title: Folding mechanism of the C-terminal domain of nucleophosmin: residual structure in the denatured state and its pathophysiological significance.
abstract: Nucleophosmin (NPM1) is a ubiquitously expressed protein and is one of the most abundant proteins found in the nucleolus. Naturally occurring mutations in the C-terminal domain of nucleophosmin (Cter-NPM1) are found in approximately 30% of patients with acute myeloid leukemia (AML). These mutations cause changes at the C terminus of NPM1 that lead to denaturation of the protein, a critical factor in determining aberrant translocation of NPM1 to the cytosol. Hence, this protein system represents an ideal candidate to investigate the relations between folding and unfolding and disease. Here we report the characterization of the folding and unfolding kinetics of Cter-NPM1. Data reveal that this small helical domain folds via a compact denatured state, displaying a malleable residual structure. Moreover, analysis of folding rate constants measured under different experimental conditions suggests that the existence of a preorganized structure in the denatured state accelerates folding, implying a native-like residual structure. Because a major feature of Cter-NPM1 mutants responsible for AML is a reduction in stability of the protein and thus prevalence of a denatured state even under physiological conditions, our findings may pave the way to further studies with the aim of designing chemicals capable of interacting with the "pathological" mutants to stabilize the native conformation.
authors.affiliation: Istituto Pasteur Fondazione Cenci Bolognetti and Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Università di Roma La Sapienza, Rome, Italy.
authors.forename: Flavio
authors.initials: F
authors.lastname: Scaloni
authors.forename: Stefano
authors.initials: S
authors.lastname: Gianni
authors.forename: Luca
authors.initials: L
authors.lastname: Federici
authors.forename: Brunangelo
authors.initials: B
authors.lastname: Falini
authors.forename: Maurizio
authors.initials: M
authors.lastname: Brunori
mesh_terms: D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D000090243:Nucleophosmin; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics
chemical_list: C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D000090243:Nucleophosmin