The predicted lipid-binding site of Arp2 and the Arp2/3 complex. The coordinates of subdomains 3 and 4 of Arp2 (PDB 1K8K) are displayed as they appear in the inactive crystallized Arp2/3 complex. The predicted lipid-binding site is colored yellow. Amino and carboxyl termini are indicated in blue and red, respectively. Arp2 subdomains 3 and 4; (a) Ribbon model, (b) Space-filling representation, and (c) Electrostatic field potentials (orientation of the protein is identical to that viewed in (a) and (b)). The crystallized Arp2/3 complex is shown as; (d) Space-filling representation (Arp2 (white), Arp3 (gold), p21 (blue), p40 (green); p34 (purple); p20 (red), p16 (brown)), and (e) Electrostatic field potentials (orientation of the protein is identical to that viewed in (d)). The colors red, white and blue are used to indicate negative, neutral and positive field potentials (e), respectively.