title: The Folding process of Human Profilin-1, a novel protein associated with familial amyotrophic lateral sclerosis.
abstract: Human profilin-1 is a novel protein associated with a recently discovered form of familial amyotrophic lateral sclerosis. This urges the characterization of possible conformational states, different from the fully folded state, potentially able to initiate self-assembly. Under native conditions, profilin-1 is monomeric and possesses a well-defined secondary and tertiary structure. When incubated at low pH or with high urea concentrations, profilin-1 remains monomeric but populates unfolded states exhibiting larger hydrodynamic radius and disordered structure, as assessed by dynamic light scattering, far-UV circular dichroism and intrinsic fluorescence. Refolding from the urea-unfolded state was studied at equilibrium and in real-time using a stopped-flow apparatus. The results obtained with intrinsic fluorescence and circular dichroism indicate a single phase without significant changes of the corresponding signals before the major refolding transition. However, such a transition is preceded by a burst phase with an observed increase of ANS fluorescence, which indicates the conversion into a transiently populated collapsed state possessing solvent-exposed hydrophobic clusters. Kinetic analysis reveals that such state has a conformational stability comparable to that of the fully unfolded state. To our knowledge, profilin-1 is the first example of an amyloid-related protein where folding occurs in the absence of thermodynamically stable partially folded states.
authors.affiliation: Department of Experimental and Clinical Biomedical Sciences, Section of Biochemistry, University of Florence, Viale Morgagni 50, I-50134, Florence, Italy.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Del Poggetto
authors.affiliation: Department of Experimental and Clinical Biomedical Sciences, Section of Biochemistry, University of Florence, Viale Morgagni 50, I-50134, Florence, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Chiti
authors.affiliation: Department of Experimental and Clinical Biomedical Sciences, Section of Biochemistry, University of Florence, Viale Morgagni 50, I-50134, Florence, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bemporad
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism; D000817:Anilino Naphthalenesulfonates / Q000737:chemistry / Q000378:metabolism; D002942:Circular Dichroism; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D051304:Profilins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D014508:Urea / Q000737:chemistry
chemical_list: C515594:8-anilino-1-naphthalenesulfonic acid; D000817:Anilino Naphthalenesulfonates; D051304:Profilins; D014508:Urea