Direct Detection of Structurally Resolved Dynamics in a Multiconformation Receptor−Ligand Complex

Structure-based drug design relies on static protein structures despite significant evidence for the need to include protein dynamics as a serious consideration. In practice, dynamic motions are neglected because they are not understood well enough to model, a situation resulting from a lack of explicit experimental examples of dynamic receptor−ligand complexes. Here, we report high-resolution details of pronounced ∼1 ms time scale motions of a receptor−small molecule complex using a combination of NMR and X-ray crystallography. Large conformational dynamics in Escherichia coli dihydrofolate reductase are driven by internal switching motions of the drug-like, nanomolar-affinity inhibitor. Carr−Purcell−Meiboom−Gill relaxation dispersion experiments and NOEs revealed the crystal structure to contain critical elements of the high energy protein−ligand conformation. The availability of accurate, structurally resolved dynamics in a protein−ligand complex should serve as a valuable benchmark for modeling dynami...