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Conformational sampling by NMR solution structures calculated with the program DIANA evaluated by comparison with
K D Berndt1, P Güntert, K Wüthrich
1Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule-Hönggerberg, Zürich, Switzerland.
Proteins
|March 1, 1996
Summary
Nuclear Magnetic Resonance (NMR) structure determination for bovine pancreatic trypsin inhibitor (BPTI) aligns well with molecular dynamics (MD) simulations. However, MD simulations reveal more conformational flexibility for surface-exposed side-chains than NMR data alone suggests.
Area of Science:
- Structural Biology
- Computational Chemistry
- Biophysics
Background:
- Nuclear Magnetic Resonance (NMR) spectroscopy is a key technique for determining protein structures in solution.
- Molecular Dynamics (MD) simulations offer insights into protein dynamics and conformational ensembles.
- Comparing NMR-derived structures with MD simulations validates computational methods and reveals dynamic behaviors.
Purpose of the Study:
- To compare the NMR solution structure of BPTI determined by DIANA with conformers generated by MD simulations.
- To assess the agreement between standard protein structure determination protocols and nanosecond-timescale MD simulations.
- To investigate the conformational sampling of constrained and unconstrained regions, particularly surface-exposed side-chains.
Main Methods:
- Distance geometry calculations using the DIANA program for NMR structure determination.
- Molecular dynamics (MD) simulations in explicit water at ambient conditions.
- MD simulations were performed with varying restraints (free, NOE-restrained, time-averaged restraints) and durations (200 ps, 1 ns).
- Conformers were collected at different time intervals from MD trajectories.
Main Results:
- The DIANA-derived NMR structure of BPTI is generally in agreement with MD simulations over a nanosecond timescale.
- Free MD simulations of 1 ns showed slightly increased conformational space sampling for well-constrained regions compared to DIANA.
- Surface-exposed side-chains, less constrained by NMR data, exhibited larger conformational space sampling in DIANA conformers than in MD trajectories.
- Side-chain dynamics on the protein surface are highly dependent on simulation length, indicating nanosecond-timescale transitions.
Conclusions:
- Standard NMR structure determination protocols (e.g., DIANA) provide a reliable structural picture consistent with MD simulations.
- MD simulations reveal greater conformational flexibility for surface side-chains than typically captured by NMR restraints alone.
- Nanosecond-timescale MD simulations are crucial for understanding protein side-chain dynamics, but longer simulations are needed for statistically significant data.