mRNA bound to the 30S subunit is a HigB toxin substrate

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.