title: Mechanisms of protein-ligand association and its modulation by protein mutations.
abstract: Protein-ligand interactions are essential for nearly all biological processes, and yet the biophysical mechanism that enables potential binding partners to associate before specific binding occurs remains poorly understood. Fundamental questions include which factors influence the formation of protein-ligand encounter complexes, and whether designated association pathways exist. To address these questions, we developed a computational approach to systematically analyze the complete ensemble of association pathways. Here, we use this approach to study the binding of a phosphate ion to the Escherichia coli phosphate-binding protein. Various mutants of the protein are considered, and their effects on binding free-energy profiles, association rates, and association pathway distributions are quantified. The results reveal the existence of two anion attractors, i.e., regions that initially attract negatively charged particles and allow them to be efficiently screened for phosphate, which is subsequently specifically bound. Point mutations that affect the charge on these attractors modulate their attraction strength and speed up association to a factor of 10 of the diffusion limit, and thus change the association pathways of the phosphate ligand. It is demonstrated that a phosphate that prebinds to such an attractor neutralizes its attraction effect to the environment, making the simultaneous association of a second phosphate ion unlikely. This study suggests ways in which structural properties can be used to tune molecular association kinetics so as to optimize the efficiency of binding, and highlights the importance of kinetic properties.
authors.affiliation: Fachbereich Mathematik und Informatik, Freie Universität Berlin, Berlin, Germany; International Max Planck Research School-Computational Biology and Scientific Computing, Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Held
authors.affiliation: Institute of Computational Science, University of Lugano, Lugano, Switzerland; Deutsche Forschungsgemeinschaft Research Center MATHEON, Berlin, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Metzner
authors.affiliation: Fachbereich Mathematik und Informatik, Freie Universität Berlin, Berlin, Germany; Deutsche Forschungsgemeinschaft Research Center MATHEON, Berlin, Germany.
authors.forename: Jan-Hendrik
authors.initials: JH
authors.lastname: Prinz
authors.affiliation: Fachbereich Mathematik und Informatik, Freie Universität Berlin, Berlin, Germany; Deutsche Forschungsgemeinschaft Research Center MATHEON, Berlin, Germany. Electronic address: frank.noe@fu-berlin.de.
authors.forename: Frank
authors.initials: F
authors.lastname: Noé
mesh_terms: D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D028044:Phosphate-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D029968:Escherichia coli Proteins; D008024:Ligands; D050505:Mutant Proteins; D028044:Phosphate-Binding Proteins