title: Single-molecule spectroscopy of the temperature-induced collapse of unfolded proteins.
abstract: We used single-molecule FRET in combination with other biophysical methods and molecular simulations to investigate the effect of temperature on the dimensions of unfolded proteins. With single-molecule FRET, this question can be addressed even under near-native conditions, where most molecules are folded, allowing us to probe a wide range of denaturant concentrations and temperatures. We find a compaction of the unfolded state of a small cold shock protein with increasing temperature in both the presence and the absence of denaturant, with good agreement between the results from single-molecule FRET and dynamic light scattering. Although dissociation of denaturant from the polypeptide chain with increasing temperature accounts for part of the compaction, the results indicate an important role for additional temperature-dependent interactions within the unfolded chain. The observation of a collapse of a similar extent in the extremely hydrophilic, intrinsically disordered protein prothymosin alpha suggests that the hydrophobic effect is not the sole source of the underlying interactions. Circular dichroism spectroscopy and replica exchange molecular dynamics simulations in explicit water show changes in secondary structure content with increasing temperature and suggest a contribution of intramolecular hydrogen bonding to unfolded state collapse.
authors.affiliation: Biochemisches Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Nettels
authors.forename: Sonja
authors.initials: S
authors.lastname: Müller-Späth
authors.forename: Frank
authors.initials: F
authors.lastname: Küster
authors.forename: Hagen
authors.initials: H
authors.lastname: Hofmann
authors.forename: Dominik
authors.initials: D
authors.lastname: Haenni
authors.forename: Stefan
authors.initials: S
authors.lastname: Rüegger
authors.forename: Luc
authors.initials: L
authors.lastname: Reymond
authors.forename: Armin
authors.initials: A
authors.lastname: Hoffmann
authors.forename: Jan
authors.initials: J
authors.lastname: Kubelka
authors.forename: Benjamin
authors.initials: B
authors.lastname: Heinz
authors.forename: Klaus
authors.initials: K
authors.lastname: Gast
authors.forename: Robert B
authors.initials: RB
authors.lastname: Best
authors.forename: Benjamin
authors.initials: B
authors.lastname: Schuler
mesh_terms: D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D019791:Guanidine / Q000494:pharmacology; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D056004:Molecular Dynamics Simulation; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding / Q000187:drug effects; D011498:Protein Precursors / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013057:Spectrum Analysis; D013696:Temperature; D013947:Thymosin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism
chemical_list: D006360:Heat-Shock Proteins; D011498:Protein Precursors; C040782:prothymosin alpha; D013947:Thymosin; D019791:Guanidine