Reconstruction of filament branch junction formed by the A. castellanii Arp2/3 complex. (A) Three views related by 90° clockwise rotations. The reconstruction was sharpened in Fourier space with 300 Å2 and is displayed at a 100% mass contour level. All other density representations are from the original reconstruction. Numbers indicate three bridges of density between the two branches. (B) Stereo view of the fit of the branch junction model (α carbon trace) into the branch junction. Actin subunits are gray. Inset shows the crystal structure of the Arp2/3 complex with the mother filament position indicated by a gray rectangle. The color code for subunits of the Arp2/3 complex is used throughout: Arp2, red; Arp3, orange; ARPC1, green; ARPC2, cyan; ARPC3, magenta; ARPC4, blue; and ARPC5, yellow.
