Protein normal-mode dynamics: trypsin inhibitor, crambin, ribonuclease and lysozyme

Area of Science:

• Biophysics
• Computational Biology
• Structural Biology

Background:

• Protein dynamics are crucial for biological function.
• Traditional molecular dynamics simulations are computationally intensive.
• Normal-mode analysis (NMA) offers a complementary approach to study protein motion.

Purpose of the Study:

• To develop and present a novel method, normal-mode dynamics (NMD), for modeling protein dynamics.
• To enable direct visualization of biologically relevant protein motions.
• To complement existing molecular dynamics simulation techniques.

Main Methods:

• Developed normal-mode dynamics (NMD) using internal coordinates.
• Performed energy minimization of X-ray coordinates with respect to torsion angles.
• Calculated second derivative matrices of kinetic and potential energy for a generalized eigenvalue problem.
• Applied analytical formulae for thermodynamic averages.

Main Results:

• NMD successfully models collective protein motion and visualizes biologically interesting modes.
• Analysis of trypsin inhibitor, crambin, ribonuclease, and lysozyme revealed collective atomic participation in each mode.
• Slow modes (below 10 cm-1) exhibit segmental motion, crucial for protein function.
• Calculated root-mean-square atomic fluctuations correlate well with experimental B-values.

Conclusions:

• Normal-mode dynamics provides an efficient method for analyzing protein collective motion.
• The method allows for direct visualization of biologically significant dynamic modes.
• Protein dynamics are collective, with slow modes driving segmental movements and agreeing with experimental data.