Biophysical characterization of intrinsically disordered proteins

Abstract

The challenges associated with the structural characterization of disordered proteins have resulted in the application of a host of biophysical methods to such systems. NMR spectroscopy is perhaps the most readily suited technique for providing high-resolution structural information on disordered protein states in solution. Optical methods, solid state NMR, ESR and X-ray scattering can also provide valuable information regarding the ensemble of conformations sampled by disordered states. Finally, computational studies have begun to assume an increasingly important role in interpreting and extending the impact of experimental data obtained for such systems. This article discusses recent advances in the applications of these methods to intrinsically disordered proteins.

Figure 1. NMR α-carbon secondary chemical shifts and NH RDCs for β-synuclein

Chemical shift deviations from random coil values indicate a preference for extended structure (negative values) in the C-terminal region and helical structure (positive values) in the N-terminal region. Large amplitude RDCs in the C-terminal region correlate qualitatively with negative shift deviations and likely reflect locally extended chain segments. Smaller amplitude RDCs in the N-terminal region occur largely in regions of positive shift deviations, although the RDCs do not change sign as would be expected for more highly populated helical structure. Adapted from [26].

Figure 2. NMR PRE in α-, β- and γ-synuclein

A paramagnetic spin label attached to a cysteine introduced at position 20 leads to clear broadening in the C-terminal tail of α-synuclein, but not of β- or γ-synuclein, suggesting long-range N- to C-terminal contacts are present in the former but not in the latter. The red lines represent the predicted broadening for an idealized random coil. Adapted from [26].