NMR structure determination of protein-ligand complexes by lanthanide labeling.

The paramagnetism of lanthanide ions offers outstanding opportunities for fast determinations of the three-dimensional (3D) structures of protein-ligand complexes by nuclear magnetic resonance (NMR) spectroscopy. It is shown how the combination of pseudocontact shifts (PCSs) induced by a site-specifically bound lanthanide ion and prior knowledge of the 3D structure of the lanthanide-labeled protein can be used to achieve (i) rapid assignments of NMR spectra, (ii) structure determinations of protein-protein complexes, and (iii) identification of the binding mode of low-molecular weight compounds in complexes with proteins. Strategies for site-specific incorporation of lanthanide ions into proteins are summarized.