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

• Published in: Journal of the American Chemical Society Vol. 140; no. 26; pp. 8096 - 8099
• Main Authors: Charlier, Cyril, Courtney, Joseph M, Alderson, T Reid, Anfinrud, Philip, Bax, Ad
• Format: Journal Article
• Language: English
• Published: United States 05.07.2018
• Subjects: Nitrogen Isotopes; Nuclear Magnetic Resonance, Biomolecular; Pressure; Protein Folding
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b04833

Pressure-jump hardware permits direct observation of protein NMR spectra during a cyclically repeated protein folding process. For a two-state folding protein, the change in resonance frequency will occur nearly instantaneously when the protein clears the transition state barrier, resulting in a monoexponential change of the ensemble-averaged chemical shift. However, protein folding pathways can be more complex and contain metastable intermediates. With a pseudo-3D NMR experiment that utilizes stroboscopic observation, we measure the ensemble-averaged chemical shifts, including those of exchange-broadened intermediates, during the folding process. Such measurements for a pressure-sensitized mutant of ubiquitin show an on-pathway kinetic intermediate whose N chemical shifts differ most from the natively folded protein for strands β5, its preceding turn, and the two strands that pair with β5 in the native structure.