| Direct observation of multiple misfolding pathways in a single prion protein molecule |
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| Posted on Wed 13 Jun 2012 by vacaresources (183 reads) |
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Direct observation of multiple misfolding pathways in a single prion protein molecule 1. Hao Yua,1, 2. Xia Liua,1, 3. Krishna Neupanea, 4. Amar Nath Guptaa, 5. Angela M. Brigleyb, 6. Allison Solankia, 7. Iveta Sosovab, and 8. Michael T. Woodsidea,b,2 + Author Affiliations 1. aDepartment of Physics, University of Alberta, Edmonton AB, T6G 2G7 Canada; and 2. bNational Institute for Nanotechnology, National Research Council Canada, Edmonton AB, T6G 2M9 Canada 1. Edited by Stanley B. Prusiner, University of California, San Francisco, San Francisco, CA, and approved January 17, 2012 (received for review May 13, 2011) 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. protein folding optical tweezers Footnotes ↵1H.Y. and X.L. contributed equally to this work. ↵2To whom correspondence may be addressed at: National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton AB, T6G 2M9, Canada. E-mail: michael.woodside@nrc-cnrc.gc.ca. Author contributions: M.T.W. designed research; H.Y., X.L., K.N., and A.N.G. performed research; X.L., A.M.B., A.S., and I.S. contributed new reagents/analytic tools; H.Y. and K.N. built experimental apparatus; H.Y., X.L., and M.T.W. analyzed data; and H.Y., X.L., K.N., A.N.G., A.M.B., A.S., I.S., and M.T.W. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1107736109/-/DCSupplemental. |
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