Green Fluorescent Protein

By Jennifer McDowall

Hydromedusa Aequorea Victoria

Courtesy of John Blinks, University of Washington (Friday Harbor Laboratories)

Aequorea victoria bioluminescence

Courtesy of the Center for Research and Biotechnology, Rutgers University

The green fluorescent protein (GFP) was first isolated from a species of jellyfish, Aequorea victoria, which was named after a coastal city on Vancouver Island where it can be found in the shores of the Northwest Pacific. This colourless, transparent hydromedusa can produce bright green flashes along the rim of its bell-shaped body in response to external stimuli. GFP acts as a companion protein to the chemiluminescent protein aequorin, transforming the blue light emitted from aequorin into green light. Most bioluminescent animals lack the GFP transformation system and emit blue light, which travels the farthest through seawater. However, many animals in coastal waters, where A. victoria is found, tend to emit light in the blue-green range, possibly to compensate for the abundance of particulate matter found in the water.

The GFP is unique amongst natural pigments for its ability to autocatalyse its own chromophore, requiring only oxygen to complete its synthesis. In this way, a single protein acts as both substrate and enzyme. Other natural pigments require multiple enzymes for their production. Biotechnology has taken advantage of this unique feature of GFP, putting it to use as an in vivo marker of gene expression and protein localisation.

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