Year-end Sale % OFF 
Abstract
Ultrafast folding proteins have limited cooperativity and thus are excellent models to resolve, via single-molecule experiments, the fleeting molecular events that proteins undergo during folding. Here we report single-molecule atomic force microscopy experiments on gpW, a protein that, in bulk, folds in a few microseconds over a marginal folding barrier (∼1 kBT). Applying pulling forces of only 5 pN, we maintain gpW in quasi-equilibrium near its mechanical unfolding midpoint and detect how it interconverts stochastically between the folded and an extended state. The interconversion pattern is distinctly binary, indicating that, under an external force, gpW (un)folds over a significant free-energy barrier. Using molecular simulations and a theoretical model we rationalize how force induces such barrier in an otherwise downhill free-energy surface. Force-induced folding barriers are likely a general occurrence for ultrafast folding biomolecules studied with single-molecule force spectroscopy.
Highlights
Ultrafast folding proteins have limited cooperativity and are excellent models to resolve, via single-molecule experiments, the fleeting molecular events that proteins undergo during folding
Whereas many fast-folding proteins share common structural features such as their small size or primarily helical secondary structure, the protein gpW is an outlier to these general trends15. gpW has 65 residues and a native α + β structure that consists of two antiparallel α-helices and a single antiparallel two-stranded β-sheet, but it folds and unfolds in only ~4 μs at the denaturation midpoint and exhibits the characteristic features of downhill folding[15], including minimally cooperativefolding that results in many different patterns at the atomic level when investigated by nuclear magnetic resonance (NMR)[16]
Detailed analysis of the experiments, coarsegrained molecular dynamics (MD) simulations, and a theoretical model indicate that the pulling force induces a free-energy barrier to thefolding of gpW, confirming experimentally the scenario of forceinduced refolding barriers observed in molecular simulations of RNA22 and predicted for protein unfolding[23]
Summary
Ultrafast folding proteins have limited cooperativity and are excellent models to resolve, via single-molecule experiments, the fleeting molecular events that proteins undergo during folding. 8 IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain These authors contributed : Jörg Schönfelder, Deciphering the mechanisms by which proteins fold has long been one of the central problems in molecular biophysics[1,2]. GpW has 65 residues and a native α + β structure that consists of two antiparallel α-helices and a single antiparallel two-stranded β-sheet, but it folds and unfolds in only ~4 μs at the denaturation midpoint and exhibits the characteristic features of downhill folding[15], including minimally cooperative (un)folding that results in many different patterns at the atomic level when investigated by nuclear magnetic resonance (NMR)[16] Both atomistic MD simulations[16] and simple statistical mechanics models[15,17] agree in classifying gpW as a downhill folder. Detailed analysis of the experiments, coarsegrained MD simulations, and a theoretical model indicate that the pulling force induces a free-energy barrier to the (un)folding of gpW, confirming experimentally the scenario of forceinduced refolding barriers observed in molecular simulations of RNA22 and predicted for protein unfolding[23]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
