Structure of the autoinhibitory switch in formin mDia1.
Diaphanous-related formins (DRFs) regulate the nucleation and polymerization of unbranched actin filaments. The activity of DRFs is inhibited by an intramolecular interaction between their N-terminal regulatory region and a conserved C-terminal segment termed the Diaphanous autoinhibitory domain (DAD). Binding of GTP bound Rho to the mDia1 N terminus releases this autoinhibitory restraint. Here, we describe the crystal structure of the DAD segment of mDia1 in complex with the relevant N-terminal fragment, termed the DID domain. The structure reveals that the DAD segment forms an amphipathic helix that binds a conserved, concave surface on the DID domain. Comparison with the structure of the mDia1 N terminus bound to RhoC suggests that release of the autoinhibitory DAD interaction is accomplished largely by Rho-induced restructuring of the adjacent GTPase binding subdomain (GBD), but also by electrostatic repulsion and a small, direct steric occlusion of the DAD binding cleft by Rho itself.
Nezami
Azin G
AG
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 44 Binney Street, Boston, Massachusetts 02115, USA.
Poy
Florence
F
Eck
Michael J
MJ
D000595:Amino Acid Sequence; D002151:Calorimetry; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D000080865:Formins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D020741:rho GTP-Binding Proteins / Q000737:chemistry*
D002352:Carrier Proteins; C491464:Diap1 protein, mouse; D000080865:Formins; D020741:rho GTP-Binding Proteins