title: Structural and mechanistic insights into the interaction between Rho and mammalian Dia.
abstract: Formins are involved in a variety of cellular processes that require the remodelling of the cytoskeleton. They contain formin homology domains FH1 and FH2, which initiate actin assembly. The Diaphanous-related formins form a subgroup that is characterized by an amino-terminal Rho GTPase-binding domain (GBD) and an FH3 domain, which bind somehow to the carboxy-terminal Diaphanous autoregulatory domain (DAD) to keep the protein in an inactive conformation. Upon binding of activated Rho proteins, the DAD is released and the ability of the formin to nucleate and elongate unbranched actin filaments is induced. Here we present the crystal structure of RhoC in complex with the regulatory N terminus of mammalian Diaphanous 1 (mDia1) containing the GBD/FH3 region, an all-helical structure with armadillo repeats. Rho uses its 'switch' regions for interacting with two subdomains of GBD/FH3. We show that the FH3 domain of mDia1 forms a stable dimer and we also identify the DAD-binding site. Although binding of Rho and DAD on the N-terminal fragment of mDia1 are mutually exclusive, their binding sites are only partially overlapping. On the basis of our results, we propose a structural model for the regulation of mDia1 by Rho and DAD.
authors.affiliation: Max-Planck-Institute of Molecular Physiology, Department of Structural Biology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Rose
authors.forename: M
authors.initials: M
authors.lastname: Weyand
authors.forename: M
authors.initials: M
authors.lastname: Lammers
authors.forename: T
authors.initials: T
authors.lastname: Ishizaki
authors.forename: M R
authors.initials: MR
authors.lastname: Ahmadian
authors.forename: A
authors.initials: A
authors.lastname: Wittinghofer
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D000080865:Formins; D006367:HeLa Cells; D006801:Humans; D008322:Mammals; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D020741:rho GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; C491464:Diap1 protein, mouse; D000080865:Formins; D010446:Peptide Fragments; D020741:rho GTP-Binding Proteins