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7st2

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Post translocation, non-rotated 70S ribosome with EF-G dissociated (Structure VII)

Structural highlights

7st2 is a 10 chain structure with sequence from Escherichia coli K-12. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	Electron Microscopy, Resolution 2.9Å
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

RL5_ECOLI This is 1 of the proteins that binds and probably mediates the attachment of the 5S RNA into the large ribosomal subunit, where it forms part of the central protuberance. Its 5S rRNA binding is significantly enhanced in the presence of L18.[HAMAP-Rule:MF_01333_B] In the 70S ribosome in the initiation state (PubMed:12809609) was modeled to contact protein S13 of the 30S subunit (bridge B1b), connecting the 2 subunits; the protein-protein contacts between S13 and L5 in B1b change in the model with bound EF-G implicating this bridge in subunit movement (PubMed:12809609 and PubMed:18723842). In the two 3.5 A resolved ribosome structures (PubMed:16272117) the contacts between L5, S13 and S19 are different, confirming the dynamic nature of this interaction.[HAMAP-Rule:MF_01333_B] Contacts the P site tRNA; the 5S rRNA and some of its associated proteins might help stabilize positioning of ribosome-bound tRNAs.[HAMAP-Rule:MF_01333_B]

Publication Abstract from PubMed

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 A. An additional 4-A 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.

Time-resolved cryo-EM visualizes ribosomal translocation with EF-G and GTP.,Carbone CE, Loveland AB, Gamper HB Jr, Hou YM, Demo G, Korostelev AA Nat Commun. 2021 Dec 13;12(1):7236. doi: 10.1038/s41467-021-27415-0. PMID:34903725^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Carbone CE, Loveland AB, Gamper HB Jr, Hou YM, Demo G, Korostelev AA. Time-resolved cryo-EM visualizes ribosomal translocation with EF-G and GTP. Nat Commun. 2021 Dec 13;12(1):7236. PMID:34903725 doi:10.1038/s41467-021-27415-0