9K0Z

EF-G2 bound 70S ribosome complex of M. smegmatis

This is a non-PDB format compatible entry.

Summary for 9K0Z

• Entry DOI: 10.2210/pdb9k0z/pdb
• EMDB information: 61959
• Descriptor: P/P-site Phe-tRNA(Phe), Small ribosomal subunit protein uS5, Small ribosomal subunit protein bS6, ... (62 entities in total)
• Functional Keywords: mycobacterium 70s ribosome, stationary phase, elongation factor g2, non-canonical factor, ribosome
• Biological source: Mycolicibacterium smegmatis MC2 155; More
• Total number of polymer chains: 58
• Total formula weight: 2325323.25

Authors

Sengupta, J.,Baid, P. (deposition date: 2024-10-16, release date: 2025-07-09)

Primary citation

Baid, P.,Sengupta, J.
Cryo-EM structural analyses reveal a unique role for elongation factor G2 (EF-G2) in Mycobacteria.
Febs J., 2025

PubMed Abstract: The gene-encoding translation elongation factor G (EF-G) has undergone gene duplication across various bacterial species including Mycobacteria, and in mammalian mitochondria, leading to the emergence of the paralogue elongation factor G2 (EF-G2). Our study reveals that mycobacterial EF-G2, unlike EF-G1, neither participates in ribosome-recycling nor significantly contributes to overall translation, suggesting that it plays an alternative role in Mycobacteria. Remarkably, our investigation found a significant overexpression of mycobacterial EF-G2 during the stationary growth phase. Moreover, EF-G2 lacks ribosome-dependent GTPase activity, an observation consistent with previous reports. Cryo-EM analysis of the M. smegmatis 70S ribosome purified from the nutrient-starved (stationary) phase and complexed with EF-G2 unveiled the structural basis for its inability to hydrolyse GTP in a ribosome-dependent manner. Furthermore, we report an unprecedented binding mode of two EF-G2 copies on the 50S ribosomal subunit that impedes subunit association, thereby preventing the formation of active 70S ribosomes. Thus, instead of performing canonical functions, mycobacterial EF-G2 acts as a translation repressor during nutrient starvation. Altogether, our findings shed light on the multifaceted mechanisms by which EF-G2 modulates protein synthesis under nutrient-limited conditions, providing insights into adaptive strategies employed by Mycobacteria to survive in hostile environments.

PubMed: 40569974
DOI: 10.1111/febs.70161

Experimental method

ELECTRON MICROSCOPY (4.7 Å)