title: Electrostatic interactions between the Bni1p Formin FH2 domain and actin influence actin filament nucleation.
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.
authors.affiliation: Department of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; Computation Institute, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Baker
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA.
authors.forename: Naomi
authors.initials: N
authors.lastname: Courtemanche
authors.affiliation: Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Parton
authors.affiliation: Department of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; Computation Institute, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: McCullagh
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA; Department of Molecular Biophysics and Biochemistry, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA; Department of Cell Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Pollard
authors.affiliation: Department of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; Computation Institute, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA. Electronic address: gavoth@uchicago.edu.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Voth
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism*; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*; D055672:Static Electricity
chemical_list: D000199:Actins; C105191:Bni1 protein, S cerevisiae; D008840:Microfilament Proteins; D029701:Saccharomyces cerevisiae Proteins