Paramagnetic NMR Spin Relaxation in IDPs

Proteins play key roles in all organisms by acting as catalysts for essential biochemical reactions, molecular scaffolds providing structural integrity and hubs in protein interaction networks. It has been common belief, that these important functionalities depend on the existence of well-defined three-dimensional structures. However, this conventional structure- function structural biology paradigm has been put into question with the discovery of intrinsically disordered proteins (IDPs), proteins that are lacking stably folded tertiary structures. Despite their enormous biological relevance detailed studies of their physico- chemical properties are challenging and mandating suitable theoretical framework and concepts to properly address the subtle interdependence between protein structure and dynamics. The pronounced structural flexibility therefore requires the application of appropriate experimental methods since X-Ray crystallography cannot be used to determine the distribution of their conformational states. Although nuclear magnetic resonance (NMR) spectroscopy has matured into an extremely powerful technique for structural and dynamic studies of IDPs there is still a need for technology improvement and further methodological development. This is the topic of the proposed research project. The approach combines protein biochemistry and NMR spectroscopy to study the structural dynamics of medically relevant IDP protein complexes. Specifically, paramagnetic spin relaxation probes are covalently attached to specific sites of the proteins of interest. These sensors are subsequently used to probe the conformational ensembles of the IDPs and the relevance of their electrostatic properties for protein complex formation. The applicability of these novel techniques will be illustrated with applications to two medically important IDPs, relevant for inflammatory processes and tumor progression. The possibility to assess the structural ensembles of IDPs constitutes a major breakthrough and will allow for exciting novel applications in drug discovery.