title: Single-molecule spectroscopy of cold denaturation and the temperature-induced collapse of unfolded proteins.
abstract: Recent Förster resonance energy transfer (FRET) experiments show that heat-unfolded states of proteins become more compact with increasing temperature. At the same time, NMR results indicate that cold-denatured proteins are more expanded than heat-denatured proteins. To clarify the connection between these observations, we investigated the unfolded state of yeast frataxin, whose cold denaturation occurs at temperatures above 273 K, with single-molecule FRET. This method allows the unfolded state dimensions to be probed not only in the cold- and heat-denatured range but also in between, i.e., in the presence of folded protein, and can thus be used to link the two regimes directly. The results show a continuous compaction of unfolded frataxin from 274 to 320 K, with a slight re-expansion at higher temperatures. Cold- and heat-denatured states are thus essentially two sides of the same coin, and their behavior can be understood within the framework of the overall temperature dependence of the unfolded state dimensions.
authors.affiliation: Department of Biochemistry, University of Zurich , Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Mikayel
authors.initials: M
authors.lastname: Aznauryan
authors.forename: Daniel
authors.initials: D
authors.lastname: Nettels
authors.forename: Andrea
authors.initials: A
authors.lastname: Holla
authors.forename: Hagen
authors.initials: H
authors.lastname: Hofmann
authors.forename: Benjamin
authors.initials: B
authors.lastname: Schuler
mesh_terms: D003080:Cold Temperature; D031541:Fluorescence Resonance Energy Transfer; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics; D006358:Hot Temperature; D033862:Iron-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation; D011489:Protein Denaturation; D058767:Protein Unfolding; D013816:Thermodynamics; D000096923:Frataxin
chemical_list: D005656:Fungal Proteins; D033862:Iron-Binding Proteins; D000096923:Frataxin