title: Ribosome dynamics and tRNA movement by time-resolved electron cryomicroscopy.
abstract: The translocation step of protein synthesis entails large-scale rearrangements of the ribosome-transfer RNA (tRNA) complex. Here we have followed tRNA movement through the ribosome during translocation by time-resolved single-particle electron cryomicroscopy (cryo-EM). Unbiased computational sorting of cryo-EM images yielded 50 distinct three-dimensional reconstructions, showing the tRNAs in classical, hybrid and various novel intermediate states that provide trajectories and kinetic information about tRNA movement through the ribosome. The structures indicate how tRNA movement is coupled with global and local conformational changes of the ribosome, in particular of the head and body of the small ribosomal subunit, and show that dynamic interactions between tRNAs and ribosomal residues confine the path of the tRNAs through the ribosome. The temperature dependence of ribosome dynamics reveals a surprisingly flat energy landscape of conformational variations at physiological temperature. The ribosome functions as a Brownian machine that couples spontaneous conformational changes driven by thermal energy to directed movement.
authors.affiliation: 3D Electron Cryomicroscopy Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
authors.forename: Niels
authors.initials: N
authors.lastname: Fischer
authors.forename: Andrey L
authors.initials: AL
authors.lastname: Konevega
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wintermeyer
authors.forename: Marina V
authors.initials: MV
authors.lastname: Rodnina
authors.forename: Holger
authors.initials: H
authors.lastname: Stark
mesh_terms: D020285:Cryoelectron Microscopy; D004926:Escherichia coli; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D009068:Movement; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism*; D054681:Ribosome Subunits, Large, Bacterial / Q000737:chemistry / Q000378:metabolism; D054680:Ribosome Subunits, Small, Bacterial / Q000737:chemistry / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D012343:RNA, Transfer