Activation and friction in enzymatic loop opening and closing dynamics

Area of Science:

• Biochemistry
• Structural Biology
• Computational Biology

Background:

• Protein loop dynamics are crucial for enzyme activity, specificity, and stability.
• The kinetic factors governing protein loop opening and closing remain largely unknown.

Purpose of the Study:

• To elucidate the molecular mechanism and rate-limiting step of WPD-loop dynamics in the PTP1B enzyme.
• To investigate the factors controlling loop opening and closing kinetics.

Main Methods:

• Combined molecular dynamics simulations with string-method determination of complex reaction coordinates.
• Analyzed torsional rearrangements and backbone friction influencing loop dynamics.

Main Results:

• Demonstrated that loop opening and closing is an activated process, not diffusive.
• Identified torsional rearrangement around a single peptide group and backbone friction as key factors.
• Calculated rate constants showed excellent agreement with experimental measurements and reproduced inter-protein kinetic differences.

Conclusions:

• The study provides a detailed molecular mechanism for WPD-loop dynamics in PTP1B.
• The findings offer insights into the factors controlling enzymatic loop kinetics.
• The methodology is applicable to other enzyme loops, suggesting potential for enzyme engineering.