BioID as a Tool for Protein-Proximity Labeling in Living Cells

BioID has become an increasingly utilized tool for identifying candidate protein-protein interactions (PPIs) in living cells. This method utilizes a promiscuous biotin ligase, called BioID, fused to a protein of interest that when expressed in cells can be induced to biotinylate interacting and proximate proteins over a period of hours, thus generating a history of protein associations. These biotinylated proteins are subsequently purified and identified via mass spectrometry. Compared to other conventional methods typically used to screen strong PPIs, BioID allows for the detection of weak and transient interactions within a relevant biological setting over a defined period of time. Here we briefly review the scientific progress enabled by the BioID technology, detail an updated protocol for applying the method to proteins in living cells, and offer insights for troubleshooting commonly encountered setbacks.