The solvent-protected core of the hairpin ribozyme-substrate complex

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• The hairpin ribozyme is a catalytic RNA molecule essential for various biological processes.
• Understanding the precise interactions within the hairpin ribozyme-substrate complex is crucial for elucidating its catalytic mechanism.
• Previous studies lacked experimental evidence defining the interface between the ribozyme and its substrate domains.

Purpose of the Study:

• To define the interaction interface between the hairpin ribozyme and its substrate.
• To identify the catalytic core of the active hairpin ribozyme-substrate complex.
• To investigate the role of cations in forming the catalytic complex.

Main Methods:

• Hydroxyl radical footprinting was employed to map the solvent accessibility of the complex.
• The study utilized magnesium and cobalt(III) hexammine as catalytic cations.
• Mutational analysis was performed to assess the importance of specific nucleotides and complex formation.

Main Results:

• Efficient catalysis by magnesium and cobalt(III) hexammine resulted in a docked complex with a protected, solvent-inaccessible core.
• Substrate nucleotides near the cleavage site were internalized into this catalytic core.
• Specific ribozyme segments (G11-A14, C25-C27, A38, U42-A43) were protected, indicating their involvement in the core.
• Loss of protection correlated with suboptimal catalysis or mutations affecting complex formation.

Conclusions:

• Hydroxyl radical footprinting successfully identified the catalytic core of the hairpin ribozyme-substrate complex.
• The formation of a solvent-inaccessible core is essential for efficient hairpin ribozyme catalysis.
• The study provides critical insights into the structural basis of ribozyme activity.