Bioinformatics Advance Access published online on December 18, 2007
Bioinformatics, doi:10.1093/bioinformatics/btm625
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Structural flexibility in proteins: impact of the crystal environment
1Centre de Biophysique Moléculaire (CNRS), Rue Charles Sadron, 45071 Orléans Cedex 2, France
2Synchrotron Soleil, Saint Aubin, B.P. 48, 91192 Gif sur Yvette Cedex, France
To whom correspondence should be addressed. Dr. Konrad Hinsen, E-mail: hinsen{at}cnrs-orleans.fr
| Abstract |
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Motivation: In the study of the str uctural flexibility of proteins, cr ystallographic Debye-Waller factors are the most important experimental information used in the calibration and validation of computational models, such as the very successful elastic network models (ENMs). However, these models are applied to single protein molecules, whereas the experiments are performed on crystals. Moreover, the energy scale in standard ENMs is undefined and must be obtained by fitting to the same data that the ENM is trying to predict, reducing the predictive power of the model.
Results: We develop an elastic network model for the whole protein crystal in order to study the influence of crystal packing and lattice vibrations on the thermal fluctuations of the atom positions. We use experimental values for the compressibility of the crystal to establish the energy scale of our model. We predict the elastic constants of the crystal and compare with experimental data. Our main findings are (1) crystal packing modifies the atomic fluctuations considerably and (2) thermal fluctuations are not the dominant contribution to crystallographic Debye-Waller factors.
Availability: The programs developed for this work are available as supplementary material from the journal website.
Contact: hinsen{at}cnrs-orleans.fr
Supplementary information: (1) A full derivation of the normal mode equations in a crystal and in a continuous medium. (2) A movie illustrating the lattice vibrations. Both supplements are available through the journal website.
Associate Editor: Prof. AnnaTramontano
Received on October 4, 2007; revised on November 19, 2007; accepted on December 15, 2007
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