If you encountered the Aequorea victoria jellyfish, you would be hard pushed to suggest that it had any major effect on modern science. However, buried deep within this tiny North-Pacific specimen is a protein that has helped revolutionise molecular biology.
This protein is ‘Green Fluorescent Protein’ (GFP). In Aequorea victoria, its job is to take some of the blue light emitted by the bio-luminescent protein aequorin and convert it to green light. This bio-luminescence is what we see when the jellyfish warns others about the danger of consuming it.
You may be asking, ‘How could this protein be useful to us?’ Well, since its discovery the uses of GFP have become almost endless. Its usefelness comes from the fact that it lets us see inside the inner workings of cells. All you have to do is shine UV light onto an area, or a specific point, of the cell that contains GFP and watch it light up. For instance, you could attach it to a virus and watch how it invades a cell, or attach it to a protein and watch how it moves around the cell.
So how does it work? GFP has a special sequence of three amino acids: serine-tyrosine-glycine. When the protein folds into its final form, this short segment is buried deep inside it. Then, several processes occur: the glycine forms a chemical bond with the serine, forming a new closed ring. Then, over the course of an hour or so, oxygen from the surrounding environment attacks a bond in the tyrosine, forming a new double bond and creating the fluorophore. Unlike a lot of fluorescent proteins, GFP makes its own chromophore (the molecule responsbile for the colour of the protein)which makes it perfect for genetic engineering. You simply engineer the cell with the genetic instructions for building the GFP protein, and GFP which is then produced folds up by itself and starts to glow.
Scientists are always looking at ways to improve GFP. Though it remains as useful as ever as a tracking device, it can also be stretched to have further uses. For example, work is ongoing into the use of GFP-tagged proteins as biosensors. These molecules sense the level of something, such as ion concentration or pH and light up in response.
However, the use of GFP isn’t limited just to science. The uses of GFP are also expanding into the world of art and commerce. Artist Eduardo Kac has created a fluorescent green rabbit by engineering GFP into its cells. Others are now following in his footsteps by creating more and more fluorescent animals. Though this practice is controversial, it hasn’t stopped its popularity.
‘Til next time…