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Protein solution structure calculations in solution: solvated molecular dynamics refinement of calbindin D9k
J Kördel1, D A Pearlman, W J Chazin
1Pharmacia & Upjohn, Stockholm, Sweden.
Journal of Biomolecular NMR
|December 9, 1997
Summary
Calculating protein structures using explicit solvent and calcium ions significantly improves accuracy, especially for metalloproteins. This refined molecular dynamics approach enhances structural definition and calcium ion coordination in binding loops.
Area of Science:
- Biochemistry
- Structural Biology
- Computational Chemistry
Background:
- Protein structures are typically calculated in a vacuum using NMR-derived constraints.
- This approach may not accurately represent protein structures in their native solution environment.
Purpose of the Study:
- To re-determine the solution structure of (Ca2+)2-calbindin D9k using advanced computational methods.
- To compare the accuracy of protein structure calculations with and without explicit solvent and calcium ions.
Main Methods:
- Restrained molecular dynamics (MD) calculations were employed.
- Four sets of MD refinements were performed: in vacuo, in vacuo with Ca2+ ions, and two protocols with explicit solvent and Ca2+ ions.
- Structural ensembles were analyzed for definition, energies, packing, solvent accessibility, hydrogen bonds, and calcium ion coordination.
Main Results:
- Refinement including Ca2+ ions and explicit solvent significantly improved structural precision and accuracy.
- Improvements were particularly notable in the calcium ion binding loops.
- Analysis confirmed enhanced structural definition and calcium ion coordination.
Conclusions:
- Explicit solvent and Ca2+ ions are crucial for accurate NMR-derived protein structure determination.
- Restrained MD (rMD) refinement strategies incorporating these factors enhance the reliability of solution structures, especially for metalloproteins.