Green Fluorescent Protein (GFP) — Revolutionizing Science and Beyond

Different variants of GFP. Source: Erin Rod

You may be unaware of the green fluorescent protein (GFP), but this protein has been around us for a while now and has been used so extensively everywhere that it is safe to consider it as a piece of technology. The protein, made out of 238 amino acids, was first extracted in the early 1960s from a jellyfish named Aequorea Victoria (Tsien, 1998; Morise et al. 1974). In the jellyfish, aequorin is a protein that glows blue in the presence of calcium ions; and when some of aequorin’s energy is transferred to GFP, GFP glows green along with it, producing green color overall (Morise et al. 1974).

Molecular structure of GFP generated with the help of JSMol using information from the RCSB PDB database. Source: Monir Riasad Fadle Aziz.

The use of this protein to humans only gained recognition in the early 1990s, when it was first utilized for lab purposes (Chalfie et al. 1994). The function of GFP was simple; it glowed or fluoresced with a bright green color, when blue or ultraviolet light was shone on it. The intensity of the light wasn’t very great, which is why over the course of time, genetic modifications such as mutations had to be done to the genes that coded for the protein to yield maximum light output (Heim et al. 1995).

The primary purpose of GFP was to act as a fluorescent tag. In simplified terms, if scientists wanted to check the presence of a certain type of protein in an organism, they would design or code the DNA that makes GFP and glue it next to the DNA that codes for their target protein. Next, they would inject it into the cells of the organism, which would naturally start making the target protein from the injected DNA. As the protein was made, GFP would be made along with it, and scientists would measure the light intensity of GFP to tell how much of the protein was made, where it was transported and so on.

Glowing variants of GFP. Source: Fernan Federici

Further work on GFP by the scientist Dr. Tsien and his colleagues led to the production of a whole family of variants, which would not just glow green but also red, blue, orange, you name it (Tsien, 1998). People were able to see in real-time how cells transported nutrients and newly manufactured proteins, not only across a small distance but over the whole body of small organisms such as mice. This, in my opinion (and of many others I’m sure), marked the beginning of a new era of biotechnology. Dr. Roger Y. Tsien, Dr. Osamu Shimomura, and Dr. Martin Chalfie were awarded the 2008 Nobel Prize in Chemistry for the discovery and development of this amazing protein.

Example of a piece of art using GFP. Source: Nathan Shaner

Because GFP is not virulent or invasive and is easy to make and isolate, its availability eventually spread to everyone, including the common people around the world. An example would be the use of GFP in surgery to detect and eliminate cancer tumors. GFP has also been used for art, detecting cancer, mapping nerves in the body, potentially lighting streets and is slowly becoming a better candidate over the traditional fluorescent products (glow in the dark toys) that are composed of the radioactive element radium.

This amazing piece of technology is technically free to use if you know how to make them. I have made and used them myself at work. All you need to know is the sequence of DNA that codes for it, and then design primers (short pieces of DNA that help you make the whole sequence of DNA you want) and order a few other ingredients (such as enzymes and vectors) that are slightly costly.

Once you have the ingredients, you can mass produce them in small organisms, and then transfer them to your products to make them glow. The best part about this is that you get to set the selling price, as anything you are making is new technology developed solely by you. However, if you want to get them commercially ready-made, you can look for catalogues provided by biotechnology or pharmaceutical manufacturers out there, but it can be quite expensive. The price of the protein may be the main reason why it’s not sold as often to the general public, but it is certainly available to everyone regardless.

References:

Tsien RY (1998). “The green fluorescent protein” (PDF). Annual Review of Biochemistry. 67: 509–44. doi:10.1146/annurev.biochem.67.1.509. PMID 9759496.

Morise H, Shimomura O, Johnson FH, Winant J (Jun 1974). “Intermolecular energy transfer in the bioluminescent system of Aequorea”. Biochemistry. 13 (12): 2656–62. doi:10.1021/bi00709a028. PMID 4151620.

Chalfie M, Tu Y, Euskirchen G, Ward WW, Prasher DC (Feb 1994). “Green fluorescent protein as a marker for gene expression”. Science. 263 (5148): 802–5. doi:10.1126/science.8303295. PMID 8303295.

Heim R, Cubitt AB, Tsien RY (Feb 1995). “Improved green fluorescence” (PDF). Nature. 373 (6516): 663–4. doi:10.1038/373663b0. PMID 7854443.