title: Factors determining electrostatic fields in molecular dynamics simulations of the Ras/effector interface.
abstract: Using molecular dynamics simulations, we explore geometric and physical factors contributing to calculated electrostatic fields at the binding surface of the GTPase Ras with a spectroscopically labeled variant of a downstream effector, the Ras-binding domain of Ral guanine nucleotide dissociation stimulator (RalGDS). A related system (differing by mutation of one amino acid) has been studied in our group using vibrational Stark effect spectroscopy, a technique sensitive to electrostatic fields. Electrostatic fields were computed using the AMBER 2003 force field and averaged over snapshots from molecular dynamics simulation. We investigate geometric factors by exploring how the orientation of the spectroscopic probe changes on Ras-effector binding. In addition, we explore the physical origin of electrostatic fields at our spectroscopic probe by comparing contributions to the field from discrete components of the system, such as explicit solvent, residues on the Ras surface, and residues on the RalGDS surface. These models support our experimental hypothesis that vibrational Stark shifts are caused by Ras binding to its effector and not the structural rearrangements of the effector surface or probe reorientation on Ras-effector binding, for at least some of our experimental probes. These calculations provide physical insight into the origin, magnitude, and importance of electrostatic fields in protein-protein interactions and suggest new experiments to probe the field's role in protein docking.
authors: Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA.
authors: Daniel L
authors: DL
authors: Ensign
authors: Lauren J
authors: LJ
authors: Webb
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D008956:Models, Chemical; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D015689:Oncogene Protein p21(ras) / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013057:Spectrum Analysis; D055672:Static Electricity; D020726:ral Guanine Nucleotide Exchange Factor / Q000737:chemistry
chemical_list: D020726:ral Guanine Nucleotide Exchange Factor; D015689:Oncogene Protein p21(ras)