Exploring CRISPR-Cas9 HNH-Domain-Catalyzed DNA Cleavage Using Accelerated Quantum Mechanical Molecular Mechanical...

Area of Science:

• Biochemistry
• Molecular Biology
• Computational Chemistry

Background:

• CRISPR Cas9 enzyme is crucial for genome editing technologies.
• Previous simulations modeled target DNA cleavage in active Cas9 conformations.
• Understanding Cas9's catalytic mechanism is key to improving gene editing tools.

Purpose of the Study:

• To model target DNA cleavage using ab initio quantum mechanical molecular mechanical (ai-QM/MM) simulations based on a catalytically active Cas9 HNH domain conformation (PDB 7Z4J).
• To investigate the role of the active-site K866 residue in the catalytic efficiency of the Cas9 enzyme.
• To compare simulation results with experimental observations regarding enzyme activity.

Main Methods:

• Utilized ab initio quantum mechanical molecular mechanical (ai-QM/MM) simulations.
• Modeled the wildtype Cas9 HNH domain and the K866A mutant.
• Analyzed free energy profiles for target DNA cleavage.

Main Results:

• The free energy profile for wildtype Cas9-mediated target DNA cleavage was consistent with previous reports.
• Modeling the K866A mutant revealed an increased reaction free energy barrier.
• The simulation results for the K866A mutant align with experimental data showing reduced enzyme activity.

Conclusions:

• The study provides insights into the catalytic mechanism of the Cas9 HNH domain.
• The K866 residue plays a significant role in the catalytic efficiency of Cas9.
• Computational modeling can accurately predict the effects of mutations on enzyme activity in genome editing systems.