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Structural analysis of protein dynamics by MD simulations and NMR spin-relaxation

Nikola Trbovic1, Byungchan Kim, Richard A Friesner

  • 1Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.

Proteins
|November 3, 2007
PubMed

Insights

Molecular dynamics (MD) simulations and NMR spin-relaxation studies reveal discrepancies in protein flexibility. Force fields overestimate flexibility, particularly in loops and secondary structure borders, suggesting hydrogen bonding descriptions may need refinement.

Area of Science:

  • Biophysics
  • Computational Biology
  • Structural Biology

Background:

  • Molecular dynamics (MD) simulations and nuclear magnetic resonance (NMR) spin-relaxation measurements are key techniques for studying protein dynamics on the picosecond to nanosecond timescale.
  • Discrepancies between simulation results and experimental data can hinder accurate predictions of protein behavior.

Purpose of the Study:

  • To analyze and explain the discrepancies between MD simulations and NMR spin-relaxation measurements for the B3 domain of streptococcal protein G.
  • To identify potential sources of error in current MD force fields.

Main Methods:

  • Utilized three common MD force fields: OPLS-AA, AMBER ff99SB, and AMBER ff03.
  • Compared MD-derived backbone N--H vector flexibility with experimentally determined generalized order parameters from NMR spin-relaxation.
  • Analyzed data in conjunction with previous residual dipolar coupling constant studies.

Main Results:

  • MD simulations consistently overestimated protein flexibility, especially at secondary structure boundaries and in loop regions, compared to experimental NMR data.
  • Slower timescale motions, as assessed by residual dipolar couplings, did not explain the observed discrepancies.
  • Structural analysis pointed to a potential imbalance in how hydrogen bonding is represented in modern MD force fields.

Conclusions:

  • Current MD force fields exhibit limitations in accurately capturing protein backbone dynamics.
  • The accurate representation of hydrogen bonding within force fields is crucial for improving the reliability of MD simulations in predicting protein structural dynamics.

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