Nuclear magnetic resonance approaches for characterizing protein-protein interactions

The gating of potassium ion (K⁺) channels is regulated by various kinds of protein-protein interactions (PPIs). Structural investigations of these PPIs provide useful information not only for understanding the gating mechanisms of K⁺ channels, but also for developing the pharmaceutical compounds targeting K⁺ channels. Here, we describe a nuclear magnetic resonance spectroscopic method, termed the cross saturation (CS) method, to accurately determine the binding surfaces of protein complexes, and its application to the investigation of the interaction between a G protein-coupled inwardly rectifying K⁺ channel and a G protein α subunit.