Protein-protein interactions as measured by bioluminescence energy transfer in Renilla

This chapter discusses protein–protein interactions that occur in a variety of biochemical systems. Classic examples include (1) proteins containing multiple subunits, (2) self-associating oligomeric proteins, (3) protein self-assembly systems, (4) antigen–antibody systems, and (5) multienzyme complexes. Firefly luciferase is active as a 50,000-molecular weight monomer at low-protein concentrations, but at higher-protein concentrations, in low-ionic strength buffer, the monomers associate to form fully active dimers. The active form of bacterial luciferase is a dimer of nonidentical subunits. In the sea pansy (Renilla reniformis), luciferase 12 can also be shown to associate with an accessory protein known as the “green-fluorescent protein (GFP).” The chapter presents experimental evidence for protein–protein interaction between luciferase and GFP in the Renilla system and describes how this interaction can be measured by the assay of in vitro energy transfer.