Building a foundation for structure-based cellulosome design for cellulosic ethanol: Insight into cohesin-dockerin...

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Cellulosomes are extracellular multienzyme complexes essential for breaking down plant biomass.
• Cohesin-dockerin interactions mediate the assembly of cellulosomal scaffolding proteins and enzymes.

Purpose of the Study:

• To investigate the molecular mechanism by which the D39N mutation disrupts cohesin-dockerin binding.
• To quantitatively compare simulation results with experimental data on binding affinity.

Main Methods:

• Molecular dynamics (MD) simulations of wild-type and D39N mutant cohesin-dockerin complexes.
• Free energy calculations, including free energy perturbation and potential of mean force (PMF).

Main Results:

• The D39N mutation significantly increases protein flexibility and alters the hydrogen-bonding network in recognition regions.
• MD simulations revealed conformational rearrangements of side chains and water molecules.
• Free energy calculations provided quantitative differences in binding energy, aligning with experimental findings.
• PMF calculations elucidated a high-free energy barrier for dissociation, indicating a stepwise binding mechanism.

Conclusions:

• The D39N mutation disrupts cellulosome assembly by affecting key hydrogen bonds and protein dynamics.
• Computational methods provide valuable insights into the molecular basis of protein-protein interactions and binding affinity.