Green Fluorescent Protein-based Probes.

The green fluorescent protein (GFP) of the jelly fish Aequorea victoria is a spontaneously fluorescent protein that can be incorporated into other proteins by genetic fusion. One of our approaches is to use two GFPs of different colors to permit fluorescence resonance energy transfer (FRET), which is highly sensitive to the relative orientation and distance between the two fluorophores and alters the ratio of their emission intensities. For example, cameleons are genetically-encoded fluorescent indicators for calcium. I describe here potentially unique features of GFP-based FRET, which would allow us to make probes for many intracellular signaling events that are currently assayed by grinding millions of cells.