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Structure of a novel antibacterial toxin that exploits elongation factor Tu to cleave specific transfer RNAs

Karolina Michalska1,2, Grant C Gucinski3, Fernando Garza-Sánchez4

  • 1Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA.

Nucleic Acids Research
|October 4, 2017
PubMed

Insights

Gram-negative bacteria use contact-dependent growth inhibition (CDI) toxins to compete. This study reveals how CDI toxins bind elongation factor Tu (EF-Tu) and cleave tRNAs, inhibiting bacterial growth.

Area of Science:

  • Microbiology
  • Structural Biology
  • Molecular Biology

Background:

  • Contact-dependent growth inhibition (CDI) is a bacterial competition mechanism.
  • Gram-negative bacteria utilize type V secretion systems to deliver polymorphic toxins.

Purpose of the Study:

  • To elucidate the structural basis of CDI toxin interaction with elongation factor Tu (EF-Tu).
  • To understand the mechanism by which CDI toxins inhibit bacterial growth through tRNA cleavage.

Main Methods:

  • X-ray crystallography to determine the structure of the CDI toxin-EF-Tu complex.
  • Biochemical assays to assess EF-Tu's role in toxin activity.
  • Structural superposition with existing GTP·EF-Tu·aa-tRNA complexes.

Main Results:

  • The CDI toxin binds EF-Tu domain 2, overlapping the aminoacyl-tRNA (aa-tRNA) binding site.
  • The toxin possesses ribonuclease activity, cleaving specific tRNAs dependent on EF-Tu.
  • Toxin binding induces conformational changes in EF-Tu, facilitating tRNA 3'-end access to the active site.

Conclusions:

  • CDI toxins remodel GTP·EF-Tu·aa-tRNA complexes to enable tRNA cleavage.
  • This mechanism provides insight into bacterial inter-cellular competition strategies.
  • The findings highlight EF-Tu as a key target for CDI toxins.

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