Intrinsically disordered proteins studied by NMR spectroscopy

Intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) of complex multi-domain proteins are now identified as a trend topic by the scientific community. NMR constitutes a unique investigation tool to access atom resolved information on their structural and dynamic properties, in isolation or upon interaction with potential partners (metal ions, small molecules, proteins, nucleic acids, membrane mimetics etc.). Their high flexibility and disorder, in contrast to more compact structures of globular protein domains, has a strong impact on NMR observables and NMR experiments should be tailored for their investigation. In this context, ¹³C direct detection NMR has become a very useful tool to contribute to IDPs/IDRs characterization at atomic resolution. 2D CON spectra can now be collected in parallel to 2D HN ones, and reveal information, which in some cases is not accessible through 2D HN spectra only, particularly when studying proteins in experimental conditions approaching physiological pH and temperature. The 2D HN/CON spectra are thus becoming a sort of identity card of an IDP/IDR in solution. Their simultaneous acquisition through multiple receiver NMR experiments is particularly useful to investigate the properties of highly flexible intrinsically disordered regions within complex multi-domain proteins, rather than in isolation as often performed to reduce the complexity of the system, an interesting perspective in the field.