title: Cryo-EM of macromolecular assemblies at near-atomic resolution.
abstract: With single-particle electron cryomicroscopy (cryo-EM), it is possible to visualize large, macromolecular assemblies in near-native states. Although subnanometer resolutions have been routinely achieved for many specimens, state of the art cryo-EM has pushed to near-atomic (3.3-4.6 Å) resolutions. At these resolutions, it is now possible to construct reliable atomic models directly from the cryo-EM density map. In this study, we describe our recently developed protocols for performing the three-dimensional reconstruction and modeling of Mm-cpn, a group II chaperonin, determined to 4.3 Å resolution. This protocol, utilizing the software tools EMAN, Gorgon and Coot, can be adapted for use with nearly all specimens imaged with cryo-EM that target beyond 5 Å resolution. Additionally, the feature recognition and computational modeling tools can be applied to any near-atomic resolution density maps, including those from X-ray crystallography.
authors.affiliation: National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Baker
authors.forename: Junjie
authors.initials: J
authors.lastname: Zhang
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Ludtke
authors.forename: Wah
authors.initials: W
authors.lastname: Chiu
mesh_terms: D000465:Algorithms; D020285:Cryoelectron Microscopy / Q000379:methods*; D018360:Crystallography, X-Ray; D056385:Group II Chaperonins / Q000648:ultrastructure*; D046911:Macromolecular Substances; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012984:Software
chemical_list: D046911:Macromolecular Substances; D056385:Group II Chaperonins