Fig. 2. (A) Domain organization of the formin family of proteins. Shown is the formin-homology 1 (FH1) domain, the FH2 domain, which controls actin nucleation, and the FH3 domain, which is important for localization of some formins. (B) Domain organization of the Diaphanous-related formins (DRFs). Unique to this class of proteins is the regulatory Rho-binding domain (RBD), which binds activated forms of Rho GTPases and the Dia-autoregulatory-domain (DAD), which mediates an intramolecular auto-inhibitory interaction with RBD. An activated formin, with the DAD-RBD intramolecular interaction relieved by Rho-GTP binding, is shown.