Light in the Dark – Green Fluorescent Protein (GFP)
Humans can experience bioluminescence most anywhere in nature. Perhaps the most famous animal that glows in the dark is the firefly. But if we leave the solid ground and delve into the ocean, we will find numerous marine species that glow, including turtles, seahorses and even some types of sharks. The black seadevil also comes to mind, with its unmistakable “fishing rod” and glowing “fishing lure” appended to its forehead, which is intended to attract prey. So, what gives some organisms this ability to “glow”? The answer is simple: green fluorescent protein (GFP). So, when was GFP first studied, and what are its practical applications?
The Origins of GFP
Though bioluminescence had been studied years earlier, it wasn’t until 1962 that Nobel Prize winner Osamu Shimomura provided the first description of green fluorescent protein (GFP) as “a companion of aequorin” in the jellyfish Aequorea Victoria, which glows when it reacts with potassium. The biological reason for the glowing remained unclear, but shortly after its discovery, GFP was intensively studied.
Soon it was found that GFP had an excitation peak close to the chemiluminescence of pure aequorin. Thus, it was suggested that GFP converts the blue light of aequorin to a greenish glowing of the GFP expressing cells. Furthermore, GFP has been purified and crystallized to survey its absorbance spectrum and fluorescence quantum yield as well as the monomer molecular weight.
But only the cloning of the gene and the successful expression of it in organisms and other species had a strong impact on the biotechnological community. It was shown that the gene carries all the information that is needed to produce the greenish glowing in organisms. This gave a first glimpse of the potential of GFP in several biological applications.
Applications of GFP
Aside from the possibility of cloning GFP there are several other characteristics that make it useful for applications in the biological fields such as biotechnology, molecular biology and cell biology. For example, “GFP is resistant to heat, alkaline pH, detergents, photobleaching, chaotropic salts, organic salts and many proteases”. However, GFP does have some drawbacks — slow posttranslational chromophore formation, oxygen requirement and background fluorescence — but those can be overlooked compared to the advantages and the potential usage of GFP.
Thus, GFP has become a commonly used tool in biological laboratories. Scientists use it for fusion tags to survey dynamic cellular events, and cell biologists have used GFP as a reporter gene to monitor gene expression. There is a long list of applications with GFP that have been developed since its discovery: Fluorescence Resonance Energy Transfer (FRET), photobleaching, protein-protein interactions and many more.
As a multifaceted tool for the biological research community, it is no surprise that GFP-related applications have been conducted to tackle some very specific questions in cell biology, molecular biology, pharma and many other research fields. In environmental biology, for example, GFP can be used to monitor the dynamics and distributions of transgenic microorganisms. GFP has even been used for studying one of the most challenging diseases of our time – cancer – it is used to survey tumor progression and to detect metastases.
GFP – A Multifaceted Tool
Discovered more or less by chance GFP has become one of the most important tools in biological science. It can be used in several applications and is used by scientists worldwide to tackle several of the biggest challenges humans face in biology, pharma and medicine. Of course, it is not the only fluorescent tool used in the scientific community, but it may be the most readily available.
If you would like to start working with the famous tool, visit the Antibodies & Proteins Hub where you can easily find the right tools for your applications, like GFP in combination with red fluorescent protein (RFP) for a dual-coloring.
- Shimomura, O et al. (1962); Extraction, purification and properties of aequorin, a bioluminescent protein from the luminous hydromedusan, Aequorea; Journal of Cellular and Comparative Physiology ; https://doi.org/10.1002/jcp.1030590302
- Tsien, RY (1989): The green fluorescent protein; Annual Review of Biochemistry ; https://doi.org/10.1146/annurev.biochem.67.1.509
- Zimmer, M (2002); Green fluorescent protein: Applications, structure and related photophysical behavior; ACS Publications https://doi.org/10.1021/cr010142r
- Errampalli, D (1999): Applications of the green fluorescent protein as a molecular marker in environmental microorganisms; Journal of Microbiological Methods ; https://doi.org/10.1016/S0167-7012(99)00024-X