Green fluorescent protein is a protein found in a luminescent jellyfish (Aquorea victoria) that lives in the cold waters of the northern Pacific. Bioluminescence is the production of light by living organisms. These jellyfish contain two proteins: a bioluminescent protein called aequorin that emits blue light, and an accessory green fluorescent protein (GFP). However, what we actually see when the jellyfish fluoresces is the conversion of the blue light emitted by aequorin to a green Iight-a metabolic reaction facilitated by the GFP. Since GFP is simply a protein, it is often used both as a marker for gene transfer and for localization of proteins. There are a variety of green fluorescent proteins that can glow different colors.
