title: Mapping the conformational stability of maltose binding protein at the residue scale using nuclear magnetic resonance hydrogen exchange experiments.
abstract: Being able to differentiate local fluctuations from global folding-unfolding dynamics of a protein is of major interest for improving our understanding of structure-function determinants. The maltose binding protein (MBP), a protein that belongs to the maltose transport system, has a structure composed of two globular domains separated by a rigid-body "hinge bending". Here we determined, by using hydrogen exchange (HX) nuclear magnetic resonance experiments, the apparent stabilization free energies of 101 residues of MBP bound to β-cyclodextrin (MBP-βCD) under native conditions. We observed that the last helix of MBP (helix α14) has a lower protection factor than the rest of the protein. Further, HX experiments were performed using guanidine hydrochloride under subdenaturing conditions to discriminate between local fluctuations and global unfolding events and to determine the MBP-βCD energy landscape. The results show that helix α4 and a part of helices α5 and α6 are clearly grouped into a subdenaturing folding unit and represent a partially folded intermediate under native conditions. In addition, we observed that amide protons located in the hinge between the two globular domains share similar ΔG(gu)(app) and m values and should unfold simultaneously. These observations provide new points of view for improving our understanding of the thermodynamic stability and the mechanisms that drive folding-unfolding dynamics of proteins.
authors.affiliation: Centre National de la Recherche Scientifique UMR 8587, Université Evry-Val d'Essonne et Cergy Pontoise, Laboratoire d'Analyse et de modélisation pour la Biologie et l'Environnement, Evry 91025, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Merstorf
authors.forename: Olek
authors.initials: O
authors.lastname: Maciejak
authors.forename: Jérôme
authors.initials: J
authors.lastname: Mathé
authors.forename: Manuela
authors.initials: M
authors.lastname: Pastoriza-Gallego
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Thiebot
authors.forename: Marie-Jeanne
authors.initials: MJ
authors.lastname: Clément
authors.forename: Juan
authors.initials: J
authors.lastname: Pelta
authors.forename: Loïc
authors.initials: L
authors.lastname: Auvray
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Curmi
authors.forename: Philippe
authors.initials: P
authors.lastname: Savarin
mesh_terms: D006859:Hydrogen / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D058619:Maltose-Binding Proteins / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D058767:Protein Unfolding; D013816:Thermodynamics
chemical_list: D058619:Maltose-Binding Proteins; D006859:Hydrogen