title: Using Molecular Simulation to Model High-Resolution Cryo-EM Reconstructions.
abstract: An explosion of new data from high-resolution cryo-electron microscopy (cryo-EM) studies has produced a large number of data sets for many species of ribosomes in various functional states over the past few years. While many methods exist to produce structural models for lower resolution cryo-EM reconstructions, high-resolution reconstructions are often modeled using crystallographic techniques and extensive manual intervention. Here, we present an automated fitting technique for high-resolution cryo-EM data sets that produces all-atom models highly consistent with the EM density. Using a molecular dynamics approach, atomic positions are optimized with a potential that includes the cross-correlation coefficient between the structural model and the cryo-EM electron density, as well as a biasing potential preserving the stereochemistry and secondary structure of the biomolecule. Specifically, we use a hybrid structure-based/ab initio molecular dynamics potential to extend molecular dynamics fitting. In addition, we find that simulated annealing integration, as opposed to straightforward molecular dynamics integration, significantly improves performance. We obtain atomistic models of the human ribosome consistent with high-resolution cryo-EM reconstructions of the human ribosome. Automated methods such as these have the potential to produce atomistic models for a large number of ribosome complexes simultaneously that can be subsequently refined manually.
authors.affiliation: Department of Chemistry, New York University, Abu Dhabi, United Arab Emirates; New Mexico Consortium, Los Alamos, New Mexico, USA; Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA.
authors.forename: Serdal
authors.initials: S
authors.lastname: Kirmizialtin
authors.affiliation: Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Justus
authors.initials: J
authors.lastname: Loerke
authors.affiliation: Structural Dynamics of Proteins, Center of Advanced European Studies and Research (CAESAR), Bonn, Germany.
authors.forename: Elmar
authors.initials: E
authors.lastname: Behrmann
authors.affiliation: Institut für Medizinische Physik und Biophysik, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Christian M T
authors.initials: CMT
authors.lastname: Spahn
authors.affiliation: New Mexico Consortium, Los Alamos, New Mexico, USA; Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA. Electronic address: kys@lanl.gov.
authors.forename: Karissa Y
authors.initials: KY
authors.lastname: Sanbonmatsu
mesh_terms: D020285:Cryoelectron Microscopy; D006801:Humans; D007700:Kinetics; D056004:Molecular Dynamics Simulation / Q000706:statistics & numerical data*; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012335:RNA, Ribosomal / Q000737:chemistry*; D012269:Ribosomal Proteins / Q000737:chemistry*; D054682:Ribosome Subunits, Small, Eukaryotic / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D012335:RNA, Ribosomal; D012269:Ribosomal Proteins
keywords: High-resolution cryo-EM; Molecular modeling; Molecular simulation; RNA structure; Ribosome; cryo-EM; cryo-EM fitting