title: The ribosome as a molecular machine: the mechanism of tRNA-mRNA movement in translocation.
abstract: Translocation of tRNA and mRNA through the ribosome is one of the most dynamic events during protein synthesis. In the cell, translocation is catalysed by EF-G (elongation factor G) and driven by GTP hydrolysis. Major unresolved questions are: how the movement is induced and what the moving parts of the ribosome are. Recent progress in time-resolved cryoelectron microscopy revealed trajectories of tRNA movement through the ribosome. Driven by thermal fluctuations, the ribosome spontaneously samples a large number of conformational states. The spontaneous movement of tRNAs through the ribosome is loosely coupled to the motions within the ribosome. EF-G stabilizes conformational states prone to translocation and promotes a conformational rearrangement of the ribosome (unlocking) that accelerates the rate-limiting step of translocation: the movement of the tRNA anticodons on the small ribosomal subunit. EF-G acts as a Brownian ratchet providing directional bias for movement at the cost of GTP hydrolysis.
authors.affiliation: Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany. rodnina@uni-wh.de
authors.forename: Marina V
authors.initials: MV
authors.lastname: Rodnina
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wintermeyer
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D008958:Models, Molecular; D009068:Movement / Q000502:physiology*; D014176:Protein Biosynthesis / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism* / Q000502:physiology; D012343:RNA, Transfer / Q000378:metabolism* / Q000502:physiology; D012270:Ribosomes / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D012333:RNA, Messenger; D012343:RNA, Transfer