A Novel Pair of Split Venus Fragments to Detect Protein–Protein Interactions by In Vitro and In Vivo Bimolecular Fluorescence Complementation Assays

Protein–protein interactions are critical components of almost every cellular process. The bimolecular fluorescence complementation (BiFC) method has been used to detect protein–protein interactions in both living cells and cell-free systems. The BiFC method is based on the principle that a fluorescent protein is reassembled from its two complementary non-fluorescent fragments when an interaction occurs between two proteins, each one fused to each fragment. In vivo and in vitro BiFC assays, which use a new pair of split Venus fragments composed of VN210 (amino acids 1–210) and VC210 (amino acids 210–238), are useful tools to detect and quantify various protein–protein interactions (including the cofilin–actin and Ras–Raf interactions) with high specificity and low background fluorescence. Moreover, these assays can be applied to screen small-molecule inhibitors of protein–protein interactions.