Dynamic footprint of sequestration in the molecular fluctuations of osteopontin.
The sequestration of calcium phosphate by unfolded proteins is fundamental to the stabilization of biofluids supersaturated with respect to hydroxyapatite, such as milk, blood or urine. The unfolded state of osteopontin (OPN) is thought to be a prerequisite for this activity, which leads to the formation of core-shell calcium phosphate nanoclusters. We report on the structures and dynamics of a native OPN peptide from bovine milk, studied by neutron spectroscopy and small-angle X-ray and neutron scattering. The effects of sequestration are quantified on the nanosecond- ångström resolution by elastic incoherent neutron scattering. The molecular fluctuations of the free phosphopeptide are in agreement with a highly flexible protein. An increased resilience to diffusive motions of OPN is corroborated by molecular fluctuations similar to those observed for globular proteins, yet retaining conformational flexibilities. The results bring insight into the modulation of the activity of OPN and phosphopeptides with a role in the control of biomineralization. The quantification of such effects provides an important handle for the future design of new peptides based on the dynamics-activity relationship.
Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France Environment, Physical Sciences and Applied Mathematics Research Institute, Keele University, Staffordshire ST5 5BG, UK.
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Lenton
Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France.
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Seydel
Division of Physical Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden.
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Nylander
Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow G12 8QQ, UK.
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Holt
Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France.
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Härtlein
Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France Environment, Physical Sciences and Applied Mathematics Research Institute, Keele University, Staffordshire ST5 5BG, UK teixeira@ill.fr.
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http://orcid.org/0000-0002-1967-0026
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Teixeira
Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble cedex 9, France C.N.R.S., Institut de Biologie Structurale, F-38044 Grenoble, France.
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Zaccai
D000818:Animals; D002130:Calcium Phosphates / Q000737:chemistry*; D002417:Cattle; D008894:Milk Proteins / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D053495:Osteopontin / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D058767:Protein Unfolding
D002130:Calcium Phosphates; D008894:Milk Proteins; D010455:Peptides; D053495:Osteopontin; C020243:calcium phosphate
biomineralization; calcium phosphate nanoclusters; elastic incoherent neutron scattering; intrinsically disordered proteins; osteopontin; small-angle scattering