood
L
L
Heuser
J E
JE
Li
R
R
Pollard
T D
TD
Hanein
D
D
D000048:Acanthamoeba; D008841:Actin Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D020285:Cryoelectron Microscopy; D003598:Cytoskeletal Proteins; D005583:Fourier Analysis; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008958:Models, Molecular; D011506:Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D051316:Wiskott-Aldrich Syndrome Protein
D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D003598:Cytoskeletal Proteins; D011506:Proteins; D051316:Wiskott-Aldrich Syndrome Protein