An NMR method to study protein-protein interactions.

Specific interactions between proteins are a fundamental process underlying the various biological events, such as cell-cell contacts, signal transduction, and gene expression. Therefore, the structural investigations of protein-protein interactions provide useful information for understanding these events. We describe an NMR method, termed the cross-saturation (CS) method, to determine the binding sites of protein complexes more precisely than conventional NMR methods. The CS method can determine the binding sites of a protein complex that undergoes fast exchange between the free and the bound states, regardless of the molecular size of the complex.