TY - GEN A1 - Best, Robert B. A1 - Zheng, Wenwei A1 - Borgia, Alessandro A1 - Buholzer, Karin A1 - Borgia, Madeleine B. A1 - Hofmann, Hagen A1 - Soranno, Andrea A1 - Nettels, Daniel A1 - Gast, Klaus A1 - Grishaev, Alexander A1 - Schuler, Benjamin T1 - Comment on "Innovative scattering analysis shows that hydrophobic disordered proteins are expanded in water" T2 - Science N2 - Riback et al. (Reports, 13 October 2017, p. 238) used small-angle x-ray scattering (SAXS) experiments to infer a degree of compaction for unfolded proteins in water versus chemical denaturant that is highly consistent with the results from Forster resonance energy transfer (FRET) experiments. There is thus no "contradiction" between the two methods, nor evidence to support their claim that commonly used FRET fluorophores cause protein compaction. Y1 - 2018 U6 - https://doi.org/10.1126/science.aar7101 SN - 0036-8075 SN - 1095-9203 VL - 361 IS - 6405 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Nettels, Daniel A1 - Müller-Späth, Sonja A1 - Küster, Frank A1 - Hofmann, Hagen A1 - Haenni, Domminik A1 - Rüegger, Stefan A1 - Reymond, Luc A1 - Hoffmann, Armin S. A1 - Kubelka, Jan A1 - Heinz, Benjamin A1 - Gast, Klaus A1 - Best, Robert B. A1 - Schuler, Benjamin T1 - Single-molecule spectroscopy of the temperature-induced collapse of unfolded proteins N2 - 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 singlemolecule FRET, this question can be addressed even under nearnative 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 temperaturedependent interactions within the unfolded chain. The observation of a collapse of a similar extent in the extremely hydrophilic, intrinsically disordered protein prothymosin 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. Y1 - 2009 UR - http://www.pnas.org/content/106/49/20740.full.pdf+html SN - 0027-8424 ER - TY - JOUR A1 - Borgia, Alessandro A1 - Zheng, Wenwei A1 - Buholzer, Karin A1 - Borgia, Madeleine B. A1 - Schüler, Anja A1 - Hofmann, Hagen A1 - Soranno, Andrea A1 - Nettels, Daniel A1 - Gast, Klaus A1 - Grishaev, Alexander A1 - Best, Robert B. A1 - Schuler, Benjamin T1 - Consistent View of Polypeptide Chain Expansion in Chemical Denaturants from Multiple Experimental Methods JF - Journal of the American Chemical Society N2 - There has been a long-standing controversy regarding the effect of chemical denaturants on the dimensions of unfolded and intrinsically disordered proteins: A wide range of experimental techniques suggest that polypeptide chains expand with increasing denaturant concentration, but several studies using small-angle X-ray scattering (SAXS) have reported no: such increase of the radius of gyration (R-g). This inconsistency challenges our current understanding of the mechanism of chemical denaturants, which are widely employed to investigate protein folding and stability. Here, we use a combination Of single-molecule Forster resonance energy transfer (FRET), SAXS, dynamic light scattering (DLS), and two-focus fluorescence correlation spectroscopy (2f-FCS) to characterize the denaturant dependence of the unfolded state of the spectrin domain R17 and the intrinsically disordered protein ACTR in two different denaturants. Standard analysis of the primary data clearly indicates an expansion of the unfolded state with increasing denaturant concentration irrespective of the protein, denaturant, or experimental method used. This is the first case in which SAXS and FRET have yielded even qualitatively consistent results regarding expansion in denaturant when applied to the same proteins. To more directly illustrate this self-consistency, we used both SAXS and FRET data in a Bayesian procedure to refine structural ensembles representative of the observed unfolded state. This analysis demonstrates that both of these experimental probes are compatible with a common ensemble of protein configurations for each denaturant concentration. Furthermore, the resulting ensembles reproduce the trend of increasing hydrodynamic radius, with denaturant concentration obtained by 2f-FCS,and DLS. We were thus able to reconcile the results from all four experimental techniques quantitatively, to obtain a comprehensive structural picture of denaturant;induced unfolded state expansion, and to identify the Most likely sources of earlier discrepancies. Y1 - 2016 U6 - https://doi.org/10.1021/jacs.6b05917 SN - 0002-7863 VL - 138 SP - 11714 EP - 11726 PB - American Chemical Society CY - Washington ER -