Green Fluorescent Protein

Green fluorescent protein (GFP) is a naturally fluorescent protein originally isolated from a jellyfish (Aequorea victoria). This protein is responsible for the bioluminescence of this organism - making it able to radiate a green glow. The 238 amino acid protein has been well characterised - contains side chains of serine, tyrosine and glycine residues that have spontaneously reacted with one another to form a fluorescent chromophore - unlike other bioluminescent reporters it does not require any additional proteins, cofactors or substrates. It is also extremely stable. The GFP gene can be introduced into living cultured cells or into specific cells of an entire animal. Cells which express the gene emit a green fluorescence when exposed to UV light - making it a particularly useful marker for studying gene expression and protein localisation in vivo, in situ and in real time.

GFP can be used to tag proteins

Similar to other tagging methods, the GFP gene can be fused to the gene of interest. The recombinant DNA encodes a chimaeric protein that contains the entirety of both proteins (a fusion protein where both protein activities are maintained). Useful for detecting the subcellular localisation and cellular trafficking of the protein in a living cell (Real Time Imaging). - see p143 and Fig. 5-7 of Lodish, ed. 4 for more details.

For more information on uses of GFP visit the Perkin Elmer Live Cell Imaging Site

Follow secretory granules (protein found in secretory granules, phogrin, is tagged with GFP )  moving around the cell in a video http://bj.portlandpress.co.uk/bj/333/bj3330193add3.htm

Reference: Aristea E. POULI, Evaggelia EMMANOUILIDOU, Chao ZHAO, Christina WASMEIER, John C. HUTTON, and Guy A. RUTTER (1998) Biochem. J. 333, 193-199