title: Dynamic transition associated with the thermal denaturation of a small Beta protein.
abstract: We studied the temperature dependence of the picosecond internal dynamics of an all-beta protein, neocarzinostatin, by incoherent quasielastic neutron scattering. Measurements were made between 20 degrees C and 71 degrees C in heavy water solution. At 20 degrees C, only 33% of the nonexchanged hydrogen atoms show detectable dynamics, a number very close to the fraction of protons involved in the side chains of random coil structures, therefore suggesting a rigid structure in which the only detectable diffusive movements are those involving the side chains of random coil structures. At 61.8 degrees C, although the protein structure is still native, slight dynamic changes are detected that could reflect enhanced backbone and beta-sheet side-chain motions at this higher temperature. Conversely, all internal dynamics parameters (amplitude of diffusive motions, fraction of immobile scatterers, mean-squared vibration amplitude) rapidly change during heat-induced unfolding, indicating a major loss of rigidity of the beta-sandwich structure. The number of protons with diffusive motion increases markedly, whereas the volume occupied by the diffusive motion of protons is reduced. At the half-transition temperature (T = 71 degrees C) most of backbone and beta-sheet side-chain hydrogen atoms are involved in picosecond dynamics.
authors.affiliation: Laboratoire Léon Brillouin, CE Saclay, 91191 Gif-sur-Yvette Cédex, France.
authors.forename: Daniela
authors.initials: D
authors.lastname: Russo
authors.forename: Javier
authors.initials: J
authors.lastname: Pérez
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Zanotti
authors.forename: Michel
authors.initials: M
authors.lastname: Desmadril
authors.forename: Dominique
authors.initials: D
authors.lastname: Durand
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D017666:Deuterium Oxide; D004058:Diffusion; D004220:Disulfides / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D006358:Hot Temperature; D015233:Models, Statistical; D009502:Neutrons; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry; D012542:Scattering, Radiation; D013696:Temperature; D009353:Zinostatin / Q000737:chemistry*
chemical_list: D004220:Disulfides; D011994:Recombinant Proteins; D009353:Zinostatin; D017666:Deuterium Oxide