title: The folding pathway of a functionally competent C-terminal domain of nucleophosmin: protein stability and denatured state residual structure.
abstract: Nucleophosmin (NPM1) is a nucleolar protein implicated in ribosome biogenesis, centrosome duplication and cell cycle control; the NPM1 gene is the most frequent target for mutations in Acute Myeloid Leukemia. Mutations map to the C-terminal domain of the protein and cause its unfolding, loss of DNA binding properties and aberrant cellular localization. Here we investigate the folding pathway and denatured state properties of a NPM1 C-terminal domain construct encompassing the last 70 residues in the reference sequence. This construct is more stable than the previously characterized domain, which consisted of the last 53 residues. Data reveal that, similarly to what was discovered for the shorter construct, also the 70-residue construct of NPM1 displays a detectable residual structure in its denatured state. The higher stability of the latter domain allows us to conclude that the denatured state is robust to changes in solvent composition and that it consists of a discrete state in equilibrium with the expanded fully unfolded conformation. This observation, which might appear as a technicality, is in fact of general importance for the understanding of the folding of proteins. The implications of our results are discussed in the context of previous works on single domain helical proteins.
authors.affiliation: Istituto Pasteur - Fondazione Cenci Bolognetti and Istituto di Biologia e Patologia Molecolari del CNR, Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Università di Roma La Sapienza, Rome, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Chiarella
authors.forename: Luca
authors.initials: L
authors.lastname: Federici
authors.forename: Adele
authors.initials: A
authors.lastname: Di Matteo
authors.forename: Maurizio
authors.initials: M
authors.lastname: Brunori
authors.forename: Stefano
authors.initials: S
authors.lastname: Gianni
mesh_terms: D004305:Dose-Response Relationship, Drug; D006801:Humans; D007700:Kinetics; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000090243:Nucleophosmin; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D013050:Spectrometry, Fluorescence; D014508:Urea / Q000737:chemistry / Q000494:pharmacology
chemical_list: C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D014508:Urea