FIGURE 6.

Proposed mechanism for dual modes of regulation of Arp2/3 complex by Crn1. Coronin trimers (cyan) bind actin filaments (gray surface representation) through their WD repeat domains and Arp2/3 complex (Arp3 is dark gray; Arp2 is light gray; other subunits are white) through the unique region CA. The unique CA interacts with Arp2, leaving a second activator binding site on Arp3 open for VCA-containing NPF. Synergistic activation may occur through simultaneous recruitment of the complex to filaments and actin monomers to the complex.