NMR-Based Determination of the 3D Structure of the Ligand–Protein Interaction Site without Protein Resonance Assignment

Molecular replacement in X-ray crystallography is the prime method for establishing structure–activity relationships of pharmaceutically relevant molecules. Such an approach is not available for NMR. Here, we establish a comparable method, called NMR molecular replacement (<i>N</i>MR<sup>2</sup>). The method requires experimentally measured ligand intramolecular NOEs and ligand–protein intermolecular NOEs as well as a previously known receptor structure or model. Our findings demonstrate that <i>N</i>MR<sup>2</sup> may open a new avenue for the fast and robust determination of the interaction site of ligand–protein complexes at atomic resolution.