Figure 3. Structure of the autoinhibited FH3–DAD complex of mDia1. The helical DAD binds into the concave site of the FH3 domain armadillo repeat structure. (A) The DAD consensus motif MDxLL extends to VMDxLLxxLx₅F in the binding interface to the FH3 domain. (B) All five armadillo repeats participate in the interaction of the N-terminal FH3 domain with the C-terminal autoregulatory domain. Mutation of the central A256 residue to aspartate on the last turn of the third armadillo repeats leads to relief of the autoinhibition and activation of the formin.¹⁵ Displayed is the structure 2F31 (ref. 16). A cartoon of the interaction scheme is shown below the atomistic model.