SNAP annotations: PDB entry 7ssd

PDB-id

7ssd; DSSR-derived features in text and JSON formats; DNAproDB

Class

ribosome

Method

cryo-EM (3.3 Å)

Summary

Mid translocation intermediate with ef-g bound with gdp (structure iv)

Reference

Carbone CE, Loveland AB, Gamper Jr HB, Hou YM, Demo G, Korostelev AA (2021): "Time-resolved cryo-EM visualizes ribosomal translocation with EF-G and GTP." Nat Commun, 12, 7236. doi: 10.1038/s41467-021-27415-0.

Abstract

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.