BiFC Magic: Shedding Light on Protein-Protein Interactions

Deciphering protein–protein interactions (PPIs) in vivo is crucial to understand protein function. Bimolecular fluorescence complementation (BiFC) is one of extensively used PCAs over the last decade in many different native contexts, including human live cells. It is based on the reconstitution of a monomeric fluorescent protein (FP) such as cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) from two complementary nonfluorescent sub-fragments (N- and C-terminal sub-fragments) upon spatial proximity. Interaction between a bait protein and a prey protein fused to such complementary sub-fragments is sufficient to lead to the reconstitution of the FP, resulting in an emission signal upon excitation (Figure 1). In this comprehensive review, we commence by tracing the development of fluorescent proteins (FPs) tailored for BiFC, followed by the highlighting of BiFC advantages over other PPI detection methods. Concurrently, the essential factors and nuanced considerations when employing BiFC are thoroughly explored. To vividly showcase the versatility of BiFC, the implementations at different throughputs are also presented, encompassing both single PPI experiments and large-scale studies, along with noteworthy variants of BiFC.