Structural basis of mRNA recognition and cleavage by toxin MazF and its regulation by antitoxin MazE in Bacillus...

Area of Science:

• Bacterial stress response mechanisms
• Molecular mechanisms of RNA processing
• Protein-nucleic acid interactions

Background:

• MazF is a sequence-specific mRNA interferase crucial for bacterial growth arrest under stress.
• MazF activity is regulated by its antitoxin, MazE, forming an inactive complex during normal growth.
• The precise molecular details of MazF-mRNA recognition, cleavage, and MazE-mediated inhibition were previously unknown.

Purpose of the Study:

• To elucidate the molecular basis of sequence-specific mRNA recognition by MazF.
• To understand the mechanism of MazF-mediated mRNA cleavage.
• To determine how the MazE antitoxin inactivates MazF activity.

Main Methods:

• X-ray crystallography of MazF-RNA complexes and MazE-MazF complexes.
• Site-specific mutational analysis of key residues.
• Biochemical assays to assess RNA binding and cleavage.

Main Results:

• Crystal structures revealed MazF's specific recognition of the UACAU motif in mRNA.
• Key residues involved in RNA cleavage were identified through mutational studies.
• The heterohexameric (MazF)2-(MazE)2-(MazF)2 complex structure showed MazE's C-terminal helix blocking the MazF RNA-binding channel.

Conclusions:

• MazF recognizes specific mRNA sequences through defined residues, enabling targeted cleavage.
• The MazE antitoxin directly inhibits MazF by physically obstructing its RNA-binding site.
• These findings provide a detailed molecular understanding of MazF-MazE regulation in bacterial stress response.