Intrinsically Disordered Proteins (IDPs): NMR Studies of IDPs

Intrinsically disordered proteins (IDPs) - polypeptides that lack a defined three-dimensional structure – are commonplace in eukaryotic proteomes and often have critical impact on correct functioning of biological processes. IDPs can mediate low affinity interactions between proteins and serve as a scaffold or intermediate binding agent. Malfunctions in IDPs can lead to protein aggregation and various diseases, such as Alzheimer's, Parkinson’s, or cancer. Relative to folded, globular proteins, their lack of defined tertiary structure, conformational flexibility, and conformational heterogeneity make investigating their structures and dynamics, and relating these to function, challenging.

Nuclear Magnetic Resonance (NMR) spectroscopy is the leading method for studying disordered proteins and disordered regions of proteins. The important functions of IDPs come from their conformational flexibility, and NMR methods are singularly well-suited for examining and revealing the complex interplay of protein structure and dynamics. NMR offers a wide range of observables, sensitive to disorder and motion, such as chemical shift, relaxation rates, and nuclear Overhauser effect (NOE) magnitude, which enable the conformational properties of disordered proteins and regions of proteins to be characterized.

The goal of this presentation is to describe the utility of NMR methods in general and to highlight specifically ¹³C-detected experiments for studying intrinsically disordered proteins. The unique advantage of ¹³C-detected experiments will be discussed, and their application for studying disordered systems under different conditions will be examined [1]. Additionally, ¹³C-detected experiments have proven to be useful in detecting important post-translational modifications, in particular lysine acetylation, which is critical epigenic modification. We’ll examine the application of these methods to studying lysine acetylation in IDPs and alternative polarization techniques involving methyl and amide protons for improving the sensitivity of the methods [2].

[1] Felli, I. C., Gonnelli, L., & Pierattelli, R. (2014). In-cell 13C NMR spectroscopy for the study of intrinsically disordered proteins. Nature Protocols. 

[2] Fraser, O. A., Dewing, S. M., Usher, G. A., George, C., & Showalter, S. A. (2023). A direct nuclear magnetic resonance method to investigate lysine acetylation of intrinsically disordered proteins.