title: Direct observation of multiple misfolding pathways in a single prion protein molecule.
abstract: Protein misfolding is a ubiquitous phenomenon associated with a wide range of diseases. Single-molecule approaches offer a powerful tool for deciphering the mechanisms of misfolding by measuring the conformational fluctuations of a protein with high sensitivity. We applied single-molecule force spectroscopy to observe directly the misfolding of the prion protein PrP, a protein notable for having an infectious misfolded state that is able to propagate by recruiting natively folded PrP. By measuring folding trajectories of single PrP molecules held under tension in a high-resolution optical trap, we found that the native folding pathway involves only two states, without evidence for partially folded intermediates that have been proposed to mediate misfolding. Instead, frequent but fleeting transitions were observed into off-pathway intermediates. Three different misfolding pathways were detected, all starting from the unfolded state. Remarkably, the misfolding rate was even higher than the rate for native folding. A mutant PrP with higher aggregation propensity showed increased occupancy of some of the misfolded states, suggesting these states may act as intermediates during aggregation. These measurements of individual misfolding trajectories demonstrate the power of single-molecule approaches for characterizing misfolding directly by mapping out nonnative folding pathways.
authors.affiliation: Department of Physics, University of Alberta, Edmonton AB, T6G 2G7 Canada.
authors.forename: Hao
authors.initials: H
authors.lastname: Yu
authors.forename: Xia
authors.initials: X
authors.lastname: Liu
authors.forename: Krishna
authors.initials: K
authors.lastname: Neupane
authors.forename: Amar Nath
authors.initials: AN
authors.lastname: Gupta
authors.forename: Angela M
authors.initials: AM
authors.lastname: Brigley
authors.forename: Allison
authors.initials: A
authors.lastname: Solanki
authors.forename: Iveta
authors.initials: I
authors.lastname: Sosova
authors.forename: Michael T
authors.initials: MT
authors.lastname: Woodside
mesh_terms: D011328:Prions / Q000378:metabolism*; D017510:Protein Folding; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D011328:Prions