title: The regulation of mDia1 by autoinhibition and its release by Rho*GTP.
abstract: Formins induce the nucleation and polymerisation of unbranched actin filaments via the formin-homology domains 1 and 2. Diaphanous-related formins (Drfs) are regulated by a RhoGTPase-binding domain situated in the amino-terminal (N-terminal) region and a carboxy-terminal Diaphanous-autoregulatory domain (DAD), whose interaction stabilises an autoinhibited inactive conformation. Binding of active Rho releases DAD and activates the catalytic activity of mDia. Here, we report on the interaction of DAD with the regulatory N-terminus of mDia1 (mDia(N)) and its release by Rho*GTP. We have defined the elements required for tight binding and solved the three-dimensional structure of a complex between an mDia(N) construct and DAD by X-ray crystallography. The core DAD region is an alpha-helical peptide, which binds in the most highly conserved region of mDia(N) using mainly hydrophobic interactions. The structure suggests a two-step mechanism for release of autoinhibition whereby Rho*GTP, although having a partially nonoverlapping binding site, displaces DAD by ionic repulsion and steric clashes. We show that Rho*GTP accelerates the dissociation of DAD from the mDia(N)*DAD complex.
authors.affiliation: Department of Structural Biology, Max-Planck-Institute of Molecular Physiology, Dortmund, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Lammers
authors.forename: Rolf
authors.initials: R
authors.lastname: Rose
authors.forename: Andrea
authors.initials: A
authors.lastname: Scrima
authors.forename: Alfred
authors.initials: A
authors.lastname: Wittinghofer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D000080865:Formins; D006160:Guanosine Triphosphate / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D020741:rho GTP-Binding Proteins / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; C491464:Diap1 protein, mouse; D000080865:Formins; D006160:Guanosine Triphosphate; D020741:rho GTP-Binding Proteins