title: Three-dimensional structures of translating ribosomes by Cryo-EM.
abstract: Cryo-electron microscopy and image reconstruction techniques have been used to obtain three-dimensional maps for E. coli ribosomes stalled following translation of three representative proteins. Comparisons of these electron density maps, at resolutions of between 13 and 16 A, with that of a nontranslating ribosome pinpoint specific structural differences in stalled ribosomes and identify additional material, including tRNAs and mRNA. In addition, the tunnel through the large subunit, the anticipated exit route of newly synthesized proteins, is partially occluded in all the stalled ribosome structures. This observation suggests that significant segments of the nascent polypeptide chains examined here could be located within an expanded tunnel, perhaps in a rudimentary globular conformation. Such behavior could be an important aspect of the folding of at least some proteins in the cellular environment.
authors.affiliation: Max Planck Institut für Molekulare Genetik, AG Ribosomen, Ihnestrasse 73, 14195 Berlin, Germany.
authors.forename: Robert J C
authors.initials: RJ
authors.lastname: Gilbert
authors.forename: Paola
authors.initials: P
authors.lastname: Fucini
authors.forename: Sean
authors.initials: S
authors.lastname: Connell
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Fuller
authors.forename: Knud H
authors.initials: KH
authors.lastname: Nierhaus
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Dobson
authors.forename: David I
authors.initials: DI
authors.lastname: Stuart
mesh_terms: D020285:Cryoelectron Microscopy; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D021621:Imaging, Three-Dimensional; D008958:Models, Molecular; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis; D020836:Protein Structure, Quaternary; D012343:RNA, Transfer / Q000737:chemistry; D012270:Ribosomes / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure*
chemical_list: D029968:Escherichia coli Proteins; D012343:RNA, Transfer