Formin localization

Interaction between the NH₂- and COOH-terminal regions of formin proteins serves two autoinhibitory functions simultaneously, report Seth et al. on page 701. The first, more familiar function is to block actin nucleation by the COOH-terminal region. More novel is the second function: preventing localization of the protein to the plasma membrane, normally mediated by the NH₂-terminal domain.

The Diaphanous-related formins nucleate unbranched actin filaments during cytoskeletal remodeling. In the case of mDia1 formin, this nucleation activity is autoinhibited by interaction between the NH₂ and COOH termini of the protein. Seth et al. show that the formin family member FRLα is autoinhibited by the same mechanism.

Blocking autoinhibition via mutation had a second consequence: FRLα moved from the cytoplasm to the plasma membrane. This plasma membrane localization was...