Gut colonization by Bacteroides requires translation by an EF‐G paralog lacking GTPase activity

W Han, BZ Peng, C Wang, GE Townsend… - The EMBO …, 2023 - embopress.org
W Han, BZ Peng, C Wang, GE Townsend, NA Barry, F Peske, AL Goodman, J Liu
The EMBO journal, 2023embopress.org
Protein synthesis is crucial for cell growth and survival yet one of the most energy‐
consuming cellular processes. How, then, do cells sustain protein synthesis under starvation
conditions when energy is limited? To accelerate the translocation of mRNA–tRNAs through
the ribosome, bacterial elongation factor G (EF‐G) hydrolyzes energy‐rich guanosine
triphosphate (GTP) for every amino acid incorporated into a protein. Here, we identify an EF‐
G paralog—EF‐G2—that supports translocation without hydrolyzing GTP in the gut …
Abstract
Protein synthesis is crucial for cell growth and survival yet one of the most energy‐consuming cellular processes. How, then, do cells sustain protein synthesis under starvation conditions when energy is limited? To accelerate the translocation of mRNA–tRNAs through the ribosome, bacterial elongation factor G (EF‐G) hydrolyzes energy‐rich guanosine triphosphate (GTP) for every amino acid incorporated into a protein. Here, we identify an EF‐G paralog—EF‐G2—that supports translocation without hydrolyzing GTP in the gut commensal bacterium Bacteroides thetaiotaomicron. EF‐G2's singular ability to sustain protein synthesis, albeit at slow rates, is crucial for bacterial gut colonization. EF‐G2 is ~10‐fold more abundant than canonical EF‐G1 in bacteria harvested from murine ceca and, unlike EF‐G1, specifically accumulates during carbon starvation. Moreover, we uncover a 26‐residue region unique to EF‐G2 that is essential for protein synthesis, EF‐G2 dissociation from the ribosome, and responsible for the absence of GTPase activity. Our findings reveal how cells curb energy consumption while maintaining protein synthesis to advance fitness in nutrient‐fluctuating environments.
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