Optimal molecular crowding accelerates group II intron folding and maximizes catalysis

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Group II intron ribozymes exhibit distinct folding and catalytic requirements in vitro compared to in vivo conditions.
• High magnesium(II) concentrations and temperatures are typically needed for in vitro ribozyme activity.
• The cellular environment's crowded nature is hypothesized to influence ribozyme behavior.

Purpose of the Study:

• To investigate the impact of molecular crowding using polyethylene glycol (PEG) on group II intron ribozyme folding and catalysis.
• To determine if PEG can reduce the high magnesium(II) requirements for ribozyme activity.
• To explore the relationship between PEG concentration and ribozyme conformational dynamics.

Main Methods:

• Utilized bulk activity assays to measure ribozyme catalytic efficiency under varying PEG concentrations.
• Employed single-molecule Förster Resonance Energy Transfer (smFRET) to analyze ribozyme folding states and dynamics.
• Combined biochemical and biophysical techniques to assess the effects of macromolecular crowding.

Main Results:

• Polyethylene glycol (PEG) was found to reduce the magnesium(II) concentration required for ribozyme activity.
• An optimal PEG concentration was identified that maximized ribozyme activity.
• smFRET data indicated an increase in the population of compact, putative active ribozyme states with increasing PEG concentration.
• Dynamic transitions between folded states of the ribozyme were enhanced by PEG.

Conclusions:

• Optimal molecular crowding conditions, achieved with specific PEG concentrations, facilitate the native folding of group II intron ribozymes.
• Molecular crowding significantly enhances in vitro ribozyme activity, bringing it closer to physiological levels.
• Macromolecular crowding is a critical factor in understanding and optimizing ribozyme function in vitro.