Binding events between biomolecules are important components of biological processes and a number of these biomolecular interactions have been targeted for the development of novel therapeutic drugs. p53 is a transcription factor and tumor suppressor protein that is activated in response to cellular stress, and MDM2 was identified as a negative regulator that binds to p53 and tags it for ubiquitination and subsequent degradation.

The p53-MDM2 protein-protein interaction has been an excellent target for therapeutic drugs and therefore makes a good model system for developing an AlphaLISA assay to screen for inhibitors of the interaction. In this technical note, we show how to develop an assay to screen for inhibitors and how to measure a dissociation constant for moderate binding protein-protein interaction using AlphaLISA^®.