title: Structure of a Bud6/Actin Complex Reveals a Novel WH2-like Actin Monomer Recruitment Motif.
abstract: 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.
authors.affiliation: Department of Cancer Biology, Dana-Farber Cancer Institute, SM1036, 450 Brookline Avenue, Boston, MA 02215, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Eunyoung
authors.initials: E
authors.lastname: Park
authors.affiliation: Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Graziano
authors.affiliation: Department of Cancer Biology, Dana-Farber Cancer Institute, SM1036, 450 Brookline Avenue, Boston, MA 02215, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
authors.affiliation: Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA.
authors.forename: Mikael
authors.initials: M
authors.lastname: Garabedian
authors.affiliation: Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA.
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Goode
authors.affiliation: Department of Cancer Biology, Dana-Farber Cancer Institute, SM1036, 450 Brookline Avenue, Boston, MA 02215, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215, USA. Electronic address: eck@crystal.harvard.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Eck
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000737:chemistry*; D009154:Mutation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013816:Thermodynamics
chemical_list: D000199:Actins; C107727:BUD6 protein, S cerevisiae; D008840:Microfilament Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins