Structure and function of G protein-coupled receptors using NMR spectroscopy

The progress that has been made using NMR spectroscopy to characterize the structure and dynamics of G-protein-coupled receptors (GPCRs) in membrane environments are discussed. The seven-transmembrane helix GPCRs have evolved to recognize and transduce signals as diverse as light, Ca²⁺, small organic molecules and proteins. There are several areas where NMR can have an impact on understanding the structure and function of GPCRs. These include ligand conformation and interactions, molecular mechanisms of activation switches, role of water in activation; and role of the membrane in activation. Dynamic nuclear polarization (DNP) is an application, using microwave irradiation to polarize spin labels and transfer the resulting magnetization to NMR spins of interest. When applied to a ¹³C-labeled rhodopsin sample, DNP results in a <20-fold increase in sensitivity. As a result, the method opens up the possibility of structural studies on >1 mg of expressed and functional GPCRs.