Whole Complex

Figure 1. 2.0 A resolution crystalline structure of the bovine Arp2/3 complex with subunits independently coloured & labelled.

Figure 1. 2.0 A resolution crystalline structure of the bovine Arp2/3 complex with subunits independently coloured & labelled.

In inactive form, the Arp2/3-complex is disc-shaped, with the two Arp-subunits (2 and 3) exposed on one side; these are folded in a way rather similar to actin, but with more extended surface loop to allow interaction with neighbouring subunits within the complex. The long C-terminal helices are associated in antiparallel fashion, holding the dimer of Arp2 and Arp3 together [3]. The structure is based on the bovine Arp2/3 complex, but comparison to 6 phylogenetically diverse other species showed that 80% of the 562 ‘core residues’ of the complex are conserved, with non-polar residues being the highest (83%) and uncharged-polar residues the lowest (67.8%). Subunit interfaces are more conserved that residues on the free surfaces; 69.6% of the 335 ‘interface residues’ are conserved. Most notably, the interface of Arp3 and ARPC3 shows 83% of ARPC3, and 90% of Arp3 residues are conserved. The interface of ARPC1 and ARPC5 are least conserved [3][4].

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