FP tethering: A screening technique to rapidly identify compounds that disrupt protein-protein interactions

Tethering is a screening technique for discovering small-molecule fragments that bind to pre-determined sites via formation of a disulphide bond. Tethering screens traditionally rely upon mass spectrometry to detect disulphide bond formation, which requires a time-consuming liquid chromatography step. Here we show that tethering can be performed rapidly and inexpensively using a homogenous fluorescence polarization (FP) assay that detects displacement of a peptide ligand from the protein target as an indirect readout of disulphide formation. We apply this method, termed FP tethering, to identify fragments that disrupt the protein-protein interaction between the KIX domain of the transcriptional coactivator CBP and the transcriptional activator peptide pKID.