Electrostatic interactions between the Bni1p Formin FH2 domain and actin influence actin filament nucleation

Structure. 2015 Jan 6;23(1):68-79. doi: 10.1016/j.str.2014.10.014. Epub 2014 Dec 4.

Abstract

Formins catalyze nucleation and growth of actin filaments. Here, we study the structure and interactions of actin with the FH2 domain of budding yeast formin Bni1p. We built an all-atom model of the formin dimer on an Oda actin filament 7-mer and studied structural relaxation and interprotein interactions by molecular dynamics simulations. These simulations produced a refined model for the FH2 dimer associated with the barbed end of the filament and showed electrostatic interactions between the formin knob and actin target-binding cleft. Mutations of two formin residues contributing to these interactions (R1423N, K1467L, or both) reduced the interaction energies between the proteins, and in coarse-grained simulations, the formin lost more interprotein contacts with an actin dimer than with an actin 7-mer. Biochemical experiments confirmed a strong influence of these mutations on Bni1p-mediated actin filament nucleation, but not elongation, suggesting that different interactions contribute to these two functions of formins.

Publication types

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

MeSH terms

  • Actin Cytoskeleton / chemistry
  • Actin Cytoskeleton / metabolism*
  • Actins / chemistry
  • Actins / metabolism*
  • Crystallography, X-Ray
  • Hydrogen Bonding
  • Microfilament Proteins / chemistry*
  • Microfilament Proteins / metabolism*
  • Models, Molecular
  • Protein Binding
  • Protein Interaction Domains and Motifs*
  • Protein Multimerization
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins / chemistry*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Static Electricity*

Substances

  • Actins
  • Bni1 protein, S cerevisiae
  • Microfilament Proteins
  • Saccharomyces cerevisiae Proteins