Visualizing the activities of proteins in live cells and organisms can yield important biological insights—from understanding when and where transcription factors are turned on in development to determining how a mutant protein’s activity differs from that of its wild-type counterpart.
The standard method for tracking real-time protein activity involves genetically fusing fluorescent reporters, such as green fluorescent protein (GFP), to target protein sequences, expressing these fusion proteins in cells, and then viewing them under a fluorescence microscope.
For many proteins this approach works well, but if the molecule of interest happens to be produced and degraded in a matter of minutes, there’s a problem. With GFP, “there’s a lag in time between the production phase and the visualization phase,” explains biologist Stephen Small of New York University. Indeed, it can take 40 minutes or so for a newly-made GFP protein to be folded and chemically modified before it starts to ...
