[NMR paper] Monitoring 15N Chemical Shifts During Protein Folding by Pressure-Jump NMR.

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Monitoring 15N Chemical Shifts During Protein Folding by Pressure-Jump NMR.

Related Articles Monitoring 15N Chemical Shifts During Protein Folding by Pressure-Jump NMR.

J Am Chem Soc. 2018 Jun 20;:

Authors: Charlier C, Courtney JM, Alderson TR, Anfinrud P, Bax A

Abstract
Novel pressure-jump NMR hardware permits direct observation of protein NMR spectra during a cyclically repeated protein folding process. While protein folding transpires, nuclei change their resonance frequencies from those of the fully disordered protein to those of the folded protein. For a two-state folding protein, the change in resonance frequency will occur nearly instantaneously when the protein clears the transition state barrier, and the ensemble average observed by NMR spectroscopy will reflect mono-exponential kinetics. However, protein folding pathways can be more complex and contain meta-stable intermediates. With a pseudo-3D NMR experiment that utilizes stroboscopic observation, we demonstrate that it is possible to measure the ensemble-averaged chemical shifts, including those of exchange-broadened intermediates, during the folding process. Measurements for a pressure-sensitized mutant of ubiquitin are incompatible with a simple two-state folding model and provide support for recent observations that approximately half the proteins fold through an on-pathway kinetic intermediate. 15N chemical shifts differ most from two-state behavior for residues in strands ?5, its preceding turn, and strands ?1 and ?3 that pair with ?5 in the native structure.


PMID: 29923716 [PubMed - as supplied by publisher]



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