Bimolecular fluorescence complementation: illuminating cellular protein interactions.

Many cellular processes depend on the establishment of selective stable or transient interactions between proteins. Therefore, the ability to identify and characterize these contacts in physiologically relevant environments is crucial to understanding the networks of contacts that allow the transmission and integration of biological information in living cells. Protein-fragment complementation assays (PCA) have emerged as approaches that report on the proximity of two given proteins in the cell at a given location and time. In particular, bimolecular fluorescence complementation (BIFC) allows noninvasive imaging of protein binding in living cells at high spatial resolution and without the requirement for exogenous substrates. In the present review, we discuss PCA and BIFC fundamentals, the implementation of BIFC assays and selected applications of BIFC in drug discovery, developmental studies or neurological disorders.