Fluorescence-activating and absorption-shifting tag

Once bound, the pair of molecules goes through a unique fluorogen activation mechanism based on two spectroscopic changes, increase of fluorescence quantum yield and absorption red shift, hence providing high labeling selectivity.

Several versions of FAST have been described differing by a small number of mutations, e.g., Y-FAST, iFAST, pFAST, greenFAST, redFAST, frFAST, nirFAST, nanoFAST, or dimers of those.

splitFAST offers a powerful alternative to conventional imaging techniques for protein-protein interactions, i.e., Föster Resonance Energy Transfer (FRET) and bimolecular fluorescence complementation (BiFC).

[6] An evolution of FAST and splitFAST, CATCHFIRE implements the genetic fusion of a pair of proteins of interest to small FAST-based dimerizing domains, FIREtag and FIREmate.

[8] Because of its unique capacity of fluorescence in zero-oxygen conditions, FAST has been widely used in anaerobes, for example to enable metabolic engineering of Clostridium or related bacteria long known in biomass fermentation.

[12] Besides, FAST allows to monitor microbial activity in low oxygen conditions such as maturing biofilms[13] or in tumors or gut microbiota.

[14] Building on their small size and reversibility, hence limited impact on protein function and interactions, FAST and splitFAST have been used in fungi, namely Saccharomyces cerevisiae, to monitor metabolic engineering,[15] and in pathological bacteria, namely Listeria monocytogenes, to explore their bacterial virulence factors.

They helped elucidate the role of a special GPCR in dendritic spine maturation[17] as well as a mechanism of action of the interferon-inducible MX1 protein against Influenza A.