Abstract
Casein proteins belong to the class of natively disordered proteins. The existence of disordered biologically active proteins questions the assumption that a well-folded structure is required for function. A hypothesis generally put forward is that the unstructured nature of these proteins results from the functional need of a higher flexibility. This interplay between structure and dynamics was investigated in a series of time-of-flight neutron scattering experiments, performed on casein proteins, as well as on three well-folded proteins with distinct secondary structures, namely, myoglobin (α), lysozyme (α/β) and concanavalin A (β). To illustrate the subtraction of the solvent contribution from the scattering spectra, we used the dynamic susceptibility spectra emphasizing the high frequency part of the spectrum, where the solvent dominates. The quality of the procedure is checked by comparing the corrected spectra to those of the dry and hydrated protein with negligible solvent contamination. Results of spectra analysis reveal differences in motional amplitudes of well-folded proteins, where β-sheet structures appear to be more rigid than a cluster of α-helices. The disordered caseins display the largest conformational displacements. Moreover their global diffusion rates deviate from the expected dependence, suggesting further large-scale conformational motions.
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Acknowledgments
A M Gaspar acknowledges the supported given by Fundação para a Ciência e Tecnologia in the form of a post-doc grant SFRH/BDP/17571/2004. The project was further supported by a grant of the Deutsche Forschungsgemeinschaft SFB 533. Tobias Unruh contributed with the construction and commissioning of the TOFTOF instrument. Valuable discussions and continuous support by Prof. Winfried Petry, as scientific director of the FRM II and supporter of the project, are also gratefully acknowledged by A.M. Gaspar.
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Advanced neutron scattering and complementary techniques to study biological systems. Contributions from the meetings, “Neutrons in Biology”, STFC Rutherford Appleton Laboratory, Didcot, UK, 11–13 July and “Proteins At Work 2007”, Perugia, Italy, 28–30 May 2007.
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Gaspar, A.M., Appavou, MS., Busch, S. et al. Dynamics of well-folded and natively disordered proteins in solution: a time-of-flight neutron scattering study. Eur Biophys J 37, 573–582 (2008). https://doi.org/10.1007/s00249-008-0266-3
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DOI: https://doi.org/10.1007/s00249-008-0266-3