title: Conformational dynamics of capping protein and interaction partners: simulation studies.
abstract: Capping protein (CP) is important for the regulation of actin polymerization. CP binds to the barbed end of the actin filament and prevents actin polymerization. This interaction is modulated through competitive binding by regulatory proteins such as myotrophin (V-1) and the capping protein interacting (CPI) motif from CARMIL. The binding site of myotrophin overlaps with the region of CP that binds to the barbed end of actin filament, whereas CPI binds at a distant site. The binding of CPI to the myotrophin-CP complex dissociates myotrophin from CP. Detailed multicopy molecular dynamics simulations suggest that the binding of CPI shifts the conformational equilibria of CP away from states that favor myotrophin binding. This shift is underpinned by allosteric effects where CPI inhibits CP through suppression of flexibility and disruption of concerted motions that appear to mediate myotrophin binding. Accompanying these effects are changes in electrostatic interactions, notably those involving residue K142β, which appears to play a critical role in regulating flexibility. In addition, accessibility of the site on CP for binding the key hydrophobic residue W8 of myotrophin is modulated by CPI. These results provide insights into the modulation of CP by CPI and myotrophin and indicate the mechanism by which CPI drives the dissociation of the myotrophin-CP complex.
authors.affiliation: Bioinformatics Institute, Agency for Science, Technology and Research, Matrix, Singapore.
authors.forename: Suryani
authors.initials: S
authors.lastname: Lukman
authors.forename: Robert C
authors.initials: RC
authors.lastname: Robinson
authors.forename: David
authors.initials: D
authors.lastname: Wales
authors.forename: Chandra S
authors.initials: CS
authors.lastname: Verma
mesh_terms: D051344:Actin Capping Proteins / Q000737:chemistry*; D008841:Actin Cytoskeleton / Q000737:chemistry*; D000494:Allosteric Regulation; D001665:Binding Sites; D003198:Computer Simulation; D017124:Conserved Sequence; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D058105:Polymerization; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D055550:Protein Stability; D055672:Static Electricity; D013379:Substrate Specificity
chemical_list: D051344:Actin Capping Proteins; D036341:Intercellular Signaling Peptides and Proteins; C065700:myotrophin