The present invention provides novel recombinant fusion proteins for detecting binding of a molecule of interest containing a detection domain, a first and optionally a second localization domain, and a binding domain. The invention also provides recombinant nucleic acid molecules and recombinant expression vectors encoding these novel fusion proteins, genetically engineered host cells containing these expression vectors, and kits for the use of these fusion proteins, nucleic acid molecules, expression vectors, and host cells. Additionally, the present invention provides methods for identifying compounds that alter the binding of a molecule of interest in a cell.