Identifying and studying ubiquitin receptors by NMR

Ubiquitin and ubiquitin chains are recognized by a large and growing family of receptor proteins. NMR spectroscopy provides a powerful means to evaluate whether and how a protein binds to ubiquitin. It can be used to measure binding affinities, to map interaction surfaces, and to solve the three-dimensional structure of ubiquitin:receptor complexes. Herein, we describe three NMR techniques of varying complexity that are valuable tools to characterize protein:protein complexes. These include heteronuclear correlation experiments, paramagnetic relaxation enhancement (PRE) experiments via spin labeling, and techniques designed to obtain intermolecular dipole-dipole interactions by nuclear Overhauser effects (NOEs).