title: Protein misfolding occurs by slow diffusion across multiple barriers in a rough energy landscape.
abstract: The timescale for the microscopic dynamics of proteins during conformational transitions is set by the intrachain diffusion coefficient, D. Despite the central role of protein misfolding and aggregation in many diseases, it has proven challenging to measure D for these processes because of their heterogeneity. We used single-molecule force spectroscopy to overcome these challenges and determine D for misfolding of the prion protein PrP. Observing directly the misfolding of individual dimers into minimal aggregates, we reconstructed the energy landscape governing nonnative structure formation. Remarkably, rather than displaying multiple pathways, as typically expected for aggregation, PrP dimers were funneled into a thermodynamically stable misfolded state along a single pathway containing several intermediates, one of which blocked native folding. Using Kramers' rate theory, D was found to be 1,000-fold slower for misfolding than for native folding, reflecting local roughening of the misfolding landscape, likely due to increased internal friction. The slow diffusion also led to much longer transit times for barrier crossing, allowing transition paths to be observed directly for the first time to our knowledge. These results open a new window onto the microscopic mechanisms governing protein misfolding.
authors.affiliation: Department of Physics, University of Alberta, Edmonton, AB, T6G 2E1, Canada;
authors.forename: Hao
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Physics, University of Alberta, Edmonton, AB, T6G 2E1, Canada;
authors.forename: Derek R
authors.initials: DR
authors.lastname: Dee
authors.affiliation: Department of Physics, University of Alberta, Edmonton, AB, T6G 2E1, Canada;
authors.forename: Xia
authors.initials: X
authors.lastname: Liu
authors.affiliation: National Institute for Nanotechnology, National Research Council, Edmonton, AB, T6G 2M9, Canada.
authors.forename: Angela M
authors.initials: AM
authors.lastname: Brigley
authors.affiliation: National Institute for Nanotechnology, National Research Council, Edmonton, AB, T6G 2M9, Canada.
authors.forename: Iveta
authors.initials: I
authors.lastname: Sosova
authors.affiliation: Department of Physics, University of Alberta, Edmonton, AB, T6G 2E1, Canada; National Institute for Nanotechnology, National Research Council, Edmonton, AB, T6G 2M9, Canada Michael.Woodside@ualberta.ca.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Woodside
mesh_terms: D000465:Algorithms; D000818:Animals; D006224:Cricetinae; D004058:Diffusion; D008647:Mesocricetus; D008956:Models, Chemical; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry; D011328:Prions / Q000737:chemistry*; D017510:Protein Folding; D055503:Protein Multimerization; D013057:Spectrum Analysis / Q000379:methods; D013816:Thermodynamics
chemical_list: D010446:Peptide Fragments; D011328:Prions
keywords: intrachain diffusion; optical tweezers; prion protein; protein aggregation; single-molecule force spectroscopy