Team UAlberta aims to develop a buoyancy-based screening system for protein-protein interactions in Escherichia coli. This system relies on a bacterial two-hybrid system (BACTH) where the reconstitution of the T18 and T25 domains of adenylate cyclase, due to the interaction between two proteins fused to the two domains, will restore the activity of the adenylate cyclase depending on the strength of the protein-protein interaction. Reconstitution of adenylate cyclase restores the production of cAMP, which will then upregulate a cluster of genes controlling gas vesicle production, therefore conferring buoyancy to E. coli cells. Thus, the observed buoyancy in bacteria is ultimately dependent on the strength of the protein-protein interaction. The purpose of this system is to utilize buoyancy to physically separate bacteria expressing successful protein interactions from unsuccessful variants. Team UAlberta will first test and characterize the system using pairs of proteins with well-characterized interactions, such as leucine zippers. After initial testing, Team UAlberta aims to use the system in conjunction with directed evolution to engineer a potent peptide inhibitor of NHERF2, a target that has been implicated with breast cancer.