title: Magnesium-cationic dummy atom molecules enhance representation of DNA polymerase beta in molecular dynamics simulations: improved accuracy in studies of structural features and mutational effects.
abstract: Human DNA polymerase beta (pol beta) fills gaps in DNA as part of base excision DNA repair. Due to its small size it is a convenient model enzyme for other DNA polymerases. Its active site contains two Mg(2+) ions, of which one binds an incoming dNTP and one catalyzes its condensation with the DNA primer strand. Simulating such binuclear metalloenzymes accurately but computationally efficiently is a challenging task. Here, we present a magnesium-cationic dummy atom approach that can easily be implemented in molecular mechanical force fields such as the ENZYMIX or the AMBER force fields. All properties investigated here, namely, structure and energetics of both Michaelis complexes and transition state (TS) complexes were represented more accurately using the magnesium-cationic dummy atom model than using the traditional one-atom representation for Mg(2+) ions. The improved agreement between calculated free energies of binding of TS models to different pol beta variants and the experimentally determined activation free energies indicates that this model will be useful in studying mutational effects on catalytic efficiency and fidelity of DNA polymerases. The model should also have broad applicability to the modeling of other magnesium-containing proteins.
authors.affiliation: University of Southern California, Department of Chemistry, Los Angeles, CA 90089-1062, USA. poelschl@usc.edu
authors.forename: Peter
authors.initials: P
authors.lastname: Oelschlaeger
authors.forename: Marco
authors.initials: M
authors.lastname: Klahn
authors.forename: William A
authors.initials: WA
authors.lastname: Beard
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Wilson
authors.forename: Arieh
authors.initials: A
authors.lastname: Warshel
mesh_terms: D001665:Binding Sites; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D019951:DNA Polymerase beta / Q000737:chemistry* / Q000235:genetics; D008274:Magnesium / Q000737:chemistry*; D008958:Models, Molecular; D009154:Mutation; D009711:Nucleotides / Q000737:chemistry; D011487:Protein Conformation; D013942:Thymine Nucleotides / Q000737:chemistry
chemical_list: D009711:Nucleotides; D013942:Thymine Nucleotides; D019951:DNA Polymerase beta; D008274:Magnesium; C024157:thymidine 5'-triphosphate