Structure of a Bud6/Actin Complex Reveals a Novel WH2-like Actin Monomer Recruitment Motif.
Publication Type:Journal Article
Source:Structure, Volume 23, Issue 8, p.1492-1499 (2015)
Keywords:Actins, Amino Acid Sequence, Animals, Binding Sites, Cloning, Molecular, Crystallography, X-Ray, Escherichia coli, Gene Expression, Microfilament Proteins, Models, Molecular, Molecular Sequence Data, Muscle, Skeletal, Mutation, Protein Binding, Protein Interaction Domains and Motifs, Protein Structure, Secondary, Rabbits, Recombinant Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Alignment, Thermodynamics
<p>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. </p>