Green fluorescent protein (GFP) is a naturally occurring fluorescent protein found in jellyfish, Aequorea victoria, and corals mostly. The protein by virtue of its green fluorescence confers the characteristic bioluminescence property upon these organisms. The protein consists of 238 amino acids, and the side chains of critically placed serine, tyrosine and glycine react with one another to form fluorescent chromophore. Thus the protein does not have any other small molecule interacting with it to produce fluorescence, rather the protein itself is capable enough to fluoresce. GFP has been used in several biotechnological applications like localization of cells within a tissue, as marker gene in transgenics, or subcellular localization of proteins. The reader is referred to a detailed review on GFP here.
Until now GFPs were known from jellyfish or corals only. However, in a recent publication in Biological Bulletin, Dimitri Deheyn and his colleagues have demonstrated for the first time the presence of green fluorescent proteins (GFPs) in amphioxus (a primitive chordate), a fish-like animal. This is an important finding from the evolutionary point of view and suggests that the property of fluorescence may be prevalent across several animal kingdoms and not restricted to corals or jellyfish only. Or is the protein also found in terrestrial animals? Why fluorescence is present in amphioxus? Deheyn hypothesizes that the protein “might be used as a form of “sunscreen,” protecting the animal by absorbing harmful ultraviolet light and shielding it away as fluorescent light.” It has also been suggested that GFPs may act as antioxidant proteins, protecting cells from temperature fluctuations or other environmental changes.
The amino acid sequence comparison of the amphioxus and jellyfish GFPs would shed light on how amphioxus GFP produces fluorescence. Are the amino acid residues forming the chromophore same in the two GFPs? Read the full story here.