title: Evolutionarily Conserved Pattern of Interactions in a Protein Revealed by Local Thermal Expansion Properties.
abstract: The way in which the network of intramolecular interactions determines the cooperative folding and conformational dynamics of a protein remains poorly understood. High-pressure NMR spectroscopy is uniquely suited to examine this problem because it combines the site-specific resolution of the NMR experiments with the local character of pressure perturbations. Here we report on the temperature dependence of the site-specific volumetric properties of various forms of staphylococcal nuclease (SNase), including three variants with engineered internal cavities, as measured with high-pressure NMR spectroscopy. The strong temperature dependence of pressure-induced unfolding arises from poorly understood differences in thermal expansion between the folded and unfolded states. A significant inverse correlation was observed between the global thermal expansion of the folded proteins and the number of strong intramolecular hydrogen bonds, as determined by the temperature coefficient of the backbone amide chemical shifts. Comparison of the identity of these strong H-bonds with the co-evolution of pairs of residues in the SNase protein family suggests that the architecture of the interactions detected in the NMR experiments could be linked to a functional aspect of the protein. Moreover, the temperature dependence of the residue-specific volume changes of unfolding yielded residue-specific differences in expansivity and revealed how mutations impact intramolecular interaction patterns. These results show that intramolecular interactions in the folded states of proteins impose constraints against thermal expansion and that, hence, knowledge of site-specific thermal expansivity offers insight into the patterns of strong intramolecular interactions and other local determinants of protein stability, cooperativity, and potentially also of function.
authors.affiliation: †Centre de Biochimie Structurale, CNRS UMR5048, INSERM U554, Université Montpellier 1, 29 rue de Navacelles, Montpellier, France 34090.
authors.forename: Mariano
authors.initials: M
authors.lastname: Dellarole
authors.affiliation: ‡T. C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 N. Charles St.. Baltimore, Maryland 21218, United States.
authors.forename: Jose A
authors.initials: JA
authors.lastname: Caro
authors.affiliation: †Centre de Biochimie Structurale, CNRS UMR5048, INSERM U554, Université Montpellier 1, 29 rue de Navacelles, Montpellier, France 34090.
authors.forename: Julien
authors.initials: J
authors.lastname: Roche
authors.affiliation: †Centre de Biochimie Structurale, CNRS UMR5048, INSERM U554, Université Montpellier 1, 29 rue de Navacelles, Montpellier, France 34090.
authors.forename: Martin
authors.initials: M
authors.lastname: Fossat
authors.affiliation: †Centre de Biochimie Structurale, CNRS UMR5048, INSERM U554, Université Montpellier 1, 29 rue de Navacelles, Montpellier, France 34090.
authors.forename: Philippe
authors.initials: P
authors.lastname: Barthe
authors.affiliation: ‡T. C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 N. Charles St.. Baltimore, Maryland 21218, United States.
authors.forename: Bertrand
authors.initials: B
authors.lastname: García-Moreno E
authors.affiliation: †Centre de Biochimie Structurale, CNRS UMR5048, INSERM U554, Université Montpellier 1, 29 rue de Navacelles, Montpellier, France 34090.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Royer
authors.affiliation: †Centre de Biochimie Structurale, CNRS UMR5048, INSERM U554, Université Montpellier 1, 29 rue de Navacelles, Montpellier, France 34090.
authors.forename: Christian
authors.initials: C
authors.lastname: Roumestand
mesh_terms: D000577:Amides / Q000737:chemistry; D019143:Evolution, Molecular; D006860:Hydrogen Bonding; D008836:Micrococcal Nuclease / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D011312:Pressure; D011485:Protein Binding; D011487:Protein Conformation; D058767:Protein Unfolding; D011522:Protons; D013696:Temperature
chemical_list: D000577:Amides; D011522:Protons; D008836:Micrococcal Nuclease