Proteins interact with each other and these interactions determine in a large part their functions. Protein interaction partners can be identified at high-throughput in vivo using a yeast fitness assay based on the dihydrofolate reductase protein-fragment complementation assay (DHFR-PCA).
Rochette, S., Diss, G., Filteau, M., Leducq, J., Dubé, A. K., Landry, C. R. Genome-wide Protein-protein Interaction Screening by Protein-fragment Complementation Assay (PCA) in Living Cells. J. Vis. Exp. (97), e52255, doi:10.3791/52255 (2015).