Nobel Fairy Dust Fluoresces Green!
(October 8th 2008) Yes, not even the chemists have been able to escape from the unending flow of Powerpoint presentations showing fluorescently-tagged proteins doing their thing. This year's Nobel Prize in Chemistry has been awarded to the Green Fluorescent Protein (GFP) and its derivatives, reports Jeremy Garwood.
Sticking to their limit of three names, the prize has been split three-ways between key figures in GFP's discovery (Osamu Shimomura), application (Martin Chalfie), and development (Roger Tsien).
In 1956, the Japanese, Osamu Shimomura, was the first person to isolate a fluorescing protein, from the crushed mollusc,
Cypridina, for which he was awarded a PhD from Nagoya University, even though he wasn't actually enrolled as a doctoral student. He went on to work with Frank Johnson at Princeton University, where he fished for the jellyfish,
Aequorea victoria, from which he purified a blue luminescent material, aequorin. In the 1962 aequorin paper, he described another protein that was slightly greenish in sunlight, yellowish in artificial light and fluorescent green in UV light - GFP!
Shimomura continued to study GFP through the 1970's. GFP is revolutionary because it does not need additives to glow, in contrast to other bioluminscent proteins that require a continuous supply of enrgy-rich molecules. GFP will glow when simply radiated with UV or blue light.
In 1988, the American, Martin Chalfie, first heard about GFP at a seminar at Columbia University. He immediately saw a potential application for the protein as an analytical tool in his research on the tiny transparent roundworm,
Caenorhabditis elegans. Chalfie's idea was to connect the GFP to other proteins in order to trace their synthesis and activity. To do this, he obtained the GFP gene, cloned by Douglas Prasher from
Aequorea victoria, and asked a graduate student, Ghia Euskirchen, to express it in
E.coli. Within a month, she had bacteria that glowed green when bathed in UV light! Contrary to general expectations, GFP required no other protein to glow making it perfect as a tool for analytical studies. In 1994, Chalfie published a paper demonstrating how the fusion of the GFP gene behind a promoter active in just six touch receptor neurons was enough to make the cells glow green within the
C.elegans worm.
The third prize-winner, Roger Tsien, another American, developed the potential of GFP as an analytical tool by investigating the molecular mechanisms underlying its fluorescence. He localised the GFP chromophore down to just three out of the 238 amino acids making up the GFP protein, showing that the reaction requires oxygen. By mutating these three amino acids at positions 65-67, he was able to develop new GFP variants that shine brighter and longer and at different wavelengths, generating different colours such as cyan, yellow and blue. He has also produced a red fluorescing protein based on DsRED, isolated by two Russian researchers, Mikhail Matz and Sergei Lukyanov, from fluoresent corals. DsRED was originally composed of four peptide chains, Tsien's group has successfully redesigned it as a smaller single chain protein that can now be readily fused to other proteins to produce red fluorescence. Other derivative proteins can produce a whole range of other colours, including plum, cherry, strawberry, orange and citrine.
Osama Shimomura, 80, is currently Professor emeritus at both the Marine Biology Lab, Woods Hole and the Medical School at Boston University. Martin Chalfie, 61, is Professor of Biological Sciences at Columbia University, New York. Roger Tsien, 56, who obtained his PhD in 1977 from the UK's Cambridge University, is a Professor at the University of California, San Diego.
As an afterthought, it has been remarked that 46 years after the discovery of GFP, nobody yet really knows just why the jellyfish,
Aequorea victoria, has evolved this biolumiscent protein.
