Structure of a Bud6/Actin Complex Reveals a Novel WH2-like Actin Monomer Recruitment Motif

Structure. 2015 Aug 4;23(8):1492-1499. doi: 10.1016/j.str.2015.05.015. Epub 2015 Jun 25.


In budding yeast, the actin-binding protein Bud6 cooperates with formins Bni1 and Bnr1 to catalyze the assembly of actin filaments. The nucleation-enhancing activity of Bud6 requires both a "core" domain that binds to the formin and a "flank" domain that binds monomeric actin. Here, we describe the structure of the Bud6 flank domain in complex with actin. Two helices in Bud6(flank) interact with actin; one binds in a groove at the barbed end of the actin monomer in a manner closely resembling the helix of WH2 domains, a motif found in many actin nucleation factors. The second helix rises along the face of actin. Mutational analysis verifies the importance of these Bud6-actin contacts for nucleation-enhancing activity. The Bud6 binding site on actin overlaps with that of the formin FH2 domain and is also incompatible with inter-subunit contacts in F-actin, suggesting that Bud6 interacts only transiently with actin monomers during filament nucleation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actins / chemistry*
  • Actins / genetics
  • Actins / metabolism
  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Cloning, Molecular
  • Crystallography, X-Ray
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gene Expression
  • Microfilament Proteins / chemistry*
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Muscle, Skeletal / chemistry*
  • Mutation
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Structure, Secondary
  • Rabbits
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism
  • Sequence Alignment
  • Thermodynamics


  • Actins
  • BUD6 protein, S cerevisiae
  • Microfilament Proteins
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins

Associated data

  • PDB/4WYB