Fast Ultra‐Selective ¹ H‐ ¹⁵ N 1D NMR Spectroscopy Unlocks Atom‐Resolved Dynamics of Low‐Complexity Protein Regions

Abstract

ABSTRACT Insight into the conformational dynamics of proteins is essential toward understanding their function at a molecular level. The motions experienced by individual atoms in the protein can be precisely quantified through NMR relaxation rates, but their measurement requires well‐resolved spectral responses. Two‐dimensional 1 H‐ 15 N correlation spectra are the standard approach to resolve amide signals in protein NMR, but come with an excessive cost in experimental time when spectra are heavily congested due to limited 15 N chemical shift dispersions. This limitation often thwarts the characterization of dynamics for intrinsically disordered proteins, especially when they feature low‐complexity or homopolymer regions, or short sample life‐times. Here, we introduce a fast, ultra‐selective 1 H‐ 15 N 1D NMR method that allows high‐quality measurement of individual 15 N spin‐relaxation constants, even when 15 N resonances are merely 6–8 Hz apart. We demonstrate the new experiment by characterizing, for the first time, pico‐ to nanosecond dynamics along a 16‐residue polyglutamine stretch within the protein huntingtin, the causal agent of Huntington's disease, as well as millisecond conformational exchange in the SH3GL3 protein. The new experiment will find wide application in the study of conformational dynamics of intrinsically disordered proteins or any other biomacromolecule that features highly dense 1 H‐ 15 N 2D spectra.