mRNA bound to the 30S subunit is a HigB toxin substrate
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Updated: Mar 19, 2026
Isolation of Translating Ribosomes Containing Peptidyl-tRNAs for Functional and Structural Analyses
Published on: February 25, 2011
Marc A Schureck1, Tatsuya Maehigashi1, Stacey J Miles1
1Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Abstract:
Activation of bacterial toxins during stress results in cleavage of mRNAs in the context of the ribosome. These toxins are thought to function as global translational inhibitors yet recent studies suggest each may have distinct mRNA specificities that result in selective translation for bacterial survival. Here we demonstrate that mRNA in the context of a bacterial 30S subunit is sufficient for ribosome-dependent toxin HigB endonucleolytic activity, suggesting that HigB interferes with the initiation step of translation. We determined the X-ray crystal structure of HigB bound to the 30S, revealing that two solvent-exposed clusters of HigB basic residues directly interact with 30S 16S rRNA helices 18, 30, and 31. We further show that these HigB residues are essential for ribosome recognition and function. Comparison with other ribosome-dependent toxins RelE and YoeB reveals that each interacts with similar features of the 30S aminoacyl (A) site yet does so through presentation of diverse structural motifs.
Insights
Bacterial toxins like HigB cleave mRNA during stress. Researchers found HigB binds the 30S ribosomal subunit, interfering with translation initiation and revealing its essential residues for function.
Area of Science:
- Bacterial molecular biology
- Structural biology
- Biochemistry
Background:
- Bacterial toxins are activated during stress, cleaving messenger RNAs (mRNAs) within the ribosome.
- These toxins are generally considered global translational inhibitors, but recent evidence suggests specific mRNA targeting for bacterial survival.
Purpose of the Study:
- To investigate the mechanism of bacterial toxin HigB's endonucleolytic activity.
- To determine the structural basis of HigB interaction with the bacterial ribosome.
Main Methods:
- X-ray crystallography to determine the structure of HigB bound to the 30S ribosomal subunit.
- Biochemical assays to assess HigB's endonucleolytic activity and functional importance of specific residues.
Main Results:
- mRNA within the bacterial 30S subunit context is sufficient for HigB endonucleolytic activity, indicating interference with translation initiation.
- The crystal structure reveals HigB interacts with 16S rRNA helices 18, 30, and 31 via basic residues.
- These specific HigB residues are crucial for ribosome recognition and enzymatic function.
- Comparison with toxins RelE and YoeB shows conserved interaction sites in the 30S aminoacyl site but diverse structural presentations.
Conclusions:
- Bacterial toxin HigB functions by interfering with translation initiation through interaction with the 30S ribosomal subunit.
- The identified structural interactions and essential residues provide insight into HigB's mechanism and specificity.
- Comparative analysis highlights conserved and divergent strategies among ribosome-dependent bacterial toxins.
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