Funding Organization(s): National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS), National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI), Czech Science Foundation
During translation, a conserved GTPase elongation factor-EF-G in bacteria or eEF2 in eukaryotes-translocates tRNA and mRNA through the ribosome. EF-G has been proposed to act as a flexible motor that propels tRNA and mRNA movement, as a rigid pawl that biases unidirectional translocation resulting from ribosome rearrangements, or by various combinations of motor- and pawl-like mechanisms. Using time-resolved cryo-EM, we visualized GTP-catalyzed translocation without inhibitors, capturing elusive structures of ribosome•EF-G intermediates at near-atomic resolution. Prior to translocation, EF-G binds near peptidyl-tRNA, while the rotated 30S subunit stabilizes the EF-G GTPase center. Reverse 30S rotation releases Pi and translocates peptidyl-tRNA and EF-G by ~20 Å. An additional 4-Å translocation initiates EF-G dissociation from a transient ribosome state with highly swiveled 30S head. The structures visualize how nearly rigid EF-G rectifies inherent and spontaneous ribosomal dynamics into tRNA-mRNA translocation, whereas GTP hydrolysis and Pi release drive EF-G dissociation.
Organizational Affiliation:
RNA Therapeutics Institute, UMass Chan Medical School, Worcester, MA, USA.
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, USA.
RNA Therapeutics Institute, UMass Chan Medical School, Worcester, MA, USA. gabriel.demo@ceitec.muni.cz.
Central European Institute of Technology, Masaryk University, Kamenice 5, Brno, 625 00, Czech Republic. gabriel.demo@ceitec.muni.cz.
RNA Therapeutics Institute, UMass Chan Medical School, Worcester, MA, USA. Andrei.Korostelev@umassmed.edu.
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