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Structural Insights into Ribosome Recycling Process Catalyzed by Elongation Factor G

Author: Update time: 2015-10-13

Protein translation is a cyclic process which could be divided into four steps: initiation, elongation, termination and ribosome recycling. Each step is assisted by a translational GTPase (trGTPase) in combination with other translation factors. Elongation factor G (EF-G) is the only trGTPase involved in two distinct steps, elongation and ribosome recycling. During translation, EF-G plays a catalytic role in tRNA translocation and a facilitative role in ribosome recycling. By stabilizing the rotated ribosome and interacting with ribosome recycling factor (RRF), EF-G was hypothesized to induce the domain rotations of RRF, which subsequently performs the function of splitting the major intersubunit bridges and thus separates the ribosome into sub-units for recycling.

In a new study published in Nucleic Acids Research, entitled “New insights into the enzymatic role of EF-G in ribosome recycling”, QIN Yan’s Group from Institute of Biophysics (IBP) of Chinese Academy of Sciences, in collaboration with GAO Ning from Tsinghua University and XIE Qiang from Nankai University, using systematic mutagenesis, FRET analysis and cryo-EM single particle approach, analyzed the interplay between EF-G/RRF and post termination complex (PoTC).

This study reveals that the two conserved loops (loop I and II) at the tip region of EF-G domain IV possess distinct roles in tRNA translocation and ribosome recycling. Specifically, loop II might be directly involved in disrupting the main intersubunit bridge B2a between helix 44 (h44 from the 30S subunit) and helix 69 (H69 from the 50S subunit) in PoTC. Therefore, the study suggests a new ribosome recycling mechanism which requires an active involvement of EF-G. In addition to supporting RRF, EF-G plays an enzymatic role in destabilizing B2a via its loop II.

Figure legends: (A) Brief model of ribosome recycling process. (B) Cryo-EM structure of PoTC•EF-G (S588P)•GDPNP. (C) Schematic representation of the catalytic role of EF-G loop II in ribosome recycling (Image by QIN Yan's Group).



Institute of Biophysics, Chinese Academy of Sciences



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