Structural Basis of Rho GTPase-mediated Activation of the Formin mDia1

Mol Cell. 2005 Apr 29;18(3):273-81. doi: 10.1016/j.molcel.2005.04.002.

Abstract

Diaphanous-related formins (DRFs) regulate dynamics of unbranched actin filaments during cell contraction and cytokinesis. DRFs are autoinhibited through intramolecular binding of a Diaphanous autoinhibitory domain (DAD) to a conserved N-terminal regulatory element. Autoinhibition is relieved through binding of the GTPase RhoA to the N-terminal element. We report the crystal structure of the dimeric regulatory domain of the DRF, mDia1. Dimerization is mediated by an intertwined six-helix bundle, from which extend two Diaphanous inhibitory domains (DIDs) composed of five armadillo repeats. NMR and biochemical mapping indicate the RhoA and DAD binding sites on the DID partially overlap, explaining activation of mDia1 by the GTPase. RhoA binding also requires an additional structurally independent segment adjacent to the DID. This regulatory construction, involving a GTPase binding site spanning a flexibly tethered arm and the inhibitory module, is observed in many autoinhibited effectors of Ras superfamily GTPases, suggesting evolutionary pressure for this design.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Crystallography, X-Ray
  • Formins
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Nuclear Magnetic Resonance, Biomolecular
  • Point Mutation
  • Protein Structure, Tertiary*
  • rho GTP-Binding Proteins / metabolism*

Substances

  • Carrier Proteins
  • Diap1 protein, mouse
  • Formins
  • rho GTP-Binding Proteins

Associated data

  • PDB/2BNX