On-Demand Proximity Labeling Using Light-Activated BioID

Membrane proteins play essential roles in the formation and maintenance of tissues. However, mapping the interactomes of membrane proteins is challenging with traditional proteomic methods. A common technique for investigating protein-protein interactions (PPIs) uses genetically encoded enzymes, such as TurboID, to label nearby proteins with biotin tags for subsequent detection. However, TurboID-mediated biotinylation cannot be switched on or off on demand, which results in high off-target or background labeling. To address this limitation and map membrane PPIs with high spatial and temporal resolution, we developed a novel light-activated proximity labeling technology: Light-Activated BioID (LAB). This innovative tool combines the two halves of the split-TurboID proximity labeling enzyme with photodimeric proteins CRY2 and CIB1, creating a user-controlled proximity biotinylation system for precise mapping of PPIs of membrane-bound proteins. In this work, we present our methods for developing, testing, and utilizing LAB to map PPIs.